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close this bookEnvironmental Handbook Volume II: Agriculture, Mining/Energy, Trade/Industry (GTZ, 1995, 736 p.)
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Documentation on monitoring and evaluating environmental impacts

German Federal Ministry for Economic Cooperation and Development Bundesministerium ftschaftliche Zusammenarbeit und Entwicklung (BMZ)


Wide-ranging and indepth specialized knowledge is needed in order to professionally evaluate the environmental relevance of a project or individual technical plans in the scope of cooperation activities, for example plans for locating industrial sites. The sixty environmental briefs in Volumes I and II provide an overview of potential environmental impacts and known environmental protection measures, they are a working aid when preparing and reviewing a project's environmental aspects and can be used during the planning phase, and also for the final evaluation. The areas covered: cross-sectoral planning, infrastructure, agriculture, mining and energy, trade and industry, are pertinent to all cooperation activities and planning work. Volume III gives an overview of the many environmental parameters and standards applicable in different countries, and facilitates the evaluation of individual environmental impacts. The handbook has been compiled in close cooperation with the Deutsche Gesellschaft fhnische Zusammenarbeit (GTZ) and the Kreditanstalt fderaufbau (KfW).

1. Scope

The following terms recur frequently in this environmental brief and therefore require definition:

- Single cropping involves growing only one crop on a particular area of land, e.g. rice. The sequence in which various single crops are grown one after the other in a field is known as the crop rotation.
- Intercropping is a system in which a number of different crops grow together for the entire vegetation period or part of it, e.g. a combination of cassava, cowpeas and millet.
- Annual crops are generally herbaceous plants with a one-year vegetation cycle (e.g. cereals, legumes, various vegetables, tobacco).
- Perennial crops are plants which are used over a number of years; each plant is sowed or planted only once, e.g. fruit trees, tea, coffee and cocoa.
- Monoculture involves growing a particular crop on the same area of land over a number of cultivation periods, e.g. sugar cane.

Taking into account the production of wood, self-regenerating raw materials, animal fodder and crops used in the manufacture of semi-luxury goods, plant production represents - in terms of area - man's major form of interference with the Earth's natural balance.

Traditional farming systems are usually based on intercropping and tend to be subsistence-oriented. External inputs such as fertilisers and pesticides are uncommon and are used on only a small scale.

By contrast, large-scale plantation farming generally takes the form of monoculture (sugar cane, cotton) or permanent cropping (coffee, tea, cocoa). These forms of cultivation are market-oriented and dependent on external inputs.

Plant production involves activities in areas such as

- plant protection
- agricultural engineering and animal traction
- irrigation
- species and variety selection
- tillage and fertilising
- crop tending and weed control, harvesting, post-harvest treatment, storage
- erosion protection and control.

Crops are grown to meet the needs of the producer or the market. They also play a role in protecting soil, air and water.

Plant production is carried out on farms, for the most part using family labour, in order to ensure subsistence and earn monetary income.

2. Environmental impacts and protective measures

In agroecosystems, man becomes the dominant element in the ecosystem (anthropogenically oriented ecosystems). Agroecosystems differ in particular from natural ecosystems in that natural regulation processes take second place to control by man.

In the natural environment, plants form part of the ecosystem and play a key role in preserving it. Depending on the cropping method used, the nature, intensity and interaction of cultivation measures give rise to specific environmental impacts. These may cause a reduction in the diversity of species, disruption of the soil structure and pollution of the soil, water and air (pesticides, salts resulting from irrigation and fertilisation, nitrate etc.) Natural ecosystems with their wide variety of functions are replaced by artificial land-use systems poor in species.

Growing use of industrially produced inputs (fertilisers, pesticides, machines, energy) and inappropriate cultivation techniques lead to contamination of drinking water by fertilisers and pesticides, as well as causing soil erosion, desertification and genetic erosion.

2.1 Environmental impacts

2.1.1 Soil

Soil forms the basis for plant production and thus performs a vital function in guaranteeing human survival.

Soil conservation is essential if man's living environment is to be maintained in a healthy state and a sustained supply of high-quality foods is to be ensured.

Opportunities for changing the conditions prevailing on a particular site are limited. Cultivation measures must therefore be geared to the natural conditions under which the land is used.

Erosion - in other words the removal of soil by water and wind - is one of the most problematic consequences of agriculture, particularly in the tropics.

The actual extent of erosion depends on the type of crop and form of cropping. To minimise erosion, efforts should be made to ensure that there is ground cover all year round. In the case of monoculture and single cropping, the risk of erosion becomes greater the more slowly the young plants develop (e.g. maize, grain legumes), the lower the planting density is and the more comprehensive the weed control measures are. As annual crops such as cereals, tubers and grain legumes entail frequent tillage, they have an adverse effect on the soil structure and are thus conducive to erosion.

Perennial crops such as fruit trees generally prevent soil erosion once the stand is complete; they provide permanent shade, which has a positive effect on the soil structure.

A soil's erodibility depends among other things on its physical properties. Fine sand and abraded particles can be displaced most easily, whereas a high stone and clay content inhibits erosion. A high humus content stabilises the soil structure and increases the water storage capacity; both of these factors inhibit erosion.

The most important ways of controlling erosion are:

- adequate ground cover (intercropping, underseeding etc.);
- "storeyed" cultivation through integration of trees and shrubs;
- division of cropping areas into small units and creation of windbreaks at right angles to the direction of the prevailing wind;
- avoidance of overstocking and measures to prevent animals from grazing on newly sown areas (see environmental brief Livestock Farming).

Excessive mechanisation of tillage and harvesting can lead to compaction, plough sole formation and puddling, particularly in the case of tropical soils with a weak structure. This may have the adverse effect of reducing water infiltration and the air supply for the soil flora and fauna as well as for the crops. Mechanisation can also lead to changes in the division of labour between men and women.

Although frequent tillage generally has a stimulating effect on microbial activity and thus also on replenishment of the nutrient supply, it has disadvantages in the tropics:

- humus decomposition is excessively rapid on account of the high temperatures,
- the soil fauna are adversely affected and formation of new humus is thereby delayed.

Single cropping promotes the spread of pests on a large scale and tends to necessitate substantial use of pesticides. Introduction of pesticides into the soil has adverse effects on the soil fauna and flora.

Organic matter plays a major role in the dynamics of tropical soils. It stores water, provides a living environment for soil organisms, promotes structural stability, and both supplies and stores nutrients. It is above all in storing nutrients that organic matter performs an especially vital function, as tropical soils seldom contain high-quality nutrient-fixing clay minerals. Use of mineral fertilisers therefore depends on the proportion of organic matter in the soil. If the amount of fertiliser used is not in correct proportion to the organic matter, there is a danger of leaching and of the fertiliser passing into deeper soil layers. Use of too much fertiliser is thus ecologically undesirable and economically disadvantageous.

The risk of unbalanced nutrient depletion is greatest in the case of monoculture and single cropping, e.g. in the case of maize, cocoa, root crops and tubers. Where a number of plant species are grown in an intercropping or crop rotation system this risk becomes smaller, as differing nutrient requirements have to be met. As such forms of cropping incorporate plants with different root systems (shallow, deep) and nutrient requirements (high, low), competition for nutrients, water and light is substantially reduced.

2.1.2 Water

The erosion referred to above can lead to eutrophication of bodies of water through the introduction of nutrients, e.g. liquid manure and nitrate, and to contamination with toxic pesticide residues.

2.1.3 Air

The climate in multi-storeyed stands growing in an intercropping system is better i.e. more balanced, than that in stands of annual crops forming a monoculture or single cropping system. The wind velocity is lower and thus better for crops susceptible to the wind (e.g. bananas).

Air pollution caused as a result of plant production stems primarily from chemical plant protection measures. Evaporation of ammonia during application of solid or liquid manure has hitherto been of only minor significance. Under tropical conditions (high temperatures, low soil sorption capacity), up to 80% of the total nitrogen may evaporate.

Pollution of the air and atmosphere is caused by waste gases resulting from use of machinery, slash-and-burn techniques and burning-off of crop residues, as well as by discharge of gases such as methane and nitrous oxide by swamp rice and large herds of cattle. These factors play a part in the greenhouse effect.

2.1.4 Biosphere

The risk of both the loss of species and a change in the balance of species increases in proportion to the intensity of plant production activities. Controlled shifting cultivation - observing the necessary fallow periods - encroaches least on the natural environment in terms of area if only level areas are cleared on a selective basis. This helps not only to preserve the forests, particularly the rainforests and their resources, but also to protect forest-dwellers, who often possess know-how about things such as plants with potential pharmacological uses and the ecological interrelationships within their living environment.

Systematic cultivation of crops and the related mechanical and chemical forms of weed control cause wild plants to be largely displaced, leading to a reduction in the number of species.

In regions subject to periodic droughts, large-scale cultivation of certain woody plants in a monoculture system substantially increases the fire risk. In addition to nutrient and leaching losses, this can also result in unwanted destruction of grass and tree species not resistant to fire.

Displacement and destruction of plants leads to a reduction in biological diversity. Extensive use of rainforests also substantially reduces the variety of animal species, e.g. in the case of primates and birds.

Natural ecosystems are adversely affected not only by land being required for plant production but also by being broken up (e.g. by traffic routes), which can result in a loss of stability.

Use of land for plant production generally leads to the loss of forest, dry, wet and aquatic biotopes and causes the landscape to take on a uniform nature, e.g. as a consequence of land clearance, drainage, levelling and irrigation.

By comparison with the natural vegetation, plant production destroys habitats and reduces regional diversity. Standardisation of products for the market and breeding to obtain specific traits (e.g. yield, shape, colour) play a part in the loss of local varieties (genetic erosion).

2.2 Protective measures

2.2.1 General conditions

Plant production is influenced to a particularly large extent by general conditions; these may relate not only to climate but also to national (e.g. land ownership situation) or international (economic relations) factors.

Many climatic and vegetation zones are highly sensitive to interference by man, whose activities generally destroy the vegetation, as in the following cases:

- clearance of the tropical rainforest in the Amazon basin for the purpose of obtaining high-grade timber
- slash-and-burn land clearance by arable farmers in Nigeria's tree-studded savannah, where the transition to permanent cultivation no longer allows the land the opportunity to regenerate
- overgrazing in the Sahel zone as a result of overstocking with large numbers of livestock which remove the already sparse vegetation.

The consequences are disastrous, not only in the humid tropics but also in places which receive less rainfall. As there are virtually no plants left to provide ground cover, the soil undergoes changes within the space of a few years; a key role is played here by the increased decomposition of organic matter in the soil and the fact that the introduction of new organic matter is reduced to a minimum.

Within the existing world economic order, the terms of trade for the countries concerned have steadily deteriorated. It is above all these countries which have been hit by the increased cost of energy and finished products. International agricultural policy likewise does nothing to ensure balanced promotion of plant production.

Rapid population growth means that farms are becoming increasingly small and the land is thus being used more and more intensively. Farms in Latin America today already have an average size of only 2.7 hectares; those in Africa on average cover 1.3 hectares, while the corresponding figure for Asia is less than one hectare. What is more, 10% of persons deriving their living from agriculture in Africa, 25% of those in the Middle East and 30% of those in Latin America own no land at all. Two thirds of those who do possess land own only a tiny area and cannot afford capital-intensive technical inputs such as pesticides, herbicides and mineral fertilisers.

As land becomes increasingly scarce, farming systems undergo a transition from shifting cultivation to semi-permanent and eventually permanent arable farming. This process has already been largely completed in Asia, while in much of Africa and Latin America it is still under way. The changeover to permanent arable farming means that there are no longer any fallow periods (forest, bush, pasture) which allow the soil to regenerate; soil fertility declines and eventually remains at a fairly low level permitting only substantially smaller yields. The shortage of land also necessitates use of areas such as slopes at risk from erosion and thus contributes to environmental degradation.

The relative importance of the crops grown also changes. In the humid and semi-humid tropics the cultivation of yams, sorghum, and maize declines in significance, while crops such as cassava and sweet potatoes become more important. The last-mentioned crops produce relatively good yields even on poor sites, but at the same time cause the soil to become exhausted more quickly.

In many countries, both intensification of agriculture and the industrialisation process are having increasingly adverse impacts on the environment. Waterlogging, salinisation and sedimentation cause the irrigated cropping areas - often created at considerable expense - to lose their fertility after only a few years, which gives a rise to a considerable drop in yield. Traces of persistent pesticides are being increasingly found in bodies of surface water and groundwater reservoirs. The past decade has seen a sharp rise in the number of people suffering pesticide poisoning, while at the same time there has been an enormous increase in the number of pest species resistant to the commonly used pesticides.

The factors described here are generally to be found wherever efforts are being made to raise yields through targeted, conventional modernisation of agriculture. However, such problems are not simply consequences of large-scale agricultural projects, but also arise as the cumulative result of numerous activities on the part of smallholders.

As the actual environmental costs have little or no impact from the farm management viewpoint, there is no incentive to take measures aimed at conserving natural resources or producing sustained improvements in efficiency. Land law, taxation policy and subsidisation policy, along with ascertainment of the external costs involved in production and consumption, are areas which the state must tackle in the interest of promoting environmentally oriented plant production.

There are certain concepts, such as that of ecodevelopment, which are based on the necessary integrated approaches. Tried and tested measures such as integrated plant protection, ecofarming and others point the way towards sustainable development.

2.2.2 Ecofarming

Ecofarming aims to achieve a high sustained level of productivity on the site in question under "low external input" conditions and at the same time to preserve or recreate a balanced ecosystem.

This applies in particular in densely populated regions with smallholder-based farming structures and under economic conditions which largely preclude use of external inputs (e.g. mineral fertilisers), for in many cases such inputs are economically non-viable, unaffordable or unavailable on account of supply shortages. Intensification of agriculture must therefore be based on more productive use of scarce goods (nutrients, water, energy) and underutilised idle resources (e.g. labour, individual initiative).

The demand for stability and sustainability stems from the obligation of each generation to pass on to future generations an environment that remains capable of guaranteeing the fundamentals of human existence. The demand for productivity coupled with stability is often seen as a conflict of objectives between irreconcilable short-term and long-term (and frequently also between microeconomic and macroeconomic) viewpoints; in most cases it is the short-term microeconomic considerations that prevail. Ecofarming must endeavour to achieve both objectives to an equal extent.

Ecofarming, or "site-appropriate agriculture" as it is also known, involves treating both regions used for agriculture and individual farms as ecological systems. However, the concept of "site" must not be restricted to natural conditions (soil, climate).

Consideration must also be given to economic development (price-cost ratios, incomes), farm-specific conditions (access to factors of production) and the internal forces influencing a farm's operations (self-sufficiency, risk minimisation, preservation of soil fertility). Last but not least, it is essential that man, together with his culture, needs, taboos and habits, be viewed as a component of the ecological system and not as an outsider.

This integrated approach requires a certain degree of geographical differentiation. Agriculture in many countries is affected by a growing shortage of raw materials and energy and by the accompanying rise in prices. This is particularly true of countries which are in debt and possess little foreign exchange. It is thus these countries above all which must develop forms of agriculture that permit a high degree of self-sufficiency (within a self-contained system) and decentralisation (as well as self-regulation) at national and regional level and within individual farms.

The major elements of ecofarming are as follows:

- creation of appropriate vegetation

· inclusion of trees and shrubs in arable farming
· creation of erosion-protection strips parallel to the incline on slopes and planting of hedges to divide a farm into numerous small fields
· afforestation on the poorest and most degraded soils

- intercropping, alternating with intensive fallow
- organic manuring
- integrated livestock husbandry
- improved mechanisation
- supplementary use of mineral fertiliser
- integrated plant protection and selective weed control

The elements listed above are given in order of precedence. As it is impossible to introduce the entire package of measures immediately, this form of classification indicates which measures must be given top priority for the purpose of preserving, increasing and stabilising soil productivity.

The following key areas of activity and options in the plant production sector should be combined with one another according to the nature of the site:

- farm planning and organisation (information systems, economic thresholds, soil investigations, climatic data)
- design of cropping system (single cropping, intercropping etc.)
- variety and seed selection (resistance, quality, quantity)
- tillage

· conventional
· minimum tillage
· direct drilling

- cultivation and land use (crop rotation, sustainable cropping capacity)
- plant nutrition (fertilising)

· organic
· mineral

- plant protection

· mechanical
· biological
· chemical

To sum up, it can be said that environmentally sound, site-appropriate agriculture aims

- to guarantee that plant production is geared to natural conditions, i.e. site-appropriate;
- to preserve the soil structure, the biological processes taking place in the soil and the soil's fertility;
- to prevent erosion damage;
- to prevent contamination of groundwater and bodies of surface water;
- to prevent adverse impacts on biotopes adjacent to agricultural land as a result of the introduction of substances or other consequences of cultivation measures;
- to preserve typical landscape features;
- to take account of the requirements of nature conservation and protection of species, particularly as regards preservation of ecologically valuable biotopes, within the scope of overall consideration of the environment;
- to make livestock husbandry an integral component of environmentally sound agriculture.

3. Notes on the analysis and evaluation of environmental impacts

In the plant production sector, the following assessment criteria lend themselves to direct or indirect measurement:

- changes in the biotope (diversity of species of flora and fauna)
- impacts on finite natural resources (minerals, ores, water, atmosphere)
- impacts on global ecological relationships (net energy production: energy audit comparing energy fixed by a crop plant/harvested product and energy used in its production)
- contamination levels (chemical products, salts, dusts, gases)

Limits varying from one country to another have been laid down for many substances occurring in agriculture. Although many countries have maximum-quantity regulations covering immissions in water, air and soil, these are generally concerned with the effect of pollutants on human health.

As the properties and sensitivity of tropical soils vary greatly, a site survey must always be conducted before project planning commences. Such a survey involves mapping the soil types with regard to their heat, water, air and nutrient balances as well as their susceptibility to erosion. The soil type can be determined in the field or by means of granulometric analysis in a laboratory; once this has been done it is possible to assess the risk of compaction. Measurement of the infiltration rate permits more accurate appraisal of the erosion risk. Tolerance limits for humus decomposition can be formulated only on the basis of the soil conditions and the land use situation. The humus content can be roughly ascertained in the field; precise determination can be carried out in the laboratory by means of ignition loss, wet incineration or gas chromatography.

Spade analysis can be used for simple assessment of soil structure and biological activity; rooting characteristics are of particular importance. The findings can be substantiated in the laboratory by means of wet screening (aggregate stability), analysis of the C/N ratio (nitrogen availability) etc. The presence of effective root symbionts (nitrogen-fixing organisms, mycorrhiza) can be detected only by way of infection tests.

The extent of the leaching risk (particularly for nitrate and pesticides) can be ascertained by determining the field capacity of the soil profile down to the effective rooting depth. This can be estimated in the field with the aid of a drilling stock; it is advisable to conduct a pore analysis of typical soil horizons in order to calibrate the response. However, excavation of a profile is essential in some cases, above all if waterlogging or crusting is suspected.

Deficiency or toxicity symptoms in crops may prompt determination of nutrient status or contamination level. Measurement of the pH value as a function of soil depth can often reduce the necessary scope of analysis and provides information about the lime requirement. Measurement of effective cation exchange capacity and base saturation yields pointers regarding nutrient imbalances and the degree of salinisation. In the case of trace elements and heavy metals, plant analysis is to be preferred. The results allow appropriate recommendations to be made regarding fertilising or - where necessary - rehabilitation.

A body of water can be characterised with relative ease by means of quality classification, which is carried out by determining the pH value, temperature, oxygen content and important indicator organisms. If such organisms are not present or are unknown, the water's ammonium and phosphate content can also yield information about the trophic level. Analysis of biochemical and chemical oxygen demand (BOD, COD) allows conclusions to be drawn regarding the degree of pollution with degradable organic substances. The requirements to be fulfilled in terms of water quality will vary depending on the planned use.

It is above all in semi-arid regions that hydrogeological investigations are necessary for assessing the groundwater reserves. Such investigations can yield information on subsoil conditions and the location of the catchment areas. Current annual evaporation and groundwater recharge rate can then be estimated on the basis of the land use and soil distribution determined in the course of the site survey. If the rate at which the groundwater is tapped (drinking water, irrigation) permanently exceeds the recharge rate, lowering of the groundwater may cause severe damage to land which is in a near-natural state or has undergone reforestation. In such cases the groundwater must also fulfil more stringent quality requirements, since its use as drinking water must not be restricted.

Areas used for plant production often serve to neutralise or reduce emissions emanating from other areas. Correctly designed intensive agroecosystems can in fact sometimes perform such functions more effectively than the potential natural vegetation, because it becomes profitable, from a certain yield level upwards, to neutralise immission-induced damage through appropriate use of inputs (e.g. liming to offset the introduction of acid). The same applies to climatic effects, which can be positively influenced if suitable land and the correct forms of cropping are selected.

Summarising assessments of energy flows and natural cycling systems, which also yield information about loading capacities, will be highly unreliable in the absence of adequate familiarity with the species involved and their interrelationships.

4. Interaction with other sectors

Plant production always has impacts on the environment, either directly or through its links with other areas. By virtue of its objectives and impacts it has particularly close links with the following areas featured in farming systems:

- Plant protection
- Forestry
- Livestock farming
- Aquaculture
- Agricultural engineering
- Irrigation

The objectives pursued in these sectors (see relevant environmental briefs) may be compatible with those of plant production, have no bearing on them or conflict with them. In the same way, impacts of plant production may be increased, reduced or offset by measures in these areas. When assessments are being carried out, attention must be paid to the possibility that impacts generated by activities in different areas could have a cumulative effect and thereby increase the amount of damage done. Such processes can be regulated with the aid of research and advisory work, backed up by instruments in fields such as legislation, poverty alleviation, self-help and advancement of women.

If plant production is on a scale extending beyond subsistence level, it also has links with agroindustry. Sinking of wells as part of schemes to provide rural water supplies can accelerate the desertification process, which has disastrous consequences for plant production.

As many countries require an increasing amount of land for settlement, transport systems, trade and industry and sometimes have to meet this need by developing areas formerly used for plant production, conflicts inevitably arise (spatial and regional planning, location planning, transport and traffic, large-scale hydraulic engineering). Although improvement of the transport system facilitates access to inputs (fertilisers, workshops) and sale of produce, land development within natural ecosystems can accelerate the destruction of such systems. The need for erosion control measures generally arises as a result of erosion caused by forms of cropping inappropriate to the site concerned. The availability of renewable energy sources and compostable domestic waste can also be of importance for plant production.

5. Summary assessment of environmental relevance

In order to prevent plant production from giving rise to unintentional developments, ascertainment of the initial situation and appraisal of potential consequences must be followed by regular assessment of forecast and actual changes in environmental conditions. The same applies to social conditions, as there is a close interrelationship between cultural and economic factors on the one hand and the natural environment on the other hand.

The impacts of plant production generally consist in reduction of the diversity of species, adverse effects on the nutrient balance as well as on the physical and chemical properties of the soil, and contamination of the environment with pollutants.

Appropriate planning techniques and technical measures have been developed and must be taken into consideration. It is essential to refute the opinion that plant production activities (including biological erosion protection measures) have little or no impact on the environment.

Resource-depleting impacts are generally unwanted side-effects which are not directly related to the production goals. It is precisely when these side-effects are ignored that the natural environment will suffer damage and adverse long-term consequences will arise in the economic and social spheres.

Careful planning and implementation will ensure that plant production has minimal environmental impacts, has no undesirable social consequences and is economically efficient.

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1. Scope

Plant protection measures are carried out to limit performance and yield losses in crop production during the growing season and afterwards (storage protection) as well as for quarantine purposes. They serve primarily to safeguard yields, although in combination with other cultivation measures they can also help to raise yields.

A wide variety of individual measures - with varying ecological, economic and socio-economic impacts - are available for keeping harmful organisms (diseases, pests, weeds) below the economic threshold. To reduce the probability of damage, preventive measures are taken in the areas listed below. Some of these can be regarded as belonging to the field of plant production (cf. environmental brief Plant Production), which reflects the close links between the two sectors:

- site design (hedges, border strips etc.)
- site and variety selection
- sowing, planting
- healthy seed and planting stock
- crop rotation, intercropping
- tillage, land improvement
- fertilising
- crop tending
- harvesting
- storage

Measures in these areas are backed up by the following direct forms of plant protection:

- physical methods
- chemical methods
- biotechnical methods
- biological methods
- integrated methods

Physical methods directly destroy harmful organisms, aim to retard their development or prevent them from spreading. They can be divided into mechanical and thermal measures. The former include tillage to control weeds and pests (hoeing, removal of affected parts of plants and intermediate hosts), flooding of fields to combat soil-borne harmful organisms (e.g. Fusarium oxysporum, which causes banana wilt), laying of sticky belts to trap flightless insect pests and other measures for catching pests or keeping them away from crops, such as fences, trenches (locust control), traps and picking-off of pests. Thermal methods utilise the harmful organisms' sensitivity to high or low temperatures. They include hot-water treatment of seed and planting stock (e.g. to combat viruses and bacteria in sugar cane cuttings), solarisation (covering the surface of the ground with plastic sheeting produces phytosanitary effects by virtue of the greenhouse effect resulting from insolation, e.g. for controlling parasitic seed plants, soil-borne harmful organisms etc.), burning-over to control weeds and burning of crop residues. Low temperatures inhibit the spread of certain storage pests.

Eradicative, protective and curative methods are used in chemical plant protection to destroy harmful organisms or keep them away from plants, to protect plants against attack and penetration by harmful organisms and to cure plants (or parts of plants) that have already become infested or diseased. Although chemical methods can be subdivided in this way on the basis of their effects, the boundaries between the individual categories are somewhat fluid, as many pesticides have more than one type of effect. Pesticides generally kill the harmful organism by influencing vital metabolic processes or disrupting the conduction system. Selectivity can be varied through appropriate selection of the active ingredient, formulation, application technique and time of application.

Biotechnical and biological methods of plant protection have gained in significance, among other things because the risks and limits of chemical measures are today assessed more realistically. Biotechnical methods utilise the natural reactions of the (almost exclusively motile) harmful organisms to physical and chemical stimuli in order to bring about changes in their behaviour for the purpose of plant protection (e.g. light and colour traps, chemical attractants, antibodies, pheromones, hormones, growth regulators). The emphasis is on measures which aim not to directly kill the harmful organisms, but rather to permit population monitoring for the purpose of forecasting, defensive action and deterrence. The harmful organisms can be killed by combining biotechnical methods with chemical measures.

Biological plant protection involves using organisms and their activity to protect plants and enhance their resistance to biotic (harmful organisms) and abiotic limiting factors. For the purpose of pest and disease control, beneficial organisms are specifically preserved and fostered, released in large numbers or introduced into habitats where they have not been found hitherto. Biological control of weeds has to date primarily involved introducing beneficial organisms into new habitats.

Another biological method is that of inducing resistance to disease. This can be done, for example, by infecting plants with pathogens having low virulence.

There are close links between biological and integrated plant protection in that both methods attach major importance to regulation by means of biotic limiting factors. If such methods are to prove effective, moreover, there must be little or no use of preventive and broad-spectrum pesticides. Biological methods can be applied on only a limited scale in intensively used agrobiocoenoses which are poor in species, but can play a more important role in areas where extensive farming is practised and in coenoses comprising a greater variety of species. Their limits are determined above all by the efficiency of the beneficial organisms and the latter's dependence on environmental conditions.

Integrated plant protection is a concept which involves coordinated use of all ecologically and economically justifiable methods in order to keep harmful organisms below the economic threshold. The emphasis is on utilising natural limiting factors. The main aim is to preserve the balance of nature as far as possible; this is to be achieved by reducing use of chemical plant protection methods and simultaneously employing a variety of measures from the other categories. It is here that the links with the plant production sector are particularly close. Use of pesticides is to be reduced to the essential minimum by abandoning the practice of routine or calendar-based spraying, gearing pesticide dosage to actual conditions, refraining from the use of broad-spectrum persistent agents (liable to harm beneficial organisms) and selecting the time of application such that beneficial organisms suffer no adverse effects.

Integrated plant protection methods generally prove more successful in permanent crops than in short-lived crops, since the biocoenoses of the former are more stable and can be more permanently influenced whereas those of the latter are inevitably subject to constant change. The limits and risks attaching to these methods become clear if the work is performed by untrained personnel. Use of integrated plant protection methods generally calls for detailed knowledge of biological, ecological and economic factors.

2. Environmental impacts and protective measures

2.1 Plant protection in general

· Environmental impacts

The environmental impacts of plant protection are caused by the influence of substances and/or forms of energy on organisms and their functioning as well as on soil, water and air. The extent to which a plant protection measure is harmful, and in particular the degree to which it is liable to cause lasting harm, is determined by its varied influences on the functioning of the ecosystem. Adverse environmental impacts are likely if plant protection measures fail to take adequate account of ecological considerations. Repeated, one-sided application of a particular active ingredient will cause the harmful organism to develop resistance to it. Although non-specific control methods curb the spread of a harmful organism, they also unintentionally affect numerous beneficial organisms. They thus adversely influence the diversity of species and biological regulation mechanisms, creating a risk that harmful organisms may multiply more rapidly and consequently necessitating additional plant protection measures. Effects on the abiotic environment are also likely (e.g. soil erosion caused by tillage carried out for the purpose of plant protection).

When combined with other plant production measures, plant protection extends the ecophysiological cultivation limits of numerous crops. Cultivation of potatoes or tomatoes in humid mountain regions necessitates increased plant protection measures for combating fungi. Plants whose underground storage organs constitute the harvested crop (e.g. potatoes, taro) jeopardise the sustainability of land use, particularly when grown on slopes, on account of the erosion risk and increased mobilisation of nutrients.

Chemical plant protection came to occupy its position of major importance by virtue of the fact that pesticides are easy to use and fast-acting. There is thus at the same time also a risk of misuse, e.g. uneconomical use of pesticides.

Socio-economic conditions can be influenced to a considerable extent by the introduction of - or changes in - plant protection methods, which at the same time constitute a key element of the production system. This is particularly true of countries whose economy is based primarily on agriculture. The transition from a cropping system incorporating fallow periods to permanent cultivation, for example, necessitates substantially increased financial outlay on weed control, giving rise to corresponding socio-economic effects. What is more, changes in the spectrum of field flora will also become apparent, with species that are more difficult to control gaining the upper hand.

The changeover from weed control by means of hoeing to use of herbicides can bring disadvantages for the population groups (children, women, men, ethnic groups) which previously performed the work. The introduction of new methods may also have an influence on health, earning capacity and standard of living. At the same time, social goals and ethical and moral concepts provide the framework within which plant protection must operate (e.g. bans on killing certain types of animal; assessment of water/air quality, freedom from residues, job safety, work preferences, leisure needs).

· Protective measures

The aim of environmental protection measures is to minimise the long-term ecological damage caused by plant protection. To this end, macroeconomic goals must be weighed against microeconomic goals and the "polluter pays" principle consistently applied. The control threshold should be determined on the basis of ecological and economic criteria, taking long-term aspects into account.

Efforts should be made to achieve this goal by making extensive use of natural limiting factors (cf. environmental protection measures described in the environmental brief Plant Production) and by reducing the probability of damage (see 1. above). The potential consequences of plant protection for the production system and ecosystem, e.g. resulting from expansion of cropping to include sites with a greater risk of pest infestation, must be taken into account along with possible impacts on economic and social conditions.

2.2 Specific plant protection methods

2.2.1 Physical methods

· Environmental impacts

Thermal methods often require the input of sizeable amounts of energy in order to kill harmful organisms through the effects of heat (burning-over, production of steam or hot water). The environmental impacts of energy generation must be borne in mind (cf. environmental briefs Overall Energy Planning and Renewable Sources of Energies). Although solarisation uses solar energy, plastic sheeting - generally made of polyethylene - has to be placed over the entire area concerned or between the crop rows in order to achieve the greenhouse effect and many countries have still to find a satisfactory way of disposing of this sheeting. The effects of thermal methods on the biocoenosis are in most cases non-selective, so that microflora and microfauna populations must then re-establish themselves and achieve equilibrium in a biological vacuum in soil which is generally pasteurised or sterilised. Mechanical weed control methods involving tillage measures will lead to changes in the soil's susceptibility to erosion, an effect which must be given particular consideration where slopes are concerned. There is also a risk of damaging plant organs and thereby creating portals of entry for mechanically transmitted viruses and secondary parasites. Both thermal and mechanical methods generally promote mobilisation of nutrients from organic matter. This humus decomposition, accompanied by the destruction of clay-humus complexes and a deterioration in the soil structure, leads to a reduction in soil fertility. There is also a danger that nutrients may be leached out or introduced into other ecosystems. Flooding to curb the spread of soil-borne harmful organisms has a major impact - albeit only in the short term - on biotic and abiotic soil factors, with the soil structure and nutrient dynamics being adversely affected. Physical plant protection methods generally require a considerable amount of labour and their effectiveness against harmful organisms is highly limited in terms of both duration and area. Use of such methods may be restricted on account of labour shortages and for economic reasons.

· Protective measures

In terms of timing, location and intensity, thermal and mechanical methods are to be employed such that they combine maximum effectiveness with minimum detriment to beneficial organisms. Where mechanical methods are used, the role played by the vegetation in protecting the soil structure and soil organisms must be borne in mind. Covering the ground with pieces of vegetable matter (mulch) is one way of controlling weeds and at the same time preventing erosion. Use of mechanical methods is promoted by the development of labour-saving and effectiveness-enhancing techniques which make it possible to avoid the damage caused by other techniques.

2.2.2 Chemical methods

· Environmental impacts

The environmental impacts of chemical plant protection essentially comprise three overlapping areas:

a) acute and chronic toxic effects

b) contamination of harvested crops, soil, water and air with pesticides and their conversion products, as well as accumulation of such substances in the system

c) impacts at system level (biocoenosis)

a) Classifying chemical pesticides on the basis of target groups gives the false impression that their toxic effect is in each case limited to their target group (herbicides - plants, fungicides - fungi, insecticides - insects etc.). Most agents are non-selective and have a lethal or inhibiting effect on organisms, as they interfere with basic metabolic processes (photosynthesis, ATP (adenosine triphosphate) formation, membrane development and functioning etc.). The toxicity of pesticides gives rise to significant impacts. The World Health Organisation (WHO) estimates that 1.5 million people are poisoned by pesticides each year, 28,000 of them fatally (54). Apart from their active ingredients, pesticides also contain additives to ensure adhesion and wettability as well as to perform various other functions. Out of 1,200 additives tested by the US Environmental Protection Agency, 50 were classified as toxic (24).

Particular risks emanate from poor-quality products, which are often to be found on the market in countries with liberal registration requirements (68). Recurrent problems include pesticides which have aged beyond the point where they can still be safely used, contamination, poor formulation and active-ingredient concentrations deviating from those declared.

Pesticides can give rise to environmental pollution during storage and transportation (soil, water, air), primarily as a result of leaking containers and subsequent problems caused by sale of large quantities.

There is also a risk of food contamination if pesticides and foods are not stored separately or are sold together, which is frequently the case in some countries.

As pesticides generally deteriorate within a short time (often less than two years), the hitherto unsolved problem of proper disposal arises. Dangerous "time bombs" exist in many countries, with sizeable quantities of pesticides sometimes concentrated in a storage area of a few square metres.

If dealers and farmers lack adequate information, knowledge and training, pesticides are liable to be incorrectly used (mix-ups, incorrect dosage, failure to observe waiting periods, etc.).

- The absence of adequate information on the containers (pictogram, labelling in a foreign language) can also result in incorrect use. Local dealers often put pesticides in food containers (fruit juice bottles, bags), while pesticide containers are frequently re-used for household purposes.
- Depending on the application technique and weather conditions, the risk of poisoning exists for pesticide users, members of their family participating in the farm work (particularly children) and neighbours. Protective clothing suitable for the tropics is virtually unavailable. Pesticides sprayed from aircraft are particularly likely to drift onto houses, neighbouring crops, pastures, bodies of water etc.
- Correct use of pesticides is based on purchase as and when needed, together with considerable outlay on appropriate storage methods and application techniques. It calls for sizeable inputs of capital.

b) Contamination of harvested crops, food and animal fodder with pesticide active ingredients or their residues and accumulation of such substances, giving rise to health risks for both man and animals [particularly likely in the case of incorrect use (see above), e.g. wrong dosages, failure to observe waiting periods etc.]. Use of chlorinated hydrocarbons on root vegetables, for example, led to accumulation in the harvested crop and intake by babies through baby food, which resulted in a subsequent ban on use of chlorinated hydrocarbons for vegetables.

- Contamination of soil, water and air with pesticide active ingredients and their conversion products: Over half of the pesticide applied is discharged directly into the atmosphere upon atomisation and is transported in aerosol form, sometimes over long distances, before rainfall washes it into the soil and water. Most of the remainder directly contaminates soil and water. The risk that active ingredients will undergo a change to the gaseous phase is particularly great in the tropics, which is why pesticides with a high vapour pressure are unsuitable for use in such regions. Failure to take ecological and toxicological aspects into account can lead to cultivation problems at a later date and to restrictions on cropping on account of the site's toxic load (use of cuprous agents on bananas). If the soil's sorption capacity (retention capacity) is low, as is the case with sandy soils, pesticides and residues can be leached into the groundwater. Their persistence may increase with soil depth, e.g. as a result of the decline in microbial activity.

c) The non-specific action of most pesticides and their conversion products has a variety of direct and indirect impacts on biotic and abiotic components of ecosystems, even at a considerable distance from the application site. The indirect impacts in particular are generally impossible to forecast; unforeseeable "cascade effects" may occur within the functional structure of ecosystems. Pimentel (61) calculates that the damage caused to the biocoenosis in North America by the use of chemical pesticides corresponds annually to a figure of US $ 500 million. Well over half of these costs can be attributed to reductions in the number of beneficial organisms and development of resistance to pesticides.

Impacts of this type include elimination of pollinating insects and other beneficial organisms (natural limiting factors) as system regulation and control elements. Use of insecticides in (irrigated) swamp-rice systems endangers fish and entomofauna, which can be seen as an indication of the conflict between aquaculture and pesticide use. The biological activity of earthworms and nitrifying bacteria is adversely affected by the use of methyl bromide for soil disinfection.

Beneficial organisms can be indirectly affected if, for example, the population density of a pest which at the same time represents the specific basis of beneficial organisms' food supply is radically reduced by the use of pesticides. Decimation of a species can weaken the pest's biocoenotic ties, leading to increased reproduction and multiplication on a large scale. For example, use of broad-spectrum insecticides in fruit growing to combat the apple-leaf sucker led to the fruit-tree red spider mite becoming a problem, as pesticides had an inadequate effect on the latter and caused beneficial organisms to be destroyed.

Pesticides can influence a crop plant's susceptibility to a particular group of harmful organisms on which the pesticide applied has no effect (for example, where a high level of fertilising is practised use of herbicides containing triazine or urea derivates can cause cereals to become more susceptible to mildew).

Lasting changes within the biocoenosis: Certain species remain unaffected by the agents used or develop resistance to them (one-sided use of atrazine in maize promotes weed infestation in the form of millet, while exclusive use of hormone weedkillers in cereals promotes the growth of grasses). Insecticides can also have an effect on pollinating insects. For instance, use of carbaryl to combat the mango leafhopper endangered or killed (wild) honeybees, thereby reducing smallholders' yield of honey and wax (32).

Over 400 arthropod species - half of them crop pests - have been found to have developed resistance to one or more active ingredients (10) (e.g. resistance of the boll weevil to DDT and other chlorinated hydrocarbons).

· Protective measures

In countries like the Federal Republic of Germany with strict legislation on the distribution and use of pesticides, agents must not be recommended and used unless they have gone through the necessary registration procedure. This procedure yields information about a pesticide's toxicological, carcinogenic, teratogenic and other properties as well as its effects on, and risks for, the balance of nature. Active ingredients are accordingly assigned to toxicity classes. Fields of application, suitable disposal methods, analysis techniques and the ways in which conversion products are broken down are also indicated. The FAO Code of Conduct, adopted in 1985, contains recommendations on the registration, distribution and use of pesticides. In countries such as the USA where legislation is strict, numerous pesticides involving comparatively high risks have been taken off the market (i.e. banned altogether) and/or restrictions imposed on their use in terms of time and place.

The reasons why certain products should not be used generally apply in all countries (30). In particular, use of persistent, broad-spectrum agents is internationally proscribed. The "dirty dozen" comprise the following fifteen active ingredients which should be banned in view of the substantial risks attaching to them:

· Insecticides

Chlorinated hydrocarbons: aldrin, chlordane, DDT, dieldrin, endrin, HCH-mixed isomers, heptachlor, lindane, camphechlor

Carbamates: aldicarb (proprietary name: Temik)

Organophosphates: parathion (E 605)

Other insecticides: dibromochloropropane (DBCP), chlordimeform, penta-chlorophenol (PCP).

· Herbicides

2,4,5-T (proprietary name: Weedone)

Pesticide containers must bear a description of their content, the necessary safety precautions, the permissible form of use and suitable antidotes. It must be ensured that the information given can be understood by population groups potentially at risk. The necessary information should be given in English and at least one national language and should be backed up by pictograms on labels that cannot easily be removed. The criteria for marketing of a pesticide are determined by the users' degree of illiteracy and awareness of the potential risks.

If chemical methods are used to combat harmful organisms, accompanying protective measures must be laid down and enforced. These minimum requirements relate above all to appropriate selection of the product to be used, the safety and functioning of the application technique and environmentally sound disposal of leftover pesticide and empty packaging.

National plant protection organisations must conduct training programmes in order to ensure that extension officers, users and everyone coming into contact with pesticides are aware of the risks involved. Internationally valid regulations governing the prerequisites for distribution and use of pesticides are to be developed and compliance with them monitored by high-level authorities.

Preference should be given to pesticides with low toxicity, a selective action and low persistence. Effects, possibilities of misuse, special regional factors, water conservation areas and ecological conservation zones must be taken into account as criteria for registration and use of pesticides. Use of dressed seed as food or animal fodder is to be prevented by means of adequate labelling. It must also be ensured that pesticide containers are not re-used for household purposes; this can be done by way of awareness-raising measures, appropriate container labelling and possible also special container design. Pesticides should be sold only in small containers holding a specific amount. Development of resistance on the part of harmful organisms can be counteracted by changing the active ingredient used.

Unauthorised production and distribution of pesticides by pirate firms is a particular problem in many countries. This underscores the importance of stringent and effective legislation on pesticides (registration) and of enforcing strict import controls (with clearance certificates required if necessary to confirm that products are pure and in perfect condition). In addition, access to pesticides can, for example, be made contingent upon production of an official "prescription", proof of adequate know-how and use of pesticides within the framework of integrated plant protection methods.

Government subsidisation of pesticides - which is common in many countries - creates special risks as regards misuse and environmental hazards (42). It must be established whether assistance measures of this type actually reach the target group and to what extent environmentally sound use and disposal of pesticides are ensured.

2.2.3 Biotechnical methods

· Environmental impacts

If harmful organisms are attracted by a stimulus or killed by combining such measures with use of a poison, other organisms can also be affected at the same time (see environmental impacts described in 2.2.2 above). Light traps attract most nocturnal winged insects. Use of noise to frighten off bird pests is non-specific and has an effect on other organisms, whose mode of life (nesting, mating, rearing of young) can be disturbed. Repeated use of growth regulators (hormones) has been shown to promote development of resistance on the part of the target organisms. There is also a risk of adverse effects on beneficial organisms; for example, bee larvae and other insects which consume contaminated pollen or the like may be prevented from moulting.

· Protective measures

Non-specific biotechnical methods are to be avoided (e.g. light traps attracting all nocturnal insects). Use of noise to combat bird pests is to be restricted in terms of time and place to the extent necessary for directly averting crop damage. The times at which growth regulators are used and the technique employed are to be chosen such that little or no harm is done to beneficial organisms. Where appropriate, use of attractants should be combined with application of insecticides. Development of resistance is to be counteracted through appropriate choice of agents.

2.2.4 Biological methods

· Environmental impacts

Although the relationship between beneficial organism and host is in many cases highly specific and is thus likely to have only minor unwanted impacts, biological methods too give rise to environmental risks. Use of predators, parasites, pathogens and genetically modified organisms involves a danger that other beneficial organisms may be displaced or harmed. Indeed, there is even a risk that the biocoenosis will undergo extensive and uncontrollable changes as a result of the inherent momentum of biological processes. For instance, biological control of the coffee berry beetle with the aid of the fungus Beauveria bassiana jeopardises silk production in the coffee-growing region, as the fungus also attacks the silkworm (Bombyx mori).

In another case, a non-indigenous species of toad was introduced to combat insect pests in sugar cane. However, these toads switched to a different source of food and themselves became an almost uncontrollable nuisance.

Where plants develop artificially-induced resistance to a pathogenic virus following initial infection with low-virulence strains of the same virus or a similar one, there is a risk of virus mutation or - if other viruses are also present - a danger of synergistic effects.

· Protective measures

To prevent adverse environmental impacts, biological plant protection measures, particularly those in the field of genetic engineering, must be subject to statutory regulations and controls.

The (further) development of genetic engineering techniques in connection with which the risk of uncontrollable biological processes can be predicted or discerned beforehand is to be prevented by way of effective legislation (cf. risks arising from biological agents, as described in the environmental brief Analysis, Diagnosis, Testing). Biological pest control programmes must be subject to effective government control. Organisations to investigate and record the import of predators and parasites are to be set up (quarantine).

2.2.5 Integrated methods

· Environmental impacts

Depending on the combination of measures chosen from the range of available options, the resultant environmental impacts will be similar to those described above for the individual types of method, albeit on a far smaller scale. Economic-threshold concepts are to be further developed, taking into account their practical applicability. Where pesticides with low active-ingredient dosages are used frequently, certain strategies may well promote development of resistance on the part of the harmful organisms. To permit repeated application of plant protection measures, permanent vehicle access to a site is often necessary and there is thus a risk of damage to the soil structure, e.g. compaction in wet weather. In many cases the only way of solving this problem is to use lightweight vehicles, which require a sizeable input of capital.

· Protective measures

The comments already made regarding the individual types of measures also apply to integrated methods involving a combination of individual measures from the four areas discussed above.

3. Notes on the analysis and evaluation of environmental impacts

Plant protection measures have a wide variety of impacts on the environment. As there are no universally applicable concepts, methods must be assessed by comparing their environmental impacts. In order to weigh up alternative plant protection methods, assessment criteria are needed. This calls for indicators which convey qualitative and quantitative impacts - including their duration - as accurately as possible so as to permit comparison (cf. environmental brief Plant Production). The active ingredients, additives and conversion products of pesticides are analysed to establish their physical and chemical characteristics (persistence, evaporability, adsorption, desorption etc.). Reproducible measured values incorporating safety factors are used to determine their toxicity and residue properties (acute 50-values), chronic toxicity (no-effect level, acceptable daily intake [ADI]), maximum-quantity regulation (permissible level). The values serve as indicators or limits and must be compared with the actual contamination levels in foods and animal fodder, flora and fauna, soil, water and air. Synergistic and additive effects resulting from use of pesticides can be identified only by studying the relationships between environmental impacts (e.g. decline in particularly sensitive species, use of indicator plants, diversity studies etc.). These relationships are as yet known only in part and are to some extent obscured by the effects of other measures; in many cases they thus cannot be ascribed to plant protection measures alone.

Findings which have emerged during implementation of plant protection measures (e.g. depletion of resources or adverse social consequences resulting from such measures) provide pointers for additional assessment criteria.

Where negative environmental impacts are likely, it must be considered whether these can be remedied without excessive outlay. Risks of irreversible damage must be ascertained separately and assessed accordingly. Plant protection methods have an influence on employment structures (e.g. division of labour between men and women, workload and capital requirements). Further assessment criteria can be developed on the basis of their impacts on farm structures and production.

4. Interaction with other sectors

Plant protection is linked to other plant production measures and is thus subordinate to the goals of plant production (cf. environmental brief Plant Production). Measures in the field of plant production also have a bearing on the goals and environmental impacts of the following sectors:

- Livestock farming (fodder, quality control)
- Fisheries (prevention of water pollution)
- Agro-industry (quality standards)
- Health and nutrition, including drinking-water supplies (toxicology, residues)
- Analysis, diagnosis, testing (quality control, development, analytical techniques)
- Chemical industry (pesticide production)

Decisions on plant protection measures may therefore be influenced by measures in these areas. When assessments are being made, attention must be paid to the possibility that impacts generated by the various sectors could have a cumulative effect and thereby increase the amount of damage done.

5. Summary assessment of environmental relevance

Plant protection measures must be assessed within the context of the overriding goals of plant production, taking into account site-specific conditions as well as economic and socio-economic factors. The substances and forms of energy used in plant protection may have adverse impacts on humans, flora, fauna, foods, animal fodder, soil, water and air. Measures to control harmful organisms affect the diversity of species as well as the population density of individual species and have impacts at system level (biocoenosis).

Numerous options are available in terms of plant protection methods. Analysis and evaluation of their environmental impacts should lead to selection of methods which are comparatively environment-friendly, thereby ensuring that undesirable or unjustifiable impacts are avoided.

Environmentally oriented plant protection strategies are characterised by targeted fostering and use of ecosystem-specific natural limiting factors, backed up by other measures from the wide range of physical, chemical, biotechnical and biological methods.

6. References

Basic literature/General

1. BAIER, C., HURLE, K. AND KIRCHHOFF, J., 1985: Datensammlung zur Abschung des Gefahrenpotentials von Pflanzenschutzmittel-Wirkstoffen in Gewern. Schriftenreihe des deutschen Verbands fserwirtschaft und Kulturbau e.V., Heft 74.

2. BICK, H., HANSMEYER, K.H., OLSCHOWY, G. AND SCHMOOCK, P. (Eds.), 1984: Angewandte ologie - Mensch und Umwelt. Band I: Einf, rliche Strukturen, Wasser, L, Luft, Abfall. G. Fischer Verlag, Stuttgart.

3. BNER, H., 1989: Pflanzenkrankheiten und Pflanzenschutz. 6. Auflage, Ulmer Taschenbuchverlag, Stuttgart.

4. BUNDESGESETZBLATT BGBL (Federal Law Gazette), 1986: Gesetz zum Schutz der Kulturpflanzen (PflSchG) vom 15.09.86 BGBL Teil I, Nr. 49, 1505 - 1519.

5. BUNDESMINISTERIUM F ERNRUNG, LANDWIRTSCHAFT UND FORSTEN (German Federal Ministry of Food, Agriculture and Forestry), 1986: Biologischer Pflanzenschutz. Schriftenreihe des BMELF, Reihe A, Nr. 344, Landwirtschaftsverlag, M-Hiltrup.

1988: Schonung und Frung von Ngen. Schriftenreihe des BMELF, Reihe A, Nr. 365, Landwirtschaftsverlag, M-Hiltrup.

6. EESA, N.M. AND CUTKOMP, L.K., 1984: A glossary of pesticide toxicology and related terms. Fresno: Thomson, 84 p.

7. FIGGE, K., KLAHN, J. AND KOCH, J., 1985: Chemische Stoffe in osystemen. Schriftenreihe Ver. Wasser-, Boden-, Lufthygiene 61: 1-234.

8. FOOD AND AGRICULTURE ORGANIZATION, 1986: International code of conduct on the distribution and use of pesticides. Rome.

9. HEINRICH, D., AND HERGT, M., 1990: DTV-Atlas zur ologie. Tafeln und Texte. DTC-Verlag, Munich.

10. HEITEFUSS, R., 1987: Pflanzenschutz. Grundlagen der praktischen Phytomedizin. 2. Auflage, Thieme-Verlag, Stuttgart.

11. HOLDEN, P.W., 1986: Pesticides and groundwater quality. National Academic Press, Washington.

12. INTERNATIONAL ORGANIZATION OF CONSUMERS UNIONS (IOCIJ), 1986: The Pesticide Handbook - profiles for action. Penang, Malaysia.

13. IVA (Industrieverband Agrar) (Ed.), 1990: Wirkstoffe in Pflanzenschutz- und Schingsbekfungsmitteln. Physikalisch-chemische und toxikologische Daten. BLV-Verlagsgesellschaft, Munich.

14. KORTE, F. et al., 1987: Lehrbuch der ogischen Chemie, Thieme Verlag, Stuttgart.

15. KRANZ, J., SCHMUTTERER, H., AND KOCH, W., 1979: Krankheiten, Schinge und Unkrer im tropischen Pflanzenbau, Parey Verlag, Hamburg.

16. FRANZ, J.M. AND KRIEG, A., 1976: Biologische Schings-bekfung. 2. Auflage, Pareys Studientexte 12, Verlag P. Parey, Hamburg.

17. MORIARTY, F., 1988: Ecotoxicology. The study of pollutants in ecosystems. 2nd ed., Acad. Press, London.

18. MLER-SANN, K.M., 1986: Bodenfruchtbarkeit und standortgerechte Landwirtschaft. Maahmen und Methoden im tropischen Pflanzenbau. Schriftenreihe der GTZ Nr. 195, Roorf.

19. NATIONAL RESEARCH COUNCIL (Ed.), 1986: Pesticide resistance - strategies and tactics for management. NAT. Acad. Press, Washington.

20. PERKOW, W., 1988: Wirksubstanzen der Pflanzenschutz- und Schingsbekfungsmittel. Parey, Hamburg (published in loose-leaf form).

21. SCHEFFER, F. AND SCHACHTSCHABEL, P., 1989: Lehrbuch der Bodenkunde. 12. Auflage, Enke Verlag, Stuttgart.

22. SCHMIDT, G.H., 1986: Pestizide und Umweltschutz. Vieweg Verlag, Braunschweig.

23. SCHUBERT, R., 1985: Bioindikatoren in terrestrischen osystemen. G. Fischer Verlag, Stuttgart.

24. SCHWAB, A., 1989: Pestizideinsatz in Entwicklungslern - Gefahren und Alternativen. Margraf Verlag, Weikersheim.

25. STOLL, G., 1988: Natural crop protection - based on local farm resources in the tropics and subtropics. 3rd edition, Margraf Verlag, Weikersheim.

26. UBA (UMWELTBUNDESAMT) (German Federal Environmental Agency (Ed.)), 1984: Chemikaliengesetz, Prund Bewertung der Umweltgeflichkeit von Stoffen. UBA Bewertungsstelle Chemikaliengesetz, Berlin.

27. VOGTMANN, H. (Ed.), 1988: Gentechnik und Landwirtschaft - Folgen felt und Lebensmittelerzeugung. Alternative Konzepte 64, C.F. MVerlag, Karlsruhe.

28. WARE, G., 1986: Fundamentals of pesticides. - Fresno: Thomson, 2nd edition.

29. WEISCHET, W., 1977: Die ogische Benachteiligung der Tropen. Teubner Verlag, Stuttgart.

30. WITTE, I., 1988: Gefdungen der Gesundheit durch Pestizide - Ein Handbuch urz- und Langzeitwirkungen. Fischer Verlag, Frankfurt.

Further/supplementary literature

31. ANON., 1987: EPA's new policy on inerts; in: Farm Chemicals International Vol. 1, No. 4, Summer 1987, pp. 22-25.

32. ARBEITSGRUPPE TROPISCHE UND SUBTROPISCHE AGRARFORSCHUNG (ATSAF), 1987: Mchkeiten, Grenzen und Alternativen des Pflanzenschutzmitteleinsatzes in Entwicklungslern. Sachstandbericht zu Projekten der deutschen Agrarforschung 1980-1987, Bonn.

33. AREEKUL, S., 1985: Ecology and environmental considerations of pesticides; Department of Entomology, Kasetsart University, Bangkok (working paper).

34. BOLLER, E., BIGLER, F., BIERI, M., HI, F. AND STBLI, A., 1989: Nebenwirkungen von Pestiziden auf die Ngsfauna landwirtschaftlicher Kulturen. Schweiz. Landw. For. 28: 3-40.

35. BIJLL, D., 1982: A growing problem - pesticides and the Third World Poor. Oxford: Oxfam.

36. CAIRNS, J., 1986: The myth of the most sensitive species. BioScience 36: 670-672.

37. CARL, K.P., 1985: Erfolge der biologischen Bekfung in den Tropen. Giessener Beitr. Entwicklungsforsch. I, 12: 19-35.

38. CHIANG, H.L., 1982: Factors to be considered in refining a general model of economic threshold. Entomophaga 27 (special issue): 99-103.

39 DEUTSCHE GESELLSCHAFT F TECHNISCHE ZUSAMMEN-ARBEIT (GTZ) GMBH,

1978: Rndsprobleme im Pflanzenschutz in der Dritten Welt. GTZ-Schriftenreihe Nr. 63, Eschborn.

1987: Nebenwirkungen bei der Anwendung chemischer Pflanzenschutz-mittel. Arbeitsunterlagen fjekte im llichen Rahmen Nr. 8, Eschborn.

1988: Technische Zusammenarbeit im llichen Raum - Pflanzen- und Vorratsschutz. Schriftenreihe der GTZ, Eschborn.

1989: ZOPP-Unterlagen, Forstschutz, Marokko, Eschborn.

1990: Kaffeerostbekfung in der Dominikanischen Republik, Gutachten, Eschborn.

1990: Bericht ie Fortschrittskontrolle zum Projekt Ausbildung und Beratung im Pflanzenschutz, Eschborn.

40. DOMSCH, K.H., JAGNOW, G. AND ANDERSON, T.M., 1983: An ecological concept for the assessment of side effects of agrochemicals on soil micro-organisms. Residue Review 86: 65-105.

41. FOOD AND AGRICULTURE ORGANIZATION, UNITED NATIONS ENVIRONMENT PROGRAMME, 1989: Integrated pest control. Report of the 14th session of the FAO/UNEP panel of experts meeting.

42. GOODELL, G., 1984: Challenges to international pest management re-search and extension in the Third World: Do we really want IPM to work? in: Bulletin of the Entomological Society of America, Vol. 30, No. 3.

43. HAQUE, A. AND PFLUGMACHER, J., 1985: Einflon Pflanzen-schutzmitteln auf Regenw Ber. Landwirtschaft 198: 176-188.

44. HASSAN, S.A., 1985: Standard methods to test the side effects of pesticides on natural enemies of insects and mites developed by the IOBC/WPRS Working Group "Pesticides and beneficial organisms". J. Appl. Ent. 105: 321-329.

45. HEINISCH, E. AND KLEIN, S., 1989: Einsatz chemischer Pflanzenschutzmittel - ein Spannungsfeld von onomie und otoxikologie. Nachrichten Mensch + Umwelt, 17: 53-66.

46. HUISMANS, J.W., 1980: The international register of potentially toxic chemicals (IRPTC). Ecotox. Environm. Safety: 276-283.

47. IGLISCH, I., 1985: Bodenorganismen f Bewertung von Chemikalien. Z. Angew. Zool. 72: 395-431.

48. KNEITZ, G., 1983: Aussagefgkeit und Problematik eines Indikator-konzepts. Verh. Deutsch. Zool. Ges. 1983: 117-119.

49. KOCH, W., SAUERBORN, J., KUNISCH, M. AND PSCHEN, L., 1990: Agrarogie und Pflanzenschutz in den Tropen und Subtropen. PLITS 1990/8(2), Verlag J. Margraf, Weikersheim.

50. KOCH, R., 1989: Umweltchemie und otoxikologie - Ziele und Aufgaben. in Umweltchemie otox. 1: 41-43.

51. KIG, K., 1985: Nebenwirkungen von Pflanzenschutzmitteln auf die Fauna des Bodens. Nachrichtenbl. Deut. Pflschutz. 37: 8-12.

52. KRANZ, J. (Ed.), 1985: Integrierter Pflanzenschutz in den Tropen. Giener Beitr zur Entwicklungsforschung. Reihe 1, Band 12, Gien.

53. LEVIN, S.A., HARWELL, M.A., KELLY, J.R. AND KIMBALL, K.D. (Ed.), 1989: Ecotoxicology: Problems and approaches. - Springer, New York.

54. LEVINE, R. S., 1986: Assessment of mortality and morbidity due to unin-tentional pesticide poisonings. Geneva, WHO. Document, VBC, 86, 929.

55. MALKOLMES, H.-P., 1985: Einflon Pflanzenschutzmitteln auf Bodenmikroorganismen und ihre Leistungen. Ber. Landw. 198: 134-146.

56. MAY, R.M., 1985: Evolution of pesticide resistance. Nature 315: 12-13.

57. MLER, P., 1987: Ecological side effects of Dieldrin, Endosulphan and Cypernlethrin application against the TseTse flies in Adamoua, Cameroon. Initiated by the GTZ and World Bank, Eschborn and Washington.

1988: otoxikologische Wirkungen von chlorierten Kohlenwasser-stoffen, Phorseestern, Carbamaten und Pyrethroiden im nordichen Sudan. Im Auftrag der GTZ, Eschborn.

58. OTTOW, J.C.G., 1982: Pestizide- Belastbarkeit, Selbstreinigungsverm und Fruchtbarkeit von B. Landwirtschaftliche Forschung 35, 238-256.

59. OWESEN, H.A., 1976: Artendiversitin der ologie. SFB 95, Rep. 16, Kiel.

60. PAN (PESTICIDE ACTION NETWORK), 1987: Monitoring and reporting the implementation of the international code of conduct on the use and distribution of pesticides. Final report. Nairobi, Kenya: Environm. Liaison Centre.

61. PIMENTEL, D. et al., 1980: Environmental and social costs of pesticides: A preliminary assessment; in: OIKOS 34, p. 126-140.

62. SCHMID, W., 1987: Art, Dynamik und Bedeutung der Segetalflora in maisbetonten Produktionsystemen Togos. PLITS 1987/3(2), Verlag J. Margraf, Weikersheim.

63. SCHMUTTERER, H., 1985: Versuche zur biologischen und integrierten Schingsbekfung in den Tropen. Giessener Beitr Entwicklungsforsch. I, 12: 143-149.

64. SCHOENBECK, F., KLINGAUF, F. AND KRAIJS, P., 1988: Situation, Aufgaben und Perspektiven des biologischen Pflanzenschutzes. Ges. Pfl. 40: 86-96.

65. STREIT, B., 1989: Zum Problem der Bioindikatoren aus zoologisch-ogischer Sicht. Geomethodica 14: 19-45.

66. SWIFT, M.J. et al., 1977: Persistent pesticides and tropical soil fertility. Meded. Fac. Landbouw. Rijksuniv. Gent 42: 845-852.

67. VELE, J.M., KASKE, R. AND SCHMUTTERER, H., 1989: Biologische Schingsbekfung im Sfik. Gutachten im Auftrag der GTZ, Eschborn.

68. WAIBEL, H., 1987: Die Einstellung von Kleinbauern in Ssien zum Pflanzenschutz, in: Mchkeiten, Grenzen und Alternativen des Pflanzenschutzmitteleinsatzes in Entwicklungslern. DSE/ZEL, Feldafing.

1. Scope

1.1 General

Forestry is generally defined as utilisation of forests to satisfy human needs. Characteristic features of forestry are the extremely long production periods extending over several decades and, in the case of timber production, the fact that the product is identical with the production input. Production of commercial timber and the use of return on investment as a success criterion for forest owners, generally state authorities (cf. REPETTO), are unsuitable for integrated problem solutions in view of the socio-economic conditions.

Probably the most important aspects of forestry activities today are protection of species and biotopes and preservation of the human habitat. In virtually no other sector are the "limits of growth" demonstrated as clearly as by the global destruction of the forests. The impacts of this process are no longer confined to specific regions, but are interlinked on a global scale, as forests - along with the oceans - represent the most important terrestrial bioregulators of global cycling systems and the Earth's climate.

The tropical forest is particularly badly affected, with around 20 million hectares being clear-cut or degraded each year (cf. ENQUETE). Tropical moist forests cover only around 6% of the land on Earth, yet they provide a living environment for over half of all species of fauna and flora and for millions of people.

Although the worldwide destruction of the forests has a wide variety of forms, causes and consequences, it can nevertheless be ascribed above all to exploitation and conversion of forest resources to satisfy short-term economic and personal interests. This form of activity eventually leads to the degradation and loss of human habitats.

This situation imposes new demands in terms of executing agency, project size and site. Holistic approaches which also include the sectors immediately related to forestry (CARILLO et al.) are therefore essential.

1.2 Subsectors

The forestry sector differs from every other sector of an economy by virtue of its production period and the fact that it produces both tangible goods and intangible benefits. It thus calls for special forms of biological production. Four subsectors are involved: planning, formation and utilisation of forest stands, and harvesting. Attention will be drawn where necessary to the special features of tropical forest management.

1.2.1 Biological production/Planning

Biological production in the forestry sector is controlled through the various methods of forest management, agroforestry and product harvesting. The purpose of these methods is to achieve, by controlling site production potential, the management goals laid down during planning; such goals may involve production, conservation or a combination of the two.

Planning, establishment of a stand and utilisation are classed as subsectors of biological production.

All forestry planning is based on inventories (e.g. ZOEHRER), which provide the framework for forest management over a period of ten years in most cases. Apart from static elements such as timber stock, dynamic and structural elements such as increment and horizontal and vertical species and diameter distribution must also be recorded, particularly in tropical moist forests, otherwise the sustainability of yield regulation cannot be guaranteed.

In addition to measurement of quantitative stand parameters, multifunctional forest management also calls for comprehensive site mapping (e.g. DENGLER, MAYER, WENGER) which ascertains geoecological factors for each stand individually.

The combination of continuous forest inventories, site mapping and specification of planning targets is known as forest management planning, the details of which are laid down in forest management plans. The management and recording unit is the compartment. The division of a forest into compartments should reflect the topographical and hydrological differences between stands. Simple geometrical shapes are appropriate only in exceptional cases for lowland plantations. In heterogeneous tropical moist forests, division can be extended to water catchment areas (sub-catchments).

The individual management goals are laid down separately for each compartment on the basis of forest management planning and economic analyses. Apart from the traditional economic indicators such as internal rate of return, cost-effectiveness analyses (cf. FSER, WENGER) can be used to assess the relative advantages of alternative management goals.

The function and structure of forest resources vary depending on the intensity with which they are utilised and the geoecological zone in question (MUELLER-HOHENSTEIN). The management concepts must be geared to the characteristic features of each type of resource, e.g. high and low forests, savannahs, mangroves and agroforestry systems or resources for gathering. The site-specific limiting factors - namely forest area, water, nutrients and light - restrict the scope for optimising forestry operations from the management viewpoint.

The different types of resource are closely interrelated and can complement one another in functional terms. These interrelationships necessitate integrated, interlinked planning. Storeyed, species-rich high forests of primary or secondary origin are best able to fulfil the necessary protective and utility functions over time and area. Commercial-timber plantations can alleviate demographic pressure on natural forests if the local population are involved in plantation management.

1.2.2 Establishment of a stand

Forests are regenerated by artificial or natural means at the end of their rotation periods or if they become overmature.

· Planting

Artificial forms of the establishment of a stand comprise conventional afforestation on open sites (EVANS, GOOR), planting under shelterwood to fill gaps in naturally regenerated stands or improvement measures in over-used forests (LAMPRECHT). The form of soil preparation and the planting technique depend on species, soil fertility, water balance and land condition. Brushwood and felled-area flora can be placed in windrows or burned unless this appears inadvisable on account of nutrient losses and soil erosion.

Planting techniques range from hole planting in clearings and deep soils through cuvette planting ("micro catchments") on slight slopes in arid regions to terracing on steep slopes in high mountain regions. For crusted laterite soils, complete turning of the soil is usual.

Irrespective of the technique used, artificial regeneration produces forests having a simple structure and largely open cycling systems. The tree species selected are generally vigorously growing, competitive pioneer species. The number of species and the degree to which they are mixed remain low for reasons of manageability. The biotic and abiotic risks to such plantations become greater as aridity increases (shortage of water, fire) and as soil fertility decreases, particularly on geologically old substrates in the inner humid tropics. The relatively small range of species on marginal sites is a result of natural factors.

Measures to protect stands against fire, storms, water stress, nutrient deficiencies and disease are frequently necessary (see FRANZ, for example, with regard to biological pest control). Controlled burning of organic surface layers (known as "prescribed burning") is a special plantation-management practice employed in arid regions to remove highly inflammable organic layers (BROWN, GOLDAMMER). Use of this method is restricted by the demands of soil and water conservation.

The planting stock needed for artificial afforestation is produced in nurseries, which usually concentrate on generative raising of planting stock from seed. Vegetative forms of plant production, such as propagation by cuttings, tissue cultures or seed production in seed plantations, are often capital-intensive and usually have to be carried out on a central basis by agencies possessing the necessary expertise (e.g. KRUESSMANN). It must be ensured that the consequences of genetic impoverishment can be overcome by means of an appropriate silvicultural strategy. Consumption and use of the inputs commonly required by nurseries (land, seed, fertiliser, substrate, water, pesticides, means of transport) depend on the specifications of the forest management plans (management goal type planning) and the propagation method employed. The high substrate consumption involved in production of pot or container plants calls for careful logistical planning.

Natural-forest programmes could involve small or temporary nurseries in the vicinity of the stand, as the provenances and varieties necessary to achieve the related management goals can best be produced on a decentralised basis. Regional afforestation programmes can be supplied by large central nurseries.

· Natural regeneration

Growth dynamics, phenology and adherence to the given spatial arrangement constitute criteria for selection of natural regeneration techniques (ASSMANN, GOLLEY, DENGLER, LEIBUNGUT, MAYER, WEIDELT, WHITEMORE). A general distinction is made between methods for clear-felling high forests, involving shelterwood and strip techniques, and the selection method for storeyed, species-rich stands. Special demands in terms of species protection and soil conservation arise in connection with conversion systems in tropical moist forests (LAMPRECHT) and management of high-altitude forests (MAYER).

Characteristic of all methods are a specific sequence and number of individual fellings over a long period, with care taken to preserve the dominated stand. During the regeneration process, the soil usually remains almost totally covered. Working of the soil is generally confined to preparing the germination bed with implements such as cultivators or harrows. Prescribed burning may become necessary for regeneration of pyrophytes (cf. section on planting).

Irrespective of the method used, the outcome will ideally be stands which, both horizontally and vertically, are more or less heterogeneous, species-rich and multi-storeyed, and which have closed natural cycling systems. Such stands are highly resistant to injurious factors and there is thus little need for protective measures and artificial raising of plants.

1.2.3 Stand utilisation

In generalised terms, distinctions can be made between the following forms of utilisation:

- conventional forest management for production of timber and to realise protective functions (e.g. DENGLER, LAMPRECHT, MAYER)
- agroforestry for integrated production of agricultural and forestry products (e.g. ICRAF)
- gathering, generally in connection with non-timber products (e.g. DE BEER).

Irrespective of the form of utilisation, it is essential to control the relevant economic (e.g. McNEELY) and demographic conditions in order to prevent over-utilisation. A key role is played by forest tending, without which it is impossible to utilise the wide range of opportunities offered by multiple-use forestry.

· Forest management

Distinctions are generally made between three types of forestry operation (e.g. DENGLER, MAYER):

- high forest created by means of natural or artificial regeneration, incorporating clear-felling (age-class) forest and all-aged (selection) forest
- middle forest originating from coppices and planting
- low forest originating from coppices

Low and middle forests are generally clear-cut in short rotation cycles. They are highly suited to production of fuelwood and other small dimensions for supplying local markets, provided that care is taken to implement the necessary protective measures such as regulation of forest grazing, terracing or cultivation of site-appropriate provenances. Management criteria are based on economic and technical data such as diameter and timber stock.

In high-forest management a distinction is made between final felling during stand regeneration and intermediate felling during forest tending. Long rotation periods and periodic tending measures make high forests suitable for achieving multifunctional goals such as production of high-grade timber and ensuring of welfare functions.

The purpose of forest tending is to raise stable stands by controlling the stages of stand development (e.g. MAYER). The management criteria relate to aspects of silviculture and forest yield science, such as basal area, number of trees, species and diameter distribution, or target diameter. Irrespective of the stage concerned, control of the limiting factor represented by light is a characteristic element of forest tending (e.g. BAUMGARTNER in MAYER).

In generalised terms, a distinction can be made between young growth tending, or pre-commercial thinning, and commercial thinning. Both chemical and mechanical methods are used, the latter being performed manually or with the aid of machines. Chemical methods are feasible only if non-persistent agents can be applied on a targeted basis. Systematic methods such as row thinning are commonly employed on monotypic plantations; only in favourable locations are they unlikely to give rise to problems (soil erosion).

Selective methods, known as selection thinning (e.g. MAYER) or timber stand improvement (WEIDELT, WENGER, WL), are the most effective in terms of yield and from the ecological viewpoint. A characteristic feature of such methods is regulation of the growing space of trees preselected for harvesting through removal of competing adjacent trees. In all-aged forests, growing-space regulation, intermediate felling, final felling and regeneration can be combined, whereas in artificially formed plantations this is possible only if at least two tree species have coordinated degrees of shade tolerance.

Tropical moist forests have special requirements where timber production is concerned (e.g. LAMPRECHT; WEIDELT; WHITEMORE 1984).Selective methods are in most cases particularly suitable for such forests in view of the diversity of species, the horizontal mosaic structure, the vertical layering, the nutrient balance (see Section 3) and the phase-controlled growth dynamics. In simplified terms, it is possible to distinguish four cyclically linked development stages (WHITEMORE, 1978): terminal stage - gap/group stage - build-up stage - maturity/climax stage. Forest regeneration and timber harvesting must be geared to these growth dynamics.

In principle, even timber harvesting in primary forests containing irregularly fruiting tree species with uneven diameter distribution is justifiable if only dying individual trees in the main stand are removed using highly mobile harvesting methods (see 1.2.4) after fruiting ("mortality pre-emption", SEYDACK 1990). In stands consisting of tree species with even diameter distribution, located on fertile and erosion-resistant sites, the trees can be removed in groups. Less selective methods are possible where stand conditions are homogeneous, as is the case for example in many natural tropical coniferous forests. However, harvesting of hitherto unutilised tree species (lesser-known species) is acceptable only if the nutrient balance (see Section 3) remains in equilibrium and the reproductive biology of the species concerned is known.

Management of special forms of tropical forest vegetation, such as gallery forests, savannahs and mangroves, cannot be treated within the scope of this environmental brief (cf. CHAPMAN, GOLLEY et al. 1978).

· Agroforestry

It is above all in the humid tropics that increasing population pressure is blurring the dividing line between agriculture and forestry. In areas on the fringes of intact forests, combining agricultural and forestry operations is often the only way of meeting the population's food and wood requirements. Agroforestry operations exhibit a higher degree of ecological stability than purely agricultural ones and in many places are the only means of permitting permanent cultivation (e.g. JORDAN).

Although there are no universally valid definitions, distinctions can be made for practical purposes between agroforestry, silvopastoral and agrosilvopastoral systems.

The degree to which agricultural and forestry elements are integrated in terms of time and area (e.g. ICRAF) depends on the available know-how, the availability of water, the soil fertility and the market. In marginal areas remote from markets it is generally possible to realise only simple forms of agroforestry, such as slash-and-burn agriculture (also known as shifting cultivation) or pasture farming in savannahs (PRATT).

· Gathering

In many geologically old, tropical moist forests, gathering of non-timber products, known as "minor produce", is often the only possible form of sustainable use. This is particularly true of Central Amazonian sites highly deficient in nutrients, where intensive forms of roundwood production result in a negative nutrient balance. In many parts of South-East Asia, for example, the production value of the minor produce far exceeds that of timber production (DE BEER). As tropical forests yield an immense number of non-timber products, it is impossible to cover all the region-specific aspects of this area within the scope of this environmental brief.

1.2.4 Harvesting techniques

Forests and trees yield numerous products important to man: commercial timber, pharmaceutical products, spices, resins, rattan, foods and tanning agents. Each of these products requires a tailor-made harvesting method (CAPREZ, STAAF, DE BEER).

· Timber

Of all activities in the forestry sector, timber harvesting requires the greatest input of capital and is most likely to cause damage. The strained nutrient balance means that timber harvesting is often impossible in tropical moist forests located on geologically old substrates. Planning and execution of timber harvesting must therefore be based on both economic and ecological criteria. The paramount aim of all timber harvesting measures is to minimise damage to the soil and stand. The following criteria must be taken into consideration in selecting the method to be used:
- management goal (rights of use, protective forest, commercial forest)
- stand density (number of trees, structure, nutrient dynamics)
- type of felling (intermediate felling, final felling, timber assortments)
- topography and soil (skidding distance, soil erosion)
- infrastructure (accessibility, construction costs)

From the operational viewpoint, actual felling of the trees is considered separately from hauling of the felled trunks. While mobile harvesting machines are generally used in non-tropical regions, felling of trees in the tropics is performed manually with the aid of an axe, handsaw or power saw. The degree of success is largely determined by the training and remuneration of the forest workers and by the way in which work at the felling site is organised. Resource-conserving methods of timber harvesting include the following features:
- marking of stand before felling (inventory)
- directional felling
- conversion of shortwood at the felling site before hauling

In roundwood handling, distinctions are made in organisational terms between skidding or hauling within the stand and (long-distance) timber transportation (road, rail, waterway), in technical terms between manual, animal-powered and mechanical techniques, and in method-related terms between whole-tree methods and roundwood methods. The damage done to the stand increases in proportion to engine power, intensity of utilisation, slope inclination, degree of accessibility, trunk length and the amount of ground skidding involved. Inappropriate hauling methods can cause soil compaction, rill erosion along wheel tracks, destruction of forest soil flora and the dominated stand, and butt and root damage to the rest of the stand. The most important hauling methods are given below in generalised terms, listed in order of the potential degree of damage that may result from them:

- Ground-based methods

· skidding hoists for clear-cutting, final felling, moderate or long skidding distances, suitable anywhere from lowland to high mountain regions
· wheeled and tracked forest tractors for clear-cutting, final and intermediate felling, short to moderate skidding distances, hilly terrain
· animals (horses, oxen, water buffalo etc.) for intermediate felling, smallwood, short distances, lowland regions

- Gravity methods

· manual floating for intermediate and final felling, short distances, in high mountain regions
· log chutes (wooden or earthen chutes), generally for final felling, long distances, high mountain regions

- Airborne methods

· travelling winches for intermediate and final felling in high mountain regions
· cable cranes for universal use
· helicopters for transportation of high-grade timber

In view of the mosaic structure of tropical moist forests, timber harvesting in such regions is liable to cause damage to resources unless the methods used take account of the conditions of single-tree harvesting in groups by way of mobility, off-ground hauling and a low-density road network (HODGSON). Homogeneous forms of stand in lowland regions allow less complicated methods to be used. Full-tree or whole-tree methods are suitable only for nutrient-rich lowland sites that are resistant to erosion.

After felling and hauling, timber is stored for a short time in the forest by the side of the road until it is removed by the purchaser. It is thus not usually necessary to protect timber stored in this way. In exceptional circumstances, for example after natural disasters, it may be essential to store large quantities of timber for lengthy periods in specially created log dumps. Steps must then be taken to limit the amount of land required and the use of pesticides and to dispose of bark shavings.

Appropriate options are to be selected on the basis of time studies, forest damage analyses and economic criteria. In addition to conventional economic assessment tools such as cost-benefit analyses, cost-effectiveness analyses (e.g. WENGER) should also be employed. Such analyses must relate to the entire rotation period (production period), rather than being confined to individual operations.

Timber harvesting can have indirect effects of environmental relevance in that it opens up forest areas in a manner permitting their subsequent use. Apart from selection of environmentally sound timber harvesting methods, an efficient forest administration capable of carrying out surveillance of forest use is essential to minimise damage to the stands.

· Non-timber products

As non-timber products encompass such a broad range, the effects of harvesting them cannot be described in detail here. It is essential to draw upon available local know-how in this connection.

A distinction must be made between products harvested for the harvester's own use and those harvested for marketing, as there is generally no danger of over-use where products are intended merely to meet subsistence needs. Special precautions must be taken in harvesting tree products such as resin, bark or climbing plants (e.g. rattan), as the function of the trees as means of production or support can be permanently impaired. Harvesting of "non-tree products" such as fruit or game requires less in the way of specific management if the products in question are not to be marketed.

2. Environmental impacts and protective measures

2.1 Sector-typical influences on the environment

In terms of area, forests constitute the Earth's most important terrestrial ecosystems. Since the "invention" of arable farming around 10,000 years ago, they have been continuously fragmented and degraded and today cover less than a third of the Earth's inhabitable land surface, extending over an area of around 42 million km2 (STARKE). As forests can perform their protective functions only where they cover a large area, man's living environment in certain regions is in jeopardy. Four protective functions will be discussed here:

· Climate regulation

Together with the oceans, the Earth's forests constitute a biological climate regulator. By means of their high evapotranspiration, they generate a large proportion of the precipitation themselves in some places. Evaporation of this water absorbs up to three quarters of the radiation energy, particularly in the tropics, and thereby prevents excessive warming of the atmosphere. Large quantities of the greenhouse gas CO2 are fixed as well. These two climate-regulating functions can be most efficiently controlled by means of near-natural, long-lived types of forest containing abundant stocks and covering large areas. By virtue of their more favourable assimilation/respiration ratio, many temperate forest formations, such as the coastal forests in the north-west of the USA, store up to three times as much CO2 as tropical rainforests (STARKE, 1991).

· Protection of genetic resources

Although tropical moist forests cover only a fraction of the Earth's surface (6%), they contain around 90% of all apes, at least 80% of all insects, at least two thirds of all plant species and roughly 40% of all species of birds of prey. As the majority of these species can exist only in near-natural forms of forest extending over large areas, monotypic artificial forests covering small areas are unsuitable for protecting species and genetic resources.

· Soil conservation

Storeyed high forests are the most efficient biological means of soil conservation. Soil erosion and soil formation under such stands are balanced and in line with the geoecological norm. The simpler stand structures found in dry forests or grass savannahs mean that such regions differ less markedly from artificial forests. The same applies to alternative forms of forest in lowland regions. Under humid tropical conditions and in high mountain regions, the erosion rates in artificial forests may far exceed the natural soil loss rate (MORGAN).

· Protection of human habitats

Rapid deforestation is constricting the human habitat, particularly in tropical moist forests, while at the same time destroying jobs. Tax concessions for large-scale projects (timber exploitation, mining, cattle rearing) can accelerate this process locally and displace the labour-intensive methods involved in traditional resource utilisation. It is thus above all in natural-forest and agroforestry projects that training and upgrading can play an important part in raising decision-makers' awareness of the relevant issues.

2.2 Sector-typical protective strategies

Forests perform vital protective functions, but at the same time require protection themselves in their function as biotopes housing a variety of plant and animal communities. However, effective protection of forests is possible only if the state, industry and the local population all have an interest in their long-term preservation. The ways in which forests are used must therefore ensure protection of forest resources and sustainable generation of added value, besides being acceptable to all interest groups involved. From the hygiene viewpoint, for example, the clearance of African savannahs infested with the tsetse fly is highly beneficial. For Iko bushmen and other game hunters, however, it means the destruction of their living environment, while for hydrologists it means flooding in low-lying areas and for nature conservationists it represents the destruction of biotopes.

Depending on site conditions, a protective strategy in the forestry sector will include components such as the following:

- Political/economic instruments

· regulating forest utilisation by interlinking protective, buffer, exploitation and settlement areas
· ensuring the generation of added value through utilisation of forests by means of diversification in the producer region and reinvestment of profits, e.g. in forest-tending programmes
· participative planning, implementation and monitoring of forest utilisation concepts
· moratorium on timber exploitation in primary forests located in tropical and temperate zones
· market-oriented incentives such as input and output taxes or subsidies for substitutes (e.g. use of cable cranes instead of bulldozers in timber harvesting)

- Technical/ecological instruments

· reducing wood consumption through improvements in wood processing
· function- and needs-oriented forest management by means of silvicultural planning on a single-stand basis
· simulation of natural growth dynamics and forest tending through long rest periods and natural-regeneration periods

An implementation-oriented discussion of the above elements can be found in the reference literature (cf. BMZ, ENQUETE).

3. Notes on the analysis and evaluation of environmental impacts

All action in the forestry sector is based on the principle of sustainability. This requires a form of utilisation which is in line with the potential of the natural resources and which preserves both the steady state of the natural cycling systems and the ecosystems' capacity for self-regulation (VESTER). Sustainability thus does not imply a constant annual yield level - in timber production, for example - but rather the achievement of goals such as ensuring species-rich natural regeneration through the use of resource-conserving timber-harvesting methods (SEYDACK et al. 1990).

As intervention by man disrupts these cycles, it is essential to use not only sustainability indicators such as annual cut but also ecological and socio-economic indicators:

· Nutrient balance

Nutrient cycles are a function of stand density, soil exchange capacity, nutrient storage and allochthonous introduction of substances via the atmosphere. As it is virtually impossible to control exchange capacity, storage and introduction of substances, management concepts must aim to minimise nutrient losses. If use of mineral fertilisers is to be avoided (since they generally necessitate use of non-renewable energy sources), nutrient losses can be offset by means of allochthonous introduction of substances only where small quantities of stem timber are removed over long production periods. Nutrient-deficient sites severely restrict production of large timber and biomass (see GOLLEY, RUHIYAT 1989 in WEIDELT 1989, ULRICH). Relevant indicators are

- nutrient reserves in kg/ha, broken down according to ecological compartments such as soil, roots, stem timber, branches and foliage, and
- nutrient flows between the individual compartments in kg/ha/a, including introduction and removal of substances.

· Water balance

Water is a limiting factor in many habitats. Its availability varies according to hydrogeological and bioclimatic conditions. As these components of the natural environment cannot be changed, the intensity of utilisation must be geared to the dynamics of the water balance in individual catchment areas. Near-natural storeyed forests are most capable of controlling the water balance. The components of the water balance - i.e. interception, evapotranspiration, run-off and groundwater recharge - can be controlled by means of forest tending and species selection (cf. MITSCHERLICH, WENGER). Depending on purpose, individual components can be used as sustainability indicators, for example to quantify groundwater recharge in arid regions.

· Soil erosion

Soil erosion is essentially a function of stocking, precipitation and relief intensity. It forms part of the Earth's natural cycling system. The smallest degree of soil erosion occurs under species-rich, storeyed high forests. The indicator for soil erosion is

- the site-specific geological norm (kg/ha/a), which can be ascertained on ecologically undisturbed sites by means of simple field trials (e.g. FAO) or, if this is impossible in totally degraded regions,
- the tolerable soil loss threshold, which can be ascertained by empirical means with the aid of the general soil loss equation after WISCHMEIER (e.g. in MORGAN).

Both of these indicators provide a criterion for the intensity of utilisation and the technical and biological protective measures required.

· Forest area

The minimum amount of forestry land required is determined by the population's requirements in terms of forest products and the economically necessary protective functions. The amount of land required depends on site-specific factors and the habits of the local people. In addition to ecological criteria, wood requirements and wood consumption must be taken into account along with the degree of fragmentation (ELLENBERG, PIELOU) of formerly continuous forest areas. One indicator is the forest area balance, expressed (in hectares) as the difference between the existing forest area and that which is economically necessary.

In the event of changes in the intensity of forest utilisation it is essential to know the parameters serving as a kind of early warning system which make it possible to spot new problems as soon as they start to develop. Apart from the ecological indicators mentioned above, such indicators may also be biological (pioneer plants, particular types of animal as anthropophilous species) or socio-economic (increased market supply of gathered products hitherto used only locally).

Economic assessment of forest resources involves various factors of uncertainty. Conventional monetary methods do not adequately cover the forest's indirect functions or the non-timber products generated "informally" to meet the population's own requirements. Cost-effectiveness and risk-analysis methods must therefore be used for evaluations in the forestry sector (BMZ, EWERS, KASBERGER-SANFTL).

4. Interaction with other sectors

Against the background of population growth and steady depletion of resources, it becomes clear that the core problem in the forestry sector, namely destruction of the forests in pursuit of economic interests, cannot be solved by technical means alone. Back-up measures in related sectors play a crucial part in permitting interdisciplinary management of general conditions for the purpose of preserving human habitats.

4.1 Complementarity

Conflicts over use of resources can be avoided by ensuring that the individual sector plans complement one another. To achieve this, it is essential to raise decision-makers' awareness of the relevant issues. Implementation of comprehensive development approaches is restricted by politico-economic realities (national and international corruption, international trade agreements, function of timber exports as a source of foreign exchange for non-diversified economies). Integrated approaches employ tools such as the following:

- population policy, for limiting population growth and mobilising young people as a potential labour force
- economic policy, for conserving natural resources by limiting demand and reducing debt
- regional planning, e.g. for implementing large-scale afforestation programmes as a means of rehabilitating the environment and alleviating poverty
- energy policy, for conserving natural resources by enhancing efficiency and promoting the use of non-biological, renewable energy sources (solar power, water power, wind etc.)
- agricultural policy, for achieving food security through land reforms, raising of productivity and refrainment from large-scale resettlement programmes

The environmental briefs on related sectors can be consulted where necessary. Among those of particular relevance are the following:

For biological production

- Agriculture

· Plant Production and Plant Protection
· Livestock Farming

- Infrastructure

· Spatial and Regional Planning
· Overall Energy Planning
· Water Framework Planning
· Mining and Energy
· Renewable Sources of Energy
For harvesting techniques

- Agriculture

· Agricultural Engineering

- Infrastructure

· Road Building and Maintenance

- Trade and Industry

· Timber, Sawmills, Wood Processing and Wood Products

4.2 Social environment

Socio-cultural factors play a major role in determining the success of measures in the forestry sector. Apart from acceptance, the following factors are among the most important:

- traditional forest utilisation rights and obligations
- system of social controls regulating resource utilisation
- target group's income situation
- health and food supply
- training

The complexity of the social environment means that difficulties are liable to be encountered in recording sociological data. Techniques such as rapid rural appraisals (CHAMBERS) may prove useful for small-scale projects but are generally inadequate for integrated approaches.

5. Summary assessment of environmental relevance

Characteristic features of the forestry sector are the extremely long production periods and the large areas needed to permit regulation of key global cycling systems. The impacts of management errors are thus difficult to limit in terms of both time and area, as the consequences of choosing the wrong species of tree may not become apparent until more than a century has passed.

To ensure the success of forestry measures, it is thus essential to simulate natural cycling processes. Involving the local population in the forestry production process plays an important role as a social management tool, particularly in marginal living environments threatened with destruction.

The concepts for forest utilisation must therefore be multifunctional and needs-oriented. Monotypic plantations may thus prove site-appropriate under certain conditions, for example to provide a fuelwood supply in arid regions. In general, however, integrated management goals can be achieved only in near-natural mixed forests. Negative impacts on the environment can be minimised by employing techniques which refrain from measures along the lines of clear-cutting and contribute to creating and preserving heterogeneous stands.

6. References

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Annex: Glossary of selected terms

Basal area: Total of the trunk cross-sections of all trees in a stand exceeding a minimum diameter, given in square metres per hectare and serving as a measure of the stand density.

Biocybernetics: Subdiscipline of cybernetics (from the Greek "kybernetes", meaning "helmsman"), which describes the control and automatic regulation of interlinked, closed-loop processes with minimum energy input in biological systems

Biomass utilisation: In forestry, limited to timber utilisation in the form of full trees, i.e. stem timber including bark, leaves and branches, or whole trees, i.e. full trees plus root wood.

Biotope: The habitat occupied by an organism or community (biocoenosis) within an ecosystem, determined by physical and chemical factors

Compartment: Permanent physical unit of forest division, serving simultaneously as a unit for planning, execution and monitoring of measures.

Cost-effectiveness analysis: Comparison of operational alternatives in which the inputs are of a monetary nature but the outputs cannot be measured in monetary terms.

Ecosystem: A unit within the natural environment, consisting of a community and its habitat (biotope) and characterised by balanced cycling systems, i.e. dynamic steady states.

Management goal: Production goal for forestry operations setting out the range and order of precedence of all requirements on the part of the forest owner and/or the general public, both material (timber, non-timber products) and intangible (soil and water conservation, nature conservation, recreation). Distinctions are made between product goals, security goals and monetary goals, with times being set for their achievement.

Management goal type: Management goal for a stand or compartment.

Savannah: Form of vegetation found in the semi-humid tropics, generally between the inner humid tropics and the latitudes marking the Tropics of Cancer and Capricorn, consisting of grassland with scattered trees and shrubs.

Silviculture: Science of forestry production concerned with systematic creation and tending of forests so as to ensure that society's material and intangible needs can be permanently satisfied

Site: Complex of location-related - i.e. natural, economic and social - factors influencing forestry operations.

Stand: Group of trees which exhibit similar features, occupy an unbroken minimum area and all require similar silvicultural treatment.

Welfare function: Also referred to as the indirect effects or non-wood beneficial effects of a forestry operation, i.e. "production" of goods with economic relevance such as water, soil conservation and recreation.

1. Scope

As a biological process, livestock farming influences, and is influenced by, the environment. With respect to the environment the aim is to change it in such a way that a maximum of food and raw materials can be obtained on a sustainable basis.

Environmental impacts vary depending on the form of livestock husbandry and type of farm involved. There are three basic forms of livestock husbandry:

- pasture usage
- pasture use with supplementary feeding
- confinement

Farming systems can be divided into the following types:

- ranches (cattle, sheep)
- traditional pastoralism (cattle, sheep, goats, camelids, equids, often mixed herds)
- smallholder livestock husbandry (cattle, buffalo, camelids, equids, sheep, goats, poultry, pigs, small animals such as guinea pigs, rabbits and bees; a farm often keeps a variety of different animal species)
- large enterprises of industrial-scale livestock production (e.g. poultry fattening, laying batteries, pig fattening, feedlots for cattle)

Fisheries and aquaculture are covered in a separate environmental brief.

Livestock farming is possible wherever arable farming is practised. It is also the only form of agriculture in semi-arid and arid regions as well as in high mountain regions in the zone beyond the arable farming limit up to the vegetation limit.

2. Environmental impacts and protective measures

2.1 Types of husbandry

2.1.1 Pasture use in general

The most noticeable consequence of grazing is the defoliation of plants by the animals, which influences the structure of the pasture vegetation and the variety of species which it contains. The precise nature of this influence depends on the type of animal concerned, the stocking rate (grazing pressure) and possibly also the time of year. Cattle and sheep tend to eat grass, whereas camels and goats prefer leaves.

An ideal sheep or cattle pasture will thus consist primarily of grass and herbaceous plants, while an ideal camel or goat pasture will contain more trees and bushes.

Grazing can stimulate plant growth and encourage the growth of creeping ecotypes of a particular plant species rather than those which grow upright. In grass/legume pastures, grazing often favours the legume component, because animals generally prefer grass during the early part of the vegetation period; with competition reduced in this way, legume growth is promoted. However, the young stages of some legumes are also popular with animals. While light grazing and browsing on bushes and trees can stimulate growth, removal of vegetation by livestock on a larger scale can reduce growth or even cause plants to die off and may hinder regeneration of fodder bushes from seeds and suckers.

The effects resulting from trampling of the vegetation by livestock depend primarily on the type of animal concerned, the stocking rate, the soil condition and the topography. Damage caused by trampling can increase soil erosion; however, the roughening-up of the ground can also create better conditions for germination and thereby promote plant regeneration. Where the soil in humid regions is heavily waterlogged, the vegetation cover can be destroyed as a result of trampling.

The seeds of many pasture plants are very small and can pass through the animals' digestive tract without any impairment of their germination capacity. Certain plants are thus dispersed with the animals' dung. Hard-shelled seeds are also scarified and the seeds are redistributed and sown by the animals.

Only a small proportion of the nutrients and energy intake by livestock actually finds its way into the animal products used by man. The remainder is excreted via dung, urine and, in the case of ruminants, methane (a gas which plays a part in the greenhouse effect). The breakdown of organic matter in the digestive tract of ruminants gives rise to energy and nutrient losses similar to those resulting from microbial breakdown in the soil; as the breakdown process in the stomach of ruminants is considerably faster, however, the grazing animals accelerate the nutrient cycle. If the animals are penned overnight, the excretion of dung in the pen means that the pasture is deprived of nutrients. Although the dung collected in pens can be used in arable farming and horticulture or for production of biogas and can thereby contribute to improving soil fertility, the loss of nutrients can accelerate degradation of the pasture vegetation.

In semi-arid and arid regions, the considerable fluctuations in annual rainfall mean that vegetation growth varies greatly not only according to the time of year but also from one year to another. The herbaceous vegetation layer in particular will thus not exhibit consistent growth. In drought years there may be so little vegetation growth that all the herbage is eaten by the animals. If shrubs and trees are not to suffer permanent damage, the amount of their vegetation consumed as fodder must not exceed a specific proportion of the annual growth, otherwise their capacity for survival and regeneration will be jeopardised.

Permanent damage is generally considered to have occurred when the vegetation's capacity for regeneration has been impaired and the surface of the ground has suffered erosion by wind or water. In view of the differences between plant communities and the differing regeneration capacities of the various species, it is not possible to lay down any universally valid standards specifying how much land can be used without impairing the productivity of the vegetation and what stocking densities are possible. American estimates work on the basis that 50% of the vegetation can be used, while studies from West Africa take figures of 30-50% (le Houerou 1980). Others graduate permissible vegetation use according to rainfall and take different levels of permissible utilisation for the bush/tree layer (25-50%) and the grass/herbaceous layer (30-50%) (Schwartz 1989). Factors which can assist in assessing degradation include the age structure and species composition of the tree and shrub community, seed reserves in the soil for the herbaceous plants and possibly also soil cover as well as depth and condition of the A-horizon.

The distribution of animals in an arid pasture area is determined primarily by the availability of water. Deep wells containing plenty of water supply a large number of animals and may thus give rise to serious overgrazing in their immediate vicinity. The size of the area around a well that can be used by animals for grazing depends among other things on the dry-matter content of the fodder, the type of animal and the animals' physiological status. Inadequately protected wells and watering places can easily be contaminated by dung and may also constitute a health risk for the local population if drinking water becomes contaminated. The concentration of animals around wells can promote the spread of epizootic diseases. Around every watering place there is a certain area which, although it contains an accumulation of nutrients by virtue of the dung produced by numerous animals, is almost totally devoid of vegetation as a result of trampling. The size of this area depends on the design of the watering place (e.g. troughs on hard ground) and the way in which access to it is controlled (e.g. fencing-in of watering places). Use of fertiliser in arable farming and horticulture in the vicinity of the watering place will not give rise to any problems.

Pastureland comprises natural pastures, fallow land and harvested fields. Forested areas, which in some cases are under the control of forest administrations, can also be used as pastures. In many cases, for instance in North Africa, the major proportion of the forest yield is derived from livestock farming. Fodder production is an integral part of agroforestry. It must be pointed out, however, that forest pastures are often over-used. If this is to be prevented, a wide variety of measures are necessary: reduction of tensions between forest administration and local farmers; employment of an adequate number of appropriately motivated personnel in order to enforce the regulations limiting pasture use; provision of alternative fodder resources for local livestock owners; steps to prevent use of pastures by non-local livestock owners not engaged in agriculture; reasonable charges (where payment is made for use of forest pastures) by comparison with the price of other fodder resources; and involvement of the local population in pasture-use planning. Both the dry and humid tropics offer examples of balanced pasture management which takes forest growth dynamics into account.

2.1.2 Pasture use with supplementary feeding

The environmental impacts of supplementary feeding depend on the context and the type of feed. Where fodder is of poor quality but available in large quantities, supplementary feeding of minerals can improve utilisation of the "standing hay". Provision of supplementary feed in the form of feed concentrate or high-quality roughage soon leads to a reduction in the amount of fodder consumed per animal during grazing, which benefits the pastureland. If, however, the number of animals is increased on account of the improved fodder supply and the natural pasture continues to be used, there is a greater risk of degradation. In some cases (e.g. in North Africa) livestock are given so much supplementary feed that this feed covers not only their performance requirement but also part of their maintenance requirement. Another reason for overgrazing is the desire to improve the quality of the animals' meat, since this will be reflected in higher meat prices. Meat quality is influenced in particular by the fact that the animals move around more and by the improved basic fodder supply.

2.1.3 Fodder production

Erosion-control strips can be used for fodder production. Appropriate planting of permanent fodder crops (such as sulla in North Africa) can serve as a form of "soft" erosion control. Fodder growing within a crop rotation system can have positive effects on soil structure and soil fertility (see Plant Production). The possibility that fodder crops may compete for land with crops that can be used as food for human beings must be borne in mind.

In the case of certain fodder crops, a large quantity of nutrients is taken from the soil together with the green matter. If these nutrients are not replaced, or if the dung is not returned to the field, there is a danger that the nutrient balance may be disturbed. If mineral fertilisers and herbicides are used in fodder production, there is a risk that surface water and groundwater may become contaminated and that the diversity of species may be reduced at the same time.

2.1.4 Confinement

While pasture use primarily involves ruminants, chickens, pigs and small livestock such as rabbits and guinea pigs are generally kept in confinement.

The environmental impacts of keeping livestock in confinement depend on the number of animals, the type of animal, the nature and origin of the feed and whether the livestock housing is open or closed. The environment prevailing in the animal-sheds (temperature, humidity, light, presence of noxious gases, dust and germs) has an effect on the animals, while livestock housing itself has an effect on its immediate environment through odours, liquid manure and noise. Where ruminants are kept, methane (a gas which plays a part in the greenhouse effect) is also released.

If livestock are kept in confinement, the vegetation suffers far less damage than if the animals are allowed to graze. However, use of cut fodder means that the soil is deprived of nutrients on a considerable scale; if these nutrients are not replaced, there is a danger that soil fertility may be reduced.

The enormous quantities of liquid manure produced where a large number of animals are kept can impair drinking-water quality and contaminate both surface water and groundwater. Large-scale chicken farms located near cities give rise to particularly adverse environmental impacts on account of their need to dispose of dead birds and droppings. Liquid and solid manure represent a major potential source of infection - especially for children - in many developing countries, particularly if no measures are taken to prevent contact with them. When used as fertilisers, liquid and solid manure can have a beneficial effect on soil fertility and soil structure, provided that they are not applied in excess.

2.2 Farming systems

2.2.1 Ranches

Ranches permit uniform management of comparatively large areas. Large-scale farms of this type nevertheless do not guarantee conservationist use of pasture resources (Harrington et al. 1984). In dry years a ranch too requires alternative fodder resources or the number of animals must be reduced in good time, otherwise heavy losses are likely. Supplementary feeding can lead to over-use of pastureland and thus increases the risk of erosion. When a large farm with "rational" stocking rates or a pasture reserve with a controlled stocking rate is established in an area where traditional livestock husbandry predominates, it should be borne in mind that although the reduced stocking rate on the land concerned may be more appropriate to site conditions than the original rate, the exclusion of animals from this land will increase the grazing pressure in the surrounding area.

Particularly in humid regions, large-scale land clearance to create pastures for ranches substantially reduces the diversity of species found in the vegetation. Apart from the resulting erosion problems, there may also be a risk of climatic changes over a wide area. The fact that ranches generally keep only cattle gives rise to one-sided utilisation of resources, which either permits only very low stocking rates or calls for sizeable inputs to preserve the pastureland. There is also a danger that the pastureland may be acidified as a result of waterlogging. Damage caused by trampling can have an adverse effect on the soil structure, leading to increased surface-water run-off and a greater risk of erosion.

Although ranches can improve the urban population's food supply, their carrying capacity per unit of area is smaller than that of traditional farming systems (e.g. Cruz de Cavalho 1974, de Ridder & Wagenaar 1986).

Environmental protection measures are difficult to realise where ranching is concerned. Attempts to standardise the carrying capacity of pastures are the subject of considerable dispute on account of the complex interrelationships and numerous variables involved, particularly in assessment of vegetation (e.g. Sandford 1983).

Some systems, such as those found in Australia, are based on detailed long-term studies and official determination of the permissible maximum stocking rate. As the land in Australia is generally not in private ownership, but is instead leased out by the government on a long-term basis, specific conditions can be imposed and the lease revoked if need be. In many countries the necessary data are not available and monitoring institutions are either non-existent or not equipped to perform the essential tasks. Rules aimed at preventing erosion should be worked out together with the ranch managers concerned.

2.2.2 Pastoral systems

In such systems, animal husbandry is the sole or principal economic occupation. Herding and a high degree of mobility make it possible to utilise resources in a manner complementing arable farming or to utilise areas that can be used for grazing only at certain times of year.

Pastoralists often keep mixed species herds, which permits intensive use of a wide variety of fodder resources. The products derived from the herds include milk, meat, traction power and manure.

· Integration of grazing and arable farming

Where pasture resources are used in combination with arable farming, the amount of land available for grazing varies greatly in the course of the year. During the growing season only natural pasture and fallow land can be used for grazing, while during the dry season harvested fields are also available for this purpose. Grazing has a variety of effects on fallow land and natural pasture. The species composition of the vegetation may change in such a way that a larger proportion of the vegetation can be used as fodder or for other purposes; at the same time, however, intensive grazing can also lead to degradation. If herded animals are penned at night, nutrients accumulate in the night paddock as a result of the droppings and urine produced by the livestock. These nutrients can be used to preserve soil fertility on arable land (dung), but are thereby removed from the nutrient cycle on the land used for grazing. Leaching from the night paddock can lead to contamination of surface water and groundwater. Use of crop residues as fodder may accelerate the nutrient cycle and result in redistribution of nutrients in a particular field or among fields. If crop residues are used on a large scale the soil cover may be reduced and this can lead to erosion. Rights to use fodder resources must be established through agreements between pastoralists and arable farmers.

· Mobility

A high degree of flexibility and mobility is required on the part of the pastoralists in order to permit ecologically appropriate and economically sound use of arid regions. Mobility in turn calls for large herds. In the course of their migration the pastoralists and their families must for the most part live on the products which they can derive from their herds. Reduced mobility generally leads to overgrazing, accompanied by increased soil erosion, in the area around the newly created settlements and to under-use of other areas. Under-use can also give rise to changes in the balance of species and reduce the vegetation's productivity.

As herds and people become increasingly sedentary and concentrated in specific areas, use of green twigs and branches to construct livestock paddocks and as domestic fuel leads to destruction of the woody vegetation.

· Grazing rights

Land and pasture use rights may comprise seasonal rights of use in specific areas and grazing rights in areas located a long way from one another. Apart from creating an opportunity to use land resources for grazing as well as for arable farming, this also helps to balance risks, as rainfall in arid regions is often highly localised. Communal grazing rights predominate in such areas. Communal pastures are traditionally used by clearly definable groups of livestock owners. Depending on the

group's structure and effectiveness, this makes it possible to stipulate stocking rates and times at which the pasture is not to be used. In regions such as East Africa, controlling access to water is an important means of controlling stocking rates. Open access pastures - frequently equated with common pasture - offer virtually no opportunity for such a step. In such a context, creation of watering places outside the traditional structures can encourage opportunistic use and thus contribute to overgrazing. The secondary consequences of such a development will be degradation of the vegetation, reduction of the soil's rainwater infiltration rate and increased soil erosion.

· Changes in ownership

Changes in the herd ownership structure can likewise adversely affect the pastoralists' resource management. When herdsmen look after cattle owned by other people, for example, they are often allowed only to use the milk. In order to have a secure livelihood they require large herds of their own if they are not to become impoverished. Moreover, the owners' desire to keep a check on their property may cause them to restrict the herdsmen's mobility and thus also their flexibility where pasture management is concerned. This too can result in over-use of the vegetation (disturbance of the balance of species within the flora, disturbance of the water balance, soil erosion).

· Division of labour

In pastoral systems, the men are generally responsible for management and marketing of the largestock, while the women frequently tend the small ruminants and have responsibility for milk processing and marketing. The women's role is often underestimated, as it is the men who represent the family vis-is other people. The decentralised processing and marketing of milk ensures a relatively reliable milk supply in rural areas, even though a woman may process and market only a few kilograms of milk a day. When milk is processed at household level, consideration must be given to possible hygiene risks (e.g. danger of infection).

· External influences

Pastoral land use frequently necessitates agreements between various population groups. External influences - and that includes government programmes - may disturb the often fragile equilibrium. If, for example, arable farming is expanded onto land used by pastoralists for dry-season grazing or as reserve pasture, the loss of this pastureland can increase the pressure on other areas and lead to overgrazing. Should the arable farmers start to keep livestock on a larger scale, the pastoralists

may find themselves driven out into marginal areas. This not only has consequences in terms of grazing management and livestock productivity but can also affect the welfare of the population groups concerned.

If their mobility is restricted, pastoralists may be forced to make intensive long-term use of marginal areas on a scale which exceeds the natural carrying capacity.

The resultant degradation process intensifies competition for the decreasing fodder resources. By promoting over-use of the available land it also reduces the number of species found locally and marginalises large sections of the pastoral population.

2.2.3 Smallholder livestock husbandry

The number of livestock owned by a smallholder can range from a few small animals (e.g. chickens) to large herds, e.g. twenty goats or ten head of cattle. Livestock management normally takes second place to the interests of arable farming. Many smallholders keep more than one type of animal.

Smallholders generally use pastures with supplementary feeding (at least on a seasonal basis) or keep their livestock in confinement. Large herds - such as village herds - may be mobile (cattle placed in the charge of a herdsman by their owners).

The animals may be allowed to graze freely, or may be herded, tethered or kept in fenced pastures. The practice of fencing off pastures with wooden posts - which may have to be replaced at frequent intervals on account of termite damage - can have adverse effects on the species composition and density of the tree stand. By contrast, use of "living fences" or hedges to subdivide pastureland has positive effects on the tree stand but requires a considerable amount of labour.

Clearing land to create improved pastures can increase the erosion risk and thus have an adverse influence on soil fertility. Creation of improved pastures, particularly with legumes, can be integrated into ley farming (seeded pasture rotation) and will improve soil structure and fertility. Competition for use of fodder resources may arise between livestock owners, above all between pastoralists and smallholders as well as between the smallholders themselves, and can thus impose increased pressure on the available land.

As in pastoral systems, management of largestock is frequently the men's responsibility, while the women are in charge of the smallstock. As women in many rural societies have no land ownership rights, livestock husbandry plays an extremely important part in enabling them to accumulate capital. The income earned from animal husbandry can be used to finance necessary expenditure for arable farming (fertiliser, seed, hired labour, creation of erosion-control strips), while the animals' dung can be used to preserve soil fertility. Livestock perform a particularly important function as a form of "risk reduction" in regions where arable yields tend to be unreliable. If the harvest is insufficient to meet the family's subsistence requirements, animals can be sold to permit the purchase of staple foods. Without this means of offsetting risks it would be necessary to extend the area under cultivation, which would have negative effects in terms of soil erosion, soil structure, nutrient balance and diversity of species.

A changeover from pasture use to keeping livestock in confinement can have beneficial effects on the diversity of plant species and assist in preventing erosion. The increased concentration of liquid manure and dung may lead to greater pollution of surface water and groundwater. Keeping livestock in confinement requires more labour than pasture use and it is generally women who are called upon to perform the extra work.

High-performance animals have more demanding requirements in terms of fodder supplies and veterinary care. If chemoprophylaxis is necessary, pathogen strains resistant to the chemotherapeutic agents used can develop (see environmental brief Veterinary Services). Introduction of high-performance animals frequently does not lead to a reduced number of livestock; it does not lessen the burden on the available fodder resources either.

The actual and potential advantages of indigenous breeds and species are often underestimated. With a one-sided promotion of the use and importation of high performance animals, there is a danger of losing genetic resources adapted to the natural environmental conditions.

Urban livestock husbandry can be regarded as a special category of smallholder livestock husbandry. As urban livestock owners purchase far more fodder than those in rural areas, their existence can encourage fodder growing in the vicinity of towns. This can have positive effects on soil structure and fertility, besides boosting the fodder growers' income. Dairy cattle are kept in urban areas to supply the urban population with fresh milk. While other animals are kept primarily to meet their owners' food requirements, they can also serve as a form of "savings bank" and as a means to accumulate capital. The dung produced by the animals can help to improve the soil structure and nutrient balance, but may well give rise to direct and indirect health risks if it is used or disposed of incorrectly. As in rural areas, women make an important contribution to urban livestock husbandry, although it can be assumed that the division of labour between the sexes is less strict than in rural society.

Smallholder animal husbandry also includes beekeeping. Apart from producing honey, bees can substantially increase fruit yields by pollinating the blossoms and help to preserve the diversity of species within the flora. Modern intensive beekeeping involves chemical control of pests (mites etc.); such measures can create health risks for humans if the chemical agents are incorrectly used and if residues find their way into the honey. Importing of higher-performance strains of bee can eradicate indigenous species. Production of honey and beeswax, which is predominantly a male domain, can be a highly profitable source of income in rural areas.

Environmental protection measures in the field of pastoral and smallholder livestock husbandry may involve steps to change framework conditions or direct intervention. Examples of measures aimed at changing framework conditions include discontinuation of subsidies for feed grains - in North Africa such subsidies contributed to widespread overgrazing - and changes in land law (land reform). Where direct intervention in pastoral and smallholder production systems is envisaged, it is essential that the groups affected be involved in the measures right from the planning stage. The measures planned may relate to a wide variety of different areas, e.g. water resources management, erosion control, fodder growing or - where smallholders are involved - promotion of confinement. Simply demanding a reduction in the number of animals - as was frequently done in the past - reflects an inadequate understanding of the way in which pastoral and smallholder production systems function.

2.2.4 Large enterprises with intensive animal production (commercial farming)

Large-unit animal production generally does not depend on the availability of land to provide forage, as fodder is imported from other parts of the country or from abroad. For the purpose of supplying the urban population, large-scale livestock production focuses on pigs and poultry.

Large farms consume far more fossil energy per product unit than traditional farms. If growth stimulants such as antibiotics or hormones are added to the fodder, there is a danger that residues may be found in foods of animal origin and that resistant pathogens may develop.

The high water consumption of large farms is also likely to lead to excessive utilisation of scarce water resources.

In confinement housing, the prevailing in-house-micro-climate (temperature, humidity, noxious gases such as ammonia, hydrogen sulphide and methane, dust and germ content of the air) can have adverse effects both on the animals and on the farm workers (health risks). The mere size of the farms means that the danger of surface water and groundwater being contaminated by liquid manure and farm effluent is far greater than in the case of smallholdings. The problems attached to the disposal of dung and animal carcasses are also likely to be greater, as is the related hygiene risk. Use of disinfectants can endanger water, soil and possibly also health.

Where cattle are involved, sizeable quantities of methane - a gas which plays a part in the greenhouse effect - are produced in the animals' stomachs and released.

If large farm enterprises are in competition with smallholdings, they can have an adverse effect on the smallholders' income. This may force smallholders operating under marginal conditions to engage in arable farming instead of livestock husbandry. Apart from giving rise to undesirable consequences with regard to the balance of species and soil fertility, such a step also increases the danger of erosion in the region concerned. Some large farms, such as commercial cattle-feed lots or large dairy farms (agricultural combinates), may also compete directly with smallholdings for agricultural land (e.g. in irrigated areas) and thereby force the smallholders into marginal areas. However, this risk is greater in the case of plantations and other crop-growing farms than in the case of livestock farms.

Environmental protection measures on large farms with intensive livestock management focus primarily on technical aspects: housing design, whole farm layout, ventilation, distance from settlements, precautions during storage and disposal of liquid manure and dung, hygiene measures such as disinfection, ban on use of growth stimulants, fencing-in of livestock housing etc. Technical standards in Central Europe are well documented (e.g. the German DIN standard 18910 on controlled environment in livestock housing, specifications laid down by the Association of German Engineers [VDI], maximum workplace concentration values (MAK), construction specifications issued by the German committee on technology and construction in agriculture [KTBL]).

3. Notes on the analysis and evaluation of environmental impacts

There are no generally applicable guidelines for analysing the environmental impacts of livestock farming. Useful background information concerning the impacts of large farm enterprises on water and the environment prevailing in the livestock housing can be obtained from German guidelines (e.g. DIN standard 18910, VDI specifications, planning documentation for livestock housing). Australian studies (e.g. Harrington et al. 1984, Squires 1981) can yield valuable pointers concerning ranches and pasture use in general. Collection of data to ascertain the impacts of livestock farming must be conducted on a long-term basis and can involve a variety of methods such as soil and plant monitoring, investigation of herd composition and livestock productivity, interpretation of aerial photographs (series) and possibly also interpretation of satellite images. An ecosystem analysis provides a sound basis for determining the carrying capacity of the ecosystem in question.

The ecological, economic and technical rationale of pastoral and smallholder livestock farming has sometimes been the subject of heated debate in recent years (Sandford 1983, Galaty et al. 1979; see also articles published within networks such as Nomadic Peoples and ODI Pastoral Development Network or by CRSP). The current state of knowledge does not permit any form of definitive assessment; the information sources cited above should instead be seen as offering pointers.

4. Interaction with other sectors

Livestock farming is interlinked above all with plant production and forestry and constitutes an element of general resource management. One link with plant production lies in the "transformation" of feedstuffs such as green forage, crop residues and cereals. Production and spreading of dung has beneficial effects on plant production, while the role played by livestock farming as a form of "savings bank" and as a means of accumulating capital can also permit investments in crop growing. The land requirements of pasture use are most likely to conflict with those of crop growing where the latter involves cash crops such as cotton and other crops cultivated in large-scale monoculture systems. Livestock farming also has a certain bearing on rural water supplies.

As natural pasture is often the major source of fodder for ruminants, the interests of livestock farming and pasture use must be taken into account in regional planning. Failure to understand livestock husbandry systems and the way in which they function can give rise to serious conflicts.

Food production and the related hygiene risks have an influence on the population's nutrition and health. Direct competition regarding product use can arise if cereals and other products that could be competition by humans without further processing are fed to livestock. Indirect competition occurs wherever feedstuffs (e.g. soya beans) are grown on a large scale for export, since this is to the disadvantage of smallholders engaged in livestock husbandry.

Livestock farming supplies raw materials for further processing by dairies, slaughterhouses, tanneries and spinning mills and is thus a source of raw materials for agro-industry.

Where draught animals are kept, livestock farming supplies "products" required in agricultural engineering; large farms are customers in this sector by virtue of their need to purchase items such as equipment for installation in livestock housing. Veterinary medicine essentially performs a service function for livestock farming. Fishery yields fish meal and thus also supplies feedstuffs for other forms of intensive livestock farming, while aquaculture can utilise wastes and by-products from livestock farming.

In the processing sector, environmental impacts depend on the nature and size of the enterprises concerned. With regard to slaughterhouses, see the environmental briefs Veterinary Services, Slaughterhouses and Agro-industry.

5. Summary assessment of environmental relevance

The environmental impacts of livestock farming are determined by the intensity of the production operations.

The following critical influencing factors are to be found in all farming systems and forms of animal husbandry:

- land clearance for the purpose of pasture improvement or to permit forage growing
- stocking rate, which is influenced by the number of animals, the herd composition in terms of species and classes of animals, and the availability of fodder
- availability of water as a function of the number of watering places per unit of area, the distribution of watering places in the region and the design of the watering places.

However, the extent of the environmental hazards created by these critical influencing factors depends on the farming system in question. Stocking rate, for example, becomes less important in intensive livestock farming systems; at the same time, an increasingly significant role is played by critical factors in fodder growing such as type of fodder, form of use and fertiliser application, as well as by dung removal and possibly also residues in feedstuffs and animal products (which may also be the result of veterinary measures).

The greatest environmental hazards are caused by industrial-scale animal production. Apart from the considerable risk of water and air pollution through noxious gases and disposal of dung and liquid manure, its energy and water requirements can also be seen as having adverse impacts on the environment.

6. References

Cruz de Cavalho E., 1974: "Traditional " and "modern" patterns of cattle raising in southwestern Angola: a critical evaluation of change from pastoralism to ranching. Journal of Developing Areas 8, pp. 199-226.

DIN 18910, 1974: Klima in geschlossenen Sten. Berlin: Beuth-Vertrieb.

Galaty J.G., Aronson D., Salzman P.C., Chouinard A. (Eds.), 1980: The future of pastoral peoples. Ottawa: International Development Research Centre (IDRC).

Harrington G. N., Wilson A. D., Young M. D. (Eds.), 1984: Management of Australia's rangelands. Melbourne: Commonwealth Scientific and Industrial Research Organisation.

Jahnke H. E., 1982: Livestock production systems and livestock development in tropical Africa. Kiel: Kieler Wissenschafts-Verlag Vauk.

King J. M., 1983: Livestock water needs in pastoral Africa in relation to climate and forage. ILCA Research Report No 7. Addis Ababa: International Livestock Centre for Africa.

Kotschi J., Adelhelm R., Bayer W., von B., Haas J., Waters-Bayer A., 1986: Towards control of desertification in African drylands: problems, experiences, guidelines. GTZ special publication No. 168. Eschborn: GTZ.

Niamir M., 1990: Herders' decision-making in natural resources management in arid and semi-arid Africa. Community Forestry Note 4. Rome: FAO.

Pastoral Development Network Discussion Papers. London Overseas Development Institute.

de Ridder N., Wagenaar K. T., 1986: Energy and protein balances in traditional livestock systems and ranching in eastern Botswana. Agricultural Systems 20, pp. 1-16.

Sandford S., 1983: Management of pastoral development in the Third World. Chichester: John Wiley & Sons.

Squires V., 1981: Livestock Management in the arid zone. Melbourne: Inkata Press.

VDI-Richtlinien 3471, 1986: Emissionsminderung Tierhaltung Schweine. Berlin: Beuth-Verlag.

VDI-Richtlinien 3472, 1989: Emissionsminderung Tierhaltung H Berlin: Beuth-Verlag.

1. Scope

Veterinary services are of even more immediate relevance to the environment than is the case for sectors such as plant or animal production. Their principal purpose is to preserve or restore animal health and their environmental impacts are thus essentially positive. However, the possibility of negative impacts - generally of an indirect nature - cannot be precluded. The veterinary sector primarily performs a service function for livestock farming and fisheries, as well as playing an important role in food inspection.

Activities in the veterinary sector cover the following areas:

- diagnosis and control of diseases, involving treatment, prophylaxis, vector control and epizootic-disease control
- artificial insemination and embryo transfer
- laboratory activities, comprising laboratory diagnostics, vaccine production and residue analysis
- food inspection, above all meat inspection in slaughterhouses and food hygiene.

In the fields of disease diagnosis, treatment and vector control, a distinction can be made between "modern" measures carried out by formally trained veterinary surgeons and traditional practices employed by the animal owners themselves or by healers.

In the agro-industry sector (meat and milk processing, fodder hygiene), veterinary services perform a monitoring function. Veterinary medicine is also closely linked with the pharmaceutical industry by virtue of its need for drugs and vaccines.

2. Environmental impacts and protective measures

Veterinary services perform a vital function through their key tasks of combating animal diseases and ensuring that foods of animal origin comply with the necessary hygiene regulations. Measures to protect health and the natural environment are necessary above all wherever veterinary drugs and pesticides are liable to have side-effects, leave residues or be used incorrectly or negligently, as well as in laboratory work and vaccine production. Disposal of wastes and of possibly infected carcasses (or parts thereof) unfit for human consumption is discussed in the environmental brief Slaughterhouses and Meat Processing.

- For drugs, the following principles should be applied: strict controls on sale and use; monitoring of production if necessary; livestock owners to be advised on potential side-effects; greater emphasis on use of traditional remedies. Although traditional remedies derived from plants may not be totally free of environmental hazards, they are in general likely to have less environmental impact than "modern" pharmaceuticals. Changes in livestock husbandry systems can also help to reduce the need for drugs.
- In prophylaxis and vector control, the following measures are essential: refrainment from use of products which are broken down in the environment only very slowly or not at all (e.g. DDT); greater emphasis on epidemiological aspects and promotion of forms of livestock husbandry likely to reduce parasite infestation.

Veterinary measures may interfere with established social structures, with adverse effects on the producers' rights and income. Women are particularly liable to be affected, since in many societies they play an important role as traditional healers, as livestock owners and in the processing and marketing of animal products.

2.1 Disease control

2.1.1 Diagnosis and treatment

Clinical diagnosis and treatment are carried out on the one hand by the animal owners themselves or by traditional healers, and on the other hand by formally trained veterinary surgeons. Clinical diagnosis has little direct impact on the environment (see environmental brief Analysis, Diagnosis, Testing).

Traditional methods of treatment often involve user-prepared plant extracts, although modern drugs are also used on a growing scale. Use of plant extracts (generally in aqueous form) can have undesirable effects on the diversity of species within the flora if medicinal plants are gathered in such large quantities that their existence as a whole is jeopardised. It can be assumed that "natural" remedies leave few residues.

Improper storage of modern drugs (chemotherapy) can have harmful effects on the environment. Certain drugs such as potent antibiotics are used too frequently or in incorrect doses; this can cause pathogens to become resistant to the antibiotic used and necessitate administration of a number of different antibiotics in rapid succession.

There is also a danger that drugs or drug residues may accumulate in products destined for human consumption - thereby giving rise to health risks - if the prescribed waiting periods are not observed before animals are slaughtered or used for other purposes (e.g. to obtain milk).

Practices such as using waste oil to treat dermatophiliasis can bring animals short-term relief but may cause contamination of water and soil.

Getting rid of disposable cannulas and containers made of plastic and other synthetic materials can give rise to problems. Incineration pollutes the air (e.g. with dioxins), while incineration residues may contaminate water and soil.

Successful treatment of sick livestock can lead to an increase in the number of animals; this in turn may result in over-use of fodder resources, giving rise to a greater risk of erosion and general degradation of fodder bushes, fodder trees and pastureland.

Where malnutrition is a contributory factor in disease, control measures should be combined with improved feeding.

2.1.2 Prophylaxis

· Immunoprophylaxis

Isolated immunoprophylaxis for infectious diseases (vaccination) can result in an increase in the number of livestock, leading to overgrazing. A shortage of fodder can in turn weaken the animals and eventually lead to their death.

The disposable equipment used (syringes, cannulas, vaccine containers) has direct impacts on the environment. Improper disposal creates a risk of injury for human beings and animals (cannulas), while disposal on landfill sites can contaminate water and soil. Waste incineration causes air pollution and incineration residues may accumulate in soil and water.

· Chemoprophylaxis

Chemoprophylaxis involves preventive treatment such as daily subtherapeutic doses of a vermifuge or prophylactic administration of trypanocides. Such treatment can also help animals adapt to new surroundings, for example new pastures, by enabling them to develop premunity. Chemoprophylaxis enables particular species or breeds to use pastureland on which they could not be kept previously, e.g. by making it possible for zebu to graze in areas infested with the tsetse fly.

However, chemoprophylaxis can cause pathogens to become resistant to the drugs used. It may also adversely influence the development of immunity or premunition, with the result that mortality will rise after chemoprophylaxis is discontinued until the animals have developed immunity of their own.

To prevent tensions from developing between population groups, veterinary measures must pay equal attention to the needs and interests of all groups concerned.

· Preventive management measures

Preventive livestock management measures that can reduce the animals' risk of infection include the following:

- appropriate herd distribution: depending on the varying spread of diseases specific to particular types of animal, certain areas are used only by cattle and small ruminants, or only by camels.
- avoidance of specific pastures (at particular times of the day or year, or throughout the year): if pastureland is not used in the early morning when the grass is wet, invasion by infectious larvae of gastro-intestinal parasites will be reduced. Areas with a large population of mosquitos and biting flies during the rainy season are only used for grazing during the dry season or not at all. Areas infested with worm eggs and larvae or ticks in various stages of development (e.g. abandoned paddocks) are avoided for a number of months.
- keeping livestock away from moist pastureland: this prevents worm infestation (liver fluke) and reduces the risk of such parasites being transmitted to man.
- during migratory herding, areas infested with parasites (worm larvae, tsetse flies, ticks) are avoided at the times of year when the parasite population is at its largest (Sutherst 1987, Sykes 1987).

These preventive practices have long been employed by ethnic groups engaged in traditional animal husbandry. They have extensive beneficial effects on biodiversity and pasture resources, as they ensure that pastureland is not over-used.

Drainage of land for the purpose of creating specific forms of landscape and vegetation can lead to the loss of wet biotopes. Both biodiversity and the landscape will benefit if wet areas are fenced off and not used for grazing.

A changeover from pasture farming to confined livestock raising in the interests of animal health (see environmental brief Livestock Farming) will increase the livestock owners' workload. At the same time, however, the fact that grazing is replaced by growing and cutting of roughage may help to reduce the risk of erosion.

The resistance of productive livestock can be enhanced by improved feeding, in particular by giving the animals high-energy and protein-rich feedstuffs along with minerals. The environmental impacts of pasture farming with supplementary feeding are treated in the environmental brief Livestock Farming.

2.1.3 Vector control

Vector control involves attempting to change the balance of species so as to hinder the transmission of diseases by intermediate hosts and vectors or interrupt the cycle of transmission to man and livestock.

Chemical control of vectors includes measures such as use of insecticides in dips and the like to combat ticks, large-scale or targeted spraying of insecticides to control flies and mosquitoes, and application of molluscicides to kill snails. Long-term use of such methods can cause resistant strains of parasite to multiply, with the result that in tick control, for example, the agents used (acaricides) must be changed at frequent intervals. There is also a danger that other arthropod species may be affected as well. Pesticides may contaminate soil and water and, if the specified waiting periods are not observed, leave residues in milk and meat. The acute and chronic toxicity of the insecticides used thus creates direct risks for both man and animal. Large-scale vector control measures, such as aerial spraying of insecticide to combat the tsetse fly, involve an additional problem, namely disposal of the insecticide containers. Such containers must be treated as hazardous waste and must not be used for storing or processing food.

A further disadvantage of chemical vector control is that indigenous animal populations may lose their natural resistance or premunity with respect to numerous diseases. If the continuity of chemical vector control is not guaranteed, man and animal frequently have an increased risk of contracting the disease transmitted by the vector.

Unlike large-scale chemical control measures, use of attractants and insecticide-impregnated traps - for example in tsetse control - admittedly does not lead to eradication of the vector but at the same time ensures an almost total absence of insecticide residues. There is also virtually no danger that livestock will lose their premunity. Biological control methods such as use of sterilised flies to combat the tsetse fly and screw-worm fly generally do not entail any risks apart from those attaching to the necessary radiation treatment in the laboratory.

Targeted attempts to eradicate wild animals serving as a "reservoir" for pathogens causing particular epizootic diseases destroy the diversity and balance of species within the wild fauna. By reducing opportunities for hunting, they can moreover jeopardise the income and food supply of specific population groups.

Land clearance has far more complex impacts. By destroying the habitat of tsetse flies and other insect pests it reduces the infection risk for both man and livestock. The balance of species will change, with grasses and herbaceous plants becoming dominant; at the same time there is a risk of increased soil erosion and a reduction in the soil's water retention capacity. Local clearance techniques which - like those used in West Africa - leave 30 to 50 trees standing per hectare and allow the topsoil to remain largely intact have considerably less environmental impact than technically sophisticated methods. The pastureland created through clearance is highly susceptible to erosion if overgrazed. However, land clearance can also help to alleviate the pressure on overgrazed areas, thereby reducing their erosion risk and enabling the vegetation to recover.

Bush fires are seldom started with the aim of improving animal health. A reduction in the presence of vectors such as ticks (West 1965) is merely a side-effect of such measures, which have complex impacts on flora and fauna. Fire can also help to keep a savannah open and thus ensure that the insect-pest population remains low. As a result of interference with the species composition, however, insect pests may penetrate into hitherto unaffected areas and subsequently multiply here.

Theoretically speaking, breeding of livestock with particularly high resistance to a disease or vector (e.g. ticks) makes it possible to introduce a particular species into areas where it could not be kept in the past (Sutherst 1987). Indigenous livestock, however, already possess a high degree of resistance. For example, West African zebu can acquire a certain "trypanotolerance" if they have lived in tsetse areas for a number of generations and are regularly exposed to the pathogen.

2.1.4 Epizootic-disease control

The purpose of epizootic-disease control measures is to prevent diseases from spreading. Such measures are necessary in connection with the export and import of animals and animal products. They comprise general control measures (e.g. export or import bans), compulsory vaccination, ring vaccination in the event of acute outbreaks of disease, quarantine measures, compulsory slaughtering of sick animals and directives governing disposal of the carcasses of animals that have died or been compulsorily slaughtered.

Compulsory vaccination is a means of keeping certain diseases effectively under control for a lengthy period of time.

Ring vaccination is often accompanied by quarantine measures. The resultant restriction of herd mobility may lead to overgrazing in some places, creating tensions between sedentary and nomadic livestock owners. To ensure their acceptance, government quarantine measures should also take account of traditional practices that help to curb the spread of epizootic diseases.

Compulsory slaughtering is the most radical control measure, but is seldom used. It gives rise to severe financial losses for the farms affected and may oblige them to change their livestock management practices. For example, pastoralists may be forced to become less mobile if their herds fall below the critical size necessary for migration and this can create an increased risk of local overgrazing.

Disposing of dead animals by burning the carcasses creates unpleasant odours and pollutes the air. If wood is used, it also increases fuelwood requirements and thus women's workload wherever women are responsible for procuring wood (see also environmental brief Meat Processing).

Compulsory slaughtering is an emergency measure which prevents the spread of epizootic diseases and has beneficial effects on the health of both man and animal.

2.1.5 Zoonosis control

Through treatment of sick animals, prophylaxis, vector control and epizootic-disease control, veterinary services help to reduce the incidence of zoonoses and thus improve human health. Epizootic-disease control measures such as banning the keeping of dogs to curb the spread of echinococcosis and reduce the risk of rabies can restrict herding or make it difficult for nomads to guard their camps and thus have far-reaching socio-cultural implications. They may necessitate changes in livestock management practices and, by reducing mobility, can lead to overgrazing in certain areas.

2.2 Laboratory activities

2.2.1 Laboratory diagnostics

Preparation, transportation and handling of infected specimens in connection with laboratory work can give rise to environmental hazards. Improper handling and disposal of infectious specimens can endanger human health and contribute to the spread of disease.

In addition to the problems involved in disposing of non-reusable materials, there is also a risk that air, water and soil may be contaminated during transportation, storage and disposal of chemicals and reagents. Incineration of specimens no longer needed likewise causes air pollution.

To protect the environment, it is essential that safety regulations be strictly observed and that glass and plastic containers, reagents, chemicals and the specimens examined be collected, recycled where appropriate and properly disposed of (see OECD 1983). Use of toxic chemicals can sometimes be reduced by selecting appropriate analytical methods.

2.2.2 Vaccine production

Apart from the usual environmental risks attaching to laboratory work, vaccine production also involves all the hazards that can arise when live pathogens are being handled.

The most essential environmental protection measures are strict compliance with safety regulations, improvement of safety facilities where necessary and appropriate disposal precautions.

2.2.3 Residue analysis

By bringing to light undesirable environmental impacts, residue analysis also helps to safeguard human health and can thus be seen as a form of environmental protection. Detailed residue analyses can often be conducted only in specially equipped laboratories (see also environmental brief Analysis, Diagnosis, Testing).

2.3 Artificial insemination and embryo transfer

Artificial insemination (AI) and embryo transfer (ET) are modern techniques for importing high-performance breeds (primarily cattle) into tropical and subtropical countries. Animals produced in this way and born in the importing country are better adapted to the environmental conditions there than those imported live. Artificial insemination is also a means of controlling the spread of venereal diseases.

AI and ET do not have any direct environmental impacts. By curbing the spread of venereal diseases they may contribute indirectly to improving livestock fertility and may thus lead to higher productivity and an increase in livestock numbers. The resultant effects on the environment depend on the prevailing husbandry system.

Importing of high-performance livestock calls for strict control of vectors and ectoparasites; it may also be necessary to step up chemoprophylactic measures (see Section 2.1 above). There is a danger that the contribution of AI and ET to raising animal production may be overestimated and existing production systems consequently neglected.

2.4 Food inspection

Veterinary control and inspection of foods of animal origin is intended to prevent human health being endangered by tainted or infected foods.

2.4.1 Meat inspection

Meat inspection has hitherto often been confined to large modern slaughterhouses. It is a prerequisite for the export of animal carcasses and thus contributes to improving the income of livestock dealers and producers.

Attempts to introduce and apply meat inspection regulations from other countries without creating the necessary infrastructure (monitoring services, analysis facilities) can lead to a loss of income. The activities of small village slaughterhouses may be considerably restricted if they too are required to comply with such regulations and this can have an adverse effect on the rural population's meat supply. As women in some countries play an important role in slaughtering and meat marketing (particularly where small livestock are involved), such a development would have particularly serious consequences for the women's income and economic status.

However, meat inspection and proper disposal of products seized by the authorities prevent the spread of epizootic diseases and zoonoses. Hides contaminated with anthrax pathogens, for example, can be a highly dangerous source of infection for tanners.

2.4.2 Food hygiene

Milk hygiene plays a particularly important role in this field. Bacteriological monitoring is intended to prevent the spread of diseases such as tuberculosis and brucellosis, while analysis of milk composition helps to ensure high product quality. Milk testing and sales bans imposed as a result can have far-reaching social consequences if they extend to smallholdings which generally process only a few litres of milk a day and on which there is little danger that large quantities of milk may be contaminated. Direct marketing of milk and other dairy produce is often a major source of income for women. Sour-milk products have the advantage that the souring process kills pathogenic germs. Boiling the milk to kill germs increases energy requirements.

Legislation on milk hygiene could conceivably be misused to force small-scale processing and marketing operations out of the milk production sector.

The possibility of health risks can be counteracted by advising and informing women about hygiene precautions to be taken during processing of dairy produce.

3. Notes on the analysis and evaluation of environmental impacts

The environmental impacts of traditional veterinary medicine have not yet been the subject of any summarising assessment. Use of traditional practices is generally confined to specific groups. Relevant references are contained in a number of annotated bibliographies (e.g. Mathias-Mundy and McCorkle 1989).

The OECD guidelines on sound laboratory practice provide pointers concerning the environmental impacts of laboratory testing and analysis. Information on this subject will also be found in the environmental brief Analysis, Diagnosis, Testing.

The environmental impacts of residue analysis are discussed in the relevant literature (e.g. Barke et al. 1983, DSA 1984, Rico 1986, Grolaus 1989).

4. Interaction with other sectors

Through treatment of disease, epizootic-disease control and vector control, the environmental impacts of veterinary measures are linked to those of animal production and fisheries. By monitoring hygiene in food production and processing, veterinary services contribute to environmental protection in other sectors (e.g. agro-industry, slaughterhouses and meat processing). Veterinary medicine is dependent on the pharmaceutical industry for its supply of modern drugs. Wastewater and solid waste disposal is of relevance to laboratory activities, which also have links with the chemical industry by virtue of the need for reagents and chemicals.

5. Summary assessment of environmental relevance

The principal tasks in the veterinary sector are disease control and food inspection. However, disease control measures and laboratory work may have adverse effects on health and the natural environment, either directly or indirectly. Regulations governing epizootic-disease control and food hygiene can interfere with the social structures forming the basis of the livestock owners' existence.

The traditional remedies used by livestock owners are often based on plant extracts, which play an particularly important role in the treatment of small animals.

Therapeutic and prophylactic measures may cause pathogens to develop resistance and can give rise to residues in food.

While traditional forms of treatment have few negative impacts on the environment, this is not true of modern drugs, particularly if they are used improperly.

The activities of veterinary laboratories may give rise to water and air pollution; disposal of laboratory waste can cause contamination of air, water and soil.

Improved animal health is reflected in lower mortality and higher productivity, providing the producers with a more secure livelihood. However, consequent expansion of livestock husbandry can increase the danger of overgrazing if veterinary measures are not accompanied by improvements in the fodder supply and appropriate livestock management measures.

Epizootic-disease control, measures to curb the spread of zoonoses and monitoring of compliance with food hygiene regulations all have essentially positive effects on human health and the livestock owners' income. In some cases, however, incomes can be adversely affected. Imposition of excessively stringent standards for food hygiene can lead to the disappearance of small-scale slaughtering and milk-processing operations. Such a development could adversely affect the supply situation in rural areas and the income of those engaged in such activities, particularly women.

6. References

Barke, E. et al. 1983: Rnde in Lebensmitteln tierischer Herkunft. Situation und Beurteilung. Verlag Chemie.

DSA 1984: Safety and quality in food. Proceedings of a DSA symposium "Wholesome food for all". Views of the animal health industries. Brussels 29/30.03.1984. Amsterdam: Elsevier.

Grolaus, G. 1989: Rnde in von Tieren stammenden Lebensmitteln. Berlin: Parey Verlag.

Mathias-Mundy, E. & McCorkle, C. M. 1989: Ethnoveterinary medicine: an annotated bibliography. Bibliographies in Technology and Social Change No. 6. Ames: Technology and Social Change Program, Iowa State University.

OECD-Grundse zur guten Laborpraxis: Bekanntmachung im Bundesanzeiger (Federal Gazette) Nr. 42 dated 2. M 1983, pp. 1814 ff.

Putt, S.N.H., Shaw, A.P.M., Matthewman, R.W., Bourn, D.M., Underwood, M., James, A.D., Hallam, M.J. & Ellis, P.R. 1980: The social and economic implications of trypanosomiasis control: A study of its impact on livestock production and rural development in Northern Nigeria. Reading: Veterinary Epidemiology and Economics Research Unit, Study No. 25.

Rico, A.G. 1986: Drug residues in animals. London: Academic Press.

Sutherst, R. W. 1987: Ectoparasites and herbivore nutrition. In: Hacker, J.B. & Ternouth, J.H. (Eds.) The nutrition of herbivores. Sydney: Academic Press, pp. 191-209.

Sykes, A.R. 1987: Endoparasites and herbivore nutrition. In: Hacker, J.B. & Ternouth, J.H. (Eds.) The nutrition of herbivores. Sydney: Academic Press, pp. 211-232.

West, O. 1965: Fire in vegetation and its use in pasture management with special reference to tropical and subtropical Africa. Hurley: Commonwealth Agricultural Bureaux (CAB), mimeographed publications 1/1965.

1. Scope

Activities for the purpose of obtaining food and other products from water bodies involve catching and gathering as well as farming and raising aquatic organisms (above all fish, crustaceans, molluscs and algae). Annual worldwide production in the fishery and aquaculture sector amounts to around 95 million tonnes.

The principal forms of activity are:

- capture fisheries
- aquaculture
- stocking and ranching

All three types of activity can be carried out in seawater, brackish water and fresh water and in both coastal and inland waters. Deep-sea operations primarily involve capture fishery, with aquaculture playing only a very small role. Stocking and ranching may include use of deep-sea areas in that fish released near the coast (e.g. salmon) may spend their growth phase in the open sea.

While inland and inshore fisheries and aquaculture are predominantly artisanal, deep-sea operations are primarily on an industrial scale where capture fisheries are concerned and exclusively so in the case of aquaculture.

Capture fisheries utilise natural stocks of aquatic organisms. Such activities influence the stocks not only by catching them but also by means of conservation measures (closed seasons, protected areas, catch quotas, use of selective gear). In aquaculture measures are taken to directly influence at least the growth stage and if possible also the reproductive stage, above all by controlling water quality (through the conditions under which the organisms are kept), nutrition (through feeding and pond fertilising) and health (by means of prophylactic and therapeutic measures). The reproductive stage can be controlled by influencing maturation, egg and sperm production, hatching and larva raising. The characteristics of the organisms bred can be genetically influenced (e.g. by means of selection, crossing or genetic engineering).

Stocking and ranching combine aquaculture with fishery (culture-based capture fisheries). Natural or artificial bodies of water are stocked with young organisms which were hatched under supervision and spent the particularly critical early stages of their life cycle under controlled conditions. When the stocks created or augmented in this way reach the end of their growth stage, they are fished using normal capture-fishery techniques.

Between the "production" process - carried out under natural conditions (fisheries) or controlled conditions (aquaculture) - and consumption of the products there are a number of other stages which may likewise have environmental impacts: keeping fresh, processing, packing, transporting and marketing.

Fisheries and aquaculture can be divided into five main areas:

- artisanal small-scale fisheries
- small-scale aquaculture
- fisheries and aquaculture in artificial lakes
- fishery in the 200-mile exclusive economic zone
- fisheries and aquaculture in mangrove swamps

In the first two areas, emphasis must be on supporting low-income groups of the population and ensuring that appropriate technologies are applied. These two aspects likewise form the focus of attention in the use of artificial lakes for fisheries and aquaculture. By contrast, activities involving fishery in the 200-mile exclusive economic zone - predominantly at industrial scale - centre on preservation of resources and on managing and monitoring their use. Particular importance must be attached to environmental protection and resource conservation when the intention is to utilise mangrove swamps for fisheries and aquaculture, as measures involving the use of this fragile ecosystem should aim from the very outset to ensure that adverse environmental impacts are avoided altogether or kept to an absolute minimum.

2. Environmental impacts and protective measures

2.1 Artisanal small-scale fisheries

The actual fishing activities have the greatest bearing on the environment, as the long-term availability of the resources depends on the extent to which these activities are geared to the resource situation and to the conditions prevailing in the ecosystem fished. Through centuries of experience, traditional artisanal small-scale fisheries based in a specific location have made sure that they do not over-fish the available resources. Any attempt to increase production can jeopardise this well-established equilibrium.

It may nevertheless be possible to increase production without endangering the resources. Such an opportunity exists in cases where the stocks fished are utilised at a level below that guaranteeing optimum yield and sustainability. The same applies if fishing activities are extended to those components of the biocoenoses within the ecosystem that were previously utilised very little or not at all.

However, utilisation of additional species may be limited by the food relationships between various components of a biocoenosis. If the prey of a predatory fish starts to be utilised in addition to the fish itself, the potential yield that can be derived from the predatory fish is automatically reduced, as the food supply has been curtailed. Since many such relationships exist, it is essential that they should be carefully reflected in the management models if it is intended to simultaneously utilise a variety of different organisms within a single ecosystem.

In management of fishery resources, a key role is played by the nature of the gear used as well as by when and where it is used. Modern fishing gear can be highly efficient (i.e. may jeopardise the existence of stocks if no restrictions are imposed on its use) and highly selective. Fishing gear is considered selective if it catches only particular species or size categories of organisms. Its selectivity can be determined by net mesh size, hook size, or the depth of water or depth zone in which it is used. The most important fishery management measures include closed seasons, protected areas, minimum mesh and hook sizes, limits on the number of sets of gear, boats or ships and on the times when they may be used, and stipulation of catch quotas and size categories for the organisms to be caught.

Stock management calls for a high level of training in fishery biology and adequate knowledge of fishery economics. Stock regulating measures should be discussed, agreed upon and implemented by the local fishermen acting on a collective basis.

Apart from the need to conserve the resources themselves, it is also essential to protect their living environment against influences that could raise problems in the short or long term; to this end, the physical, chemical and biological condition of fishing areas must be monitored. Product quality depends on the chemical and biological conditions of the water and on the sanitary conditions prevailing ashore (village hygiene). The destructive effects of using wood resources for smoking fish can be curbed in two ways: by employing energy-saving kilns which permit more rational use of wood and by ensuring appropriate management of the forest resources concerned. The amount of wood required for boat-building can be reduced by replacing dugout canoes with boats made of planks and by using alternative construction materials.

Where it is likely that infrastructure for landing places used in artisanal fishery can be modified or removed only with difficulty, such facilities should not be constructed unless their necessity and expediency have been thoroughly reviewed. Concrete structures can also mar the aesthetic value of their surroundings (tourism).

2.2 Small-scale aquaculture

Aquaculture offers considerably greater options than capture fishery as regards both the type of organisms to be produced and the production sites. The natural stocks of organisms suitable for aquaculture can be most effectively conserved if aquaculture controls the entire life cycle, beginning and ending with the reproductive stage, and does so not just for one or two generations but on a long-term basis. As yet, however, this is possible only in the case of a few aquatic organisms. The only way of overcoming this problem is to promote applied basic research in the fields of reproductive physiology and reproductive ecology.

The production site should be chosen with the aim of conserving natural ecosystems and scarce water resources. The choice of the type of organism to be produced can contribute to conserving heavily used food resources if preference is given to species whose food requirements can be met by waste products or by-products from other sectors. Such products can either be fed directly to the fish or be used to fertilise the water and thereby promote the multiplication of food organisms (algae, microfauna). This could, for example, reduce demand for fish meal as a constituent of fish food. However, producers have a tendency to concentrate on expensive organisms (e.g. certain species of predatory fish) which generally require food of extremely high quality.

Water quality within and downstream of an aquaculture facility is determined by management practices. Efforts must be made to ensure that as little leftover food as possible remains in the water and that the quantities of nutrients and pollutants washed out of the installation are kept to a minimum. The amount of leftover food can be minimised by gearing the quantities of food given and the frequency of feeding to the absorption capacity and appetite of the fish. If sizeable quantities of waste are nevertheless discharged (e.g. from intensively operated through-flow ponds), they can be caught in settling ponds and thus largely prevented from entering rivers and lakes.

Drugs for preventing and treating disease and for combating parasites should not be used in running water (through-flow ponds) for reasons of effectiveness and economy and should not be used at all in open systems (cages, pens), even if the fish then have to be transferred to special containers for treatment and are thereby exposed to stress situations.

The main way of saving energy in aquaculture is to obviate the necessity of pumping for the purpose of water renewal. Introducing new water benefits the oxygen supply and helps to wash out wastes, besides compensating for evaporation and seepage losses. The extent of the necessary water replacement depends largely on the stocking density. Pumping energy can be saved wherever natural gradients can be used to create a water flow. Artesian springs are sometimes also available.

Considerable ecological advantages are offered by ponds in which wastes can be utilised by plants and microfauna which for their part are suitable as food for productive aquatic organisms. Such ponds can be fertilised by livestock (poultry, pigs) kept above or next to them. The profitability of this type of integrated aquaculture depends on the ecological appropriateness of the aquatic organisms kept, their popularity with consumers, the production costs and market prices. A role is also played by the way in which aquaculture is integrated into the overall production system, which usually involves other forms of production requiring labour. It is important, however, to know what constitutes the basis of the microfauna's food supply (there is a risk that pesticide residues could find their way into the food chain).

When setting up ponds in tropical countries, it is essential to bear in mind the risks originating from diseases whose pathogens spend at least one stage of their life cycle in water or in aquatic organisms (malaria, schistosomiasis etc.).

Cage farming not only involves high feeding costs, but also gives rise to problems in procuring the necessary materials for making the cages, as nets, support rods and floats are expensive. Only in forested regions is the use of wood unlikely to present any problems.

Elimination of potential health risks attaching to consumption of aquaculture products must be given particular attention wherever human excrement and domestic wastewater are used for fertilising ponds. In wastewater aquaculture systems, the critical factors in this respect are the number of pond stages, the degree of dilution and the period for which the water is retained before it enters the fish ponds. Accurate management, along with regular checks on sanitary conditions and water quality, are essential in such cases.

2.3 Use of artificial lakes in fisheries and aquaculture

As use of artificial lakes involves a combination of fish farming and fishing (and can thus be placed in the category of "culture-based capture fisheries"), the environmental protection measures described in both 2.1 and 2.2 above are of relevance in this connection. However, the fact that an artificial lake is a man-made entity creates a substantially different situation, both in limnological and ecological terms as well as from the sociological and economic viewpoints. Man-made lakes

differ from natural ones by virtue of their artificial nature, the fact that they are subject to continuous management to enable them to fulfil their primary purposes (drinking-water supplies, energy generation, irrigation), their initial biological "void" which - depending on the actual and to some extent random sequence of colonisation by flora and fauna - can offer scope for a variety of biological development possibilities, and last but not least the new options which this may offer in terms of fisheries and aquaculture. While an artificial lake thus allows man a considerable degree of freedom in shaping ecological conditions, it nevertheless confronts him with far-reaching social and economic problems when it comes to developing and establishing the ways in which it is to be used.

Two important principles should be observed when determining how a new artificial lake is to be used:

- Organisms that are foreign to the ecosystem and region concerned should be introduced only with strict observance of internationally recognised precautionary measures or not at all.
- No attempt should be made to regulate fishery activities until local traditions have been studied in detail; regulation measures should be realised in consultation with existing local fishermen and those willing to settle in the area.

When a new dam is being planned, consideration should be given to the various options for fisheries and aquaculture which the newly created lake will offer. Where appropriate, such aspects should be taken into account when deciding on dam design.

2.4 Fishery in the 200-mile exclusive economic zone

Optimum fishing of the 200-mile exclusive economic zone (EEZ) calls for use of advanced technology. This will inevitably lead to conflicts in the transition area between industrial deep-sea fishing and artisanal inshore fisheries unless depth conditions and coastline configuration create a natural division between the two. Such conflicts are often to the detriment of the available resources, causing them to be over-exploited or even destroyed. They may also adversely affect the economic and social position of the artisanal inshore fishermen, who usually come off worst in such conflicts if their interests are not effectively safeguarded through government intervention.

While old-established, traditional fishing communities have developed fishing practices designed to ensure that resources are preserved in the long term, the technical potential of modern deep-sea fishing - which can totally exhaust resources within a short time - means that use of resources must be strictly limited and monitored. Minimum mesh and hook sizes must be laid down to make sure that the gear does not catch young organisms which are not yet mature enough to reproduce and thereby preserve the existence of the fish stocks. Such regulations can also reduce the pointless destruction of small food organisms caught in the nets together with the fish.

The only way to prevent trawls with "ploughing" structures from causing serious damage to entire communities of sea-bed organisms is to ban the use of such gear. Depending on local conditions (sea-bed conditions, reproductive cycle and migration of fish or other organisms), use of such nets must be banned either completely, or in specific areas or at certain times of year.

Complete bans must be imposed on catching certain types of organism while they are still going through their development phase in the "nursery areas". As such bans are often impossible to enforce, efforts are being made in many places to create artificial refuges - in the form of submerged concrete blocks, for example - to which fish and other aquatic organisms can retreat and from which they can repopulate areas which have been subject to adverse influences or whose stocks have been exhausted. However, the effectiveness and cost-benefit ratio of these "artificial reefs" are still the subject of considerable debate.

The death of numerous fish and large marine fauna (dolphins, turtles, birds etc.) in lost drift nets made of plastic that does not decompose in water can be prevented by using degradable thread to attach the net sections to the floats. The net sections would then collapse after a time and sink to the bottom. However, this method appears to be too complicated for general use and it is not known what damage the nets might cause on the sea bed.

Considerable problems are still posed by the question of what to do with the "by-catch" (of non-target species), in other words the organisms with little financial value that are caught together with the highly lucrative species (e.g. prawns or shrimps) constituting the intended catch. These organisms are large or bulky enough to be retained by the net together with the main catch even if the minimum mesh sizes are adhered to. However, their market value is so low by comparison with that of the main catch that it is not worthwhile landing them, despite the fact that a considerable proportion of this "by-catch" would often be suitable for human consumption. If a worldwide solution to this problem could be found, for example by having the by-catch continuously collected by special boats at sea or by means of other methods, several million additional tonnes of fish would become available as food each year.

As is generally the case with motorised seagoing shipping, deep-sea fishing vessels' high consumption of fossil fuel necessitates special measures to dispose of residues on land. Environmental problems on land as a result of fishing stem primarily from industrial processing of the catch. Mandatory standards regarding disposal of solid wastes and wastewater must be observed; in some places such standards have still to be introduced. Some of the solid wastes can be made into fish meal, while valuable constituents of liquid waste can be recovered in the form of extracts and used as feed additives (cf. environmental briefs Inland Ports, Shipping on Inland Waterways, Wastewater Disposal and Solid Waste Disposal).

2.5 Use of mangrove swamps in fisheries and aquaculture

The traditional ways of using the flora and fauna in mangrove swamps can be viewed in the same light as artisanal small-scale fisheries in other areas: they take into account the regeneration capacity of the resources and are thus ecologically sound. However, this is not true of modern aquaculture on large fish farms whose construction necessitates complete clearance of the mangrove vegetation. One example of this type of operation is the large-scale raising of brackish-water prawns. As production of these much sought-after crustaceans can yield high profits, the potential suitability of mangrove swamps as sites for brackish-water ponds has given rise to dangerous pressure on these areas. Since mangrove areas are subject to the daily ebb and flow of the tide, the water has the necessary salt content and water replacement can be achieved at relatively little expense because the tidal cycle can be used to minimise the amount of energy required for pumping.

Efforts should be made to counter the pressure on the mangrove swamps in as realistic and flexible a manner as possible. The paramount principle should be that no form of use is to be permitted without thorough advance planning. The principal purpose of such planning is to completely rule out non-traditional use of areas which are irreplaceable as nature reserves, genetic resources, nursery areas for important aquatic organisms or protective belts guarding against coastal erosion. Clearance of mangrove swamps for the purpose of aquaculture can also be prevented by making areas immediately upstream of the mangrove belt available for the creation of ponds. Provided that the installations are well-managed, the necessary pumping costs could be offset by earnings.

Where use of mangrove swamps appears unavoidable for economic reasons, activities should be concentrated in areas with clayey soils. In such areas the mangrove vegetation can easily re-establish itself if the ponds (or swamp-rice fields) are abandoned at a later date, whereas areas with sandy and peat soils will be nothing more than wasteland for a long time afterwards. Continuing efforts should also be made to find ways of utilising the natural productivity of suitable mangrove areas for semi-intensive small-scale aquaculture, without clearing them of all vegetation

and without major additional expenditure on feed or fertiliser. The success of such experiments will depend on whether or not it proves possible to keep costs down to a level ensuring that even low yields per unit of area offer attractive economic prospects.

3. Notes on the analysis and evaluation of environmental impacts

The environmental aspects of fisheries and aquaculture fall into five categories:

- impacts on the natural environment which have adverse effects on aquatic organisms but which do not stem from either fisheries or aquaculture (pollution of water through disposal of wastes from industry, agriculture and households or caused by nutrients, pesticides and residues being washed out of soil on land; water-resources management measures); such impacts may affect both fisheries and aquaculture.
- influences on the existence and renewal of fish resources resulting from their use (such influences relate only to natural stocks and not to those maintained and controlled by man, i.e. aquaculture is affected only where it is dependent on young organisms from natural stocks).
- environmental impacts caused by fisheries and aquaculture (disturbance of ecological equilibrium, impairment of water quality etc.).
- influences on use of resources (and thus on the resources themselves) caused by changes in the social and socio-economic situation of producers and consumers (e.g. as a result of population growth).
- effects of fishery and aquaculture activities on the social and socio-economic situation of producers and consumers (e.g. in the event of local overproduction without sufficient access to more distant markets).

Computer-aided simulations of both the ecological and economic situation, using a standard model, can help to ensure that natural fish resources are optimally utilised in a manner which preserves their capacity for renewal. Such models are essential for developing a reliable long-term utilisation strategy which takes into account the economic interests of both the fishermen and the country concerned without jeopardising in the long run the natural resources on which fishing depends.

There as yet exist no summarising overviews or evaluations of the serious impacts which various modern techniques can have on resources (use of explosives and pesticides, bottom trawling, use of drift nets etc.).

Considerable efforts are currently being devoted to studying and evaluating the environmental impacts of aquaculture activities. In September 1990 the International Centre for Living Aquatic Resources Management (ICLARM) held a symposium on environment and aquaculture (results to be published in 1992).

4. Interaction with other sectors

Activities in the fisheries and aquaculture sector can be combined with agricultural production and with water resources development. The following are examples of the ways in which fisheries and aquaculture can be integrated with agricultural production:

- combining fish farming (or artisanal fisheries) with plant production and animal husbandry in an agricultural production system without physical integration of the individual components
- combining fish farming in ponds with keeping of poultry, pigs or other livestock above the ponds
- fish farming in swamp-rice fields

The following are examples of the ways in which fisheries and aquaculture can be combined with water resources development:

- fishing in artificial lakes of all kinds (including those designed to provide drinking-water supplies)
- fish farming in small, shallow irrigation reservoirs
- fish fattening in large irrigation canals
- cage fish farming in adequately large and deep artificial lakes not used to provide drinking-water supplies

(cf. environmental briefs Large-scale Hydraulic Engineering, Irrigation and Rural Hydraulic Engineering).

Fisheries and aquaculture also have extensive links with agriculture through the use of waste products, by-products and (in exceptional cases) main products of agriculture as food or fertiliser in aquaculture and through the use of fish meal in the production of livestock fodder (cf. environmental brief Livestock Farming).

Links with the forestry sector exist by virtue of the wood required for making boats and fishing gear, for preserving and processing fish by means of smoking and for making cages. The close ecological links between forests and waters are of particularly far-reaching significance and must be taken into account in both forestry and fishery activities.

Fisheries and aquaculture also have links with the energy sector through the operation of boats, ships and sophisticated fishing gear, fishing ports, refrigeration plants and industrial processing facilities, technically complex aquaculture installations and vehicles for transporting people, equipment, supplies and products.

Attention has already been drawn in the text to links with other sectors.

5. Summary assessment of environmental relevance

Fisheries and aquaculture are dependent on the existence of an environment which is intact or at least not permanently damaged, but can themselves have negative effects on the environment and on resources. As fisheries rely on continuous natural renewal of fish resources, activities in this field must treat these resources and their habitats with care.

Wherever resources have already been overfished and their habitats adversely affected by environmental changes, they must be rehabilitated if possible. Once fishing reaches a certain level of intensity, improved utilisation of catches is the only way of raising production. To this end, particular efforts should be made in the future to promote consumption of types of fish which are currently still unattractive from the commercial viewpoint and are simply used for making fish meal, and to ensure that fewer fish are lost as a result of spoilage.

Aquaculture is for the most part still a relatively new field of activity in the fishery sector. To promote its future development it requires tailor-made strategies which take particular account of the fact that most of the natural resources employed in aquaculture (water, land, feedstuffs; spawn in the case of most cultivated species) are already used for other purposes and can thus become sources of conflict. One of the most important strategic principles must therefore be to avoid such conflicts or resolve them with a minimum of adverse consequences in the ecological, economic and social spheres. This means, for example, that

- the impacts of aquaculture must initially be compared with those of other ways of utilising resources (e.g. mangrove forests as a means of preventing coastal erosion, tourism), with aquaculture activities then being designed as far as possible such that they complement use of water resources for other purposes;
- by-products or waste products that cannot be put to beneficial use elsewhere should be used as far as possible for feeding aquaculture organisms and fertilising the water. It is vital, however, that such products should be free of contamination (e.g. by pesticides).

Observance of the basic principles can be encouraged if the long-term advantages are demonstrated by effective examples and appropriate political and ecological conditions create a balanced combination of incentives and restrictions.

When involved in the development strategy and given appropriate training, women can play a key role in helping to prevent, reduce and eliminate environmental and health risks. Particular importance must be attached to awareness-raising measures that take religious considerations and cultural aspects into account.

6. References

Alabaster J.S. & Loyd R., 1980: Water quality criteria for freshwater fish. FAO/Butterworths.

Beveridge M.C.M., 1984: Cage and pen fish farming: carrying capacity models and environmental impact. FAO Fishery Technical Paper 255.

DANIDA, 1989: Environmental issues in fisheries development. Copenhagen.

Deutsche Forschungsgemeinschaft, 1980: Forschungsbericht: Methoden der Toxizitpran Fischen; Situation und Beurteilung. H. Boldt Verlag.

Dwippongo A., 1987: Impacts of trawl ban on fisheries and demersal resources in the Java Sea. Ph.D. Thesis, Nihon University, Tokyo.

FAO, 1975-1983: Manual of methods in aquatic environment research. Part 1 - 9.

FAO, 1981: Conservation of the genetic resources of fish; problems and recommendations. FAO Fish. Tech. Paper 217, 43 pp.

FAO, 1981: The prevention of losses in cured fish. FIIU/T219.

FAO, 1987: The economic and social effects of the fishing industry - a comparative study. FIP/C314/Rev. 1.

ICLARM, 1982: Mismanagement of inland fisheries and some corrective measures. Contribution 110.

Johannes R. E., 1981: Working with fishermen to improve coastal tropical fisheries and resource management. Bulletin of Marine Science 31.

Lasserre & Ruddle, 1983: Traditional knowledge and management of marine coastal systems. Biology International, Special Issue 4.

Metzner G., 1983: Fischtests im Rahmen nationaler und internationaler Regelungen. In: Untersuchungsmethoden in der Wasserchemie und
-biologie unter besonderer Berhtigung des wasserrechtlichen Vollzugs. Mr Beitr zur Abwasser-, Fischerei- und Fluiologie 27, 47-69.

Mienno J. L. & Polovinci J. J., 1984: Artificial Reef Project - Thailand. ADB.

Nauen C. E., 1983: Compilation of legal limits for hazardous substances in fish and fishery products. FAO Fishery Circular 764.

Pauly D. & Tsukayama I., 1987: The Peruvian anchoveta and its upwelling ecosystem: three decades of change. ICLARM Studies and Reviews 15. (IMARPE/GTZ/ICLARM).

Pauly D., Muck P., Mende J. & Tsukayama I., 1989: The Peruvian upwelling ecosystem: dynamics and interactions. ICLARM Conference Proceedings 18. (IMARPE/GTZ/ICLARM).

Rosenthal H., Weston D., Gowen R. & Black E. (Ed. committee), 1988: Report of the ad hoc Study Group on "Environmental impact of mariculture". ICES Cooperative Research Report 154, Copenhagen.

Ruddle K. & Johannes R. E., 1985: The traditional knowledge and management of coastal systems in Asia and the Pacific. UNESCO/ROSTSEA Regional Seminar. UNESCO Regional Office, Jakarta, Indonesia.

UNDP/FAO, 1982: Fish quarantine and fish diseases in South-East Asia. UNDP/FAO South China Sea Fisheries Development and Coordination Programme and IDRC.

UNESCO, 1984: Coastal zone resource development and conservation in S. E. Asia with special reference to Indonesia.

UNIDO, 1987: Environmental assessment and management of the fish processing industry. Sectoral Studies Series 28.

World Bank, 1981: Socio-cultural aspects of developing small-scale fisheries: delivering services to the poor. World Bank Staff Working Paper 490.

World Bank, 1984: Harvesting the waters - a review of Bank experience with fisheries development. Report 4984.

World Bank, 1985: Integrated resource recovery, aquaculture: a component of low coast sanitation technology. Technical Paper 36.

1. Scope

The fundamental components of agriculture are plant production and - based upon this - animal production. Agricultural machinery and implements are used by man for the purpose of influencing the natural process of plant and animal growth. Such mechanical aids can be divided into three categories on the basis of their energy source:

- hand-held implements
- animal-drawn implements
- motorised implements (with internal combustion engine or - less commonly - electric motor)

Agricultural engineering covers all aspects of using and manufacturing technical aids for agricultural production, the upstream and downstream sectors, and decentralised generation and use of energy in rural areas.

It is in plant production that agricultural engineering plays by far its most important role, although it is also becoming increasingly significant in livestock farming (intensive livestock husbandry). Mechanical aids are most commonly used in tillage and transportation, as well as in threshing and - where appropriate - for supplying water. As an area of project activity, agricultural engineering can thus be viewed in particular as an extension of the plant production sector; links frequently also exist with animal production, irrigation and agro-industry. The comments made in the relevant environmental briefs regarding objectives, impacts and protective measures apply by analogy.

2. Environmental impacts and protective measures

2.1 Man, ecosystem and agricultural engineering

2.1.1 Man and agricultural engineering

Agricultural operations are generally mechanised for reasons of labour efficiency, namely

- to raise per-capita productivity (worker performance) and
- to reduce the burden imposed by physical labour.

The changeover to a different source of power - i.e. from manual labour to animal traction to motorisation - brings major new technical and economic factors into play. This means that operation, maintenance and management must all meet correspondingly higher standards.

While the burden of heavy physical labour is reduced, work may subsequently become one-sided or monotonous. Animals or machines determine the pace of the work. Noise prevents communication and can adversely affect health, as can engine exhaust emissions.

Operators and other people can be endangered if machines get out of control. Moving parts (shafts, belts, rods) increase the accident risk.

Operation of machinery generally enjoys higher status than manual labour or handling of animals. Mechanisation can lead to changes in the division of labour and distribution of income, with "women's work" becoming "men's work" (seldom the reverse).

The way in which technical aids are used is generally the crucial factor determining whether they have positive or negative impacts. As motorised techniques tend to magnify errors, however, such methods can have considerably more serious negative effects than may result, for example, when hand-held implements are used.

It is particularly important that the right equipment be selected for a particular operation and that machinery and implements be used properly and at the right time. This can be achieved above all by training and advising the operators and by imposing legislative requirements (accident prevention, technical inspection etc.).

2.1.2 Ecosystem and agricultural engineering

As the degree of mechanisation increases, cropping areas and roads and tracks are geared to the demands of the machines and implements. Use of tractors and self-propelled machines such as combine harvesters - or indeed even the use of animal traction - calls for large cropping areas, which should be as free as possible of obstacles such as stones, trees and tree stumps.

Intercropping - i.e. simultaneous cultivation of several different crops in a single field - offers few opportunities for mechanisation and single-cropping systems therefore predominate. Following tillage, the surface of the ground remains unprotected for several weeks and may be exposed to the risk of erosion by wind and water. Broadcast sowing is replaced by row seeding; rows which follow the slope of the terrain can increase the danger of erosion by water. Roads and bridges, as well as irrigation and drainage channels, are often designed to meet the requirements of mechanisation. Ecologically valuable areas such as forests, hedges and fallow land are increasingly lost.

The spectrum of flora and fauna in a region may be diminished or altered; ecological diversity is reduced. An absence of windbreak vegetation in arable-farming areas increases the risk of erosion by wind.

Top priority must be given to promoting mechanisable land use systems which take both economic (including labour efficiency) and ecological aspects into account. Such production and farming systems have already been designed for certain regions (particularly in temperate climates) and their use is to be encouraged. Applied research and development work is still needed in other regions. It is not enough, however, to provide purely technical training and advice on proper use of machinery and implements. A new awareness is required on the part of all concerned (from agricultural workers to decision-makers) if the inherent potential of mechanisation is to be utilised and risks are to be recognised and reduced.

It is important to preserve refuges, forests, hedges, wetlands and other niches for flora and fauna. Such areas do not hinder large-scale mechanised farming, as there are few labour-related advantages in having cropping areas larger than 20 hectares. Row seeding is essential in order to permit mechanical weed control techniques, for example, to be used instead of chemical methods.

2.2 Agricultural engineering in general

2.2.1 Energy sources, drive systems, fuels and lubricants

The principal sources of power are manual labour, animal traction and engines or motors. Wind and water power are used all over the world to drive stationary machines (mills and pumps).

In many countries, biomass (particularly wood, but also straw and dung) is the major source of energy for cooking in rural areas (see also environmental brief Renewable Sources of Energy).

The demands of agriculture may sometimes compete with those of rural households. If draught animals are kept, land must be used for cultivating forage crops and is thus not available for growing food; use of dung as fuel deprives the cropping area of nutrients; both stationary and mobile engines (e.g. those of tractors) are still fuelled for the most part by non-renewable forms of energy, particularly petroleum products.

As such engines are not required to power vehicles travelling long distances, they emit only limited quantities of nitrogen oxides and carbon monoxide. Use of clean fuel and correct engine tuning can nevertheless help to minimise harmful emissions.

Where internal combustion engines are used (e.g. in tractors and water pumps), surface water may be contaminated by fuels and lubricants. The risk is particularly high in parking areas and workshop yards where fuel tanks are filled and oil changes performed.

The technical facilities used for transporting and storing fuels and lubricants are often in need of improvement. Tanks must be checked for leaks and contamination. Oil collectors for use during oil changes are to be provided and a used-oil processing system is to be set up. Negligence in handling fuels and lubricants (which can create fire hazards and lead to contamination of soil and water) can be reduced only by means of long-term training measures and appropriate technical facilities. Efficient governmental or private monitoring institutions (e.g. like Germany's water authorities and technical inspectorates (T)) must be established.

Use of biodegradable oils is to be promoted. Where power saws (whose chains require a great deal of oil) are used in water conservation areas, for example, only vegetable-based lubricating oils (rape-seed oil) should be employed as is the case in Germany. This regulation is to be extended to cover hydraulic oils for vehicles operated in water conservation areas. It is recommended that use of such oils in agriculture also be encouraged.

2.2.2 Production of technical aids

Hand-held implements and simple animal-drawn implements are often made by the family wishing to use them or by local craftsmen. Such production activities have few if any environmental impacts. The comments made in the environmental brief Mechanical Engineering apply in the case of industrially manufactured agricultural machinery and implements.

2.3 Specific aspects of plant production

2.3.1 Tillage

Loosening the soil with the aim of improving conditions for the crops plays a crucial part in arable farming. One purpose of turning the soil is to eliminate plants competing with the crop.

The extent to which the soil structure is changed depends on the form of tillage, which may involve

- loosening the soil with hooks or tines,
- turning the soil with the plough, or
- crumbling and breaking up the soil with a powered rotary cultivator or harrow.

If greater drive power becomes available, this may lead to selection of implements (e.g. rotary cultivator rather than plough) which modify the soil structure to a greater extent. In addition, less suitable (marginal) sites may be "put to the plough". Both of these steps increase the risk of soil degradation, which may involve reduction of pore volume, water absorption capacity and water storage capacity, the danger of puddling and crusting and a loss of organic matter. Crusting impedes water penetration and plant growth.

The optimum degree of soil moisture for tillage lies within narrow limits. If the soil is tilled when it is too wet it will be compacted, while tilling a soil which is too dry will result - depending on its clay content - in formation of clods or pulverisation. Compaction may assume sizeable dimensions if heavy tractors and implements are used.

Among other things, compaction of the soil has effects on plant growth, soil organisms and the availability and breakdown of plant nutrients and pesticides. On slopes, soil layers above the compacted horizon may slip.

Loosening of the soil and introduction of organic matter have positive impacts on the soil fauna. By contrast, compaction and puddling, frequent disturbance of the soil by tillage and application of pesticides and fertilisers all adversely affect the development of soil organisms.

Measures for preventing soil erosion and compaction include the following in particular:

- The soil should if possible have permanent vegetation cover in the form of living crop plants (permanent cropping, intercropping, alley cropping) or dead plants (mulch).
- Crops should be sown directly into the remnants of the preceding crop (without the soil being turned).
- Crop residues should be left on the surface and should not be ploughed under.
- Coarse soil structures are to be created or preserved through appropriate crop rotation measures and use of suitable implements.
- Contour ridges or terraces are to be created on slopes. This may be a somewhat complicated operation; there may be no vehicle access to the land in question.
- Windbreaks are to be planted at right angles to the direction of the prevailing wind.
- Organic matter is to be preserved and increased if possible.
- The pressure to which the soil is subjected when vehicles are driven over it is to be reduced as far as possible by using small/light-weight tractors and machines or larger tyres.
- Where possible, the soil should be driven over and tilled only when the moisture content is optimum.
- Shallow and deep tillage implements are to be used alternately over the course of time.

Emphasis must be placed on promoting a willingness to abandon excessive exploitation of the soil in favour of sustainable, site-appropriate forms of cultivation.

2.3.2 Sowing/planting, crop tending and fertilising

Sowing and planting, which are performed after the soil has been tilled, are intended to create optimum conditions for the growth of the seed or young plant.

After tillage, the soil may be totally or partly without cover until the crops have fully developed. It is thus exposed to the risks of erosion and to puddling as a result of heavy rainfall or severe evaporation.

With large cropping areas, mechanical aids are virtually essential for distributing chemical pesticides. Such equipment calls for highly skilled operators. Unsuitable, defective or incorrectly operated equipment can result in overdosage of fertilisers and pesticides, which will have negative effects on soil, plants and water as well as on the equipment users.

Application of highly concentrated liquid pesticides using the ULV (ultralow-volume) technique may lead to severe air pollution, with drift causing contamination over wide areas.

Pesticide users can be exposed to serious health hazards by touching or inhaling the chemical substances. It is often difficult to empty the containers completely and water used to rinse them out can contaminate surface water and drinking water. Pesticides and the equipment used to apply them are often stored improperly and are frequently kept in the same place as food for want of any other lockable rooms (see also the detailed remarks in the environmental brief Plant Protection).

Under unfavourable conditions, mechanical weed control measures (hoeing) can destroy the soil structure and encourage erosion; despite this fact, they should still be preferred to chemical methods.

Agricultural engineering can make a major contribution to ensuring that pesticides and fertilisers are used and applied correctly. Apart from selection of the right equipment, which is determined in part by the formulation of the agents used (e.g. powder or liquid), correct operation is equally important. If the time of application is appropriately chosen and economic-threshold concepts are used, quantities can be cut, drifting reduced and risks thereby minimised. Protective clothing, including face masks, is to be provided.

Under the climatic conditions prevailing in the tropics and subtropics, however, wearing of such clothing imposes considerable physical stress.

The stresses and risks for the equipment operators can be reduced to a large extent if the work is appropriately organised (e.g. operators proceed in the direction in which the wind is blowing).

2.3.3 Harvesting, threshing, processing, preservation, storage

The technical aids used in harvesting and threshing are intended to enable the work to be performed more easily and rapidly, besides minimising losses and risks. Harvesting and processing of "dry goods" (e.g. grain, burned-off sugar cane) can give rise to dust emissions which affect only a small area but are highly intensive. Such emissions affect people working and living in the vicinity, as well as animals. They can be reduced by taking technical measures at their source or their effects mitigated through the wearing of face masks and protective clothing.

Threshing and processing may yield by-products (glumes, hulls etc.). However, the quantities occurring at farm level do not constitute a serious environmental hazard, since the farm can generally utilise such products itself.

When crops are harvested, various substances are removed from the natural cycling systems on the site concerned. Efforts should be made to ensure that at least the by-products are returned to the soil either directly, after use for other purposes (e.g. as livestock fodder) or after composting.

Technical measures for preserving and storing produce at farm level seldom have any environmental impacts, unless chemicals are used. Crop drying calls for an energy supply, however, and in certain cases this may lead to over-use of local forest resources. Efforts to alleviate this problem should focus on ways of reducing energy consumption (heat sources).

2.3.4 Supplying and distributing water

To supplement the environmental brief Irrigation, attention must be drawn here to a number of important interrelationships and areas of overlap between these two sectors.

The water application and distribution system (gravity-flow method with open channels, pressure method with pipes or hoses) has a considerable influence on mechanisation:

- Channels determine the field size and bridges are needed to cross them.
- Small embankments and ditches in the field are damaged when driven over.
- Pipes have to be removed before a field can be tilled or urgent plant protection measures carried out.

2.4 Aspects of animal production

Pasture farming has always been the traditional form of livestock husbandry. The use of technical aids is confined to protective and security measures (pens etc.); the same applies to the keeping of small animals (e.g. poultry, rabbits, bees). It is not until livestock farming is intensified, with livestock kept in confinement, that technical aids become increasingly important. In industrialised countries where intensive animal husbandry is practised (particularly in Europe), technical equipment has come to play just as vital a role in livestock farming as it does in crop growing.

In poorly ventilated livestock housing, heat, dust and gases - particularly ammonia - can create stresses for both man and animal.

Sizeable quantities of ammonia can escape into the air when animal excrement is stored and applied to fields as manure. In industrialised countries, ammonia is one of the principal factors causing the gradual death of the forests in regions where intensive livestock husbandry is practised. One effective countermeasure is to make sure that solid or liquid manure is immediately worked into the soil.

Improper storage and spreading of animal manure can lead to over-fertilising (eutrophication) of both surface water and groundwater.

Protective measures must often focus first of all on bringing about changes in awareness, for only when this has been achieved can technical measures contribute to reducing negative environmental impacts. Animal excrement must be regarded and treated as a valuable fertiliser and not as waste. It is also important that this fertiliser be spread over the cropping area precisely in line with the plants' nutrient requirements. Only if such measures can be realised will it be possible to develop intensive livestock farming methods that are environmentally sound in the long term.

3. Notes on the analysis and evaluation of environmental impacts

Among the negative consequences of cultivation - magnified by use of mechanical aids - it is erosion that has by far the greatest significance worldwide. While there are numerous ways of reducing erosion (e.g. crop-growing measures such as mulching, technical measures such as terracing and planting of windbreaks), standards for evaluating the effect of erosion are largely confined to criteria for recording and assessing the removal of soil. Specific cultivation bans or requirements are occasionally imposed in the catchment areas of reservoirs particularly at risk from sediment.

Manufacturers of tractors and agricultural machinery in industrialised countries are called upon to fulfil widely varying national environmental requirements. These include

- standards and guidelines on design and durability;
- provision of safety devices, protective circuits etc., particularly for motorised vehicles and machines;
- provision of special equipment if the vehicles use public roads (danger to other road users);
- emission standards (exhaust emissions, noise).

Institutions performing official functions, such as agricultural-machinery testing stations, carry out type approval testing whose results are binding on manufacturers. Compliance with requirements is relatively easy to monitor.

It is far more difficult to ensure that regulations are observed by users. Safety devices may be removed, protective clothing and masks not worn or emission standards, speed limits and the like disregarded.

4. Interaction with other sectors

Agricultural engineering is closely linked to the following sectors:

- Plant production: agricultural engineering constitutes an extension of this sector in virtually every respect
- Plant protection: mechanical methods, application techniques
- Livestock farming: use of animal traction, intensive animal husbandry (still on only a small scale in developing countries, but extremely widespread in industrialised nations), livestock farming practices
- Irrigation: particularly supply, application and distribution of water, gravity-flow and pressure irrigation methods (sprinkling, drop irrigation)
- Agro-industry: primary products ("large-area products" such as grain and sugar), use of wastes
- Rural hydraulic engineering: correlation with plot size
- Renewable sources of energy (biomass)
- Mechanical engineering
- Mills handling cereal crops

5. Summary assessment of environmental relevance

The fundamental elements of agriculture are plant production and - based on this - livestock farming. Man uses technical aids in order to influence the production systems and enhance their productivity. Agricultural engineering is an integral component of these systems; its environmental impacts cannot be considered without reference to those of plant and animal production. Mechanical aids are most commonly used in tillage and transportation, with effects above all on soil, plants and man.

Among the negative consequences of cultivation, it is erosion that has the greatest significance worldwide. All other effects resulting from the use of technical aids in agriculture remain limited to the locality or at most the region concerned.

Improper storage and application of pesticides, mineral fertilisers and animal excrement can lead to contamination and/or over-fertilising (eutrophication) of both surface water and groundwater.

Most agricultural operations are mechanised for reasons of labour efficiency. Machines and implements call for a high degree of expertise in operation, maintenance and management if their use is not to have negative impacts. In many countries, responsibility for certain types of work passes from women to men.

Intensification of agriculture with the aid of agricultural engineering can lead to a change or reduction in the spectrum of flora and fauna found in a region.

The most important protective measures comprise

- provision of training and advice, and
- development and introduction of mechanisable land-use systems which take both economic (including labour efficiency) and ecological aspects into account.

6. References

Krause, R., F. Lorenz and W. B. Hoogmoed: Soil tillage in the tropics and subtropics. Schriftenreihe der GTZ No. 150, Eschborn 1984, p. 320.

Derpsch, R., C. H. Roth, N. Sidiras and U. K: Erosionsbekfung in Parana, Brasilien: Mulchsysteme, Direktsaat und konservierende Bodenbearbeitung. Schriftenreihe der GTZ No. 205, Eschborn 1988, p. 270.

Zweier, K.: Energetische Beurteilung von Verfahren und Systemen in der Landwirtschaft der Tropen und Subtropen - Grundlagen und Anwendungsbeispiele. Forschungsbericht Agrartechnik des Arbeitskreises Forschung und Lehre der Max-Eyth-Gesellschaft (MEG), Band 115, 1985, p. 341.

GTZ: Sustainable agriculture in German and Swiss technical cooperation. Register Nr. 15 der "Working paper for rural development", GTZ, Division 4210, Farming Systems, Eschborn, Feb. 1989, p. 148.

UNEP: Agricultural mechanisation. No., UNEP environmental management guidelines, United Nations Environment Programme, Nairobi, 1986, p. 17.

FAO: Agricultural mechanisation in development - guidelines for strategy formulation. Agricultural Services Bulletin 45, Rome 1984, p. 77.

World Bank: Agricultural Mechanisation - Issues and Options. A World Bank policy study. Washington D. C., June 1987, p. 85.

Examples of German regulations and standards:

BBA: Regulations laid down by the Biologische Bundesanstalt (BBA - German Federal Biological Research Centre for Agriculture and Forestry) concerning use of pesticides.

Berufsgenossenschaften: Accident prevention regulations (Unfallverhvorschriften) laid down by agricultural and industrial employers' liability insurance associations ("Berufsgenossenschaften").

DIN: German Standards and regulations on construction and design.

STVZO: Provisions of the German road transport licensing regulations.

TA L: Technical Instructions on Noise Abatement, 1968/1974.

TA Luft: Technical Instructions on Air Quality Control. First general administrative regulation accompanying the Federal Immission Control Act,

27 February 1986.

1. Scope

It is not just in arid climatic zones that irrigation and drainage are today increasingly coming to play an essential role in agriculture. Sprinkler systems or other types of irrigation schemes are also used in rain-fed farming to raise production and/or provide a safeguard against unfavourable weather conditions. Irrigation is the only way of permitting arable farming in some places at all; it has made it possible, for example, to reclaim what was once desert or steppe in countries such as Egypt, Israel, India and Mexico.

Apart from the demands of the market and the progressively more monetary nature of rural trade, it is above all rapid population growth that is making it necessary to introduce or improve (artificial) irrigation as one means of raising production on land which is in some cases in increasingly short supply. High growth rates are thus likely in this sector, which means that the importance of providing a water supply and the quantity of water required will both increase dramatically.

While in many places totally unutilised water resources are still to be found or existing resources are used on only a moderate scale, the provision of a water supply has already led elsewhere to immense and generally irreversible ecological damage.

Just as wastewater disposal plays a significant role in drinking-water or process-water supply systems (cf. environmental briefs Wastewater Disposal and Urban Water Supply), irrigation must always be accompanied by drainage measures. Although efficient drainage is often guaranteed simply by the natural structure of the terrain, planning of water conveyance systems frequently also has to address the question of drainage.

Failure to implement drainage programmes immediately after the introduction of all-year irrigation can lead to irreversible damage - primarily as a result of soil salinisation - and to a rise in the groundwater. Even small-scale irrigation projects have given rise in many countries to salinisation problems (= adverse influence on the soil's nutrient balance) in cases where no drainage system exists. Depending on soil type, between 10% and 20% of the irrigation water should be drained off in order to prevent long-term damage from salinisation.

In the light of the increasing demand for irrigation water and the related water supply and conveyance costs, there is a risk that drainage measures may be spread over a lengthy period of time or realised on as small a scale as possible. There is also a tendency for water-saving but more expensive conveyance systems to be over-hastily rejected on the grounds of cost in favour of open, unlined or overstrained low-tech systems. Insufficient use has been made to date of "appropriate" solutions which are not only inexpensive but also effective and thus help to conserve resources.

Irrigation covers the following areas:

- provision of a water supply through storage in small reservoirs, use of river water and tapping of groundwater
- conveyance and distribution of irrigation water by open channels and pipelines
- application systems of irrigation water by means of flooding, basins, border strips, rills, sprinkling, drop irrigation and subsurface
- drainage by means of open and concealed systems

This environmental brief is concerned only with small and medium-sized irrigation projects. It deliberately excludes large-scale dam projects and irrigation schemes for entire regions with measures involving entire river systems.

2. Environmental impacts and protective measures

Given that water resources are limited, water consumption is rising and irrigation and drainage systems are often inappropriate to their context, priority should be given to

- considering the question of water supply, as projects entailing large-scale utilisation of natural resources generally involve major environmental risks;
- making sure that irrigation and drainage measures are well matched;
- establishing whether the technology of the measures implemented is geared to the financial capacity of the country concerned and to other specific conditions (e.g. available technical know-how) and thus ensures that potential environmental hazards can be reduced or ruled out.

2.1 Impacts on components of the natural environment

2.1.1 Supply, conveyance and distribution of water

Depending on the activity involved, every aspect of the environment (soil, water, air/climate, species, biotopes/landscape) may be affected. Impacts on the soil vary in nature. The embankments of small reservoirs and open channels for conveying water can create erosion risks. All construction measures change (destroy) the soil structure, while irrigation itself alters the soil dynamics. The risk of erosion can be counteracted by stabilising embankments, for example with ground-covering plants having a dense root system.

A wide variety of impacts on water can be observed. Although small reservoirs improve the availability of surface water, they may also - depending on the subsoil - cause groundwater resources to become contaminated. In addition, small reservoirs too are liable to exhibit impairment of surface-water quality and the nutrient balance (particularly as a result of warming and eutrophication). It should be borne in mind that impounding measures in a particular area can reduce the available water supply in the lower reaches of the watercourse concerned. If rainfall is highly seasonal, however, the opposite effect is likely. If river water is used for irrigation the amount of available surface water will be reduced, while if the groundwater is tapped groundwater resources will be depleted. In the case of groundwater the quantity withdrawn depends not least on the tapping method. The easier (or in economic terms, the less expensive) it is to raise the water, the more wasteful the use of water resources may be.

The effect which tapping of groundwater has on the dimensions of water resources is of particular significance. This may apply even to small-scale schemes or micro-projects (e.g. where cropping areas are situated primarily on geological basement formations, often with few water reservoirs, or in wadi systems on the fringes of the Sahara). Tapping of fossil groundwater with no natural inflow will by definition exceed the available quantity. It thus constitutes destructive exploitation of a vital resource and should be permitted only in exceptional justified cases.

There is a danger that the groundwater may become contaminated if the sites where water is raised are left unprotected and/or if substances such as faecal matter or oil are discharged into the water.

In addition to having effects on the microclimate, small reservoirs also have an influence on the range of species found in the area. However, the precise nature of their impacts in the latter sphere is not clear. Certain species of flora and fauna may be destroyed or displaced, while the water and its surroundings may favour other species or indeed attract them. A (negligible) reduction in dry biotopes must be set against the creation of new aquatic biotopes. Wetlands may increase (above all around the edges of the reservoir) or decrease (as a result of reduced flow in the lower reaches of the watercourse). Increases and decreases in the presence of particular species may have both positive and negative consequences for man and nature. Particular attention must be paid to the effects of fluctuations in the reservoir's water level. It can be assumed that small reservoirs make for a more varied landscape.

Open water conveyance and distribution systems lead to water losses on account of evaporation and have a (slight) influence on the microclimate. Water conveyance systems in the form of earth cross-sections may have effects on flora and fauna; as is the case with small reservoirs, however, the precise nature of these effects is not clear. Depending on context, open water conveyance and distribution systems may enhance or mar the varied nature of the landscape.

Unless installed above ground, enclosed systems generally have only minor impacts on the natural environment.

2.1.2 Water application and drainage

Depending on the method used, water application - in other words the actual process of irrigation - can affect the soil to varying degrees. It is also likely to have impacts on water, species and the microclimate. The main problem encountered with many irrigation methods is that of soil salinisation, particularly if the system is poorly managed and there is no drainage. In simplified terms, salinisation can be defined as an extreme nutrient imbalance (excess of salts) and damage to the soil structure (puddling, crusting, compaction).

Traditional irrigation methods often involve water dosage problems (e.g. flood, basin, border-strip and furrow irrigation). The possibility of erosion cannot be ruled out where such techniques are used. Sprinkling and in particular drop irrigation may also lead to salinisation if not carried out properly.

Particular attention should be paid to methods in which modern components have been inappropriately added to traditional techniques. Water conveyance systems or application methods that gave rise to no problems in the past can cause erosion or scouring if the introduction of power pumps changes the way in which the water is supplied. It may be necessary for the entire system to be modified at considerable expense.

All irrigation methods can have adverse effects on the soil microflora and microfauna. When geared to local conditions and properly managed, however, irrigation can also contribute to the nutrient balance and benefit microflora and microfauna.

Drainage can do much to counteract the problem of salinisation. It thus contributes to the nutrient balance and to stabilising the soil structure. Water application methods can be used to achieve at least partial desalinisation.

Drainage ditches in the form of earth cross-sections create a risk of erosion. Impacts affecting water are likely to take two forms. Traditional irrigation methods, sprinkling and open drainage systems cause surface water to be lost through evaporation. However, traditional methods and drainage ditches in the form of earth cross-sections can also induce recharging of the groundwater. Where over-irrigation recharges the groundwater, the crops may be adversely affected because the groundwater level is too high.

In arid regions, seepage represents a waste of water and can lead to over-exploitation of resources. Priority should therefore be given to lining the water conveyance systems. Evaporation losses in conveyance systems tend to be negligible (e.g. 1 - 2% in desert regions compared to seepage losses of up to 85% from unlined water conveyance systems in sandy terrain). Traditional irrigation methods, sprinkling and open drainage systems can all have an influence on the microclimate. Depending on local conditions, their effects may be beneficial (e.g. as regards oasis ecology) or detrimental.

All water application methods are likely to have an influence on flora. The natural balance of species will generally be disturbed, while the number of species may either increase or decrease.

As only relatively small irrigated areas are involved, there are still enough refuges available to the local fauna to prevent permanent changes in the balance and number of species. The fauna are more likely to be affected by the enlargement and use of the cropping area per se and by the type of crop growing practised (cf. environmental brief Plant Production).

Open drainage ditches in the form of earth cross-sections can have influences on flora and fauna. As is the case for water conveyance systems and small reservoirs, however, the precise nature of these impacts cannot be defined. The same applies to the potential influence of such drainage systems on the diversity of the landscape.

2.2 Impacts on the socio-economic environment resulting from water supply, conveyance, distribution and application as well as from drainage

2.2.1 Factor requirements, labour, income and distribution

General assertions regarding impacts on the socio-economic environment are bound to be fairly vague, if indeed they are possible at all. In order to reach any conclusions, it is essential to analyse the circumstances of the particular case in question.

Technically sophisticated systems generally not only call for a sizeable input of capital but may also require a great deal of energy. Attention must be drawn to the possibility of using small reservoirs and water conveyance systems in generating energy and of meeting energy requirements by using renewable energy sources. One way of reducing the amount of external energy required is to make use of the available water power in cases where irrigation water is obtained from rivers (water wheels with a lift ranging from 0.5 m to over 20 m).

The major problem encountered in operating irrigation schemes involving new technologies is generally that of meeting the considerable training and management needs. Introduction of irrigation systems is usually also accompanied by a move in the direction of technically more sophisticated and more intensive forms of agriculture, which are not automatically accepted everywhere. A great deal of advice and encouragement is required if this difficulty is to be overcome.

Women are often excluded from discussion, extension services and training measures, even though they may be responsible for certain areas of farm work or may be farmers in their own right. This factor is of particular significance when traditional technologies are to be replaced by new ones.

Construction and operation of irrigation systems necessitate a considerable amount of extra work, particularly when labour-intensive techniques are used, and in many societies it is primarily women who bear this additional workload. Income levels are satisfactory, however, especially in the case of capital-intensive methods. Social disparities may be increased.

The introduction of irrigation frequently brings financial disadvantages for women. It is often only the men who are registered as the owners of the land covered by irrigation schemes; in other cases, men may simply appropriate the irrigated land, which is considerably more valuable than that used for rain-fed farming.

Farmers may run into serious economic problems on account of the fact that operating, maintenance and monitoring costs and expenditure on renewal of irrigation systems are often inadequately calculated at the planning stage, or as a result of sudden changes in government support policy (cuts in extension services, equipment subsidies and even water subsidies). It should be established whether the technical design and dimensioning of irrigation systems allow the systems to be used profitably by the farmers even under changed conditions.

It can generally be assumed that irrigation makes for more reliable yields and incomes. This is not the case, however, where workers are paid only for work performed over a limited period, for example during system construction or for seasonal work, the volume of which varies considerably. If women participate in this seasonal work their workload may be increased at the expense of other activities (feeding the family etc.).

Irrigation is likely to influence the distribution of income (and not just the relative incomes of men and women). Capital-intensive methods can place less prosperous farmers at a disadvantage and cause income distribution to become more unbalanced. Women are often excluded where conversion of land to irrigation is carried out on the basis of a loan scheme. Social distinctions generally increase in proportion to the technical complexity and cost of an irrigation system. Titles to land should therefore be distributed as widely as possible or upper limits set for ownership of land within specified areas covered by irrigation schemes.

It is important to make sure that women's traditional land-use rights are taken into consideration, for example by making certain that women too are entered in the cadastral register as land owners.

2.2.2 Health

Irrigation schemes are likely to create a variety of health risks. The main problems are caused by waterborne diseases, particularly schistosomiasis and onchocercosis, whose foci may be located at different points within the irrigation system (stagnant/flowing water). By virtue of the way in which it is transmitted (via human excretion), schistosomiasis in particular may well occur in areas being irrigated for the first time. Irrigated farming can also promote the spread of hookworms (Ankylostoma duodenale) and eelworms (Ascaris lumbricoides).

Malaria, which often spreads in areas where large irrigation schemes are being realised, can also constitute a problem in small-scale projects using open reservoirs and water conveyance systems. The possibility of rheumatic ailments and accident risks must likewise be taken into account. Health risks are liable to arise in cases where irrigation systems are also used to provide a drinking-water supply (see environmental brief Rural Water Supply). It is particularly important to raise women's awareness of these risks by means of targeted information and education measures, as it is usually women who are responsible for providing the family's drinking-water supply. Vector control measures (using chemicals) in turn create environmental hazards.

2.2.3 Subsistence, housing and leisure

Unless the land is used exclusively for growing non-food crops, irrigation schemes generally contribute to subsistence in that land owners grow food for their own consumption or workers are paid in kind. Particular efforts must be made during crop planning to ensure that food crops are grown (cf. environmental brief Plant Production). Irrigation in arid regions generally increases the range of food crops that can be grown.

Irrigation can cause damage to the fabric of houses where construction materials such as lumps of clay, tamped earth, air-dried clay bricks or materials of plant origin have been used. Houses on irrigated land can be protected against rising damp by being built with stone foundations.

Irrigation projects may have effects on leisure if they considerably increase the workload of the land owners and their families. This applies in particular in areas where only rain-fed farming was practised previously. It is often the women and children who are called upon to perform the extra work. In extreme cases this may prevent the children attending school or force the women to abandon other important activities.

Irrigation systems should not unnecessarily ruin the natural landscape or disrupt communications. The population should not be obliged to make long detours on account of changes in the landscape (e.g. pipelines installed above ground on supports or in/on embankments, or wide open channels). Adequate crossing facilities, including routes for driving livestock, should be provided (e.g. routes passing underneath system components, bridges).

2.2.4 Training and social relationships

Many irrigation methods or activities lend themselves to on-the-job training, although they often call for a high prior level of skill and know-how.

If activities can be organised and carried out on a communal basis, they can encourage participation and social interaction. Although irrigation can as a whole be seen as a communal task, it does not necessarily always help to consolidate social relationships. In many regions, irrigation establishes unrestricted private ownership of land for the first time, with the result that neighbourly cooperation is increasingly replaced by a system of hired labour.

It is above all women who are affected by the decline in communal activities (e.g. fetching water or washing clothes together, possibly also communal field work). In Islamic countries, for example, such activities give women an important opportunity for communication not afforded in any other way because of the restrictions imposed by social norms.

3. Notes on the analysis and evaluation of environmental impacts

General guidelines on quantitative water management exist in the Federal Republic of Germany. With the exception of technical guidelines for hydraulic engineering measures, however, there are no standards governing activities in connection with irrigation schemes. Standards could nevertheless be laid down to cover aspects such as

- permissible changes in the groundwater level resulting from tapping (lowering), seepage (rise) and drainage (lowering);
- reduction of flow where river water is used for irrigation purposes;
- limits on use of surface water, in order to prevent adverse effects on and/or destruction of aquatic organisms (defining minimum water quantity and depth etc.);
- the quality of the irrigation water, e.g. in order to prevent soil salinisation;
- the degree of salinity of flowing water where it receives discharges from drainage systems, etc.

The following could also serve as the starting points for standards governing measures affecting the water balance:

- The quantity of groundwater used must not exceed the medium-term recharge rate (often difficult to ascertain).
- Fossil groundwater may be tapped only in cases of extreme need.
- The low-water flow represents the critical factor for surface water quality when water is drawn off.

4. Interaction with other sectors

The environmental brief Plant Production should be additionally consulted in order to assess the impacts originating from crops grown on irrigated land.

The individual areas involved in irrigation also interact with other agricultural subsectors, including the following:

- Plant protection, in respect of the need to ensure that irrigation and drainage water is free of pollutants, for drainage water particularly in cases where it is discharged into surface water or groundwater
- Livestock farming
- Fisheries and aquaculture
- Agricultural engineering, e.g. in connection with use of organic manures and mineral fertilisers and their possible polluting effects

Use of water resources for irrigation purposes may conflict with other interests, above all in the light of the general demand for conservation of natural resources. Utilisation of artesian and/or fossil groundwater represents just one example of such a conflict. Other conflicts may arise with respect to the wastewater and rainwater subsector, leading to impacts on health in particular.

In certain cases there may also be links with

- large-scale hydraulic engineering, in connection with dams and weirs;
- rural hydraulic engineering, above all in connection with weirs (use of water for irrigation), contour canals and small earth embankments forming part of water storage facilities;
- wastewater disposal, in connection with disposal of wastewater by means of discharge onto agricultural land or into receiving waters (surface waters).

5. Summary assessment of environmental relevance

Irrigation systems of virtually every degree of technical complexity can be planned and constructed with a minimum of environmental (and social) impacts provided that the scheme incorporates measures appropriate from the ecological, technological, economic and social viewpoints. Caution must be exercised during assessment, as financial constraints and other criteria often restrict essential measures to a minimum. The technical practicality of an irrigation system must be established, since it represents an important prerequisite for success. Although raising technical standards may have impacts on the natural environment, it is above all within the context of the socio-economic environment that problems are most likely to arise.

The small-scale irrigation projects discussed here are bound to have fewer impacts than measures which involve large-scale hydraulic engineering schemes or raising large quantities of groundwater. The potential technological solutions are often interchangeable; in other words, a number of different options may produce the same result, making it possible to choose the soundest alternative from the environmental viewpoint. It should be remembered that traditional irrigation technologies may well be geared to the natural environment, but can cause environmental problems if used in combination with "modern" technologies. Where appropriate combinations of old and new technologies are used, however, they can help to prevent negative impacts on both the natural and social environment.

6. References

Basic literature

Achtnich, W. (1980): Bewerungslandbau. Stuttgart.

American Society of Agr. Engineers (1981): Irrigation Challenges of the 80's. The Proceedings of the Second National Irrigation Symposium. Lincoln/Nebraska.

Baumann, W. et al. (1984): ologische Auswirkungen von Staudammvorhaben. Forschungsberichte des BMZ Nr. 60, Cologne.

Biswas, A. K. (1981): Role of Agriculture and Irrigation in Employment Generation. ICID-Bulletin 30, 46-51.

Bher, J.-U. (1983): Umweltvertrichkeitsprund planerisches Abwngsgebot in der wasserrechtlichen Fachplanung. Bonn (Jur. Diss.).

Deutsche Stiftung fernationale Entwicklung DSE [German Foundation for International Development]/UNEP (1984): Environmental Impact Assessment (EIA) for Development. Feldafing.

Feachem, R. et al. (1977): Water, Wastes and Health in Hot Climates. New York.

Framji, K. K. (1977): Assessment of the World Water Situation. Irrigation Systems in Total Water Management. ICID-Paper, UN Water Conference, Argentina.

Framji, K. K. and Mahajan, I. K.: Irrigation and Drainage in the World. A Global Review (ICID). New Delhi.

Fukuda, H. (1976): Irrigation in the World. Comparative Developments. Univ. of Tokyo Press. Tokyo.

H, R. (1988): Entwicklungstendenzen der Beregnungstechnik im internationalen Vergleich, in: Zeitschrift ferungswirtschaft 23, 111-143.

H, R. (1988): Verbesserte Methoden der Wasserverteilung im Bewerungslandbau, in: Der Tropenlandwirt, 89 Jg., 143-163.

H, R. and Wolff, P. (1990): Fortschritte in der Technik der Oberflenbewerung, in: Z. fturtechnik und Landentwicklung 31, 34 - 43.

Huppert, W. (1984): Landwirtschaftliche Bewerung. Ein konzeptioneller Rahmen fblembezogene Projektanse, Vorentwurf. Band 2, Anlagen. Anhang 2 - Umweltvertrichkeit von Bewerungsmaahmen, GTZ Division 15. Eschborn.

Jenkins, S. H. (1979): Engineering, Science and Medicine in the Prevention of Tropical Water-Related Diseases. Progress in Water Technology 11.

Jensen, M. E. (1981): Design and Operation of Farm Irrigation Systems. ASAE Monograph. St. Joseph.

Larson, D. L. and Fangmeier, D. D. (1987): Energy in Irrigated Crop Production. Trans. ASAE 21, 1075-1080.

McJunkin, F. E. (1975): Water, Engineers, Development and Disease in the Tropics. AID, Dep. of State, Washington D.C.

McJunkin, F. E. et al. (1982): Water and Human Health. AID, Dep. of State, Washington D.C.

Mann, G. (1982): Leitfaden zur Vorbereitung von Bewerungsprojekten. Forschungsberichte des BMZ 26, Cologne.

Rudolph, K. U. (1988): Die Umweltvertrichkeitsprbei der Planung und Projektbewertung wasserbaulicher Maahmen, in: Wasser, Abwasser 129 Heft 9, pp. 571-579.

Tillmann, G. (1981): Environmentally Sound Small-Scale Water Projects: Guidelines for Planning, Cooel/Vita.

Tillmann, R. (1981a): Environmental Guidelines for Irrigation, prepared for USAID and US Man and the Biosphere Program, New York.

U.S. Environmental Protection Agency (1978): Irrigated Agriculture and Water Quality Management. Washington D.C.

White, G. (ed.) (1978): L'irrigation des terres arides dans les pays en dloppement et ses consences sur l'environnement. UNESCO, Notes Techniques du MAB 8.

Wolff, P. (1978): Bewerungstechnik in der Evolution, in: Z. ferungswirtschaft 13, 3-20.

Wolff, P. (1985): Zum Einsatz von neuen Wasserverteilungssystemen - eine Betrachtung aus bodenkundlich/kulturtechnischer Sicht, in: Z. ferungswirtschaft 20, 3-14.

Zeitschrift ferungswirtschaft (cf. various recent volumes). DLG-Verlag, Frankfurt.

Zonn, I.S. (1979): Ecological Aspects of Irrigated Agriculture, ICID Bulletin 28 No. 2.

Institutional guidelines

Asian Development Bank (AsDB): Environmental Guidelines for Selected Agricultural and Natural Resources Development Projects, 1987.

BMZ: Compendium of Environmental Standards, 1987.

Commission of the European Communities (CEC): The Environmental Dimension of the Community's Development Policy (84) 605 Final, 1984.

Federal Republic of Germany (BMZ): Environmental Guidelines for Agriculture, 1987.

Food and Agriculture Organisation (FAO): The Environmental Impacts of Irrigation in Arid and Semi-Arid Regions: Guidelines, 1979.

FAO: Man's Influence on the Hydrological Cycle. Irrigation and Drainage Paper, Special Issue 17, 1973.

FAO: Irrigation and Drainage Paper 31: Groundwater Pollution, 1979.

FAO: Irrigation and Drainage Paper 41: Environmental Management for Vector Control in Rice Fields, 1984.

FAO: Preliminary Operational Guidelines for Environmental Impact Studies for Watershed Management and Development in Mountain Areas, 1979.

FAO: Environment Papers No. 1: Natural Resources and the Human Environment for Food and Agriculture, 1980.

FAO: Soils Bulletin No. 44: Watershed Development - with Special Reference to Soil and Water Conservation, 1985.

FAO: Soils Bulletin No. 52: Guidelines: Land Evaluation for Rainfed Agriculture, 1983.

FAO: Soils Bulletin No. 54: Tillage Systems for Soil and Water Conservation, 1984.

FAO: Soils Bulletin No. 55: Guidelines: Land Evaluation for Irrigated Agriculture, 1985.

FAO: Conservation Guides No. 1: Guidelines for Watershed Management, 1977.

FAO: Conservation Guides No. 2: Hydrological Techniques for Upstream Conservation, 1976.

FAO: Conservation Guides No. 8: Management of Upland Watersheds: Participation of the Mountain Communities, 1983.

FAO/UNESCO: Irrigation, Drainage and Salinity. London, 1973.

International Union for the Conservation of Nature and Natural Resources (IUCN): Ecological Guidelines for the Use of Natural Resources in the Middle East and South West Asia, 1976.

Organisation of American States (OAS): Environmental Quality and River Basin Development: a Model for Integrated Analysis and Planning, 1978.

United Nations Educational, Scientific and Cultural Organisation (UNESCO): MAB Technical Notes Series No. 8: Environmental Effects of Arid Land Irrigation in Developing Countries, 1978.

UNESCO: MAB; Expert Panel on Project 4: Impact of Human Activities on the Dynamics of Arid and Semi-Arid Zone Ecosystems with Particular Attention on the Effects of Irrigation, 1975.

United Nations Development Programme (UNDP): Environmental Guidelines for Use in UNDP Project Cycles, 1987.

World Health Organisation (WHO): Establishing and Equipping Water Laboratories in Developing Countries, 1986.

WHO: Environmental Health Impact Assessment of Irrigated Agricultural Development Projects, 1983.

World Bank: Environmental Policies and Procedures of the World Bank (Operational Manual Statement OMS 236), 1984.

1. Scope

This brief describes the environmental consequences and potential means of pollution control in connection with the reconnaissance, prospection and exploration of geological resources.

Geological resources in the present context comprise mainly raw minerals and groundwater, with attention to soil being restricted to the reconnaissance aspect. Reconnaissance, prospection and exploration are the terms used for steps taken in preparation for the commercial extraction, i.e., utilization, of geological resources. The environmental consequences of extracting, dressing, refining and distributing such resources are not dealt with in this brief. The entire petroleum/natural-gas exploration complex has also been excluded. Those areas and related sectors are investigated in separate briefs.

The purpose of reconnaissance, including stock taking and mapping of resources, is to obtain regional overviews and to identify and demarcate mineral prospects and/or pedological location factors.

Prospection aims to locate prospects and exploitation areas by way of geological, geophysical and geochemical methods of field investigation.

Exploration - the detailed study of prospective areas - uses the same methods as those employed for prospection, but also involves direct disturbance of the environment.

While there are various basic types of reconnaissance, prospection and exploration projects, their respective environmental impacts depend primarily on the individual activities involved.

Both direct and indirect geoscientific methods are employed in the reconnaissance, prospection and exploration of geological resources. As a rule, the indirect methods yield less accurate results but offer the capacity for covering large areas at low specific expense. More precise, and substantially more expensive, direct methods applied preferentially to prospective zones and already identified anomalies or deposits enable the refinement of data bases. The raw minerals sector, for example, employs the following methods of investigation (listed in the order of increasing exactitude):

- interpretation of satellite photographs
- interpretation of aerial photographs
- interpretation of thematic geoscientific maps
- interpretation of geophysical test data
- interpretation of borings with the help of geochemistry and well logging; analysis of core samples
- investigation of explored deposits via shafts and tunnels
- interpretation of dressing tests

Groundwater prospection investigates the demand for water, its quantitative management, quality and protection, and the ecological consequences of its extraction (for details, cf. section 4). The protection-worthiness and sensitivity of the existing ecosystems, the volumetric and pollution-load capacities of the receiving waters, the effects of relevant road-building measures, and the social, sociocultural and ecological impacts of the anticipated settlement effects must be duly considered and assessed (for details, cf. section 4).

The "soils" subsector involves the evaluation and assessment of soils on the basis of soil surveys and the appraisal of soil utilization potentials. Moreover, measures designed to protect the soil from erosion, salinization and the effects of fertilizers and plant phytopharmaceutical products demand appropriate illumination.

2. Environmental impacts and protective measures

The environmental consequences of the subject sectoral measures are extensively limited, and the relevant protective measures are for the most part uncomplicated and inexpensive. Unavoidable damage of tolerable extent demands settlement by material compensation.

Reconnaissance, prospection and exploration activities can impose various hazards on the environment. The environmental consequences tend to increase as the activities progress from reconnaissance to prospection to exploration. In the first two cases, the impacts are usually modest and temporary. Exploratory measures are more elaborate and expensive, and the cost factor therefore helps retard their excessive implementation.

The main purpose of protective measures is to minimize the environmental consequences and to prevent environmental damage with respect to both time and space. The avoidance of permanent damage is especially important. Since geological resources are immobile, field investigations are usually limited to a particular site. Proper consideration of seasonal weather conditions can help avoid damage to the environment, e.g., by performing such work outside of the growing/breeding season.


Potential forms of environmental damage resulting from geological reconnaissance, prospection and exploration

Damage to the environment can be extensively avoided, or at least limited, by:

- careful execution of exploratory work - e.g., by avoiding the use of heavy (and accordingly expensive) equipment - inclusive of soil- and water-protection measures, stabilization measures, recultivation, etc.,
- choosing environmentally benign (micro-)sites for (prospecting) lanes in order to minimize the environmental burden, e.g., through dissection; the same applies to the choice of locations for camps and support facilities,
- taking measures to prevent environmental mishaps, e.g., by installing traps for oil and chemicals.

Environmental consequences can also be limited by recovering and recycling materials and substances. Recycling is preferable to (controlled) disposal. The ultimate goal is to restore the site as closely as possible to the state it was in prior to commencement of the work, or at least to preclude lasting detriment to the environment.

2.1 Access to work area

2.1.1 Access roads

It is frequently necessary to fell trees and move earth to make way for access roads. The damage resulting from such activities can by far exceed that caused by reconnaissance, prospection and exploration. Moreover, establishing access to a previously inaccessible area can lead to such social consequences as public unrest and land speculation. Controlling access to such roads can help prevent the subsequent uncontrolled generation of settlements.

2.1.2 Lanes

Geophysical investigations may require the cutting of narrow lanes as footpaths. This can cause temporary damage to the vegetation and expose the soil and subsoil to erosion.

In the tropics and subtropics, much more so than in semi-arid regions, the vegetation is normally able to close off such lanes within a year or two, so that no permanent damage remains. Protective measures are rarely necessary. The inadvertent provision of general access to the area in question must be avoided.

In areas characterized by a very fragile balance of nature (marginal locations, slopes) it may be necessary to impose certain restrictions and to carefully accommodate the local situation, e.g., by disturbing as small an area as possible and reducing the felling of trees to a minimum. If farmland is involved, the competent authorities and those affected must be consulted with regard to compensation.

2.2 Topographical and geological mapping

Unless mapping activities are intensive and require extensive field checking, little impairment of flora and fauna need be anticipated.

2.3 Camps and support facilities

In many cases, permanent camps comprising lodgings, workshops, field laboratories, storeyards, etc. can be required. The attendant land use, sealing of soil and general detriment to and disturbance of local flora and fauna are disadvantageous. Controlled disposal of liquid and solid wastes must be ensured.

2.4 Geophysics

2.4.1 Airborne techniques

The noise caused by flyovers, most notably in connection with helicopter-assisted methods of surveying, is disturbing to local animal populations.

2.4.2 Prospection seismics

The environmental consequences of prospection-seismic activities (blasting) on lanes can be extensively minimized by carefully plugging the blasting charges in the boreholes. Such activities cause no permanent damage to the environment.

2.4.3 Nonseismic geophysical investigations

All nonseismic geophysical investigative methods involve the use of portable measuring instruments at or slightly above ground level (£ 1.5 m). The hauling and handling of the requisite equipment and the movements of personnel within the areas of interest can be expected to cause modest impairment of the local environment.

The electricity required for a camp and, possibly, for one or the other electric-powered piece of equipment may necessitate the use of a diesel- or gasoline-fueled generator. Environmental damage can result from improper or careless handling and storage of fuels and lubricants.

2.4.4 Well-shooting

Well-shooting is the term applied to measurements conducted in an existing borehole according to radiometric, electric, magnetic, acoustic, mechanical and thermal techniques to gain information on the immediate surroundings of the hole itself. Consequently, any effects on the environment are limited to the immediate vicinity of the measuring point - one exception to the rule being radiometric measurements performed with the aid of active radiation sources that require certain precautionary measures in connection with calibration and introduction of the probe - the loss of which must be avoided - into the borehole. Radioactive cores must be duly marked, and appropriate protective measures up to and including the services of a radiological safety officer must be taken in case of high-level radiation.

2.5 Hydrogeological investigations

2.5.1 Long-time pumping tests

The sustainable yield and/or groundwater permeability of wells and boreholes is determined by long-time pumping tests. Lowering of the groundwater level in the vicinity of the tested well can cause temporary detriment to other wells situated nearby.

2.5.2 Injection tests

Long-time injection tests serve in determining the sustainable injectivity of drainage wells. Such tests can temporarily alter the groundwater regimen. Care must be taken to ensure that the injected water is environmentally compatible.

2.5.3 Tracer tests

In karst areas, tracer tests are conducted to locate and determine watercourses and groundwater retention times. The methods employed rely on fluorescent dyes (1), radioactive substances (2), salts (3) and pollen (4). Tracers (1) and (4) have no

environmental consequences, although fluorescent dyes could be perceived as a visual infringement. The initial activity and concentration levels of tracers (2) and (3) must be kept low enough to avoid detrimental effects on the environment.

2.6 Exploratory work

Exploratory work serves to enable sampling activities. Depending on the depth of the planned sampling point and on the geological situation, different opening operations are appropriate:

2.6.1 Trial pits

The main environmental consequences of establishing a project result from removal of the local vegetation and soil. It is sometimes necessary to penetrate more deeply into the exposed rock, although such measures normally involve depths of a few meters at most. Cutting into a steep slope causes erosion. Upon completion of the exploratory work, the prospect must be refilled with the excavated material and separately stored topsoil to prevent aggravated erosion and accidents. Additional case-specific measures may be necessary to preclude erosion.

2.6.2 Shafts/tunnels

If boreholes and trial pits are insufficient for the envisioned scope of exploratory work, horizontal or slightly inclined tunnels and/or vertical shafts can be dug to enable underground reconnaissance, including sampling. Due consideration must be given to the fact that tunnels require appropriate entrances and that they tend to collect groundwater, possibly resulting in the dewatering/drainage of overlying rock. Special protective measures may be required in connection with the location and exploration of uranium deposits. In the absence of appropriate national directives, the radiation protection ordinance of the Federal Republic of Germany should be applied accordingly.

Major exploratory operations quickly equate to regular mining operations, the environmental consequences and relevant protective measures of which are dealt with in detail in the respective sections of this handbook.

Tunnel faces and shaft mouths must be closed off for safety reasons whenever the work is interrupted and following its completion.

Any shaft or tunnel that interrupts the flow of groundwater can simultaneously jeopardize its quality. Consequently, when the work is finished, all such holes should be completely refilled. As long as the work is ongoing, shafts must be secured to prevent unauthorized access and accidents. If regular measures are not possible, a sturdy cover must be installed.

Dug wells providing potable water in rural areas of dry-climate regions are especially important. If the exposed groundwater is not effectively protected against pollution, such wells can have negative qualitative effects on the environment. The same applies in essence to groundwater trial pits, while groundwater stemming from an adit is, as a rule, hygienically unobjectionable.

2.6.3 Drilling

Drilling serves as a means of subterranean geological exploration. It allows geological surveys, geophysical measurements and sampling. Pumping tests are conducted for hydrogeological purposes (cf. 2.5.1). Drilling can cause a substantial noise nuisance, with attendant disturbance of the local populace and animal life. Thus, all requisite active and passive means of noise control must be adopted, and the applicable work safety directives in particular must be followed.
Depending on the climatic zone, some extent of land may have to be cleared around the drilling site.

Wells and boreholes are potential hazards for groundwater. In the absence of protective measures, detrimental effects can result from cutting through confined groundwater (artesian, for example), from interconnecting different groundwater stories (possibly of divergent quality), and/or from piercing the bases of multiaquifer formations.

Bleeding artesian wells are a waste of groundwater reserves and can do damage to the borehole environs, e.g., by causing the soil to salt up. The hydraulic interconnection of different groundwater stories can detract from both the quantity and the quality of the entire resource. Intermediate groundwater stories can drain out to such an extent that wells run dry and the work of fetching potable water - mainly by women - for household purposes increases in relation to the distance to the next intact well.

Appropriate technical measures, however, can be taken for drilling operations (pressure regulating valves, special flushings, packers, clay seals) to prevent such damage. In areas with a relevant hazard potential, the geological and technical aspects of drilling must be carefully planned in all detail, with all the appropriate equipment provided and properly serviced. (For details, please refer to the environmental brief Petroleum and Natural Gas.)

In semi-arid regions, drill bits often encounter aquifers filled with fossil, nonrenewable groundwater. Thus, in any such case the demand forecasts and proven reserves must be carefully balanced in order to avoid both an unprofitable investment and consequential damage to the ecology.

Drilling operations can also have negative environmental consequences as a result of drill cuttings, chemicals, process water and improper fuel storage procedures. The incidental drill cuttings and flushings must be collected and properly clarified at the end of the drilling operations, so that only cleansed wastewater is returned to the environment. The drilling site must be cleaned up and restored as closely as possible to its original condition.

2.6.4 Solid waste/dumps

Solid waste can derive from laboratory work as well as from exploration and production operations. All scraps, e.g., worn drill rods, must be collected and either properly disposed of or recycled. The same applies to sludgy residues from flushing operations.

Trial pits, tunnels and shafts yield excavated material that requires temporary or permanent storage. The size of the requisite storage area depends both on how much material is excavated and on the local topography. Wind, precipitation and percolation can erode, leach, scour and elutriate excavation dumps and cause water pollution in the process. In particularly severe cases, the dump may slump or slide. The storage of any material with a high hazard potential, e.g., due to radioactivity, requires appropriate measures for:

- preventing washout and dust deflation,
- collecting wastewater/effluent (packing and possible percolation drainage) with subsequent clarification, and
- monitoring its discharge.

Environmental detriment attributable to erosion can be extensively avoided - and the dump's stability enhanced - by turfing, greenbelting or otherwise covering it.

2.7 Sampling

2.7.1 Surface sampling

Sampling for analytical purposes often requires either the removal of near-surface strata or the extraction of material from special-purpose exposures. In some rare cases, sampling can impose a burden on the environment in the form of noise given off by jackhammers. As a rule, though, such problems are short-lived and

not particularly serious. By comparison, the work involved in establishing exposures is more likely to have negative environmental impacts, as described in section 2.6.

2.7.2 Marine sampling

Marine sampling operations can have environmental consequences for ecosystems in shelf waters as well as in the deep sea: alteration of the seafloor morphology, disruption of pediment, destruction of marine life, turbidity.

The following techniques and technology must therefore be employed for minimizing such effects:

- exploration of the seafloor via TV probes in order to confine and delimit the sampling area,
- selective sampling with TV-guided grabs,
- no large-scale clearance or scavenging of the seafloor,
- separating the sludge and fine slush from the liquid phase (undissociated suspensions can jeopardize marine fauna, especially if they get into the photic zone.),
- avoiding the local release (into the seawater) of acidic processing residues.

In some cases, in-situ analytical instruments use radioisotopes as a source of excitation, with a possible attendant (normally harmless) increase in radioactivity.

2.8 Laboratory testing

2.8.1 Laboratory analysis

Activities in connection with chemical and physical laboratory testing and analysis can yield substantial amounts of solid, liquid and gaseous wastes, some of which may contain toxic reagents. Exhaust air and exhaust gases may require filtration or scrubbing, while liquid wastes and effluents can be neutralized, precipitated, clarified, separated, etc. Organic solvents must be collected and the escape of noxious fumes and vapors to the atmosphere prevented. Additionally, appropriate

measures must be adopted to ensure either the orderly disposal (incineration, dumping, ultimate storage) or recycling of liquid and solid waste products. The environmental brief Analysis, Diagnosis and Testing contains pertinent information in detail.

2.8.2 Dressing tests

Deposit exploration projects sometimes necessarily include dressing tests. The incidental wastewater must be collected in settling tanks and appropriately treated to the extent that it contains substances capable of polluting the recipient body or groundwater; cf. environmental brief Minerals Handling and Processing.

3. Notes on the analysis and evaluation of environmental impacts

Distinction must be drawn between the environmental consequences dealt with in section 2 and those which may result from follow-up measures. Any study, expert opinion or commentary prepared in connection with such projects should include references to the potential environmental impacts of subsequent project implementation. Even at the initial reconnaissance and exploration stage, such consequential effects should be appraised. If necessary, pertinent studies must be conducted in parallel with the prospecting activities. Such preliminary studies should focus on the data requirements of the subsequent environmental impact assessment. Section 4 and other environmental briefs offer further-reaching information on the scope, evaluation and possible countermeasures.

4. Interaction with other sectors

The following other environmental briefs are also of relevance:

- Spatial and Regional Planning
- Water Framework Planning
- Urban Water Supply
- Rural Water Supply
- Road Building and Maintenance, Building of Rural Roads
- Rural Hydraulic Engineering
- Large-scale Hydraulic Engineering
- Surface Mining
- Underground Mining
- Petroleum and Natural Gas - Exploration, Production, Handling, Storage
- Minerals - Handling and Processing
- Cement and Lime, Gypsum
- Glass.

The groundwater domain is a focal point of interest in that connection. Regional planning, in particular for rural development, is heavily dependent on access to properly protected groundwater, and timely evaluation of the potential environmental consequences of project measures is therefore of major significance. Diverse cross-links also exist between the groundwater domain and the mineral resources and mining sector, since potential environmental impacts often become apparent at the feasibility-study stage.

5. Summary assessment of environmental relevance

The project goals encompass preparations for the environmentally appropriate satisfaction of basic needs (e.g., access to potable water), the protective use of resources (such as water), appropriate use of soils, self-sufficiency in the environmentally sound exploitation of mineral and fuel resources and, as a result, improved employment perspectives in conjunction with the extraction and exportation of resources. Two of the most important project objectives are the transfer of know-how and the enhancement of environmental awareness.

As long as the project is carefully planned and executed with due regard for the described consequences and protective measures, activities in connection with the reconnaissance, prospection and exploration of geological resources can be expected to have only limited impacts on the environment.

Appropriate and available means of controlling or remedying environmental damage can be implemented with relatively modest inputs.

The subject studies and investigations also serve to supply the environmentally relevant data and information needed to achieve sustainable utilization of soil and groundwater and the protective extraction of nonrenewable mineral resources.

In connection with the implementation of protective measures, the interested and concerned parties must be made aware of environmental concerns. The analysis and evaluation of potential environmental impacts must be considered an integral part of the project appraisal phase.

Pertinent directives serve to ensure that:

- intervention in the environment is limited to the smallest possible, essential scope;
- unavoidable encroachments are accommodated to the natural situation;
- resultant damage is remedied or, if that is not possible, at least controlled;
- permanent damage is avoided to the greatest possible extent.

The necessary measures and corresponding responsibilities must be defined and established during the project planning phase.

Controls aimed at ensuring the success of the protective measures should be conducted during and at the end of the project.

Attention must be drawn to potential environmental consequences resulting from the continuation or expansion of a project.

6. References

Bender, F. (Ed.): Geologie der Kohlenwasserstoffe, Hydrogeologie, Ingenieurgeologie, Angewandte Geowissenschaften in Raumplanung und Umweltschutz. In: Angewandte Geowissenschaften III: Stuttgart (Enke) 1984.

Der Bundesminister ftschaftliche Zusammenarbeit [BMZ - German Federal Minister for Economic Cooperation and Development] (Ed.): Sektorkonzept Mineralische Rohstoffe. Bonn 1985.

Der Bundesminister ftschaftliche Zusammenarbeit [BMZ - German Federal Minister for Economic Cooperation and Development] (Ed.): Umweltwirkungen von Entwicklungsprojekten, Hinweise zur Umweltvertrichkeitspr(UVP), Bonn 1987a.

Deutsche Gesellschaft fhnische Zusammenarbeit (GTZ) GmbH (Ed.): Consultant-Tag 1985, "Umweltwirkungen von Infrastrukturprojekten in Entwicklungslern". Sonderpublikation 1981, Eschborn 1986.

Doornkamp, J.C.: The Earth Sciences and Planning in the Third World. - Liverpool Planning Manual, 2. Liverpool (University Press & Fairstead Press) 1985.

Ellis, D.V.: A Decade of Environmental Impact Assessment Marine and Coastal Mines. - Marine Mining, 6, 4, New York, Philadelphia, London 1987.

FINNIDA: Guidelines for Environmental Impact Assessment in Development Assistance, Draft 15, July 1989.

Gladwell, J.S.: International Cooperation in Water Resources Management - Helping Nations to Help Themselves. - Hydrological Science Journal, 31, 4, Oxford 1986.

Loucks, D.P. & Somlyody, L.: Multiobjective Assessment of Multipurpose Water Resources Projects for Developing Countries. - Natural Resources Forum, 10, 1, New York, 1986.

McPherson, R.B., et al: Estimated Environmental Effects of Geologic and Geophysical Exploratory Activities, Office of Nuclear Waste Isolation (ONWI), Technical Report, December 1980.

Meyer, H.J.: Bergrecht und Geoforschung in Entwicklungslern. - Studien z. int. Rohstoffrecht, 10, Frankfurt am Main (Metzner), 1986.

Overseas Development Administration (ODA): Manual of Environmental Appraisal, without address, without year of publication.

Schipulle, H.P.: Umweltschutz im Rahmen der entwicklungspolitischen Zusammenarbeit der Bundesrepublik Deutschland - In: Tagungsbericht "Eine Umwelt fi Welten", 23.02.1988, Dortmund (Inst. f. Umweltschutz) 1988.

Urban, K.: Bewerung in Sahel - Eine kommentierte Literaturcht. - GTZ-Sonderpublikation, 217, Eschborn, 1988.

Zimmermann, G.: Strahlenschutz. 2. Aufl., Stuttgart (Kohlhammer) 1987.+ = 26959 Zeichen; dies entspricht 539,18 Zeilen oder 17,97 Seite(n).

1. Scope

Surface mining is the term used to describe diverse forms of raw-material extraction from near-surface deposits. It involves the complete removal of nonbearing surface strata (overburden) in order to gain access to the resource. Depending on the physical characteristics of the raw material and on the site-specific situation, various surface-mining techniques are applied:

Dry extraction of loose or solid raw materials: In hardrock mining, the product must first be "worked" (loosened). Then, it can be loaded, hauled and processed by mechanical means similar to those employed in loose-rock mining. Accordingly, dry surface mines require appropriate dewatering.

In wet-extraction, or dredging, operations, loose raw materials are mechanically or hydraulically extracted and transferred to a processing facility. The entire extraction equipment is normally located on/in the water, often floating on a river or artificial lake.

Offshore, or shelf, mining is the term used to describe the extraction of loose material from nearshore deposits (marine beach placers). Like in wet extraction, the material is excavated and conveyed by mechanical or hydraulic means.

Deep sea mining is a - future - form of mining in which raw materials are extracted from ocean beds; not to be dealt with in the present context.

The various surface mining techniques are applied to different types of raw material reservoirs.

Table 1 - Forms of surface mining and major raw-material products

Hardrock mining


Loose-rock mining



dry extraction


dry extraction


wet extraction


terrestrial

offshore

building stones diamonds gems feldspar gypsum limestone/ raw materials for cement

metalliferous ores (copper, iron, silver, tin) oil shale hard coal uranium ore

brown coal diamonds gold kaolin/ china clay phosphates sand, gravel

heavy minerals (ilmenite, rutile, RE-minerals1), zircon) clay tin ore

diamonds gold heavy minerals tin ore sand, gravel

diamonds heavy minerals (ilmenite, rutile, zircon, monazite) tin ore

1) RE-minerals = rare-earth minerals

Surface mines vary in size according to the nature of the deposit and the employed techniques of extraction. Among terrestrial workings, one encounters mines ranging in size from small one-man operations to huge strip mines measuring several kilometers in diameter. Due to the elaborate, expensive technology required, marine workings always strive toward minimum dimensions.

Since mining amounts to a site-bound activity, new and expanding operations often have to compete with other potential users of the premises in question, and the infrastructure required for surface mining operations may still have to be established. As regards the demarcation of surface mining activities, it is inherently difficult to separate them from the required mineral dressing facilities, because such processing normally takes place directly at the place of extraction.

2. Environmental impacts and protective measures

The environmental consequences of surface mining operations are strongly dependent on the project type. Consequently, this section distinguishes between impacts and control measures.

2.1 Potential environmental consequences of surface mining

Common to all surface mining activities is that their environmental impacts are both size-dependent and location-dependent, particularly with regard to climatic, regional and infrastructural contexts. For the sake of simplicity, the potential environmental impacts of surface mining operations are categorized in the following sections according to the employed type of raw-material extraction.

Table 2 - Forms of surface mining and their main environmental impacts

dry extraction

wet extraction

nearshore extraction

deep-sea mining

earth's surface

areal devastation; altered morphology: danger of falling rocks at the faces; destruction of cultural assets

areal devastation; altered morphology and river course; formation of large dumps

altered ocean-floor morphology; coastal erosion

air

noise; percussions from blasting; dust formation due to traffic, blasting, wind; smoke and fumes from self-ignited dumps; blast damp, noxious gases; vibrations

noise due to power generation, extraction, processing and conveying; exhaust gases

noise, exhaust gases

noise; exhaust gases

surface water

altered nutrient levels (potential eutrophication); pollution by contaminated wastewater; pollution by aggravated erosion

denitrification; burdening of recipient with large quantities of muddy wastewater; pollution by contaminated wastewater

turbidity; oxygen consumption; wastewater pollution

turbidity; oxygen consumption wastewater pollution

groundwater

recession of groundwater; deterioration of groundwater quality

altered groundwater level; altered groundwater quality

soil

denudation in the extraction area; loss of (agric.) yield, dryout, ground sag, danger of swamping due to local groundwater recovery, soil erosion

denudation in the worked area

altered seafloor; deterioration of seafloor nutrient content

deterioration of seafloor nutrient content

flora

destruction in worked area; partial destruction/alteration in surrounding area due to altered groundwater level

destruction in the worked area

fauna

expulsion of fauna

expulsion of fauna

destruction of stationary marine life (corals)

destruction of stationary marine life (corals)

humans

land-use conflicts; induced settlement, destruction of recreation areas

land-use conflicts; social conflicts in boom times; induced settlement

impaired fishing (destruction of spawning grounds)

impaired fishing (destruction of spawning grounds)

structures

water damage due to groundwater recovery

mis-cella-neous

potential modification of microclimate

modification of microclimate; growth of pathogens in still-water areas

2.1.1 Dry extraction

Differentiation is made between loose-rock and hardrock mines. Wherever necessary, the following sections include reference to specific influences. The environmental consequences are broken down according to physical, biological and social effects.

· Physical environmental impacts of dry surface mining

In essence, the foremost environmental impact of surface mining is the extraction of nonrenewable resources. The processes and activities involved in the extraction of a raw mineral can involve mining losses, free-standing ore pillars, presently uneconomical sections of deposit, overcutting, etc., with resultant destruction of sections to the extent of their becoming inaccessible for future extraction. The strip mining of carbonizable or combustible raw materials such as coal or peat can lead to the destruction of resources by fire (seam fires).

The space requirements of surface mining operations can be quite substantial, comprising the quarry itself and dumps for overburden, which can be very sizable for deep hardrock mines (e.g., open-cast ore mines), tailings heaps, which also can become very large for low-grade ore, and room for infrastructural facilities (miners' lodgings, power supply, transportation, workshops, administration building, processing equipment, etc.). Since surface mining operations are inherently bed-bound, their size and location are determined by the given geological conditions of the bedding and associated strata. And since major disruption of the earth's surface is unavoidable in connection with surface mining operations, the question of tolerability under the prevailing conditions must be given due consideration prior to commencing with any extractive processes.

In and around the mine and its dumps, some of the soil has to be removed, and some gets covered over. Nearly all industrialized countries have regulations governing the treatment of cultivable soil (topsoil). As a rule, its removal and temporary storage prior to the beginning of direct mining activities is mandatory. In addition, subsequent replacement of the topsoil and recultivation of backfilled ground may also be prescribed.

Surface mining operations also alter the morphological makeup of the mine site as a (temporary) result of shaping the quarry and its dumps and heaps. Once an abandoned mine has been recultivated, some such changes remain behind in the form of permanent, residual (submorphic) hollows, the size of which depends on how much material has been extracted from the mine. Morphological changes can be particularly pronounced in hardrock mines, which tend to have very steep slopes and for which little material is left for refilling (e.g., in stone quarries).

By comparison, the morphological changes occurring in loose-rock mines consist primarily of the overburden dumps established at the time of opening the mine, and ground subsidence caused by dewatering.

Surface mining activities also interfere with the surface water regimen. Relevant intentional intervention aims to keep surface water and groundwater out of the workings by collecting and channelling the water from around the perimeter as well as from the mine proper. Riverbeds are bypassed around the mine, and runoff water from precipitation and drained slopes is collected in ponds and discharged into the natural hydrographic network. Increased sedimentation and altered chemism resulting from such measures can cause qualitative degradation of the recipient water body.

Loose-rock surface mining can also interfere with the groundwater regimen, with resultant loss of groundwater quality due to the infiltration of contaminated wastewater and in washout and leaching of dumps, heaps and the mine itself. If the groundwater level is not lowered in time, groundwater will flow into the pit. Consequently, all around and within the mine, wells are sunk to below the lowest pit bottom in order to enable dry extraction while enhancing the stability of both the slopes and the floor by relieving the effective hydraulic pressure. The well water is generally unpolluted and can be fed directly into the natural river system. Lowering the groundwater level has major consequences for the surrounding area, e.g.:

- drying up of nearby wells,
- settlement/subsidence,
- disturbance of the vegetation due to altered groundwater supply.

When the mine is closed down, hollows resulting from extraction of the resource and removal of overburden during the opening phase remain behind. The hollows eventually form groundwater-fed ponds and lakes reflecting the return of the groundwater level, which may proceed very slowly, depending on the depth of the erstwhile mine and on the given hydrogeological situation. Indeed, it may take more than 50 years for a new state of equilibrium to be achieved. If the zone of contact between the water and the soil contains soluble substances, power-plant ash and/or industrial residues, the water quality may suffer. The most well-known problem in that connection is an excessively low pH in the lakewater. A lack of affluxes and effluxes aggravates the problem, promoting eutrophication, particularly if the surrounding areas are intensively farmed.

The extraction activities impose a noise nuisance on their surroundings, with major noise sources including the machines and devices required for getting, loading, hauling, reloading, etc. In hardrock mines, drilling and blasting constitute two additional sources of noise. In addition to the sound of the explosion, the attendant vibrations and reverberations amount to an additional dynamic burden on the environment that not only annoys the neighbors, but can also cause damage to structures.

Finally, dry surface mining activities also lead to air pollution, the causes and effects of which are multifarious:

- Blasting in hardrock causes dust pollution in that rock dust becomes entrained in the blast damp. The wind can stir up any and all exposed materials, especially during loading, reloading and dumping operations, all of which adds to the dust nuisance;
- Air pollution in the form of gases results from the exhaust of vehicles and engines, which tend to be diesel-driven, as well as from the escape of blast damp. Open-pit coal mines are susceptible to still other, deposit-specific hazards: the extraction of deep-lying coal can give rise to the escape of methane, and spontaneous combustion can release other noxious gases.

Hot, dry weather poses a considerable fire hazard - by spontaneous combustion - for exposed coal at the bottom of the pit and at the loading and unloading points.

Additionally, self-ignition can cause hard-to-extinguish smoldering fires in overburden dumps and feigh heaps containing small amounts of coal. Such fires can pollute the environment with odors and noxious gases for years or even decades.

- Radiation exposure can occur in special cases, i.e., in connection with the mining of uranium ore or rare-earth pegmatites.

· Interference with the biological environment by dry surface mining

The surface extraction of raw materials necessitates areal exposure of the deposit. Removal of the soil in and around the mine itself, the surrounding dumps and the requisite infrastructure destroys the local flora.

In turn, fauna is driven out of the area by the destruction of its natural habitat.

Aquatic ecosystems can be disrupted by qualitative and quantitative changes in surface water conditions, while wetlands can be emburdened by an altered groundwater level, e.g., its lowering or recovery with subsequent lake/swamp formation. Fragile ecosystems in extreme locations are particularly susceptible to permanent damage or destruction.

Terrestrial ecosystems are also affected by mining-induced situational changes (in connection with the groundwater level, for example). Even after the mine has been abandoned and recultivated, the residual changes in soil physics and chemistry, available water resources, etc. can lead to the appearance of different plant and animal associations constituting an irreversible alteration stemming from the original disruption.

· Effects of dry surface mining on the social environment

The areal nature and deposit dependence of surface mining activities engender the presumably most serious effects on human living conditions. Frequent consequences include:

- the necessity of resettling the inhabitants of the area to be mined. Surface mining operations demand the relocation of settlements as well as traffic routes and communication infrastructure. The consequences range from economic loss to sociological and cultural disruption. The latter will be all the more serious, where the local population feels strongly attached to a limited natural environment, cultural or religious localities, established tribal structures, territorial sovereignties, etc.;
- land-use conflicts when the area to be mined is being used for agricultural or forestry purposes or contains significant cultural monuments, recreation areas/facilities or the like that stand to be destroyed or negatively affected by the mining operations.

If, due either to the large area to be affected by a surface mining operation and/or to attendant damage to the local flora and fauna, farmland and, hence, income potentials are lost, or even the relocation of entire settlements necessitated, those responsible and those affected must investigate in advance which special consequences and impacts the project can be expected to have for existing groups - women in particular. Likewise, the extent to which women will be able to partake of the economic advantages the region stands to gain from the mining operation must be duly investigated.

Moreover, the environmental effects of mining operations can affect the health of both the miners themselves and the people living in the surrounding area.

Finally, the establishment of mining infrastructure can inadvertently induce the uncontrolled generation of settlements in areas which otherwise may have remained undisturbed.

2.1.2 Wet extraction

With regard to the environmental consequences of wet surface mining, the previous subdivision according to physical, biological and social impacts is maintained. In case of identical consequences, the reader is referred to section 2.1.1.

· Physical environmental impacts of wet surface mining

Since the wet extraction of raw materials is a function of site- and mineral-specific factors such as a low degree of consolidation, certain particle-size spectra, well-balanced, shallow topography and adequate quantities of water, the number of potential locations and, hence, the scope of environmental consequences are more limited than for dry extraction.

The differences begin with the space requirement. Wet extraction normally involves a very limited extraction area. Precious-metal and tin dredgers, for example, rarely require more than one hectare, unless overburden has to be removed in advance. On the other hand, the extraction area wanders more or less rapidly over the entire explorated field, which eventually becomes completely modified: when dry land is being worked, the soil is removed, but when a river is being worked, the entire riverbed is altered, and the entire course of the river is likewise affected. Cutting and winning leaves behind rubble containing large amounts of classified material that is extensively lacking in fine and superfine contents. Consequently, pedogenisis, or soil formation, as an essential prerequisite for recolonization by plant associations, is seriously impeded. Meanwhile, the fine and superfine fractions emburden the river with large quantities of muddy wastewater. Such wet-extraction sludge plumes sometimes develop into water pollution loads that remain clearly visible over hundreds of kilometers before the clay fraction finally settles out of suspension. The situation can be additionally aggravated by contaminated wastewater. The escape of mercury from gold-placer processing activities, for example, or the uncontrolled disposal of used oil, constitute serious pollution potentials.

With regard to resources, noise and air, the reader is referred to the hazards discussed in item 2.1.1.

· Effects of wet surface mining on the biological environment

Like dry extraction, wet extraction also destroys flora and drives away fauna. Also and in particular, however, wet extraction disturbs the aquatic ecosystem. The aforementioned mining-induced sludge contamination of affected rivers degrades the water quality, alters the river bed by depositing fine and superfine material, and disrupts the nutrient balance of the rivers, with consequential effects on river fauna and flora. Frequently, such pollution leads to lower fish populations due to dying and migration away from the affected sections of the river.

In tropical areas, wet extraction of mineral resources poses an additional serious environmental hazard in that resultant still waters can serve as breeding places for pathogenic agents such as malaria-carrying mosquitos. Indeed, it can happen that regionally eradicated tropical diseases flare up anew.

· Effects of wet surface mining on the social environment

In otherwise infertile areas, the loss of fertile flood plains or easily irrigated areas to wet surface mines can lead to bitter land-use conflicts. Even if the areas in question are recultivated afterwards, irreversible damage may remain behind on a location- and situation-specific basis. The impairment of fish-farming activities by the aforementioned sludge pollution of rivers counts more as a temporary effect. By contrast, health impairment resulting from the contamination of rivers with mercury, for example, counts as irreversible, permanent damage.

Social conflicts in connection with wet mining activities become particularly serious when boom times (a local gold rush, for example) draw large numbers of small miners (diggers, garimpieros, pirquineros) into a particular area. Many such newcomers lack legal mining titles and either breed or intensify diverse problems (crime, speculation, exploding prices, disease, social tension among the native population, etc.). As the originally rich deposits become harder to work and eventually depleted, such problems tend to intensify.

2.1.3 Nearshore marine mining

In dealing with the environmental consequences of marine mining, deep-sea mining is not gone into separately, because it does not yet actually contribute to the production of raw materials. The environmental effects of deep-sea mining are comparable to those of nearshore marine mining, with the latter limited by definition to the use of bucket chain (scoop) and suction dredgers in waters with a maximum depth of about 50 meters.

· Physical environmental effects of marine mining

The most serious effect of extracting minerals from the ocean is that such activities alter the ocean floor. The ground is removed by mechanical or hydraulic means in order to separate it from its ore in an on-board processing facility. Altering the morphology and composition of the ocean bed amounts to its total restructuring, since natural classifying processes take place when the oversize, tailings and perhaps overburden is re-deposited - assuming, of course, that the raw material in question contains low-grade ore (e.g., heavy mineral sand) and that processing leaves behind large quantities of nonbearing materials. When a large percentage of the material being extracted is commercially valuable (sand, gravel), its removal in large volumes also modifies the seafloor morphology, possibly resulting in intensified coastal erosion and accumulation of sediments, since the "new" ocean floor is less compact and lacking in fine and superfine particles.

The fine and superfine fractions that are left over from ore processing and which swirl up from the ocean floor remain in suspension for a long time, causing turbidity that can be carried off by ocean currents to pollute areas as far as 10 km away from the source.

If the water flows slowly, the fine and superfine particles settle out, covering the ocean floor with a layer of clay.

Moreover, by way of analogy to dry mineral extraction, the mining equipment, machines and apparatus generate noise and pollute the air and water.

· Effects of marine mining on the biological environment

The altered seafloor interferes with the natural ocean-bottom nutrient balance, both within the mined area and in the emburdened vicinity. The effects are particularly devastating for immobile marine organisms such as corals, which can be partly or completely destroyed by the combination of high turbidity and fine-particle sedimentation.

The clouds of turbidity also impair marine life in the water itself, e.g., by reducing insolation, lowering the available oxygen level due to oxidation of stirred-up particles, obstructing the respiratory passages of marine organisms, and possibly even poisoning them with trace metals.

Mobile marine fauna can evade the polluted environment by moving off, but are nonetheless unable to prevent the destruction of their spawning grounds.

· Effects of marine mining on the social environment

Since marine mining has no direct impact on the human environment, its social effects are limited to usufructuary conflicts, most notably with fish farmers, whose livelihood can be prejudiced by such mining, and with the operators of recreation facilities that can be adversely affected by mining-induced pollution.

2.2 Measures for limiting the environmental consequences of surface mining
activities

A selection of technical options for use in limiting the pertinent environmental impacts prior to, during and subsequent to surface mining activities are pointed out below. Naturally, the limitation of environmental consequences (= pollution control) entails a suitable institutional basis and the existence, adherence to and monitoring of appropriate directives.

2.2.1 Measures prior to commencement of mining activities

The most important precommencement measure is to ascertain the momentary condition of the environment as a basis for evaluating subsequent environmental impacts. The relevant studies should give due consideration to cultural and historical monuments, soil conditions, groundwater and surface water qualities and quantities, as well as flora, fauna, land use, etc.

In the case of marine placers, the marine flora and fauna, prevailing currents, seafloor gradients, etc. also should be determined in advance.

Careful planning of operational sequences enables significant limitation of environmental consequences even before mining activities begin. For example, a suitable time schedule with provisions for the archiving and conservation of archeological finds, the harvesting of standing timber in the area to be worked, and/or keeping the mine open only as long as necessary is extremely useful. Likewise, careful separation and separate storage of humus and the upper soil horizons of the overburden ensure that suitable material will be available for subsequent recultivation. Selective dewatering according to a time scale and the use of modern drainage techniques and/or sealing methods can help minimize the problems arising from groundwater recession.

With a view to precluding potential social tensions, all relevant planning must - in order to protect their interests - involve the groups of persons who will be affected either directly, e.g., by having to resettle, or indirectly, e.g., by impaired fishing conditions. It is particularly important that all parties concerned and affected, as well as the local authorities, be allowed to appropriately participate in the planning and execution of relocating measures, compensation and possible resettlement.

Finally, both the decision makers and the miners must be instructed and sensitized in and toward the environmental and health aspects of surface mining activities prior to their commencement.

2.2.2 Measures in the course of mining activities

In order to avoid excessive land consumption, inside dumps should be established, i.e., the overburden should be stored within the open spaces of the mine.

The noise nuisance must be limited by appropriate soundproofing of individual pieces of equipment. Whole units of equipment can be encapsulated or equipped with special exhaust systems (mufflers). Additionally, the miners must be required to wear personal noise-protection gear, e.g., ear protectors. Finally, time limits can be imposed on noise emissions, e.g., by limiting blasting operations to once a day. Moreover, the propagation of acoustic waves in the near vicinity of noise emitters can be reduced by such measures as noise-control embankments.

In hardrock mines, optimized blasting methods can substantially reduce noise and dust emissions. By optimally matching the explosive quantities to the drilling pattern and by stemming the holes, the overall quantity of explosives and, hence, the magnitude of the explosion (vibrations), the incidence of microfine dust, and the intensity of the blasting noise can be substantially reduced.

Dust control measures in surface workings can encompass such individual measures as sprinkling water on the roads and other conveying routes, washing down transport equipment (trucks, etc.), irrigating and turfing dumps and exposed areas, and applying dust bonding agents as necessary. Also, individual pieces of equipment such as crushers over belt feeders can be encapsulated and surrounded with trees or hedges that filter out dust and reduce the overall drift (deflation). Drills and boring tackle can be fitted with wet or dry dust precipitators.

Wastewater can be cleansed of suspended solids, neutralized and clarified in wastewater treatment facilities to meet minimum quality standards for release into a recipient body. For each and every solution or suspension, there are appropriate liquid/liquid and solid/liquid separation processes for use in purifying contaminated water. For metal-polluted acid mine drains (a.m.d), electrolysis is indicated, while an ion-exchange technique is more suitable for radioactive wastewater. In general, all means of countering the causes of pollution should be exploited. For example, the use of bypass microfilters in engine lubrication systems can reduce the incidence of used oil by up to 90 % by prolonging its useful life.

The dredges used for working nearshore marine placers should be equipped with long rubbish chutes for use in covering the tailings/trash and oversize with overlay shelf in order to restore a close-to-natural particle-size spectrum to the seafloor.

Wet extraction from an artificial lake is preferable to working directly in a river, because it involves much less of a sludge load for the latter. Wells and other large boreholes that are no longer needed but could disturb groundwater barriers (aquitards) should be sealed.

Particularly for fragile working faces, the angle of slope around the perimeter of the mine must be designed to preclude major flank movements (slides and falling rocks).

In dry coal mines, care must be taken at the planning stage to protect coal-bearing dumps from spontaneous ignition by appropriate surface compaction and air-exclusion measures. The same applies to coal pillars and abandoned working faces, which also require sealing to prevent smoldering fires.

Such special measures as the posting of trespassing notices, installation of fences and blocking of roads can help protect and preserve adjacent ecosystems.

Persons likely to be affected can and must be afforded appropriate protection through, say, the appointment of environmental affairs and/or safety officers and occupational physicians. Since damage to the environment cannot be limited exclusively to the mining area, the right to medical services should also be extended to persons living in the general vicinity.

Continuous monitoring of all important factors must accompany all surface mining activities and attendant pollution-control measures. Such factors include exhaust gases, noise levels, vibrations, water pollution, particulate emissions, slope movement/stability, ground subsidence and groundwater levels.

2.2.3 Measures following termination of mining activities

As soon as any section of a deposit has been fully exploited and refilled with waste from new operations, appropriate rehabilitation measures can and must be taken. Since surface mining operations tend to be quite expansive, ongoing mining operations in one area can be accompanied by rehabilitative measures in another. The same is true of wet mining operations outside of riverbeds. To rehabilitate means to immediately transform the areas concerned into as natural a landscape as possible.

Following wet extraction, particularly in tropical locations, all worked-out areas must be drained and graded to eliminate all open bodies of water that could serve as breeding grounds for pathogenic vectors like malaria-transmitting mosquitos. On the other hand, bodies of water created by surface mining activities can, on a case-by-case basis, also be utilized as dry-season water reservoirs or for such commercial purposes as fish-farming.

Dumps, open-pit perimeters, outside dumps and erstwhile extraction areas require immediate greenbelting or planting with indigenous vegetation in order to limit or prevent erosion, especially in humid, tropical climates, and deflation in arid climates. Special erosion control methods such as drainage and consolidation must be employed in particularly vulnerable areas.

The ultimate aim must be to fully recultivate the worked out areas to enable appropriate and corresponding use, or to renature them for another purpose. To reclaim the land, it must be graded, compacted and covered with soil and humus to allow immediate oversowing and subsequent soil management. It should be borne in mind, however, that recultivation is not the only means of limiting environmental detriment. Recultivation is very time-consuming, and the ultimate success is usually uncertain. Especially recultivation in tropical areas has not yet been adequately researched and developed with regard to planting sequences, site-appropriate species, etc. Moreover, successful recultivation entails extensively natural soil physics (permeability, granularity/type of soil) and soil chemistry (pH, nutrients, absence of pollutants). Otherwise, the soil would not be able to fulfill its diverse functions as a water reservoir, a biotope for plants and animals, and a basis of agricultural production.

3. Notes on the analysis and evaluation of environmental impacts

The principal regulations governing mining activities and pertinent environmental protection in Germany are the Bundesberggesetz BBergG [Federal mining law] dated August 13, 1980, and the UVP-VBergbau (ordinance on the environmental impact assessment of mining projects) dated July 13, 1990, the TA-Luft (Technical Instructions on Air Quality Control), the TA-L (Technical Instructions on Noise Abatement), the BImSchG (Federal Immission Control Act) and its various implementing provisions, as well as the respective mining regulations of the various states and their laws governing landscape, preservation of nature and excavation. In addition, the Verein Deutscher Ingenieure (Association of German Engineers) has issued a number of guidelines dealing primarily with the relevant mechanical equipment.

Other industrialized countries like the USA, Canada and Great Britain have similar, in part more stringent, laws and regulations - including, for example, the U.S. "Clean Water Act" (1977) and the "Surface Mining Control and Reclamation Act" (public law 95/87, 1977), with supplementary provisions drawn up by the Office of Surface Mining Reclamation and Enforcement (OSM) and by the Environmental Protection Agency (EPA).

A precommencement status quo study with thorough investigation of all matters relevant to the physical, biological and social environment provides a crucial basis for evaluating the environmental consequences of surface mines and planning recultivation measures; cf. environmental brief Reconnaissance, Prospection and Exploration of Geological Resources.

Growing awareness of the environment and the will to protect it is emerging in many parts of the world. To some extent, however, that new awareness has not yet found its expression in appropriate national laws. But even where laws protecting the environment already are in place, their enforcement is frequently neglected for a lack of control and monitoring options. The absence of an appropriate legal basis and/or of its proper implementation has serious large-scale and small-scale consequences for the environment, whereas mining regulations could be adopted with which to hold mine operators responsible for the consequences of their own mining activities. For small mines that are difficult to monitor, a pertinent recommendation was proposed at the UN-sponsored International Round Table on Mining and the Environment Congress in Berlin: recultivation guarantee funds can be set up, e.g., included in the concession fee. If the mine operator fails to rectify substantial environmental damage when he leaves his concession, financial reserves will be available to pay for recultivation. Otherwise, the withheld funds could be returned to the mine operator following satisfactory inspection of the properly recultivated areas.

Illegal mining is the biggest problem with regard to environmental destruction and recultivation. When large numbers of gem seekers and gold diggers intrude into and begin working an area in a completely uncontrolled manner - especially in developing countries - their activities are bound to cause areal destruction, often accompanied by pollution of the soil and rivers (with mercury and cyanide in the case of gold diggers). Legal measures have proven totally inadequate as a means of control, because the form of mining involved requires very little equipment, thus promoting a high level of mobility and, hence, good chances of evading control. Moreover, supervision becomes nearly impossible when large numbers of such people converge on an area and are willing to use force in defense of their interests. Consequently, damage to the physical and biological environment is accompanied by pronounced social tensions between the various interest groups.

4. Interaction with other sectors

In sparsely populated and undeveloped regions, mining tends to serve as a pacemaker for infrastructural development. Frequently, mining projects have to carry the major share of the relevant cost of building access roads and establishing rail links to deposits for hauling away the mineral products and of building homes for the miners and their families, including all the requisite supply and disposal facilities. The new infrastructure can act as a catalyst for extensively uncontrolled settlement and economic development of the area in question.

Ore mines in particular tend to include an initial processing stage for local first-step product enrichment. Frequently, the purchaser and the mine operator agree to share the storage and supply facilities. In many brown-coal and hard-coal strip mines, the raw (possibly upgraded) coal is used directly for fueling thermal power plants. Accordingly, power generating facilities and distribution systems tend to be installed near such mines. Storage grounds for disposing of residues can be established in worked-out parts of the mine for some future use. Fly ash from power plants, for example, is often used for consolidating mine roads.

Land-use conflicts can quickly arise due to the space requirements of surface mining. The various interests must be reconciled within the context of appropriate regional planning.

While land-use problems occur less frequently in sparsely populated countries, legal problems nonetheless may arise. Property rights, for example, may not have been duly registered, and the boundaries may have been inaccurately mapped. Such problems intensify when those concerned happen to be groups of people with no lobby and a life-style and social status that afford them few options for preserving their traditional habitat. The very existence of such groups can be threatened. What is needed is a form of regional and development planning that duly accounts for ecological and ethnic concerns alongside of economic interests.

The following sectors, the environmental consequences of which are described in other environmental briefs, can be affected by surface mining activities and therefore require consideration:

- Spatial and Regional Planning
- Planning of Locations for Trade and Industry
- Overall Energy Planning
- Water Framework Planning
- Wastewater Disposal
- Transport Planning and Traffic
- Reconnaissance, Prospection and Exploration of Geological Resources
- Underground Mining
- Minerals - Handling and Processing
- Thermal Power Stations.

5. Summary assessment of environmental relevance

Surface mining of mineral resources involves different methods: wet and dry, marine and terrestrial. Common to all, however, is that they have serious environmental consequences.

Although most mining activities are temporary by nature (approx. 20 - 50 years), they often cause permanent damage to the environment through irreversible disruption. The earth's surface and the groundwater and surface-water regimens tend to sustain the most serious direct damage. Mineral extraction by surface mining methods also causes air pollution, noise nuisance, alteration of the soil, flora and fauna, and social problems arising from land-use conflicts, resettlement, etc. Such impacts are invariably dependent on the area involved, the location and the climate. Additionally, points of law and control options play major roles in determining the extent of environmental damage caused by surface mining activities and/or its limitation by such means as recultivation or renaturation. Recultivation, however, always amounts to substituting a new ecosystem for the original one in the affected area. Moreover, the ultimate success of such measures can rarely be guaranteed, especially in locations for which no relevant empirical data is available.

The extent of damage can be limited through careful planning, preparation and implementation of the mining activities. A thorough analysis of the actual situation in the region is an indispensable prerequisite and basis for planning with due consideration of the mining activities' anticipated effects in the form of environmental impacts and structural modification of the subject region. This must include the regulation of compensation and the planning of resettlement measures as well as the elaboration of recultivation plans.

As a flanking measure, concerned organizations, institutions and individuals must be sensitized and informed to prepare the way for the ecologically oriented implementation of the project.

The need to minimize costs must not be allowed to induce the promotors and others responsible for the project into cutting back on expenditures for environmental protection. Consequently, project desk officers should see to it at the project appraisal and authorization stage that the project encompasses adequate landscape and environmental protection measures, including the optimal use of resources, and that a sustainable structure with the appropriate control and regulatory functions is in place.

6. References

Agbesinyale, P.: Small Scale Traditional Gold Mining and Environmental Degradation in the Upper Denkyira District of Ghana, Spring Phase 1, UniversitDortmund 1990.

Bender, F. (Ed.): Geologie der Kohlenwasserstoffe, Hydrogeologie, Ingenieurgeologie, Angewandte Geowissenschaften in Raumplanung und Umweltschutz. In: Angewandte Geowissenschaften III: 674 pages, Stuttgart (Enke) 1984.

Chironis, N.P. (Ed.): Coal Age Operating Handbook of Coal Surface Mining and Reclamation, McGraw Hill, New York 1978.

Crawford, J.T.; Hustrulid, W.A.: Open Pit Mine Planning and Design, SME/AIME, New York 1979.

Cummins, A.B.; Given I.A. (Ed.): SME Mining Engineering Handbook, Vol. 1 & 2, SME/AIME, New York 1973.

Down, C.G.; Stocks, J.: Environmental Impact of Mining. Applied Science Publishers Ltd. London 1977.

E.I. du Pont de Nemours & Co. (Inc.) (Ed.): Blasters' Handbook, 16th ed., Wilmington, Delaware, USA, 1977.

Gg, D.: Die Umweltvertrichkeitsprbeim Abbau von Steinen und Erden. Inaugural-Dissertation, Institut frobiologie und Landeskultur der Justus-Liebig-UniversitGien, 1987.

Hermann, H.P.: Schwerpunkte der Verwaltungsvorschrift zur derung der TA-Luft, in Braunkohle 35, 1983, Heft 6, p. 190 - 194.

Hofmann, M.: Bundesforschungsanstalt furschutz und Landschaftsogie: Dokumentation feltschutz und Landespflege. Bibliographie. Abgrabung (Bodenerosion, Tagebau, Gewinnung oberflennaher minera-lischer Rohstoffe und Landschaft). Deutscher Gemeindeverlag, K1988.

Hn, W. v.: Technische und rechtliche Probleme bei der Schaffung von Tagebauseen der Bayerischen Braunkohlen-Industrie AG in Schwandorf, in Braunkohle, 1980, Heft 9, p. 273 - 277.

Jung, W. et al.: erblick der aus der bergbaulichen Tgkeit resultierenden Umweltauswirkungen in der ehemaligen DDR. In: Z. Erzmetall 43, 1990, Heft 11, p. 478 ff.

Karbe, L.: Maahmen zum Schutz der Umwelt bei der Frung metallischer Rohstoffe aus dem Meer. Vortrag gehalten auf der Tagung Meerestechnik und Internationale Zusammenarbeit. Tagungsband erschienen im Verlag Kommunikation und Wirtschaft. Oldenburg 1987.

Knauf (Ed.): Praktizierter Naturschutz. Dokumentation ekultivierungsverfahren abgebauter oberflennaher Lagersten, 1987.

Koperski, M.; Musgrove, C.: Reclamation Improves With Age, in Coal Age, 1980, no. 5, pp. 162 - 169.

Kries, O. v.: Braunkohle und Landesplanung, in Raumforschung und Raumordnung, 1965, Heft 3.

Kr, K.: Theoretische Grundlagen von Lemissionen und -immissionen bei Frsystemen des Braunkohlenbergbaus, in Braunkohle 30, 1978, Heft 9, p. 260 - 266.

Krug, M.: Angewandte Planungsmethoden beim Aufschludes Tagebaues Hambach 1978/79, in Braunkohle, 1980, Heft 4, p. 71 - 81.

Pfleiderer, E.P.: Surface Mining, 1st ed., AIME, New York 1968.

Robinson, B.: Environmental Protection: A Cost-Benefit Analysis, in Mining Magazine 151, 1984, no. 2, pp. 118 - 121.

Salomons, W.; Fner U. (Eds.): Environmental Management of Solid Waste. Dredged Material and Mine Tailings. Berlin, Heidelberg, New York, London, Paris, Tokyo (Springer-Verlag) 1988.

Schultze, H.J.: Braunkohlenbergbau und Umwelt im Rheinland, in Erzmetall, 1985, Heft 2, p. 65 - 72.

Seeliger, J.: Eine europche Umweltvertrichkeitspr in Umwelt- und Planungsrecht, 1982, Heft 6, p. 177 - 185.

Seeliger, J.: Kohlennutzung und Umwelt, in Gl 121, 1985, Heft 14, p. 1103 - 1107.

Sengupta M.: Mine Environmental Engineering, Volumes I and II, Boca Raton, Florida, 1990.

Stein, V.: Anleitung zur Rekultivierung von Steinbrund Gruben der Steine-und-Erden-Industrie, K(Deutscher Instituts-Verlag) 1985.

Thiede, H.-J.: Immissionsschutz in den Braunkohletagebauen des rheinischen Reviers, Energiewirtschaftliche Tagesfragen, 1979, p. 535 - 540.

Welch, J.E.; Hambleton, W.W.: Environmental Effects of Coal Surface Mining and Reclamation on Land and Water in Southeastern Kansas, Kansas Geological Survey, Mineral Resources Series 7, 1982.

Yundt, S.E.; Booth, G.D.: Bibliography. Rehabilitation of Pits, Quarries, and other Surface-Mined Lands. Ontario Geological Surveys Miscellaneous Paper 76, Ministry of Natural Resources, 1978.

Zepter, K.-H.: Schutz der naten Umwelt - Mchkeiten und Grenzen, in. Erzmetall, 1979, Heft 9, p. 357 - 418.

No Single Author

Bundesberggesetz (BBergG) und Verordnung ie Umweltvertrichkeitsprbergbaulicher Vorhaben (UVP-V Bergbau - federal mining law and ordinance on the environmental impact assessment of mining projects), Verlag Gl GmbH, Essen 1991.

Environmental Aspects of Selected Non-ferrous Metals (Cu, Ni, Pb, Zn, Au) Ore Mining: A Technical Guide, Draft Report, unpublished UNEP/IEO.

Environmental Protection Agency (EPA), USA 1986.

Part 11 - Natural Resource Damage Assessment
Part 23 - Surface Exploration, Mining and Reclamation of Lands
Part 434, Subpart E - Post Mining Acres

Mining and Environment Guidelines, International Round Table on Mining and the Environment, Berlin 1991. UNDTCD/DSE.

Reclamation, in Mining Magazine, 1982, no. 11, pp. 449 - 451.

Texas Water Commission, 1985. Instructions and Procedural Information for Filing Applications for a Permit to Discharge, Deposit or Dispose of Waste.

Update on Reclamation Regulations, in Coal Age, 1981, no. 7, pp. 68 - 73.

World Bank Environmental Guidelines: Mining and Mineral Processing, Draft Report.

1. Scope

Mining is defined as the extraction of mineral resources from the earth. Underground mining is the extraction of raw materials below the earth's surface (deep mining) and their conveyance to the surface. Access to the vein or lode is by shafts and tunnels with links to the surface. (The subsequent stages of raw material processing are dealt with in a separate brief: Minerals - Handling and Processing.) The present brief examines only the underground extraction of solid mineral resources.

There are some 70 individual types of useful minerals that occur in minable concentrations either alone or in combination with other minerals, frequently as natural mixtures (aggregates).

Underground mining includes all work involved in the winning of raw materials by people using technical contrivances. Apart from the actual extraction and conveyance processes, the term underground mining also covers development of the deposit and provision of the requisite infrastructure (transportation/handling, storage facilities, surface plant, e.g., administration building, workshops, etc.) and all measures devoted to ensuring the safety of the miners. This includes:

working

conveyance

ventilation

loading

drainage

support

Small-scale mining activities in many countries frequently include a transitional form of extraction referred to as trench mining, or burrowing.

In special cases, the mineral can be made transportable and hauled off from its natural surroundings with no need of exploratory work (brine mining, in-situ leaching and in-situ gasification of coal).

Deep mining creates underground spaces in which people work. Their working conditions with regard to air temperature and humidity, presence of harmful or explosive gases or radiation, as well as moisture, dust and noise, can be specific to the mined mineral and/or the surrounding rock, the depth of the mine, and the type of machinery in use.

The locations of deep mines are dictated by the presence of potentially profitable raw materials. Underground extraction is practiced in all climate zones, in remote areas as well as under large cities, on the ocean floor and in alpine regions. The size, or output, of such mines ranges from less than 1 to more than 15 000 tons a day, and the depth at which extraction takes place ranges from a few meters to more than 4 kilometers.

2. Environmental impacts and protective measures

Deep mining impacts the environment in three different areas: in the deposit itself and the surrounding rock, in the underground spaces created by and for the mine, and aboveground. Optimal exploitation of the resource with attendant limitation of environmental effects is dependent on detailed planning of the sequence of operations and on the mining methods and technology to be employed.

2.1 Environmental impacts on the deposit and the surrounding rock

2.1.1 Exploitation of resources

The most important environmental consequence of underground mining is that it involves the exploitation of a nonrenewable resource. The process of extracting the raw material necessarily also involves mining losses and impairment of other parts of the deposit. The best way to counter the latter effects is to carefully plan the extraction operations, stowing measures, etc.

Some raw materials (coal and several sulfidic ores) can under certain circumstances ignite spontaneously and cause mine fires.

2.1.2 Disruption of rock structure

The opening up of underground workings creates cavities and leads to stress and motion in the surrounding rocks. The effects of mining on the rock structure can include:

- subsidence due to cave-ins in the cavities. The resultant settling can propagate to the surface, possibly causing damage to structures and facilities (subsidence damage; cf. section 2.3.3 for protective measures);
- destruction of hanging parts of the deposit (most likely as a result of inadequate extraction planning).

2.1.3 Disruption of groundwater flow

The opening up of underground workings modifies the formerly stable water balance of the rock structure by creating new water conduits. Water drainage, for example, can cause significant recession of the groundwater level with substantial attendant detriment to vegetation within the affected area (cf. section 2.3.2).

2.1.4 Alteration of groundwater quality

Mining activities can pollute groundwater in several ways: mine waters (cf. item 2.2.4), for example, can enter the groundwater system, and various alkaline and other solutions used in in-situ dressing processes, as well as leakage losses of refrigerants used in the sinking of shafts, all can contaminate the groundwater, just as the leaching of dumps produces percolating water that can alter the character of groundwater. Effective preventive measures include the sealing off of soils, shafts and worked-out parts of the deposit, drainage and/or canalization.

2.2 Underground environmental impacts

Man, machine, rock and climate all interact underground, whereas man is impacted most significantly. Matters concerning the health and safety of miners are therefore given priority consideration.

2.2.1 Air / climate

The underground climate is influenced by the elevated temperature of deep rock and by the gases and liquids it contains.

Table 1 - Factors influencing the atmosphere in underground mines

Potential hazard /

caused by...

danger of...

Preventive measures

Reference values

Oxygen deficiency (O2) --------- 19 % min.

displacement by irrespirable (black) damps and firedamps, respiration, open mining lamps, mine fires

fatigue, asphyxia

ventilation

Radiation

radioactive rock compo-nents, measuring probes

radiation affection

limited exposure time with dosimetric control

Radon

gas evolution from surrounding rock

radiation affection

ventilation, limited exposure time

Methane (CH4) --------- 5 - 14 % = explosive

gas evolution from coal

explosion

gas extraction, ventilation, flameproof equipment

Coal dust

mining, handling of coal

explosion

dust precipitation, flameproofing

Carbon monoxide (CO) --------- > 50 ppm

exhaust, gas evolution in abandoned hard-coal mines

poisoning

ventilation

Carbon dioxide (CO2) --------- > 1 %

gas eruption in salt, exhaust, gas evolution from thermal waters

asphyxia

ventilation

Hydrogen sulfide (H2S) --------- > 20 ppm

gas evolution from mine and thermal waters

poisoning

ventilation

Oxydes of nitrogen (NOx) and blast damp

blasting

poisoning

ventilation, specification of blasting times

Exhaust gases

engine exhaust

poisoning

ventilation

Low-temperature carboni-zation gases, smoke

mine fires

poisoning

extinguishment, damming off, precautionary measures

Aerosols of oil

pneumatic equipment

poisoning

oil precipitation

Heat

elevated rock temperatures, off-heat from engines

fatigue

ventilation, air cooling

2.2.2 Noise

In underground workings, noise is generated by drilling and blasting, by internal-combustion engines and pneumatic and hydraulic motors, and by various means of conveyance (conveyor belts, trains, vehicles) and fans.

Machine-generated noise can be reduced by various design measures, and ear protectors are mandatory beginning at certain sound intensity levels.

2.2.3 Dust

Exposure to dust (stone dust in coal mines, for example) must be limited to minimize the incidence of related diseases, the most dangerous of which is silicosis resulting from the inhalation of silica particles. Dust forms when rock is destroyed by mechanical means (drilling, blasting, crushing, handling, etc.).

Dust consisting of the following mineral substances poses a hazard to human health: asbestos, beryllium, fluorspar, nickel ores, quartz, mercury, cinnabar, titanium dioxide, manganese oxide, uranium compounds and tin ores. Pulverized asbestos and respirable dust containing nickel ore and/or beryllium, as well as soot from diesel engines, are carcinogenic. Coal dust can cause dust explosions.

Countermeasures against dust pollution include its consolidation during drilling and conveying, either by spraying it with water or by saturating the face through appropriately arranged boreholes prior to extraction. Gas masks prevent the inhalation of dust, and filters on engines bond soot particles.

2.2.4 Mine waters

Mining activities alter the characteristics of mine waters.

Appropriate safety clothing protects miners against aggressive mine waters, and appropriately resistant materials prevent corrosion of material goods.

Table 2 - Pollution of mine and surface waters

Type of pollution

Typical polluting substances

Preventive Measures

Altered pH

neutralization

Soluble inorganic substances

heavy metals, salts, sulfur

precipitation

Insoluble inorganic suspended solids

mud

agglomeration and settling

Organic substances

oil, grease, lubricants, emulsifying agents

precipitation in settling tanks

Heat

cooling, mixing

2.3 Aboveground environmental impacts

The aboveground environmental consequences derive from communication between the mine and the surface in the form of ventilation, mine pumping and conveyance of the product, in combination with establishment of the requisite aboveground mining infrastructure. Vibrations caused by blasting and ground movement are also perceptible aboveground.

2.3.1 Air / climate

The harmful effects of air pollution, particularly on nearby vegetation can be alleviated by filtering the outgoing air from the shafts and tunnel faces. Dumping and wind-induced erosion of dumps can cause substantial air pollution, most notably in the form of dust.

Dust evolution can be controlled by appropriate sprinkling in connection with dumping and by immediate greenbelting, oversowing and protective dams. In arid regions where land planting is hardly possible, preventive measures must be taken in the form of restricted use in the prevailing wind direction.

Coal mining releases large quantities of methane (CH4), one of the most notorious "greenhouse gases". The best way to control methane is to "drill and extract" (with subsequent utilization). Particulate solids in the vitiated air from underground mines can be extensively eliminated by filtration.

2.3.2 Water

The pH of mine waters, particularly in the presence of sulfidic ores, can range below 5.5 (acidic). Adherence to the limits prescribed for sulfates, chlorides and metals is essential.

If the groundwater is being used as drinking water and ore is being discharged into a body of surface water, the relevant values must be monitored. It is important to know which anions and cations can occur in mine water and which of them constitute potential hazards on the basis of their concentration or toxicity.

It is also important to mention that heaps of material extracted from an underground mine are liable to contain high concentrations of chlorides and sulfates and that, in a humid climate, such salts can be leached out by precipitation.

Whenever minewater is discharged into a body of surface water, care must be taken to avoid damaging any sensitive ecosystems and to ensure that no long-term accumulation of pollutants occurs in the sediment and that overall use of the water in question, e.g., for fishing purposes, is not impaired.

Marine pollution and alteration of the ocean floor or fishing/spawning grounds can result from the conveyance of polluted water through rivers leading to the coast.

Finally, underground mining consumes water for such activities as drilling, gobbing/stowing, hydro-mining, etc.

The measures described in section 2.2.4 (table 2) should be adopted to prevent pollution of surface and groundwater by mine waters.

2.3.3 Subsidence

For the day surface, the most frequent danger resulting from underground mining activities is subsidence, or settling. Subsidence-induced tilt, curvature, thrust, stretch and compression of the day surface can cause damage to buildings and infrastructural facilities as well as to the natural environment. Watercourses such as canals and rivers - and rice paddies, for example - react very sensitively to the slightest change in ground inclination.

Protective measures begin with early regional planning with due consideration of the potential mining-induced consequences of ground subsidence.

Settling can also be avoided or at least reduced by properly lining the mine with support material and backfilling the face workings with rejects and/or the use of certain suitable extraction techniques. Well-planned and controlled extraction allows slow areal settling that is unlikely to damage buildings or public utility lines and facilities.

2.3.4 Dumps, land consumption, landscape

Underground mining activities are usually accompanied by the appearance of large rubbish heaps within the immediate vicinity of the mine, where rejects and other useless material are dumped. The residual metal contents of such material should be ascertained, even though the metal burdens emanating from dressing heaps can be expected to be higher. Frequently, rubbish dumps are difficult to recultivate, and appropriate measures therefore should be included in the working plans.

Underground mines require a certain extent of surface area for the requisite infrastructure (hoists, buildings, workshops, storage areas, power generating equipment, access road, etc.). The aboveground facilities can impair the appearance of the landscape, and relevant architectural measures have limited effects. The establishment of any such industrial complex is bound to alter the landscape in the vicinity of the mining facilities. To the extent that resettlement is necessary, the affected parties must receive appropriate compensation.

Lowering the groundwater level can have detrimental effects on the local vegetation, including the drying out of ponds, streams, etc. Moreover, the local fauna and human population can be adversely affected by a diminishing supply of drinking water as a result of the altered water regimen.

Adequate protection of wetlands against such negative impacts may require the artificial recharge of groundwater, particularly since receding groundwater tends to cause settling, with damage to structures as one likely result.

Finally, vibrations caused by blasting and ground movement are also perceptible aboveground.

2.4 Other consequences of underground mining

Establishing mining operations in remote areas can have the inadvertent effect of opening the area up to uncontrolled settlement and land use. Appropriate planning-stage backup measures are therefore called for.

The intensive use of wood for timbering mines can trigger the large-scale felling of trees and, hence, erosion of the exposed soil. Orderly silvicultural activities in the area around the mine can help prevent such problems, especially if fast-growing species of trees are planted. Nonetheless, long-term effects on the ecosystem remain unavoidable. The use of anchoring techniques and steel supports in underground mines can extensively reduce wood consumption.

The world over, underground mining provides employment almost exclusively for men, because cultural and traditional conceptions forbid women to work underground. If at all, jobs for women are to be found in the areas of mineral processing, marketing and attendant services. Children should never be allowed to work in underground mines. Other social problems can arise in connection with mining if the housing for the miners and their families is either inadequate or not accompanied by the appropriate infrastructure (water, markets, schools, etc.) and if the miners are not covered by social insurance.

3. Notes on the analysis and evaluation of environmental impacts

3.1 Air / climate

The gas contents of air in underground mines is regulated in Germany by pertinent laws such as the mining ordinances (Bergbauverordnung) BVOSt and BVOE of the North Rhine-Westphalian mining inspectorate (Landesoberbergamt LOBA) and its pertinent and specific directives.

For methane (CH4), the following limits apply to free airflow:

more than 0.3 %: tram shutdown
more than 0.5 %: recorded monitoring
more than 1.0 %: electrical equipment shutdown
more than 2.0 %: monitoring equipment shutdown

Gas extraction equipment is subject to measures in accordance with the relevant gas extraction directives.

Carbon monoxide (CO) in concentrations of 50 ppm and higher calls for special rescue, recovery and security measures according to a life-saving plan (Hauptstelle f Grubenrettungswesen der Bergbau-Forschung GmbH, 1982).

Mines must be evacuated if the carbon dioxide (CO2) level reaches 1.0 % or higher.

Nitrous gas levels of 300 ppm NOx, including 30 ppm NO2, allow a maximum exposure time of 5 minutes. A level of 100 ppm NOx (including not more than 10 ppm NO2) extends the maximum exposure time to 15 minutes per shift.

The oxygen content must amount to at least 19 %.

The hydrogen sulfide (H2S) concentration must not exceed 20 ppm.

All gas measurements must be performed using calibrated commercial-type instruments.

The airflow velocity should amount to at least 0.1 m/s in large spaces and at least 1.0 m/s in fast-line sections. The air velocity in levels used for travel (tram levels) should not exceed 6.0 m/s.

Minimum air volumes amount to 6 m3/min per person, plus 3 - 6 m3/min per diesel horsepower for CO levels ranging from 0.06 % to 0.12 %.

Airflow velocities are measured with anemometers, and the airflow volumes are calculated by multiplying the velocity by the cross-sectional area.

The regulations governing gas contents, air volumes and airflow velocities differ from country to country (hard-coal mines in India, mines in Chile, the People's Republic of China, etc.).

3.2 Noise

Underground noise limits can be drawn up along the lines of rules issued by the North Rhine-Westphalian Mines Inspectorate (LOBA) in Dortmund.

The sound intensity level of noise generated by drills should not exceed 106 dB (A) at a distance of 1 m (LOBA Rundverf/I>).

Transgression of a certain reference intensity calls for the use of ear protectors. The 1988 EC directive on noise in mining came into force in Germany in 1992. Noise measuring specifications have been developed by the Westphalian miners' union fund Westfsche Berggewerkschaftskasse in Bochum, and the appropriate measuring instruments are commercially available.

3.3 Dust

In the Federal Republic of Germany, the German Research Foundation (DFG - Deutsche Forschungsgemeinschaft) publishes yearly dust emission limits/standards in the form of occupational exposure limits (MAK-Werte), technical exposure limits (TRK) and biological tolerance values for working materials (BAT). To the extent that the limit values in question are directly relevant to human health, the above or comparable guidelines, e.g., from the World Bank or other international organizations, should be adhered to.

The most important occupational exposure limit, or MAK-value, is that pertaining to fine silica dust, which amounts to 0.15 mg/m3. The corresponding value for siliceous fine dust is 4 mg/m3. In hard-coal mining, the limits for fine silica and siliceous dust presently (as of this writing) amount to 0.60 mg/m3 and 12 mg/m3, respectively, and were scheduled for reduction in 1992. Fine dust is referred to as siliceous if it contains more than 1 % quartz.

The maximum personal dust exposure, measured in mg/m3 x number of shifts worked in five years, shall not exceed 2500. All underground work is classified according to different dust-exposure categories.

Workers suffering from incipient pneumonoconiosis (or anthracosis) may not be exposed to more than 1500 (mg/m3 x number of shifts worked) in the span of five years. In North Rhine-Westphalia, the German land with the largest number of mines, the mining ordinance for hard-coal mines Bergbauverordnung finkohlebergwerke, section 44 - 48, version dating from February 19, 1979) governs the measurements and interpretation.

Table 3 - Miscellaneous dust limits (MAK-values) with mining relevance

Fibers/m³

mg/m³



Asbestos, crocidolite

0.5 x 106*

0.025*



All other types of asbestos-laden fine dust

1 x 106* --

0.05* 2.0*



Beryllium

carcinogenic



Iron-oxide powder

--

6



Fluorspar

--

2.5



Nickel-ore dust (sulfid.)

carcinogenic



Mercury

0.1



Cinnabar

0.01



Titanium dioxide

6



Manganese oxide

1



Uranium compounds

0.25



Determined by means of atomic absorption analysis and X-ray fluorescence analysis. Application to projects in developing countries in accommodation of local measuring techniques and analytical methods (cf. references) is recommended. * technical exposure limit (TRK)





3.4 Water

The discharge of industrial process water and mining effluent is strictly regulated in Europe. The EC Council Directive 80/778 relating to the quality of water intended for human consumption, dated July 16, 1975, supplemented July 15, 1980, lists three water categories requiring less extensive (category A1) or more extensive (categories A2 and A3) treatment. The guideline values (G) and imperative values (I) for the third category are listed in the following table along with the threshold values (TV) and limit values (LV) stipulated by the North-Rhine Westphalian State Agency for Water and Waste (Landesamt fser und Abfall Nordrhein-Westfalen) in the draft ordinance on potable water Trinkwasserverordnung (TVO) dated July 26, 1994, selected on the basis of relevance to deep-mine waters.

Table 4 - Potable water obtainment guidelines

Element

EC-values



NRW (North-Rhine/ Westphalia)



Element

EC-values




NRW






















[g/l]

G

I

TV


LV

[mg/l]


G

I


TV



LV



Fe

-

0.2

-


0.2

Cr


-

0.05


0.03



0.05



Mn

-

0.1

-


0.1

Pb


-

0.05


0.01



0.04



Cu

1

-

0.03


-

Se


-

0.01


-



-



Zn

1

-

0.1


2.0

Hg


0.0005

0.001


-



-



B

1

-

-


-

Ba


-

1


-



-



Mg

-

-

25


50

NO3


25

50


5



11



Na

-

-

50


150

SO4


150

250


120



240



K

-

-

5


12

Cl


200

-


25



-



Ni

-

0.05

0.03


0.05

F


0.7/1.7

1


-



-



As

-

0.1

0.006


0.04







Cd

-

5

2


5

pH


5.5-9





6.5-8




3.5 Soil

Oversown dumps are rarely used for agricultural purposes. In the event that such a use is envisioned, the applicable heavy-metal tolerance values for soils are to be found in the guidelines and directives issued by the Darmstadt-based Verband Deutscher Landwirtschaftlicher Untersuchungs- und Forschungsanstalten (German association of agricultural research and analysis stations) and by the Biologische Bundesanstalt fd- und Forstwirtschaft (Federal Biological Research Centre for Agriculture and Forestry) in Berlin. It is generally necessary to determine the constituents of the dump and any leaching behavior that could impose limits on the available soil utilization options.

4. Interaction with other sectors

With regard to environmental consequences, underground mining is closely linked to a number of other sectors, including in particular:

- prospection and exploration of deposits in preparation for the actual underground extraction activities;
- processing of the raw materials to obtain marketable products, with such processing normally taking place in centralized plants situated directly at or near the mine;
- conversion into electricity in thermal power stations, many of which are located in the near vicinity of brown-coal mining operations;
- building construction and civil engineering as sectors pertinent to establishment of the requisite mining infrastructure and means of transportation to the market. (Mines tend to be found in isolated locations, accordingly intensive construction activities are required.);
- waste disposal, e.g., for thickener sludge, hydraulic oil, spent oil and the like, and problems concerning ultimate disposal;
- water management, since natural water is quantitatively and qualitatively altered by the discharge of mine water into surface waters or groundwater as well as by the extraction of water for use as process water;
- forestry as a bulk provider of timbering wood;
- and, finally, regional development, which consistently derives strong impetus from mining activities.

5. Summary assessment of environmental relevance

In sum, underground mining can be referred to as an activity with substantial impact on the environment. The consequences can be very detrimental to the environment, especially through the extraction of resources, alteration of the rock structure and groundwater regimen, pollution of the air, the effects of noise and dust, pollution of surface water and alteration and disruption of the landscape. Compared to surface mining, underground mining has modest surface area requirements, both for the winning of raw materials and for other industries. With the exception of leftover rubbish dumps, the area in question is only needed for as long as the deep mine remains in operation.

Among the most significant environmental effects of underground mining is its impact on the miners themselves, whose health and safety are quickly and seriously jeopardized, if the protective rules, regulations and measures are not systematically adhered to.

Finally, underground mining has social consequences, especially in connection with speculative forms of mining, e.g., for precious metals or gems.

Many environmental consequences can be moderated but not prevented. Extensive data is needed as a basis for assessing the environmental impacts and designing protective measures; the uncertainty levels are accordingly high. Even the preparatory activities (reconnaissance, prospection and exploration) necessitate good coordination between the relevant environmental impact assessments and their data requirements.

The stipulation, enforcement, monitoring and control of limit values and underground mining operations has, to a certain extent, evolved to exemplary levels. Direct application of limit-value enforcement and monitoring to other countries is only conditionally possible, since the basic prerequisites usually differ. Nevertheless, every attempt should be made to apply and meet standards designed to preclude detrimental effects on man and the environment. Probably the biggest problem from an environmental standpoint are the uncounted "informal" small-scale mining activities employing uncontrolled, inadequate, unsafe methods that also tend to be hazardous to the environment.

Proper and orderly mining operations require stringent supervision (routine measurements, data collection and monitored adherence to essential limit values). That, in turn, calls for competent executing agencies.

6. References

General Literature

Arndt, P., Luttig, G.W.: Mineral resources, extraction, environmental protection and land-use planning in the industrial and developing countries. Stuttgart 1987.

Bender, F. (Ed.), 1984: Geologie der Kohlenwasserstoffe, Hydrogeologie, Ingenieurgeologie, Angewandte Geowissenschaften in Raumplanung und Umweltschutz. - In: Angewandte Geowissenschaften III: 674 pages; Stuttgart (Enke).

Bundesberggesetz (B Berg G) - 2. Auflage, Gl-Verlag, Essen 1989.

Deutsche Forschungsgemeinschaft: Maximale Arbeitsplatz-Konzentrationen und Biologische Arbeitsstofftoleranzwerte, Weinheim 1990.

Down, C. G.; Stocks, J.: Environmental Impact of Mining. Applied Science Publishers Ltd., London 1977.

EEC 85/337: Council Directive of 27 June 1985 on the assessment of the effects of certain public and private projects on the environment - Off. J. no. L175, 05/07/85, p. 0040.

Environmental impact of iron ore mining and control. Jain N.C.J. Mines Metals Fuels, vol. 29, no. 7/8, July/Aug. 1981.

Environmental monitoring and control. Wld. Min. Equip., vol. 10, no. 5, May 1986.

Franke, H., Guntermann, J. und Paersch, M.: Kohle und Umwelt, Gl-Verlag, Essen, 1989.

Inter-American Development Bank - Environmental Checklist fing Projects.

Johnson, M.S., Mortimer A.M., comps.: Environmental aspects of metalliferous mining. A select bibliography. Letchworth, Herts.: Technical Communications, 1987.

Jones, S.G.: Environmental aspects of mining developments in Papua New Guinea. Prepr. Soc. Min. Engrs. AIME, no. 88 - 155, 1988.

Kelly, M.; assisted by Allison, W.J., Garman, A.R., Symon, C.J.: Mining and the freshwater environment. (Elsevier Applied Science)

Klima-Bergverordnung (Klima Berg V), Gl-Verlag, Essen 1983.

Lambert, C.M., comp.: Environmental impact assessment, a select list of references based on the DOE/DTp. London, Department of the Environment and Department of Transport Library, 1981.

Rawert, H.: Die Erschlieng neuer Abbraure als landes- und regionalplanerisches Problem - das Beispiel Haard. In: Markscheidewesen 86 (1979), Nr. 2, p. 31 - 41.

Schmidt, G.: Umweltvertrichkeitsprbei Projekten des Bergbaus. Gl 125 (1989) Nr. 5/6.

Sengupta, M.: Mine Environmental Engineering, Volume I and II, CRC Press, Inc., Boca Raton, Florida, 1990.

Servicio Nacional de Geologia y mineria - Chile: Reglamento de Seguridad Minera. Decreto Supremo No. 72 of October 21, 1985, Ministerio de Mineria, 1988.

Solving environmental problems. World Min. Equip., vol. 9, no. 6, June 1985.

Stein, V.: Bergbau und Umwelt, Erzmetall 37, 1984 Nr. 1, p. 9 - 14.

United Nations Department of Technical Cooperation for Development (UNDTCD): Proceedings International Round Table for Mining and Environment, DSE Berlin, 1991.

World Health Organisation: Environmental pollution control in relation to development, report of a WHO Expert Committee. (World Health Organisation technical report series, no. 178). Geneva 1985.

Specialized Literature

Methane

Landesoberbergamt Dortmund: Rundverf33-111.15/7455/64-17.2.65; Bergbauverordnung Steinkohle (BVOSt) § 158, § 150; Bergbauverordnung Erzbergwerke (BVOE), § 97; Sonderbewetterungsrichtlinien; Gebirgsschlagrichtlinien; Gasausbruchrichtlinien; Gasabsaugrichtlinien

Carbon Monoxide

Landesoberbergamt Dortmund: BVOSt § 150.

Plan fbenrettungswesen, Hauptstelle f Grubenrettungswesen der Bergbau-Forschung GmbH, Essen, 1982.

Carbon Dioxide

Landesoberbergamt Dortmund: BVOSt, § 150.

Hydrogen Sulfide

Landesoberbergamt Dortmund: BVOSt, § 150.

Oxides of Nitrogen

Landesoberbergamt Dortmund: Sprengschadenrichtlinie.

Air Velocity

Landesoberbergamt Dortmund: BVOE, § 19; BVOSt, § 151; Sonderbewetterungsrichtlinien.

Airflow

Landesoberbergamt Dortmund: BVOSt, § 150.

Temperatures

Landesoberbergamt Dortmund: Klima-Bergverordnung, § 3.

Noise

Landesoberbergamt Dortmund: Maahmen f Lschutz Kleinkaliber-Bohrger (Bohrhammer, Drehbohrmaschinen), Rundverf12.21.11-4-7 (SB1.A 2.4).

Westfsche Berggewerkschaftskassen, Bochum: Gerchmeorschriften DIN 45, 365; 52 Gruben-Diesellokomotiven; 53 Dieselkatzen; 54 Gruben-Gleislos-Fahrzeuge; 55 Rangierkatzen.

Dust

Landesoberbergamt Dortmund: BVOSt, § 44 bis 48, mit Plan f Staubmessungen an ortsfesten Metellen zur Feststellung und zur gravimetrischen Beurteilung der Feinstaubbelastung, MAK und BAT.

Water

Landesamt fser und Abfall Nordrhein-Westfalen: Grundwasserbericht 84/85, Dorf 10/85.

EEC 75/448: Council Directive of 16 June 1975 concerning the quality required of surface water intended for the abstraction of drinking water in the Member States - Off J. no. L194, 25/07/75, p. 0026

EEC 80/778: Council Directive of 15 July 1980 relating to the quality of water intended for human consumption - Off. J. no. 2229, 30/08/80, p. 0011.

Dumps, Soil

Kloke, A.: Orientierungsdaten ferierbare Gesamtgehalte einiger Elemente in Kulturb, Mitteilungen des Verbandes deutscher landwirtschaftlicher Untersuchungs- und Forschungsanstalten, Heft 1 - 3. Januar, Juni 1980.

Kloke, A.: Die Bedeutung von Richt- und Grenzwerten fwermetalle in B und Pflanzen, Mitteilungen der Biologischen Bundesanstalt fd- und Forstwirtschaft, Berlin-Dahlem, Heft 223, Oktober 1984.

Stein, V.: Anleitung zur Rekultivierung von Steinbrund Gruben der Stein und Erden Industrie, K Deutscher Institutsverlag, 1985.

er die Schwermetallbelastung von B, Pflanzenschutzamt Berlin, 1985.

Clarifying Ponds

Davis, R.D.; Hucker, G.; L'Hermite, P.: Environmental Effects of Organic and Inorganic Contaminants in Sewage Sludge, Commission of the European Communities, 25./26.05.1982, Reidel D. Publishing Company Dordrecht, Boston, London.

1. Scope

Processing constitutes the technological link between the extraction, or mining, of raw minerals and their conversion into industrially useful working materials. The techniques applied are designed to separate the valuable from the barren material while upgrading, or concentrating, the former. The large variety of raw materials and the many different types of deposits in which they are found naturally necessitate an accordingly broad array of processing routes, from the simple classification and washing of sand and gravel to the more elaborate methods of processing hard coal, and on to the material beneficiation of disseminated metal ores. Ores processing (dressing) does not, however, include the various stages of metallurgical processing described in the brief dealing with the production of nonferrous metals.

In many cases, the environmental relevance of a given stage of processing increases in relation to its scope and/or degree of difficulty. The present brief therefore focuses on the environmental aspects of ore processing facilities as the source of most damage potentials.

It must be noted in that connection that no account is made of special cases such as uranium ore processing, which is already subject to special statutory regulations around the world. Likewise, no processes are dealt with that serve in the reclamation or reprocessing of spent merchandise such as worn-out batteries, scrap glass, etc.

2. Environmental impacts and protective measures

2.1 Handling

The loading and unloading of trucks and railroad cars can generate large amounts of dust. During transportation, fine dust is lost to relative (head) wind, while trucks emit pollutant-laden exhaust gases, and both trucks and trains are noisy. Transportation by truck or rail entails the consumption of land area for roads and railways. The construction and use of traffic routes can have detrimental effects on nature and residential quality; cf. briefs dealing with transport and traffic planning, provision and rehabilitation of housing, and road traffic.

In the interest of environmental protection, the mineral processing plant should be located either directly on or in the immediate vicinity of the mine premises. That way, the ore can be moved from the mine to the processing facility by conveyor belt instead of by truck or rail. If transportation by truck is unavoidable, the haul roads should be provided with a course of bituminous road-building material or concrete and kept clean at all times. A wheel-washing stand and/or routine washing of the vehicles helps reduce dust emissions. Low-emission, noise-abated trucks are designed to help reduce overall emissions of carbon monoxide, hydrocarbons, oxides of nitrogen, soot and noise. Other in-transit protective measures include moistening the load with water, tarping it over, or using closed containers. Dust extraction and control devices are required for loading and unloading operations, i.e., on loading equipment such as downcomers, and on unloading equipment such as dumping chutes. When filling closed containers with dust-generating products, the displaced air must be dedusted. The required degree of dust extraction depends on the hazardousness of the dust in question. Cyclone separators and fabric filters are inherently suitable.

Conveyor belts should be encapsulated as a pollution-prevention measure (not for maintenance purposes), i.e., as a means of restricting dust and noise emissions. The conveyor drives at the corners (diversion points) emit sound intensity levels reaching as high as 120 dB (A). Any sound insulation employed should be harmonized with that used for other noise sources within the processing plant. The use of noise locks on bunkers also helps reduce noise emissions, since the size of the opening is decisive for the amount of sound radiated during unloading.

2.2 Crushing, screening, milling, classifying

The rock material is preferably rough crushed in jaw crushers and subsequently screened, with the oversize being returned for recrushing. The normal fractions are collected in a surge bin. A conveyor transfers the material from there to the fine crusher. Classification to standard sizes involves continuous feedback of the oversize and interim storage of the standard-size fractions. Additional classification and particle-size reduction can be effected in rod or ball mills, with separation of the desired size fractions and raw materials.

All of the above processing steps involve dust and noise emissions that can emburden both the workplace and the environment.

There are no generally applicable values for the dust quantities encountered, because they depend on the crystalline structure of the minerals and of their geological association, requisite extent of crushing and various engineering factors. However, in view of now-common ore throughputs of up to 50 000 t/d, even minimal proportional dust emissions can put pressure on the soil and vegetation around ore processing facilities. In particular, the attendant deposition of heavy metals can jeopardize human health by way of the food chain, and the presence of fibrogenic dust at the workplace can cause silicosis or asbestosis.

In order to minimize dust pollution, the machinery should be encapsulated. Wherever that would be unfeasible for technical reasons, the dust-laden exhaust air should be collected and put through a dust precipitator. The type of filter to be used depends on the composition and particle-size distribution of the dust. Generally, cyclone filters are used for coarse filtering, while fabric filters serve to remove fine dust particles. Such equipment can achieve residual dust contents (clean gas dust loads) of less than 10 mg/m3. Equipment operators at dusty workstations must be required to wear dust masks (particle respirators). Masks designed for use in very warm climates should have appropriately large filtering surface areas.

In the interest of noise control, such facilities must have enclosures with a minimal number of openings. Since processing plants operate around the clock, suitable noise control measures in the form of safety distances, embankments, shielding walls and the like must be planned in at an early stage to preclude excessive prejudice to adjacent residential areas.

The only real options for limiting the workplace noise nuisance is to automate and install control centers. The operators of noisy equipment generating high acoustic intensities must be provided with ear protectors and made aware of their importance for preventing noise-induced deafness.

2.3 Separation, flotation

Ore processing facilities use water for separating buoyant and nonbuoyant, i.e. floating and nonfloating, materials: in cyclones and screen classifiers for grading by gravimetric separation or for pulp preparation, where water serves as a working medium for separating the useless material by gravimetric means and for eliminating suspended solids from the concentrate. The overall water requirement varies widely, depending on the type of raw material, the nature of the deposit, and the processes employed.

Dense-medium techniques are used exclusively for the coarse-size range, with medium solids consisting of magnetite, lead glance (galena), ferrosilicon and, occasionally, heavy spar (barium sulfate). Between 0.3 and 1 g of sodium hexametaphosphate can be added per liter of pulp to reduce its consistency. The water used in heavy media separation processes should be recirculated. Accordingly, the entrained solids have to be separated out in settling tanks, irrigated electrostatic precipitators or hydrocyclones. Even if the water from pulp regeneration is recirculated, the fresh water requirement can still amount to 0.5 - 1.5 m3/ton of crudes.

Concentration by flotation is achieved with the aid of flotation agents. Special chemicals induce physicochemical surface reactions that are useful for separating and separately concentrating mixed and disseminated ores that have been sufficiently comminuted to eliminate most intergrowth between the constituents of interest. Consequently, the solid contents of flotation slimes in part occupy the microfine to colloidal size range. Since such slimes sediment out very slowly, part of the process water can be recovered more quickly by dewatering the flotation products in thickeners. The still-wet mining wastes (tailings) are then pumped into settling tanks and given ample time - perhaps a week - for extensive sedimentation of solids. The liquid phase can be recaptured as gravitation water.

Among the various flotation agents, distinction is made between collectors, frothers and modifiers. Collectors, or collecting agents, are surface-active substances that make the surface of the ore water-repellent. Organic compounds serving as collectors are selectively employed according to the type of ore. In the flotation of sulfide ore, for example, between 10 and 500 g of xanthate is needed per ton of ore, while anywhere from 100 to 1000 g of sulfonates or unsaturated fatty acids are consumed per ton of nonsulfide ores.

Frothers, or frothing agents, which influence the size of air bubbles and help stabilize the froth in the flotation apparatus, include terpenes, cresols, methyl isobutyl carbinol, and monomethyl esters of various propylene glycols. Consumption levels run between 5 and 50 g/t for flotating crude sulfide ores.

The modifiers, or modifying agents, include chemicals for regulating the pH: lime, soda and caustic soda for adjusting the alkalinity, and predominantly sulfuric acid for acidification. Passifiers and actifiers, which are used to intensify the differences between the water-repelling properties of the ores to be separated, include copper sulfate and zinc sulfate. Alkali cyanides serve in the selective flotation of sulfide ores. Cyanides can only be added to an alkaline pulp; otherwise, hydrogen cyanide could evolve and be released to the atmosphere. The amounts required range from 1 to 10 g/t ore. Sodium sulfide, dichromate, water glass and complexing agents also belong to the group of selective flotation agents.

Many flotation agents and other chemical additives constitute a hazard to water. Consequently, carefully monitored dosing apparatus is required to preclude overdosing, and special safety requirements must be met by plant and equipment used for storing, decanting, handling and using such hazardous-to-water flotation agents. The facilities must be designed to safely preclude contamination of surface water and groundwater to an extent reflecting both the pollutive potential of the substances in question and the protection requirements of the relevant locations, e.g., potable water protection areas. Impervious, chemical-resistant, drainless collection and holding vessels must be provided to the extent

necessary for intercepting in a controlled manner any media that may escape as a result of leakage, overfilling or accidents. The retention volume must suffice to hold back the escaped substances until such time as appropriate countermeasures can be brought to bear. Additional safety precautions include double-walled storage tanks, overflow prevention devices and leakage sensors.

All requisite measures and precautions for avoiding hazards due to potential water pollutants in the form of flotation agents should be stipulated and communicated via appropriate handbooks. Plans pertaining to monitoring, repair and alarm response to malfunctions should also be compiled in handbook form. In addition, occupational safety measures must be instituted and monitored in connection with the handling of potentially dangerous flotation agents.

Sensitization and training measures are of essential importance, because the inexpert handling, storage and transportation of working agents are frequent sources of environmental pollution.

Along with the depleted material, small amounts of flotation agents, leaching chemicals and/or heavy medium can get into the tailings ponds. The gravitation water collecting in the drains should be tested for the presence of flotation agents and chemicals prior to its return to the process water circuit. Most of the agents and chemicals remain in the floated concentrate. When the concentrate is dewatered, the agents and chemicals are washed out and re-injected into the fine-grinding cycle.

Once the concentrate has been thickened, filtered and dewatered, its residual moisture content will amount to roughly 8 %. Thus, the freshwater requirement for such processing facilities can amount to about one third of the overall process water consumption rate of about 5 m3/ton of ore. The water consumption of a given concentration plant must be carefully attuned to the existing original water budget, i.e., to the available volumes of groundwater and surface waters, in order to avoid both detrimental effects on the environment and problems with the supply of drinking water.

The process water should be appropriately treated and recirculated. Processes in which the water is discharged into a recipient body on a once-through basis can cause silting and contamination of the receiving water due to high sediment contents and residual chemical additives.

The disposal of barren rock and tailings is also problematic in that it consumes land area. As the percentage of valuable material diminishes, the throughput quantities increase, and the long-term areal requirement rises proportionately. An ore processing facility with a throughput of approximately 45000 tons/d, for example, requires a settling basin measuring some 400 to 500 hectares in area and 300 to 350 million m3 in volume for 20 years of operation. In some cases, the tailing ponds can be kept somewhat smaller by extracting dried material for use in refilling underground mines. Due to the altered material properties, however, this option is only conditionally appropriate and would never be able to fully replace tailings ponds and rubbish dumps.

Large settling basins should never be constructed prior to painstaking pertinent investigation including precise specification of the physical and chemical compositions of the tailings as well as of the geological and, above all else, the hydrological set-up. The permeability of soil strata, for example, and natural drainage systems are very important with regard to groundwater protection. Since many tailings ponds stay in service for decades on end, building up all the while, the relevant accident analysis must consider a possible dam failure due to excessive surface runoff.

Rubbish dumps must be established with due attention to the fact that precipitation can induce leaching processes with attendant pollution of surface and gravitation water. Any mining waste containing large amounts of water-soluble substances or heavy metals can jeopardize the groundwater, unless the soil under the dump is sufficiently impermeable. Thus, the essential protective measures include an adequately dense subgrade, minimal sprinkling and the collection of runoff water. Before the first load of material is dumped, observation wells should be sunk for monitoring the groundwater.

It would be impossible to preclude all dust generation in connection with dump operations, but it can be minimized by keeping the discharge heights of dry tailings as low as possible and by encapsulating the transfer points. Wind erosion can be limited by compacting the surface, sprinkling the pile, applying suitable, environmentally benign binders to the surface, or planting the windward side of the heap. The equipment required for dump operation (pumps, dump trucks, conveyor belts, bulldozers,...) can be quite noisy. Noise control measures in the form of quiet tools and vehicles, acoustical barriers, etc. are called for whenever sensitive legitimate residential areas are located nearby.

The surface and gravitation water (percolation) from rubbish dumps should be collected by way of an impermeable peripheral trench and tested before being released to a recipient body. Moreover, before the water is discharged, its settleable solids content must have been ascertained as appropriate to the outlet channel's own sensitivity and intended use. Depending on the material composition of the tailings in the pond and/or of the rubbish in the dumps, additional testing for the presence of environmentally relevant pollutants such as heavy metals and processing chemicals may be necessary. The treatment required for the impounded water may consist merely of settling in an appropriate basin or, depending on the entrained substances, of physicochemical processes (precipitation, flocculation, chemical oxidation, evaporation,...).

Long-term, if not permanent, monitoring of the surface runoff and gravitation water is called for, because the nature and extent of discharge can change over time due to weathering (surface disintegration).

In addition to flotation, leaching and amalgamation also serve as separation processes. In gold mining, for example, the gold is extracted from the gravity-separated concentrate by making it react with metallic mercury to form amalgam. The concentrated residue is then leached with a cyanide solution. Both processes have negative environmental impacts that are very difficult to control. The mercury content of the effluent is particularly problematic, if the wastewater is discharged to the outlet channel without having been treated. It is still an open question as to whether or not the new ion-exchanger resins will, in the long run, be able to bind enough mercury to meet the residual concentration requirements. Leaching involves the use of numerous different chemicals. In gold processing, for example, these include cyanide, lime, lead nitrate, sulfuric acid and zinc sulfate. The processes themselves also jeopardize the air, water and soil. All measures and precautions that would apply to the concerns of environmental protection and occupational safety in connection with an industrial-scale inorganic chemical process must be allowed for at the planning stage. This would include, for example, capturing the exhaust vapors from the reaction tanks and vessels and installing vapor scrubbing equipment (vapor stacks) to prevent harmful emissions. The aqueous solutions emerging from filter presses should be recirculated, and the waste sludge from suction filters must be tested for disposability and treated as necessary. The wastewater from amalgamation and leaching processes requires periodical monitoring.

2.4 Roasting

The processing of sulfide ores includes roasting. The roasting gases contain large amounts of sulfur dioxide and therefore require gravitational separation (inertial impaction) and electrostatic precipitation. Further processing of the incidental sulfur dioxide should be obligatory, because release of the unprocessed roasting gases would unavoidably destroy most of the vegetation around the roasting plant. It is particularly important that the feed and discharge devices on the roasting furnace be airtight. Fabric filters mounted on the roasted-ore silo can extensively preclude dust emissions. To the extent that the blowers give off too much noise, their encapsulation is recommended. A chlorinating roasting process may involve the formation of polychlorinated dibenzodioxins and furans in the exhaust gas, the roasting residue and/or the slag, depending on the operating conditions and on the nature and extent of organic substances. Whenever the formation of any such harmful substance is detected in connection with a chlorinating roasting process, the operating conditions must be altered such as to minimize the level of emissions.

2.5 Storage and handling of concentrate; recultivation

If concentrates are stored outdoors and unprotected, wind- and precipitation-induced erosion can pollute the air, the soil and the waters.

The ground in the storage area should be sealed to prevent contamination of the topsoil. Continuous maintenance of adequate surface moisture and/or covering the ground with mats does not always suffice to prevent all wind erosion. Consequently, the concentrate storage area should be roofed over and enclosed, and appropriate measures, e.g., low dumping heights, should be taken to minimize dust generation during loading and unloading.

The measures to be taken in connection with hauling correspond to those described in section 2.1.

The extent to which planned heaps and sedimentation facilities would occupy the former life space, i.e., the habitats, of local flora and fauna must be ascertained on a case-by-case basis. The possibility of promptly recultivating slopes should also be examined as a means of preventing wind- and water-induced erosion while achieving a certain degree of ecological compensation. The nature and extent of early recultivation must be discussed and coordinated with those responsible for regional/landscape planning and defined in a catalogue of measures. If the area in question is to be used for agricultural or horticultural purposes, the anthropogenic pollutive burdens in the stored material and their mobility (pollutant transfer factors) must be accounted for by appropriate measures such as sealing or compacting of the subsoil to interrupt the paths of emission. Even at the planning stage, information should be gathered on the availability of cultivable materials fit for land restoration.

3. Notes on the analysis and evaluation of environmental impacts

The processing, handling and transportation of raw minerals can cause substantial environmental pollution by dust evolution. The most effective available means of dust collection and precipitation must be applied to dust containing cadmium, mercury, thallium, arsenic, cobalt, nickel, selenium, tellurium or lead. Quartzose dust (silica dust) can cause silicosis and therefore must be allowed for as an occupational safety consideration. Depending on the mass flow, the material must be analyzed for the presence of the aforementioned heavy metals, and clean-gas limits need to be defined, whereas those for cadmium, mercury and thallium should be lower than those pertaining to the other heavy metals. The workplace dust concentrations must be monitored as a basis for controlling the silicosis hazard. Industrial medical care must be provided for the workers.

The local vegetation is liable to be destroyed by the caustic effects of mineral constituents dissolved by rain. Also, a thick layer of dust can so strongly impede the plants' natural assimilation process that they die off. The soil around processing facilities for ores containing heavy metals can eventually become contaminated. The geogenic contents of the soil should be determined prior to erection of any such facility.

Well-proven dust collecting and precipitating devices are available for use in controlling dust emissions. Their adequate separation efficiency in continuous operation must be monitored. The nature and extent of inspections, preventive maintenance and repair of precipitators should be specified in a service manual.

Under certain unfavorable conditions, an accumulation of heat, an overheated bearing or a spark can trigger the ignition or fulmination of fine dust. Good ventilation, possibly in combination with inertization, pressure-surge-proof encapsulation and/or the use of pneumatic drives, can substantially reduce the hazard.

Substances constituting a hazard to water in connection with ore dressing processes can lead to soil and water pollution due to leakage, carelessness, accidents, etc. Consequently, all facilities required for storing, decanting, handling and using potentially water-polluting substances must be designed and operated such as to avoid contamination of the soil and water. Appropriate precautionary measures also must be taken for the transportation and disposal of the chemicals, and pertinent occupational safety measures must be specified for handling them. The potential environmental hazards emanating from the chemicals (cyanides, mercury, etc.) and from the acidic roasting gases involved in separation and concentration processes based on leaching, amalgamation and roasting can be particularly severe. Thus, appropriate measures must be taken to hold back the mercury, cleanse the roasting gases, control the leaching process, and otherwise contribute toward the minimization of emissions.

Tailings ponds, settling basins and rubbish dumps for the residues of dressing processes all have substantial space requirements. Knowledge of the subsoil structure is important for properly assessing the effects of harmful emissions. With a view to ensuring the long-term protection of groundwater and surface waters, relevant special studies and analyses must be conducted at the planning stage. There are as yet no official limit values for acceptable levels of ground contamination by mill slurries from the processing of raw minerals. Consequently, planners of new facilities have to rely on experiential values gleaned from settling basins for similar dressing plants. In the case of coal mud heaps, good compaction is required to prevent spontaneous combustion.

To the extent that farmland and, hence, income potential must be sacrificed for processing activities, the consequences for the affected subpopulation, women in particular, must be investigated and suitable alternatives developed as necessary. Early involvement of the local populace in the dissemination of information and decision-making processes is an effective means of avoiding or alleviating conflicts in advance.

The effluent from mineral processing activities and the gravitation water emerging from tailings ponds and rubbish dumps may contain heavy metals or potentially water-polluting chemicals that pose a hazard to surface water, groundwater and the soil. Special attention must be given to the possible jeopardization of potable water supplies. In case of excessive sediment contents, the river bed is liable to silt up and accumulate harmful substances. The wastewater from ore processing plants therefore has to be continuously monitored. Depending on the nature and extent of settleable solids, heavy metals or chemicals posing a hazard to water, the effluent will require appropriate treatment.

Properly sized equipment enclosures with adequate acoustic insulation properties are very important for reducing the amount of noise emitted by processing plants. Appropriate safety clearances should also be planned in for between the plant and neighboring residential areas. Suitable noise control measures also should be applied to the operation of tailings ponds and rubbish dumps located in the near vicinity of residential areas.

Permissible noise emission levels are specified in Germany's TA-L (Technical Instructions on Noise Abatement). The site surroundings - e.g., an industrial zone, commercial area or residential district - are decisive for the maximum allowable noise intensity level.

As in Germany, ore processing plants should have immission-control, water-pollution-control and waste-management officers, whose positions should be independent of the production division. A safety officer and an occupational physician should be available for matters concerning occupational safety.

4. Interaction with other sectors

As a rule, mineral processing plants are attached directly to the relevant mining operations. The environmental briefs pertaining to mining therefore apply.

The large area required for a processing plant necessitates its coordination with present and planned regional land use. As such, the environmental briefs Spatial and Regional Planning, Planning of Locations for Trade and Industry should also be consulted.

If the processing plant cannot be installed directly at the mine, appropriate roadbuilding measures become necessary, in which case important details can be found in the briefs Road Building and Maintenance, Building of Rural Roads.

In arid regions, the water neeeded for operating the processing equipment is a very important resource, and its judicious use must be incorporated into Water Framework Planning.

5. Summary assessment of environmental relevance

If the planned site of a processing plant is located in a thinly populated area, it must be brought in line with the goals of regional development planning. In selecting the site, importance should be attached to choosing a location with a relatively low level of ecological sensitivity and which is not crucial to the vitality of the regional natural household.

Most processing plants emit large amounts of material- and process-generated dust and noise. Within the plant premises, such nuisances/pollution can be reduced to tolerable levels by the use of suitable enclosures and dust retention devices. Dust emissions from dry heaps and dumps, however, is more difficult to control, particularly when finely comminuted material is exposed to wind and weather. Such material must be kept moist and/or covered, and the surface should be consolidated or sown over.

Large volumes of low-grade material accumulate at processing plants and have to be pumped into tailings ponds for sedimenting. Before any such settling basin is established, its long-term environmental impacts must be carefully analyzed, because it could well remain in operation for several decades, becoming larger and larger all the while. The analysis must cover important aspects of protection for the soil and groundwater, stability (e.g., in case of flooding) and subsequent recultivation, including definition of appropriate measures.

Prior to establishing and operating rubbish dumps, the site-specific hazard potentials for the subsoil, groundwater and surface waters must be carefully investigated. The subgrade must be sealed and a means of collecting all surface runoff and gravitational water provided.

Old tailings ponds and dumps should be given close-to-natural shapes prior to their recultivation in order to fit them into the landscape in a manner appropriate to their planned future use.

Process effluent and gravitational water from processing plants, tailings ponds and rubbish dumps must be put through wastewater treatment facilities, the nature and extent of which depend on the sensitivity and manner of utilization of the recipient body. Silting should be avoided, of course, and pollution by mercury and other heavy metals should be minimized. Observation wells should be sunk to allow monitoring of the groundwater.

Bulk transportation by road or rail can have negative impacts on the environment: through construction of the required hauling routes (and attendant erosion potential) and in the form of airborne dust and noise. Dust emissions can be avoided by hauling the material in closed containers. Quiet, low-emission trucks should be given preference. Fine-grained material should not be stored in the open air for any length of time. Otherwise, wind- and precipitation-induced erosion could cause pollution of the soil and water. Frequently, the cost of relevant environmental protection measures is more than offset by resultant reductions in the loss of resources.

6. References

Rules and Regulations

Anforderungskatalog f-Anlagen: Anforderungen an Anlagen zum Herstellen, Behandeln und Verwenden wassergefdender Stoffe (HBV-Anlagen) Ministerialblatt f, Nr. 12, 1991, p. 231 - 234.

Deutsche Forschungsgemeinschaft: Liste maximaler Arbeitsplatzkonzentrationen (MAK-Wert-Liste), 1990, Mitteilung XXVI, Bundesarbeitsblatt 12, 1990, p. 35.

EC Directives: Protection of workers from the risks related to exposure to noise at work, May 12, 1986 - 86/188/EEC, and of June 14, 1989 - 89/392/EEC - on the approximation of the laws of the Member States relating to machinery.

Environmental Protection Agency (EPA): Standard of Performance for Nonmetallic Mineral Processing Plants, EPA 40, Part 425 - 699 (7-1-86 Edition) 60, Subpart 000, Preparation Plants and Coal Preparation Plants, EPA 40, Part 425 - 699 (7-1-86 Edition) 434.23.

Katalog wassergefdender Stoffe: Lagerung und Transport wassergefdender Stoffe. LTWS Reihe No. 12, 1991, Umweltbundesamt [German Federal Environmental Agency] Berlin.

Technische Anleitung zum Schutz gegen L: TA-L, (Technical Instructions on Noise Abatement) vom 16.07.1968, Beilage BAnz. (supplement to the Federal Gazette) Nr. 137.

Unfallverhvorschriften: Hauptverband der gewerblichen Berufsgenossenschaften, Bonn - u.a. UVV-L, VBG 121 v. 01.01.1990.

VDI Guideline 2560: Personal Noise Protection, December 1983.

VDI Guideline 2058, sheet 1: Assessment of Working Noise in the Vicinity, September 1985.

VDI Guideline 2263, sheets 1 to 3: Dust Fires and Dust Explosions; Hazards, Assessment, Protective Measures, November 1986, November 1989, May 1990.

Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsgesetz, vom 27.02.1986 (Technische Anleitung zur Reinhaltung der Luft - TA-Luft), GMBI. (joint ministerial circular) 1986, Ausgabe A, p. 95.

16. Allgemeine Verwaltungsvorschrift: Mindestanforderungen an das Einleiten von Abwasser in Gewer. Steinkohleaufbereitung und Steinkohlebrikettfabrikation. GMBI. (joint ministerial circular) No. 6, 1982.

27. Allgemeine Verwaltungsvorschrift: Mindestanforderungen an das Einleiten von Abwasser in Gewer, Erzaufbereitung. GMBI. (joint ministerial circular) No. 8, 1983, p. 145.

Wiedernutzbarmachung von Bergehalden des Steinkohlebergbaus Bellmann Verlag, Dortmund, Verlags-No. 614, 1985.

Zulassung von Bergehalden: Richtlinien f Zulassung von Bergehalden im Bereich der Bergaufsicht, MBI. NW. (North-Rhine/Westphalia ministerial circular), p. 931, dated July 13, 1984.

Technoscientific Contributions

Alizadeh, A.: Untersuchungen zur Aufbereitung von Golderzen. Aufbereitungstechnik 5, 1987, p. 255 - 265.

Alizadeh, A.: Grundlagenuntersuchung zur mathematischen Beschreibung der Flotation von oxidischen Eisenerzen. Aufbereitungstechnik 2, 1989, p. 82 - 90.

Atmaca, T.; Simonis, W.: Freistrahlflotation von oxidischen und sulfidischen Erzen im Feinstpartikelbereich. Aufbereitungstechnik 2, 1988, p. 88 - 94.

Diesel, A.; L.P.: Lagerung und Transport wassergefdender Stoffe, Erich Schmidt Verlag, 1990.

Kirshenbaum, N.W.; Argall, G.O.: Minerals Transportation, Proceedings of First International Symposium on Transport and Handling of Minerals, Vancouver, 1971.

Sciulli, A.G. et al: Environmental approach to coal refuse disposal, Mining Engineering, 1986.

Ullmanns Enzyklope der technischen Chemie, 4. Auflage: Band 2 Verfahrenstechnik I, 1972, Band 6, Umweltschutz und Arbeitssicherheit, 1981, Verlag Chemie, Weinheim.

Williams, R.W.: Waste Production and Disposal in Mining, Milling and Metallurgical Industries, Miller Freeman Publ., San Francisco, 1975.

1. Scope

In the year 2000, petroleum and natural gas together will cover between 50 % and 70 % of the global energy requirement, and the energy-coverage ratio between the two will be about 2: 1 to 1.5 in favor of petroleum. Obviously, in view of the corresponding scale of petroleum and natural-gas production, countries with major resources and corresponding development projects in the mining sector will have continued exposure to consequential environmental impacts. Due to the immobility of deposits and to the technical processes required to obtain the crude product, petroleum and natural-gas mining activities have their own specific environmental consequences. According to prevailing international definitions, a typical petroleum/natural-gas development project comprises the following three phases:

- exploration, on- and offshore, mainly by geophysical methods and exploration drilling, including a test phase following any discovery;
- production, beginning with field development drilling as a precondition for actual production, in the course of which certain phases are run through, up to and including basic conditioning of the raw material. The production of crude oil and natural gas requires a certain infrastructure;
- handling and storage directly following the production stage, i.e., prior to the further processing of crude oil and natural gas into energy-market products. These activities utilize part of the overall infrastructure.

2. Environmental impacts and protective measures

2.1 Exploration

Exploration is the term used to define the scientific prospecting and reconnaissance of raw material deposits by means of

- mapping/charting
- geophysics
- exploratory drilling.

Exploration for petroleum and natural-gas is based on a large-scale, onshore-specific aerial mosaic (photomap). In many regions of the world, superficial analysis of such maps can suffice to detect promising areas. Exploration then continues according to geophysical and geochemical methods of prospection. Finally, the superficial geological, geophysical and geochemical reconnaissance of promising structures requires confirmation by way of exploratory drilling, incl. well shooting, and the interpretation of drill cuttings and cores.

The environmental consequences of exploration are relatively minor on the whole, though the attendant drilling has a substantially higher disruptive hazard potential; cf. environmental brief Reconnaissance, Prospection and Exploration of Geological Resources.

2.1.1 Nature and ecology

Modern airborne mapping techniques employed at the beginning of the exploration phase pose no direct threat to the environment.

Depending on the applied techniques, the environmental consequences of geophysical prospection can extend over a period of months or years. Distinction must be drawn between gravimetric techniques and predominantly airborne magnetic measuring methods on the one hand, and seismic measuring methods on the other. The latter put geophysicists in a position to locate geological bedding boundaries at depths of several thousand meters by registering reflected compression waves. Indeed, the seismic reflection method is the most important prospecting tool, but it is not without consequences for the environment.

Even assuming a relatively brief disturbance, negative environmental impacts must be limited. Geophysical surveying teams, for example, live more or less self-sufficiently in remote areas for various lengths of time. Their access and transportation routes should preferably be by air or water, depending on the circumstances. Overland routes must include any deviations/detours necessary to avoid ecological disruption. With regard to blasting, the magnitude of the explosions used to generate pressure surges must reflect the state of the art. In some cases, vibroseismics may constitute a less disruptive alternative. Advanced receivers and amplifiers yield extensive information at lower pulse levels. Offshore blasting has destructive effects on marine life, particularly in the littoral zone. Alternative use of the air-pulse technique effectively protects marine flora and fauna.

On a regional basis, the most pronounced environmental consequences for nature and the ecology derive from deep drilling. If, however, state-of-the-art drilling equipment is (properly) used, the environmental impact frequently will remain far below what laypeople would expect. The main objective for drilling operations is to carefully plan, equip and conduct terminal exploration projects such as to either avoid negative environmental impacts altogether or at least reduce them to a tolerable level.

In connection with the preparation of drilling sites and the construction of access roads, due consideration must be given to subsequent renaturation, and disruption of the surface must be limited to the necessary minimum. The topsoil must be protected as well as possible (in covered heaps, etc.).

Drilling must be conducted such as to preserve the intactness of the rock strata and water-bearing horizons in their original, virgin separations through appropriate casing and cementation programs.

The media required for drilling, in particular the drilling fluid, should be chosen with attention to low environmental impact and subsequently recycled to the greatest possible extent.

Borehole safety, which is understood mainly as uninterrupted control over the dynamic pressure situation and borehole stability, must be ensured by adequately sized casings and cementation in combination with a blow-out preventor serving as a drilling-phase closure system (state of the art). Preventive measures in the form of technical equipment and disaster plans must be taken to limit the consequences of blow-outs. Such precautionary measures can prevent major environmental damage, which, while seldom irreversible, can be very expensive to repair.

Unavoidable, unrecyclable mining refuse like borehole cuttings and spent drilling fluid must be properly disposed of. With due regard for the environmental circumstances, preference must be given to dilution, thermally optimized incineration and/or encapsulation.

The slim-hole drilling technique must be considered as an alternative to conventional deep-well drilling. The technique is characterized by a much-reduced diameter, minimal use of operating media, less technical inputs overall, and such substantial time savings that the cost of drilling can be cut in half. Slim hole drilling does, however, presuppose certain geological conditions and is inherently unfeasible for deep wells.

The exploration drilling phase is not complete until all appropriate protective measures have been taken to counter the adverse environmental consequences of activities pursued in connection with successful exploration, i.e., the discovery of an exploitable field, which may last several years.

Any well that remains dry must subsequently be properly plugged, and the attendant aboveground facilities, including access routes, must be either recultivated or surrendered to some other controlled form of utilization.

2.1.2 Sociology

Exploration projects can seriously alter the social fabric of a country or region. Practically overnight, they expose native social systems to the activities and influence of multinational companies employing modern technical know-how. Conflicts of interest resulting from the immobility of prospective petroleum and natural gas deposits must be dealt with appropriately. The project must be integrated into the prevailing social structure as quickly as possible. That, in turn, requires the involvement of all social groups.

2.1.3 Human health and occupational safety

In general, urgent priority must be attached to occupational safety and to preservation of the health of petroleum and natural-gas exploration workers. The effects of such projects on parties not directly involved in the exploration work are insignificant.

The most obvious problems are those deriving from the difficult, privative work of geophysical surveying crews, especially in remote regions, and which continue through the end of exploratory drilling.

Since local personnel can be hired and trained relatively quickly for some of the work, appropriate individual support must be planned in. Medical care, hygiene and occupational safety must be guaranteed, and acceptance of worker protection measures, which demand a certain amount of training, must be ensured.

2.2 Production

Successful exploration is followed by the petroleum and/or natural-gas production phase, which includes:

- field development drilling, incl. complete preparations for production,
- aboveground installations and processing facilities,
- infrastructural measures.

A substantial share of the petroleum and natural gas resources that took millions of years to develop has been used up within a relatively short span of time. In the interest of long-term utilization, the human race must exercise a sense of responsibility in dealing with those natural resources - which are only renewable in terms of geological time spans. In reality, however, traditional oil-producing countries tend to adopt volume-oriented production strategies, accepting substantial environmental consequences as attendant phenomena. Production strategies in general are heavily influenced by the demand situation and as yet inadequate alternatives.

The time between exploration and production should be used to carefully analyze the project's anticipated environmental impacts for the duration of an average production field life (15 to 25 years for an oilfield and 50 to 100 years for gas) - and beyond. The analysis must be based on timely local and individual registration of the sociological, cultural economic, climatic and ecological situation, which, of course, differs widely around the world. The results of analysis must then be incorporated into each and every relevant resource production project.

The beginning of the field development drilling work should coincide with the establishment of requisite infrastructure, e.g., access routes, incoming and local service lines, and even the aboveground pumping facilities, processing plant, etc. With regard to the attendant environmental consequences, the reader is referred to the corresponding brief Road Building.

2.2.1 Nature and ecology

The long-term production phase of a typical petroleum/natural-gas project begins with the first regular output. Field development drilling prepares a deposit for production on the basis of the production geological and field engineering targets defined to reflect the underground conditions prevailing in the reservoir. The environmental consequences of exploration, as described in section 2.1.1 apply in full.

Especially in sensitive areas with valuable biotopes, the equipment used must be chosen with a view to minimizing space requirements. Thanks to advanced drilling technology (directional drilling with deflecting tools), a single onshore or offshore location now often suffices for tapping several square kilometers of a reservoir. And horizontal drilling can help to drastically reduce the overall number of boreholes.

Large-scale destruction or alteration of an area's flora and fauna (e.g., in a rain forest, tundra or coral reef) need not occur in connection with petroleum/natural-gas projects, which have relatively modest aboveground space requirements for technical equipment and infrastructure.

Through state-of-the-art plant dimensions in combination with necessarily redundant automatic monitoring equipment, emissions occurring under normal and disturbed operating conditions can be held at low levels.

Damage to the environment as a result of accidents, oil spills in particular, must be limited by safety-relevant controls, e.g., valving. Oil-contaminated water and soil must be rehabilitated by chemicobacterial means of artificially accelerating the biodegradability of hydrocarbons. A properly managed oil well causes no problems with regard to groundwater protection.

The economically efficient exploitation of natural energy vehicles must attach priority to controlling the environmental impacts while conserving the resource itself. For petroleum and natural gas, the conservation of resources covers both the effective utilization of their entire energy potential (by avoiding such activities as the pollutive flaring off of surplus production that cannot be directly utilized) and the alternative employment of high-tech production techniques.

2.2.2 Sociology and economics

The productive phase of an oil or gas field lasts on average about as long as a normal person's working life - if not even longer, as is frequently the case in gas production. That fact alone imposes a major social responsibility on the project. In continuation of the initial exploratory-phase measures, the living conditions, nutrition, education, health and cultural environment, including religion, of the personnel must be treated as importantly as the purely technical production facilities. Ghettoization must be countered, and the growth of social fabric must be promoted. Industrialization must be conducted cautiously and in a manner to allow incorporation of the cultural heritage of the aboriginal society.

2.2.3 Human health and occupational safety

One of the project executing organization's most important tasks is to promote health care, not only among the workers themselves, but also throughout the entire project region.

The same applies to occupational safety, which can and should be implemented in imitation of measures applied in industrialized countries. The assignment of well-trained and qualified personnel to such tasks is a crucial prerequisite.

2.3 Handling and storage

Handling and storage is understood here as the last step following exploration and production. The rough-processed crude products are transported by pipeline, railroad car or road tanker, and by inland waterways and oceangoing vessels, all of which requires special infrastructure. The products are stored in aboveground tank farms and underground stores, cavities and pore spaces.

The transportation/shipping, distribution mechanisms and finished-product storage scopes are not covered by this brief; please refer to the briefs relevant to adjacent sectors, e.g., shipping, ports and harbours, inland ports.

2.3.1 Nature

The requirements stated in section 2.3.1 apply analogously to transportation.

The large-scale storage of crude oil and/or natural gas requires special environmental safety measures, particularly with regard to the prevention of fires and explosions. Special importance is attached to leakage detection, alarm sounding and catchment techniques. Underground tanks are preferable to aboveground tanks, though they do call for more sophisticated safety engineering.

As an alternative to tank farms, underground storage in depleted mines, rock caverns, salt caverns and pore spaces has the least extensive environmental consequences. Pore spaces are only suitable for storing gas, and salt caverns demand appropriate utilization or disposal options (proximity to the ocean) for the brine. Both alternatives - pore spaces and salt caverns - presuppose the appropriate geological formations.

2.3.2 Human health and occupational safety

The large-scale handling and storage of oil and gas poses hazards such as the escape of hydrocarbons and the possibility of accidental explosions. Technical transportation monitoring measures and redundant storage safety engineering substantially reduce the risks involved. Pipeline safety can be ensured via monitoring stations, self-acting pressure control devices and aerial line inspections. Storage tanks and piping must be protected against corrosion.

3. Notes on the analysis and evaluation of environmental impacts

The environmental impacts must be evaluated with due consideration of the individual, project-specific situation. Project planning should be conducted with emphasis on the potential sociological consequences and the earliest possible involvement of local nationals. Environmentally relevant experience drawn from comparable projects must be duly considered.

The training of local manpower for all levels constitutes an important step in the direction of responsible management with a capacity for controlling environmental consequences. The project must be implemented in line with the pertinent laws, standards, codes, limit values and technical know-how of industrialized countries.

4. Interaction with other sectors

As the profitability of exporting natural gas is limited by the long transportation distances involved, many countries neglect its production. In that connection, the technical utilization of liquid natural gas (LNG) would appear worthy of promotion, since the transport problems would be relativized by the use of accordingly large tankers. By reason of its high efficiency, natural gas makes a good, nonpolluting substitute for other primary energy carriers.

The petroleum/natural-gas sector has numerous points of contact with other sectors, among the more important of which are:

- regional planning
- overall energy planning
- water supply
- planning of locations for trade and industry
- mechanical engineering, workshops, shipyards
- oil and fats.

References to adjacent sectors have been included in the appropriate passages of the above text.

5. Summary assessment of environmental relevance

Global experience shows that the petroleum and natural gas industry can maintain an ecological orientation with the aid of modern science and technology. Environmental awareness must be promoted by applying the standards of the most advanced industrialized countries.

Risks and undesirable environmental consequences must be minimized by responsibly implementing each project in accordance with its own ecological and sociological significance. Interdisciplinary management with the direct involvement of all sections of the population is appropriate and advisable.

Ecologically oriented operations presume the existence and adequacy of the requisite control organs. In that connection, an environmental protection officer carrying the responsibility for training the workers and instilling them with environmental awareness can be a major asset.

6. References

ASUE: Erdgas als Beitrag zur Milderung des Treibhauseffektes, AG Sparsamer Umweltfreundlicher Energieverbrauch, Frankfurt/Main, 1989.

ASUE: Die Richtung stimmt - Erdgas als Brur idealen Energie, AG Sparsamer Umweltfreundlicher Energieverbrauch, Frankfurt/Main, 1990.

BMFT (German Federal Ministry for Research and Technology): Schriftenreihe Risiko- und Sicherheitsforschung, S. Lange, Ermittlung und Bewertung industrieller Risiken, Berlin, 1984.

BMI (German Federal Ministry of the Interior): Beirat LTwS Lagerung und Transport wassergefdender Stoffe, diverse publications.

CONCAWE: Methodologies for hazard analysis and risk assessment in the petroleum refining and storage industry, Den Haag, 1982.

CONCAWE: 1989 Annual Report, Brussels, 1990.

Deutsche BP: Das Buch vom ErdKleins Druck- und Verlagsanstalt, Langerich, 1989.

DGMK: Forschungsbericht zum Umweltschutz, Hamburg, 1974 - 1986.

Deutsche Shell: Neue Aspekte der - und Gasfrung, Deutsche Shell AG, Hamburg, 1989.

Enquete-Kommission, Bundestag: Schutz der Tropenwer, Economica Verlag, Bonn, 1990.

Enquete-Kommission, Bundestag: Schutz der Erde, Teilband II, Economica Verlag, Bonn, 1991.

Friedensburg/Dorstewitz: Die Bergwirtschaft der Erde, Ferdinand Enke Verlag, Stuttgart, 1976.

Hoffmann, JP.: - vom ersten bis zum letzten Tropfen, Westermann Verlag, Braunschweig, 1983.

IMO: Inter-Governmental Maritime Organization, Results of International Conference on Tanker Safety and Pollution Prevention; with Regulations and Amendments, London, 1981.

Konzelmann, Gerhard: , Schicksal der Menschheit? Sigloch Service Edition, Kau, 1976.

Mayer, Ferdinand: Weltatlas Erdnd Erdgas, Westermann Verlag, Braunschweig, 1976.

M Karlhans: Jagd nach Energie, Sonderausgabe, Regel und Meechnik GmbH, Kassel, 1981.

OECD: Emission standards for major air pollutants from energy facilities in OECD member countries, Paris 1984.

OTA: Office of Technology Assessment of the Congress of the United States, Technologies and Management Strategies for Hazardous Waste Control, Washington, 1983.

UBA Materialien: Symposium Lagerung und Transport wassergefdender Stoffe, 2/83.

UBS Texte 32/83: Vorhersagen von Schadstoffausbreitungen auf See - insbesondere nach unfen.

Ward, Edward: in aller Welt, Orell FVerlag, Zurich, 1960.

World Bank: Environmental guidelines, Washington, 1983.

World Bank: Environmental requirements, Washington, 1984.

1. Scope

This environmental brief covers various coal upgrading technologies, incl. coking and low-temperature carbonization as processes yielding the target products coke and gas plus tar products and diverse raw chemicals.

The relevant facilities can be installed and operated either separately or in conjunction with neighbouring industrial technologies; cf. environmental briefs Planning of Locations for Trade and Industry, Spatial and Regional Planning.

Interconnected operations can be characterized by proximity to either collieries or iron works.

While in the former case the working product coal can be conveyed directly to the upgrading facility located only a short distance away, close proximity to a metallurgical plant avoids the necessity of transporting the product coke over long distances and enables direct supply of the gas to the consumer by way of a low-pressure network; blast furnace gas from the metallurgical plant can serve as low-sulfur fuel gas for, say, a coking plant.

If the coal upgrading facility is instead located separately and independently, substantial infrastructural measures will be required for conveying, loading, unloading and storing the working materials, process materials and products; cf. environmental briefs Transport and Traffic Planning, Railways and Railway Operation, Inland Ports.

In addition, the generated gas has to be compressed and purified to piped-gas quality before it can be supplied to the consumers.

The low-temperature-carbonization and coking processes, as applied to coal in the sense of this brief, are based on heating in exclusion of air in appropriate reactors.

Depending on the temperature at which the process takes place, distinction is made between:

- low-temperature carbonization (450 - 700°C)
- medium-temperature coking (700 - 900°C)
- high-temperature coking (>900°C).

While the above processes do not differ at all in principle, the different temperatures yield different products and process conditions and call for the use of different reactor systems.

a) Low-temperature carbonization processes

Low-temperature carbonization processes, as applied primarily to lignite (brown coal), take place in fixed-bed reactors, fluidized-bed reactors or entrained-bed reactors.

The heat supply derives from:

- the use of hot coke as a heat transfer medium or
- the direct supply of heat to the working material via hot cycle gas (circulation gas).

The gas produced by low-temperature carbonization is cooled (condensed), detarred, compressed and purified prior to delivery. Residual coke is cooled by means of either wet quenching or cold gas before being supplied to the users.

Low-temperature carbonization processes are used primarily for obtaining tar products, diverse raw chemicals and low-temperature-carbonization gas. The incidental coke is of no particularly high quality and therefore not used for metallurgical purposes. Consequently, other uses must be found for such coke, preferably uses that do not require high crush resistance.

b) Coking processes

Hard coal is coked in batteries of regenerative horizontal chamber ovens. Distinction is made between top charging and stamping operation, depending on the extent to which the coal is likely to produce high-quality, adequately stable blast-furnace coke.

Coke ovens are heated indirectly by fuel gas, the heat of which is transferred to the charge (feed coal) via heating walls. The fuel gas can consist of partially purified coke oven gas, blast furnace gas or a mixture of combustible gases. Even if the entire operation is heated exclusively with coke oven gas, the plant will still yield surplus quantities of gas with calorific values ranging from roughly 16 000 to 20 000 kJ/m³. Following appropriate purification, that gas can be supplied to diverse consumers.

Oven service equipment is needed to fill coal into the ovens (charging cars), transfer the coke to quenching stations (quenching cars) and convey the hot coke to the wet quenching or dry cooling plant.

Coke oven gas is produced above the charge at coking temperatures of 750 - 900°C. Through riser pipes, the gas passes into a so-called collecting main, where it is sprayed with recirculating water to induce cooling and partial condensation, thus precipitating most of its crude tar content.

The next stage of treatment consists of additional cooling to approximately 25°C, followed by final tar removal in electrostatic precipitators, and the primarily absorptive extraction of such constituents as H2S, NH3, HCN, CO2, benzene and naphthalene.

Those ingredients are further processed according to various techniques to obtain:

- ammonium sulfate (after transformation of H2S into sulfuric acid)
- Claus sulfur (with simultaneous cracking of ammonia)
- crude benzene and
- crude tar.

If the surplus coke oven gas cannot be injected into an LP (low-pressure) network, it is put through a gas compression stage that includes additional purification to remove H2S and raw benzene/naphthalene and to lower its dew point.

Wastewater deriving from condensation of the gas and from the H2S/NH3 scrubbing stage is treated in multiple stages including distillation in so-called strippers and dephenolating processes (extraction, biological elimination).

Modern coking plants can handle between 6 000 and 10 000 tons of feed coal a day for a coke output of 4 500 - 7 500 t/d.

The attendant gas production amounts to between 80 000 and 150 000 m³/h, and process wastewater accumulates at the rate of 80 - 150 m³/h.

c) Classification of process options

From the standpoint of environmental protection, carbonization and coking are roughly equivalent.

With regard to production capacities and technological applications, however, coking takes priority over carbonization, as evidenced by the fact that most laws, regulations and guidelines pertaining to the control of emissions refer mainly to coking processes. Nonetheless, carbonizing facilities should be dealt with under the same premises.

2. Environmental impacts and protective measures

2.1 Environmental impacts

The erection and operation of coking and/or coal carbonizing plants at locations previously not used for industrial purposes alters the landscape and consumes land to an extent that depends on the size of plant.

In addition to ascertaining the potential effects of emissive pollution, it must also be determined to which extent the requisite extraction of water from given resources would interfere with existing ecosystems, since make-up water is required at various points of both operations. The required volume of water can range from 200 to 500 m³/h; cf. environmental briefs Water Framework Planning, Water Supply.

Particularly in connection with coke oven batteries, emissions must be anticipated both from certain operating points (e.g., exhaust stacks) as well as from diffuse sources such as leaky shutoff valves and cracks in the masonry of coke ovens.

The following emissions are deemed particularly relevant:

a) Air pollutants

Including:

- suspended solids (coal and coke dust)
- gaseous and vaporous emissions, e.g.:

· sulfur dioxide (SO2)
· hydrogen sulfide (H2S)
· oxides of nitrogen (NOx)
· carbon monoxide (CO)
· benzene, toluene, xylene (BTX)
· polycyclic aromatic hydrocarbons (PAH)
· benzo(a)pyrene (BaP)

b) Wastewater pollutants

Including:

- various nitrogen compounds
- phosphorus
- chemical and biological oxygen demand
- phenols
- polycyclic aromatic hydrocarbons
- cyanides
- sulfides
- BTX
- sum of all toxic substances classified as such on the basis of, say, toxicity toward fish (fish test).

c) Noise emissions

Coking plants have numerous noise emitters at all points of the operation. Each and every drive unit, for example, constitutes a source of noise.

The equipment used for mixing, crushing and screening coal and coke and for compressing gas is particularly noisy and therefore requires comprehensive noise-control measures. Otherwise, some emitters are liable to develop noise intensity levels significantly above 85 dB(A).

In order to preclude noise-induced detriment to human health, both the sound sources themselves and the general vicinity of such equipment are subject to certain emission and immission limits.

d) Soil and groundwater

The handling and storage of coking products, crude tar, crude benzene, sulfuric acid and various purchased chemical additives pose a hazard potential for soil and groundwater.

Environmental consequences result from emissions, the effects of which in the vicinity of the installations can be damaging both to human health and to nature and which are monitored by way of ground-level pollutant concentrations. Also, near-source pollution occurring directly at and around the workplace demands careful attention. In the interest of occupational safety, so-called maximum working-site concentrations (MAK-values), so-called occupational exposure limits, and technical concentration guidelines (TRK-values) have been specified.

Improper handling of substances constituting a hazard to water can cause contamination of the soil and groundwater; contaminated effluent can be toxic (toxicity as a common parameter), cause bad taste (phenols) and/or excessive fertilization and, hence, consumption of oxygen (nitrogen, phosphorus).

Consideration must also be given to the fact that the construction and operation of technical facilities affects the living conditions of sundry groups. The relevant socioeconomic and sociocultural aspects therefore have to be analyzed.

2.2 Protective measures

Environmental protection and occupational safety at coking plants are governed by statutory provisions; in Germany, these include the TA-Luft (Technical Instructions on Air Quality Control), the Gefahrstoffverordnung (Hazardous Substances Ordinance), and the Wasserhaushaltsgesetz (Federal Water Act).

In accommodation of amended laws with in part substantially more stringent provisions, technical advances have emerged which now enable comprehensive protection of the environment.

One such advance is the development of large coke ovens, so that the operation of new coking plants of equal capacity now requires less frequent opening (around 80%) and has a far smaller sealing area to be cleaned (approximately 65% reduction). At least the following basic emission control measures are now being implemented on new facilities:

a) Coal handling, including unloading, storage, conditioning (mixing, grinding) and hauling

- erection of stationary sprinkling systems over coal storage areas to keep the coal moist, with provision for climatic boundary conditions;
- minimized dumping heights for mobile discharge and transfer stations;
- use of enclosed conveyors;
- installation of dedusting facilities on grinding and mixing equipment, plus dust silos.

b) Coke oven batteries

- collection of charging gas and transfer by two separate routes to the crude gas, e.g., via so-called mini risers leading to the adjacent oven and then through the "real" riser into the collecting main;
- charging gas aspiration by means of stationary or mobile systems equipped for aftercombustion and dedusting;
- mechanical cleaning of charging hole lids and frames, plus sealing after each charge;
- mechanical cleaning (aspiration) of the oven roof;
- mechanical cleaning of the risers (closures equipped with water seals);
- installation of mechanical cleaning devices for the doors and chamber frames of the coke oven machines;
- collection and treatment of emissions emerging upon removal of the doors;
- use of special-purpose door maintenance cars;
- installation of tight door sealing systems with gas relief channels to avoid excessive gas pressure in the vicinity of the sealing elements;
- installation of aspiration hoods for the door and frame cleaning devices;
- leakage gas aspiration for emissions resulting from leakages around oven doors, with injection of exhausted air into the batteries' combustion air supply;
- use of combustion gases with sulfur contents safely below 0.8 g/m³ to limit SO2 emissions;
- gradual air feed and internal/external flue gas recirculation to reduce NOx emissions in connection with heating of the ovens;
- use of highly heat-conductive stone linings for the heating walls;
- collection and purification of emissions from coke pushing.

c) Coke cooling

- use of dry coke cooling technology, comprising:

· moistening of the dry cooled coke to suppress dust evolution at the transfer points
· dedusting of the delivered coke
· dedusting of surplus gas by means of bag filter
· intergas generation to replace cooling cycle gas based on the use of low-sulfur gas;

- emission control measures for wet quenching, e.g., provision of baffle plates for the wet quenching towers.

d) Coke treatment

- installation of enclosed coke conveying equipment;
- encapsulation of coke screening plant;
- collection and removal of particulate emissions, e.g., at the feed bunkers, sieving lines, crushers, belt feeders, etc.;
- installation of remoisteners for dry cooled coke to limit dust generation at the coke transfer points.

e) Gas treatment and coal-constituent recovery systems

- use of effective sealing systems/elements for pumps, valves and flanges;
- forced ventilation of tanks, water lutes, etc. and injection of the ventilation gases into the crude gas suction line;
- use of Claus systems with injection of tail gas into the crude gas (tail gas recirculation);
- provision of waste gas filtration and additional catalyst installation for the H2SO4 systems to extensively preclude SO2/SO3 emissions.

f) Wastewater treatment; cf. environmental briefs Wastewater Disposal and Mechanical Engineering, Workshops, Shipyards

- use of upstream strippers employing alkaline additives (e.g., caustic soda solution) to reduce the so-called fixed ammonia compound burden of the coking plant's process water;
- installation of multiple-stage biological wastewater treatment facilities, including a nitrification/denitrification stage to enable elimination of nitrogen compounds in the coking plant's process effluent.

g) Conservation of soil and water

- separate drainage systems for surface runoff and process wastewater (from gas treatment and coal-constituent recovery systems);
- placement of all tanks and apparatus used in the handling or treatment of substances constituting a hazard to water in collecting tanks; installation of intercepting sewers for wastewater, e.g., by way of biological water treatment;
- installation of monitorable tank bottoms (on strip footing); use of overfill protection devices;
- use of suitable materials and external anti-corrosion measures to substantially improve the availability of plant components.

h) Noise control

- noise control at the source, e.g., encapsulation of machines, pumps, etc.;
- noise control for structures, e.g., solid construction, sandwich construction, use of vibration dampers, partitions;
- erection of acoustical barriers;
- individual examination of noise sources with a view to satisfying equipment-noise and neighbor's-rights requirements.

The measures listed under a) through h) are technically tried and proven and routinely implemented for new facilities.

Stated in proportion to the total investment for a new coking plant, the cost of environmental protection measures accounts for 30 - 40 %.

The operational reliability and availability of environmental protection provisions - like that of the entire coking plant - is highly dependent on the qualifications of the operating personnel. Consequently, appropriate training is required to put the personnel in a position to operate and use the equipment in an expert, competent manner.

3. Notes on the analysis and evaluation of environmental impacts

3.1 General

Any evaluation of the detrimental effects of coking plant emissions must allow for numerous factors, some of which are difficult to quantify, e.g.:
- baseline pollution by other emitters,
- climatic influences, particularly of wind, on propagation behavior,
- accumulative capacity of surrounding ecosystems.

It has been qualitatively determined that some such emissions, BTX and benzo(a)pyrene in particular, have carcinogenic effects on humans and animals and that particulate emissions and some gases can cause diseases of the respiratory tract.

The fact that coking plants, most notably in the near vicinity of the coke oven batteries, have both definite and diffuse sources of emissions complicates the stipulation of tolerable emission levels, e.g., in the form of emission factors. This problem is evidenced in pertinent German directives and regulations such as TA-Luft, which states allowable concentrations in the exhaust gases/air from definite points, but also applies qualitative technical measures to the erection of numerous different systems and types of plant.

Hence, only a narrow selection of emission limits/factors is available for reference.

That information, however, is supplemented by MAK/TRK-values which define limits for airborne workplace pollution and allow for the registration and monitoring of emissions from diffuse sources.

3.2 Summary of limit values and standards

Proceeding on the basis of Germany's Federal Immission Control Act Bundesimmissionschutzgesetz), the following directives and regulations apply in essence to the design and planning of coal processing in the Federal Republic of Germany:

- Technical Instructions on Air Quality Control (TA-Luft) dated February 27, 1986,
- Limit values for pollutants in coking plant wastewater according to the Federal Water Act, section 7a,
- Limit values according to the Technical Instructions on Noise Abatement (TA-L) dating from July 1984 (5th update),
- Hazardous Substances Ordinance.

Additional directives and regulations to be heeded for planning purposes are listed in section 6 (References).

The following tables (1.1, 1.2, 2, 3 and 4) survey the presently valid limit values for emissions, pollutant concentrations and MAK/TRK-values according to German standards.

It must, of course, be kept in mind that more stringent requirements may apply, depending on the baseline pollution level (initial load) at the location in question.

The tables compare the emission limits imposed by various industrialized countries of Europe with those reflected in German standards. With few exceptions, as quickly becomes apparent, the German standards impose the most stringent environmental protection requirements.

Table 1.1 - Emission limits according to TA-Luft (general exhaust emissions)

Component

Definition of mass-flow range

German emission limits

European comparative values

Remarks

Dust

> 0.5 kg/h < 0.5 kg/h

50 mg/m³ 150 mg/m³

50 - 115 mg/m³, 94 mg/m³ 150 mg/m³

Nox (as NO2)

> 5 kg/h

0.5 g/m³

0.35 - 0.8 g/m³, 0.55 g/m³

0.35: Belgian outlier

SO2

> 5 kg/h

0.5 g/m³

0.5 - 0.8 g/m³, 0.6 g/m³ alternative: limitation of annual load to 10 000 - 12 000 t

H2S

> 50 g/h

5 mg/m³

5 mg/m³

HCN

> 50 g/h

5 mg/m³

5 mg/m³

C6H6

> 25 g/h

5 mg/m³

5 mg/m³

Benzo(a)pyrene

> 0.5 g/h

0.1 mg/m³

no emission limit defined

1) The comparative values derive from the Netherlands, England, Belgium, France, Spain, Austria, Sweden and Finland; the -values represent the arithmetic mean of the respective limit values.

Table 1.2 - Emission limits for coking-plant waste gas/purified exhaust air

Component


Definition of mass-flow range


German emission limits


European comparative values


Remarks

Coal plant

Dust


50 mg/m³


100 mg/m³



Coal drying and preheating

Dust


100 mg/m³


115 mg/m³



Coke screening

Dust


50 mg/m³




Coal charging (filling process)

Dust PAH for mass flows > 0.5 g/h


25 mg/m³ 0.1 mg/m³


15 - 230 mg/m³, 92 mg/m³ 0.1 mg/m³, alternative: limitation of daily load to 2 kg


15: Dutch outlier


Coke pushing (operation)

Dust


5 g/t coke


5 - 115 mg/m³, 46 mg/m³ or 5 g/t coke



Dry coke cooling

Dust


20 mg/m³


20 mg/m³



Wet coke quenching

Dust


50 g/t coke


50 - 800 mg/m³, 330 mg/m³ or 80 g/t coke



Exhaust stack, coke oven batteries (new facilities)

NOx as NO2 SO2 CO Dust


0.5 g/m³ 0.8 g sulfur in UF gas 0.2 g/m³ 10 mg/m³


0.2 - 0.8 g/m³, 0.53 mg/m³ 0.5 - 1.7 g sulfur in UF gas 9 g sulfur in UF gas or 0.5 g H2S in UF gas 100 - 200 mg/m³, 130 mg/m³


0.2: Dutch outlier 0.5: Spanish outlier


Exhaust stack of by-product plants (new facilities)

Dust CO NOx SO3 (H2SO4 systems) SO2 (H2SO4 systems) H2S (Claus systems) Sulfur (tolerable emission level) Production capacity: < 20 t S/d Production capacity: 20 - 50 t S/d Production capacity: > 50 t S/d


60 mg/m³ SO2-to-SO2 conversion rate: > 97.5 % or 2500 mg/m³ 10 mg/m³ 3 % 2 % 0.5 %


50 mg/m³ 200 mg/m³ 0.1-0.35mg/m³,0.225 g/m³ 60 - 10 mg/m³, 70 mg/m³ 500 - 3000 mg/m³, 1750 mg/m³ 10 mg/m³ 3 % 2 % 0.5 %


500: Austrian outlier


2) cf. table 1.1 footnote

Table 2 - General administrative framework regulation (Rahmen-Abwasser VwV) on minimum requirements for the discharge of wastewater from coking plants, Appendix 46 (draft dated August 1990), valid for direct discharge

Parameter

Totals:

NH4-N

NO2

40

mg/l

NO3-N

Phosphorus

2

mg/l

BOD5

30

mg/l

Filterable substances

50

mg/l

COD

200

mg/l

Phenol index

0.5

mg/l

PAH

0.1

mg/l

BTX

0.1

mg/l

CN (volatile)

0.1

mg/l

Sulfide

0.1

mg/l

Fish toxicity

4

(dilution factor)

Note: The above emission limits apply to undiluted coking plant wastewater occurring at the rate of 0.3 m³/t of coal.

Coking plants equipped for HP gas treatment and with installations for collecting and recycling contaminated rainwater, or with appropriate supplementary process stages, can increase the specific wastewater discharge to as high as 0.42 m³/t of coal.

Table 3 - Standard immission values for noise emissions (July 1984)

The noise immission levels are specified for:

a)

areas containing only commercial or industrial facilities and living quarters for supervisory and standby personnel, to:

70 dB(A)

b)

areas containing primarily non-residential buildings, to:

(daytime) (nighttime)

65 dB(A) 50 dB(A)

c)

areas containing nonresidential and residential buildings accommodating neither mostly nonresidential occupants nor primarily residential occupants, to:

(daytime) (nighttime)

60 dB(A) 45 dB(A)

d)

areas containing primarily residential buildings, to:

(daytime) (nighttime)

50 dB(A) 40 dB(A)

e)

areas containing exclusively residential buildings, to:

(daytime) (nighttime)

50 dB(A) 35 dB(A)

f)

areas containing health resorts, hospitals, nursing homes, to:

(daytime) (nighttime)

45 dB(A) 35 dB(A)

g)

residential buildings attached to industrial/business premises, to:

(daytime) (nighttime)

40 dB(A) 30 dB(A)

· Comments

- The acoustic engineering of industrial facilities and the requisite prognostical calculations rely heavily on the algorithms elucidated in VDI (Association of German Engineers) guideline 2714 (E) "Outdoor Sound Propagation" and VDI guideline 2571 "Sound Radiation from Industrial Buildings".
- If the above guideline values are exceeded and/or adulterated by superimposed extraneous noise to such an extent that accurate measuring becomes impossible, appropriate correction factors must be allowed for, as generally laid down in TA-L (technical instructions on noise abatement). If measurements cannot be conducted, sound propagation calculations must be performed.
- "Nighttime" is understood as the eight hours between 10:00 p.m. and 6:00 a.m.
- In supplementation of the workplace ordinance Verordnung rbeitssten (section 15: protection against noise), the following provisions shall apply to workplace noise nuisance:

(1) The workplace noise level must be kept as low as possible for the type of operation in question. The workplace reference intensity, inclusive or exclusive of extraneous noise, shall not exceed:

· 55 dB(A) for primarily intellectual work
· 70 dB(A) for simple or mostly mechanized office work and comparable activities
· 85 dB(A) for all other activities; to the extent that the prescribed sound intensity level cannot be adhered to by available, reasonable means, it may be exceeded by 5 dB(A).

(2) The sound intensity level prevailing in breakrooms, duty rooms, rest rooms and first-aid rooms shall not exceed 55 dB(A). The reference sound intensity level shall be set by taking into account only the noise generated by installations inside the rooms plus the extraneous sounds entering the rooms in question.

Table 4 - MAK-values (occupational exposure limits) and TRK-values (technical concentration guideline values)

Component

Limit values in Germany

Comparative values in Europe*

Remarks

Dust

6 mg/m³

10 - 15 mg/m³, 11 mg/m³

NOx (as NO2)

9 mg/m³

4 - 6 mg/m³, 5.3 mg/m³ 30 mg/m³ NO

SO2

5 mg/m³

1.5 - 5 mg/m³ 4.7 mg/m³

1.5: Spanish outlier

CO

33 mg/m³

29 - 57 mg/m³ 45 mg/m³

29: Dutch outlier

Benzene

164) mg/m³

3 - 32 mg/m³

3: Swedish outlier

Toluene

375 mg/m³

375 mg/m³

Xylene

440 mg/m³

425 - 435 mg/m³, 430 mg/m³

Benzo(a)pyrene

2-5 mg/m³

2 - 5 µg/m³

H2S

15 mg/m³

14 - 15 mg/m³

HCN

11 mg/m³

10 - 11 mg/m³

NH3

35 mg/m³

17 - 18 mg/m³

Phenol

19 mg/m³

19 mg/m³

Mercaptans

1 mg/m³

1 mg/m³

Biphenyl

1 mg/m³

1 - 1.5 mg/m³

Carbon disulfide

30 mg/m³

30 mg/m³

Naphthalene

50 mg/m³

50 mg/m³

3) cf. table-1.1 footnote
4) TRK-values
5) In the direct vicinity of the batteries, higher levels (measured in µg/m³) can be tolerated but then call for supplementary organizational and/or hygienic measures in addition to personal protective equipment, e.g., breathing masks.

Adherence to the permissible emission levels and the efficiency of the airborne emission control equipment must be monitored by measurements.

Subsequent to commissioning of facilities, it shall be determined by measurements whether or not the numerical data assumed at the planning stage correspond to the actual operating conditions. The measurements shall be conducted by neutral institutions, authorities or the like with due consideration of pertinent guidelines.

The TA-Luft and relevant VDI guidelines describe in detail the conduct of emission and ground-level pollution measurements.

3.3 Evaluation of environmental impacts

The aforementioned emission limits can be complied with by implementing the protective measures described in section 2.2.

Compared to existing facilities, the following reductions in emission levels (referred to a complete coking plant, including so-called diffuse sources) are foreseeable:

SO2 by 20 - 40 %
NOx by 20 - 40 %
CO by 30 - 35 %
BTX by > 95 %
Dust by approx. 50 %
PAH by approx. 90 %
BaP by approx. 90 %

The following emissions can be completely avoided by replacing wet quenching facilities with dry coke cooling systems:

- H2S up to 80 g/t of coke, amounting to 160 t/a of H2S for an annual coke output of 2 million tons;
- NH3 up to 15 g/t of coke, amounting to 30 t of NH3 per year.

4. Interaction with other sectors

Coking plants are closely allied with the iron-producing industry (cf. environmental brief Iron and Steel). However, some coking plants are located near mines (see briefs on mining), with a coal processing facility (coal washing plant) operating at the mine.

New developments in the steel-making industry such as those enabling the use of both oil and coal in the blast furnace process can help reduce the specific coal requirement of blast furnace operation. At present, however, there is no sign of coke becoming dispensable as a fuel and mainstay medium (reducing agent) for blast furnaces.

References to other adjacent sectors are to be found at the appropriate text passages.

5. Summary assessment of environmental relevance

Without the safe and sure operation of comprehensive antipollution devices, coking plants can cause substantial pollution of the air, soil and water.

In addition to emission reduction measures to avoid pollution from definite sources, the avoidance of emissions from diffuse sources is also important. Moreover, the maximum allowable workplace concentrations (occupational exposure limits) must be observed.

Systematic implementation of well-tested modern environmental protection measures, in combination with the observance of pertinent rules and regulations, can ensure that coking plants, like other coal processing facilities such as carbonization systems, need not be classified as environmentally hazardous.

With due regard to local circumstances, official ordinances must ensure that environmental protection measures are properly executed.

To that end, it is advisable to designate environmental protection and environmental safety officers, who, with proper training and technical support, are in a position to assume supervisory functions and attend to the interests of environmental protection and occupational safety in connection with all relevant industrial activities.

Early involvement of affected groups (women in particular) in the planning and decision-making processes enables consideration of their interests and helps alleviate environmental problems, e.g., in connection with the contamination of foodstuffs and/or health impairment in the vicinity of such undertakings.

6. References

Laws, Regulations, Directives

AD-Merkbler

Bergverordnung zum gesundheitlichen Schutz der Beschigten (Gesundheitsschutz - Bergverordnung - GesBergV) dated 31.07.1991.

Druckbeherverordnung (pressure vessel code), Bundesarbeitsblatt Nr. 3, Teil Arbeitsschutz, March 1990.

Hinweise f Ableiten von Abwasser in ntliche Klnlagen, ATV Arbeitsblatt 115.

MAK-Liste, Liste maximaler Arbeitsplatzkonzentrationen, 1990, Mitteilung XXVI, Bundesarbeitsblatt 12/1990.

Richtlinie frleitungsanlagen zum Befrn wassergefdender Stoffe, Gemeinsames Ministerialblatt GMBL (joint ministerial circular) Nr. 8, 02.04.1987.

Technische Regeln zum Umgang mit brennbaren Fleiten, TRbF, BGBL III (Federal Law Gazette III).

Unfallverhvorschriften UVV, Hauptverband der gewerbliche Berufsgenossenschaften, Bonn.

VDI-Richtlinie 2058, Blatt 1, Beurteilung von Arbeitsl in der Nachbarschaft, September 1985.

VDI-Richtlinie 2058, Blatt 3, Beurteilung von L am Arbeitsplatz unter Berhtigung unterschiedlicher Tgkeiten, April 1981.

VDI-Richtlinie 2560, Perscher Schallschutz, December 1987.

VDI-/VDE-Vorschriften.

Verordnung rbeitssten (Arbeitsstenverordnung), Ausgabe 1983, Bundesminister feit und Sozialordnung (German Federal Minister of Labour and Social Affairs).

Verordnung efliche Stoffe (Gefahrstoffverordnung), BGBL (Federal Law Gazette), Aug. 26, 1986.

Wasserhaushaltsgesetz, insbesondere mit dem § 7a, Mindestanforderungen an Kokereiabwer, BGBL I (Federal Law Gazette I) (1986)

Other applicable provisions cited in diverse rules and regulations.

Miscellaneous

Mitteilungen des Europchen Kokereiausschusses zu Emissionsgrenzwerten und MAK-/TRK-Werten (unverntlicht).

Bernd Schr, Article "US Clean Air Act" in Staub - Reinhaltung der Luft 52 (1992) 1 - 2, Springer Verlag.

1. Scope

Thermal power stations are facilities in which the energy content of an energy carrier, i.e., a fuel, can be converted into either electricity or electricity and heat. The type of power plant employed depends on the source of energy and the type of energy being produced.

Possible energy sources include:

- fossil fuels such as coal, petroleum products and natural gas
- residual and waste materials such as domestic and industrial refuse and fuel made from recovered oil
- fissionable material

Thermal power plants can be designed for different fuel sectors in the interest of greater fueling flexibility and/or higher efficiency - one example being a combination power plant with a gas turbine running on natural gas and an oil- or coal-fired steam generator feeding a steam turbine.

Renewable sources of energy such as wood and other forms of biomass are not dealt with here, as they are the subject of a separate environmental brief. Nuclear thermal power plants have also been omitted from this catalogue. The frame of reference concentrates extensively on fossil-fueled power plants, in particular types using coal and petroleum products, the present and near-future use of which is of eminent importance in most developing countries. With regard to hydropower, the reader is referred to the environmental brief Large-scale Hydraulic Engineering.

As far as the form of energy being generated is concerned, there are three main types of thermal power stations:

- condensing power plants used exclusively for generating electricity
- steam- or hot-water producing heating stations for domestic or industrial purposes
- district heating power stations, or cogenerating plants, for the simultaneous generation of electricity and available heat.

It is important to note that, for economic reasons, process heat and heat for heating purposes should only be generated in close proximity to the users. For thermal outputs ranging from 50 to 100 MW, the distance between the power plant and the user should not exceed 2 to 5 km. Conversely, electricity can be economically transmitted over very substantial distances; cf. environmental brief Power Transmission and Distribution.

The unit power ratings of fossil-fueled thermal power plants range from a few hundred kW (diesel stations) to more than 1000 MW (oil- and coal-fired stations). In many countries, preference is given to unit ratings of 200 - 300 MWel with deference to power system stability. The better the boundary conditions, the higher the achievable capacities.

2. Environmental impacts and protective measures

The environmental consequences of any given plant are both plant- and site-dependent. Thermal power stations can impact the environment in different ways and at different locations. A typical thermal power plant is likely to comprise the following principal components:

- facilities for preparing and storing working materials
- facilities for burning fuel and generating steam
- facilities for generating electricity and available heat
- facilities for treating exhaust gases and solid and liquid residues
- cooling facilities

In Appendix A-1, a thermal power plant is reduced to a block diagram showing the most likely material inputs, outputs and environmentally relevant flows of material.

Table 1 surveys the potential emissions occurring at different stages of the generating process:

Table 1 - Potential emissions from thermal power plants

Step of process







Type of emission

Fuel storage and processing

Combustion and steam generation

Flue-gas cleaning

Power generation

Cooling systems

Treatment of residue

Particulates

*

*

*

*

Noxious gases

*

*

Wastewater

*

*

*

*

*

Solid residues

*

*

*

Waste heat

*

*

*

Noise

*

*

*

*

*

*

Groundwater contamination

*

As the table indicates, thermal power stations can affect the media air, water and soil, as well as human beings, plants, animals and the landscape.

The disposal of residues, e.g., those associated with oil- and coal-fired facilities, is dealt with in section 2.3.

The main environmentally relevant effects of a thermal power plant derive from the combustion process and its particulate and gaseous emissions. As a rule of thumb, the environmental impacts of thermal power plants, i.e., pollution, spatial requirements and residues, tend to increase in severity for gas, light fuel oil, heavy fuel oil and coal, in that order.

Prior to examining the environmental consequences and possible protective measures for the various domains, let us begin with a few basic introductory remarks. The running text contains information essential to the subject environmental consequences and protective measures, while the relevant technical measures are detailed in the appendix.

In addressing the environmental consequences of a thermal power plant, distinction is drawn between emissions, i.e., the release of pollutants from various parts of the plant, the smokestack in particular, and immissions, i.e., the actual environmental effects of the pollutants, normally referred to ground level - as indicated by the terms "ground level concentration/pollution" and "ambient air quality concentration/standards". Emissions and immissions are interlinked by a number of factors, e.g., plant-specific technical parameters (emission volumes, outlet velocity, temperature), meteorological factors (weather category, wind speed) and range-specific data (distance between the emitter and the ground-level pollution point). Parameters belonging to the first and last categories, e.g., height of stack and distance from residential areas, are more or less freely selectable for new power plants, while the actuating variables for existing plants all belong to the first category. According to the laws of physics (conservation of matter), practically all noxious emissions with the notable exception of CO2, for example, eventually fall to earth. The height of the smokestack, the outlet velocity of the exhaust, and the prevailing wind velocity determine the size of area that will be affected. From a technical standpoint, it is relatively easy to reduce ground-level concentrations for a given area by increasing the height of the smokestack. Since, however, the specific emission volume does not change, but is simply distributed over a wider area, the extent to which such a measure would aggravate the environmental impact outside of the subject area would have to be clarified.

Measures aimed at reducing the environmental consequences of thermal power plants can be categorized as follows:

- alteration of boundary conditions

· incentives for the efficient utilization and conservation of energy, e.g., cost-covering power rates and taxes
· appropriate siting

- nontechnical protective measures

· regulations dictating the mandatory use of piped energy (district heating) in congested urban areas
· compensation models for the replacement of major emitters

- technical protective measures

· reduction of ground-level concentration, e.g., by extending the height of the smokestack
· emission-reducing measures

* pollution-control measures to prevent or reduce pollution by combustion modification, e.g., choice of an appropriate low-impact fuel such as natural gas (in place of coal), homogenization of fuel to avoid peak emissions, efficiency-enhancing measures, and NOx limitation by combustion engineering measures

* post-combustion measures, i.e., flue gas clean-up.

The order in which the protective measures are taken is subject to the principle of attaching priority to avoidance or reduction over subsequent rectification. First of all, pollution-control measures must be taken to preclude, or at least minimize, the occurrence of pollutants, before any further-reaching post-combustion technical remedial processes are initiated.

One very important relevant measure is to achieve higher efficiency, e.g., by erecting combination power plants or opting for the combined generation of heat and power (cogeneration) in efficient heating power stations with an accordingly low specific pollution level. High efficiency is also the most effective way to reduce CO2 emissions and, hence, their greenhouse effect. For additional means of reducing CO2 emissions, e.g., through the use of renewable sources of energy for power generation, cf. the brief Renewable Sources of Energy.

With regard to environmental consequences, distinction is made between direct consequences, e.g., the emission of pollutants, and indirect consequences such as the transfer of pollutants from the atmosphere to water via scrubbing processes (assuming that the liquid effluent is not subsequently processed) or the environmental impact of limestone mining and attendant road traffic, e.g., the transfer of limestone by truck from the mine to the power plant. Moreover, consequential problems can arise, e.g., the need to properly dispose of the gypsum resulting from flue-gas desulfurization processes (FGD).

The environmental consequences and potential protective measures applicable to the aforementioned areas are explained below.

2.1 Air

The particulate and noxious gas emissions from thermal power plants primarily and directly pollute the air.

Eventually, the particulate emissions and, for the most part, the noxious gases and any atmospheric transformation products that may have formed (e.g., NO2 and nitrate from NO) fall to earth either by way of precipitation or dry deposition, thereby imposing a burden on the water and/or soil, with resultant potential damage to flora and fauna.

Depending on the fuel employed (type, composition, calorific value) and the type of combustion (e.g., dry or slag-tap firing), given amounts of pollutants (particulates, heavy metals, SOx, NOx, CO, CO2, HCl, HF, organic compounds) become entrained in the exhaust gases. Table 2 shows the potential concentration ranges of different emissions for various fuels in facilities devoid of flue-gas emission control measures.

Table 2 - Potential ranges of pollutant concentration levels in untreated gas Type of fuel

Type of emission

Natural gas

Light fuel oil

Heavy fuel oil

Hard coal

Lignite (brown coal)

Sulfur oxides (SOx) [mg/m³STP]

20 - 50

300 - 2000

1000 - 10000

500 - 800

500 - 18000

Oxides of nitrogen (NOx) [mg/m³STP]

100 - 1000

200 - 1000

400 - 1200

600 - 2000

300 - 800

Particulates [mg/m³STP]

0 - 30

30 - 100

50 - 1000

3000 - 40000

3000 - 50000

Table 2 lists the noxious emissions in mg/m³STP, as prescribed by the applicable German rules and regulations [TA-Luft (Technical Instructions on Air Quality Control), and Groeuerungsanlagenverordnung (Ordinance on Large-scale Firing Installations)]. SOx and NOx are postulated as SO2 and NO2. Some emissions are limited in terms of mass flow, e.g., in kg/h, or of minimum separation efficiency (cf. Appendix A-6). With a view to enabling conversion of the stated concentrations to other units such as ppm, g/GJ or lb. of pollutant per 106 BTU energy input, as commonly employed in the U.S.A., Appendix A-6 includes an appropriate conversion table.

The ranges quoted in table 2 for oxides of sulfur relate to differences in fuel-specific sulfur content, whereas many countries use large quantities of indigenous fuels like lignite with comparatively low calorific values and high sulfur contents. Such a combination naturally produces relatively high SOx concentrations in the (untreated) flue gas.

The lesser part of the NOx concentrations derives from the nitrogen content of the fuel (fuel NOx). The major share results from the oxidation of atmospheric nitrogen at combustion temperatures exceeding 1200°C (thermal NOx). Consequently, high combustion temperatures go hand in hand with relatively high NOx emission levels. Appropriate combustion engineering measures that are

relatively inexpensive for new plants can keep the emissions at the lower end of the respective range. However, care must be taken to ensure that a high quality of combustion is maintained. Otherwise, excessive combustion engineering measures aimed at reducing NOx emissions could result in a disproportionate increase in other emissions, e.g., carbon monoxide and combustible (unburned) hydrocarbons.

In general, CO2 emissions are mainly limited by controlling the burnout process such as to minimize the discharge of CO and the escape of combustible hydrocarbons. Unlike particulates, SO2, NOx and halogen compounds, CO and combustible hydrocarbons effectively defy retentive measures. Combustible hydrocarbons in particular include numerous chemical substances that can cause toxicological problems, e.g. benzpyrene.

Plants fueled with coal or heavy fuel oil also emit small amounts of hydrogen chloride and hydrofluoric acid (HCl and HF) ranging from 50 to 300 mg/m³STP. As a rule, the concentrations stay well below the SO2 levels and respond favorably to desulfurization processes, by which they are reduced even more than S2.

There are many combustion-stage and post-combustion alternatives for use in reducing air pollution from thermal power plants. Appendix A-2, for example, sketches out an integral set of DeNOx, particulate-control and desulfurization measures for the flue gas of a steam generating facility. The various measures are individually described in the following subsections.

2.1.1 Dust control

Dust control for power plants can be based on ordinary and multiple cyclone separators and electrostatic precipitators or fabric filters - with the order of mention corresponding to their respective separation efficiencies: from 60 % - 70 % for cyclone separators to >99 % for electrostatic precipitators and fabric filters. To be sure, the cost of the various options rises disproportionately for increasing separation efficiency. The separation efficiency of electrostatic filters depends on the number of consecutive fields. Like fabric filters, they can achieve extremely low residual emission levels, i.e., about 50 and 30 mg/m³STP, respectively. The drawback of cyclone separators is that they tend to eliminate coarse particles much more efficiently than respirable - and, hence, toxicologically critical - microparticles. Fabric filters are very good at separating out fine dust and its accumulated heavy metals. The capital outlay for flue-gas dust control depends

on such parameters as the type of fuel, the required separation efficiency and the technique employed. As a rule, the initial cost ranges from 20 to 70 DM/kWel, while the operating expenses amount to 0.1 - 0.6 DM/MWh. The high-ash fuels used in some countries makes flue-gas dust control a difficult problem - including

the proper disposal of the dust yield, either by recycling it in, say, building materials, or by depositing it in a landfill. Certain characteristics of the fly ash may require the use of additives to obtain a solidified product that is less susceptible to leaching, this with a view to preventing groundwater contamination.

2.1.2 Desulfurization

SOx from combustion plants can be reduced either by combustion modification measures (use of low-sulfur fuel, direct desulfurization in the furnace, dry-additive method) or by post-combustion clean-up measures such as extracting the SOx from the flue gas.

The use of low-sulfur fuels is frequently precluded by economic considerations. In each case, the lowest total-cost concept must be ascertained. For example, while the use of a low-sulfur fuel may increase the cost of operation, it could save the cost of installing and operating desulfurization equipment, thus yielding lower overall costs for the power station. Of course, such considerations must also account for other criteria, e.g., using indigenous fuels in order to assure their safe supply.

Like solid fuels, sulfurous petroleum products are also amenable to pre- and post-combustion measures. The pollution-control measure of choice is to hydrate the sulfur by adding hydrogen in order to extract the product from the oil, e.g., as vacuum gas oil or a remanent of atmospheric or vacuum distillation. Such processes are only cost-efficient for large capacities and therefore only feasible for oil refinery applications. In a thermal power station, the appropriate measures for reducing SOx emissions are restricted to the use of a low-sulfur petroleum product, mixing different fuels and, primarily, flue-gas desulfurization according to the same principle as that employed in solid-fueled facilities (described below and in Appendix A-3).

For coal-fired power plants, particularly in response to the pronounced compositional variance observed in the indigenous coals of many countries, appropriate mixing and homogenization can have the positive effect of lowering the peak-value extremes that have to be accounted for in the design of desulfurization systems. Consequently, major importance must be attached to a conscientious analysis of the calorific values and the water, ash and sulfur contents

of fuel deriving from, say, different sections of a coal mine. It is also important to ascertain the possible extent of spontaneous desulfurization attributable to the presence of calcium compounds in the coal.

Coal can be desulfurized directly at the mine or pit as part of a process in which sulfur and various inert constituents are extracted primarily by wet methods. Depending on the type of coal and on the kind of sulfur linkage, the sulfur content of the coal (glance coal in particular) can be reduced by 5 % to 80 %. No such conditioning measures, however, can reduce the organosulfur content. Sulfite in the form of pyrite (FeS2) can be separated out if it is freely present in the raw coal or is so coarse-grained in intergrowths that it becomes amenable to removal following crushing.

Direct in-boiler desulfurization is applied to solid fuels in fluidized-bed combustion systems. Separation efficiencies of 80 % to 90 % are achievable. Dry additive techniques remove between 60 % and 80 % of the sulfur from coal (cf. Appendix A-3 for details).

Flue-gas desulfurization techniques enable SO2 separation efficiency levels of 90 - 95 %. Since flue-gas desulfurization equipment is expensive to install and operate, it is more judicious in some cases to install a component-flow desulfurization system in which only part of the flue gases are desulfurized, while the remaining, undesulfurized flue gases can be used for heating the treated gases.

Of all the described alternatives, flue-gas desulfurization is the most expensive and elaborate. In each case, particularly for retrofitting projects, the spatial integration options must be carefully investigated in advance.

A comparison of the aforementioned pre- and post-combustion desulfurization measures shows that the former offer the lower separation efficiencies, but are also less expensive and more conducive to retrofitting. Fluidized-bed combustion, however, is an exception to the rule, as it can only be implemented in new facilities (maximum capacity of commercial-scale systems to date: 150 MWel).

All methods of desulfurization and dust control involve the consequential problem of properly recycling or disposing of the residues and, possibly, of wastewater resulting from operation of the equipment (cf. section 2.3).

Depending on the size of the plant, the process employed, the separation efficiency achieved, and other factors, the investment cost of a desulfurization system can amount to anywhere from roughly 30 to 550 DM/kWel. Also the increase of auxiliary power consumption to run the system is unavoidable. Dry-additive methods are the least expensive, while regenerative techniques producing compounds of sulfur as their end product are the most costly.

The various desulfurization processes also and incidentally precipitate halogen compounds such as HCl and HF even more efficiently than sulfur.

2.1.3 De NOx

The available means of nitrogen removal also comprise pre- and post-combustion alternatives. With regard to sulfur content, a careful choice of fuel can do much to limit NOx emissions. On the other hand, the NOx formation process is more complicated than the conversion of fuel sulfur into SO2, as described in section 2.1. The combustion modification measures aim to reduce the rate of NOx formation during the combustion process, essentially by lowering the maximum temperature of combustion. This can be achieved by design measures, e.g., the combustion-chamber geometry, burner design and configuration, staged air supply, reduced excess air, and such operational measures as reduced combustion-air-preheating temperature or the use of low-nitrogen fuel.

The post-combustion DeNOx measures are concerned with reducing the exhaust-side NOx emissions by various means designed to remove the NOx either alone or together with SOx.

The only process to have gained commercial-scale acceptance to date is the selective catalytic reduction of NOx (SCR method). In this process, ammonia (NH3) reacts with NOx in a catalytic converter to form water and nitrogen. The process therefore produces no residues (like those from dust-control and desulfurization processes) that would require subsequent disposal. The SCR process takes place at temperatures of 300 - 400°C and can be integrated either on the raw-gas end, e.g., upstream of the air preheater (SCR (r) economizer) or on the clean-gas end behind a desulfurizing system (SCR (r) FGD).

SCR-base processes achieve NOx separation efficiencies of approximately 80 - 90%.

Another approach that is particularly well-suited for relatively low separation efficiencies of about 60 % or less is the SNCR process (selective non-catalytic reduction), in which NOx reduction is achieved by spraying ammonia into the boiler at a temperature of some 1000°C.

The initial cost of flue-gas DeNOx equipment depends on the size of the plant, the required separation efficiency, configuration, etc. and ranges from roughly 120 to 250 DM/kWel.

2.1.4 Greenhouse effect

The greenhouse effect, i.e., the long-term warming of the earth's atmosphere due to the presence of anthropogenic trace gases, is chiefly attributable to the accumulation of gases such as carbon dioxide (CO2), methane (CH4), chlorinated fluorocarbons (CFCs), tropospheric ozone (O3) and nitrous oxide (N2O) - with the order of mention corresponding to the relevant significance of the gases. Their specific contributions to the greenhouse effect are widely variant. Methane, for example, has roughly 21 times the effect of CO2, but occurs globally in much smaller mass volumes than does CO2 as the end product of any combustion process involving carbonaceous (organic) fuel.

The principal protective measure to counter CO2 emissions is to ensure high combustion efficiency, e.g., by way of a combination or cogeneration process.

Other measures like the use of renewable sources of energy - hydropower in particular - for generating electricity, in addition to measures aimed at steering the demand for electricity, are very important, but would never suffice to render superfluous the generation of electric power in fossil-fueled thermal power plants.

2.1.5 Diffuse emissions

In addition to the aforementioned types of emissions, most of which emanate from the smokestack, thermal power plants can also emit pollutants from other areas (cf. table 1). Particulate emissions, for example, can occur in connection with fuel storage, handling and processing. Such emissions can be extensively reduced by suitable measures such as moistening with water or enclosing/encapsulating critical areas. The same applies in effect to the storage and handling of petroleum products, i.e., via suitable contrivances on the tanks and pumping facilities, either to minimize evaporation or to return the condensate to the system. Such measures can be of major importance in countries with a warmer climate than that encountered in Central Europe.

2.2 Water

Most water in thermal power stations is used for cooling. After absorbing enough heat to raise its temperature by 4 - 8°C, the water normally is returned to the extraction point. Power plants designed for non-circulating water cooling require about 160 - 220 m³/h·MWel (with cooling water losses usually staying below 2 %).

In pure power generation, the cooling water absorbs approximately 60 % to 80 % of the fuel's energy content as waste heat. Less energy is wasted by plants with inherently higher efficiency, e.g., cogenerating facilities. Depending on local conditions, the waste heat can impose a thermal burden on surface water, e.g., cause an increase in the temperature of a river, with the volumetric flow and/or water regimen as an actuating variable. Particularly in developing countries, water bodies are subject to pronounced seasonal variation. Oxygen depletion therefore has two main causes: accelerated consumption due to rapid metabolism, and the lower solubility of oxygen in warm water. Oxygen deficiency can be seriously detrimental to aquatic life.

The in/out temperature gradient of cooling water can be limited by putting it through a cooling tower (once-through or circulation cooling) before it is returned to the river. Depending on the prevailing climatic conditions, however, such cooling systems involve major evaporative water losses and, hence, locally elevated atmospheric dampness. Such problems can be avoided or minimized by the use of closed-loop cooling systems in combination with dry or hybrid cooling towers. Natural-draft cooling towers are relatively expensive to build but comparatively inexpensive to operate, while induced-draft cooling towers have the disadvantage of operating on electricity, the generation of which increases the overall ecological burden.

Apart from their cooling-water consumption, power plants have very modest water requirements (0.1 - 0.3 m³/h·MWel) for topping up the steam cycle, cooling the ashes and operating certain types of flue-gas purification equipment (spray absorption, wet processes).

Water effluent from thermal power stations, particularly from coal-fired plants, can pollute surface waters.

The following types of wastewater can occur in power plants:

- regenerate from the conditioning of makeup water and desalination of condensate
- water used for washing condensate filters
- effluent from coal handling and coal storage
- sensitive wastewater, e.g., from pickling and conservation
- ash-laden water (deslagging water) from liquid ash removal
- water from the boilers, turbines and transformers
- cooling-tower discharge and makeup-water conditioning
- wastewater from flue-gas purification.

The quantities of such wastewater depend on the type of fuel and on various plant-specific boundary conditions and can be expected to range between 10 and 100 l/h for each MWel power output. Such effluent can be polluted by entrained suspended solids, salts, heavy metals, acids, alkalies, ammonia and oil.

Wastewater treatment can be based on physical, chemical and thermal methods. For some forms of wastewater, e.g., filter backwashing water and coal-storage effluent, physical treatment in the form of filtration, sedimentation and/or ventilation will usually suffice. Other forms of wastewater such as regenerate from makeup-water and condensate polishing, flue-gas cleaning water or other wastewater streams require chemical treatment - flocculation, precipitation, neutralization - or even thermal treatment - evaporation, drying - before they can be discharged; cf. environmental briefs Wastewater Disposal and Mechanical Engineering Workshops, Shipyards.

As mentioned in section 2, wastewater occurring as a consequence of certain flue-gas desulfurization processes can contain various pollutants deriving from the flue gas. The composition of such wastewater depends on a number of parameters, e.g., the type of fuel, the process water and the quality of the additives.

As a rule, wastewater from flue-gas cleaning requires physicochemical conditioning in the form of neutralization, flocculation, sedimentation and filtration to remove heavy metals and suspended solids (gypsum, etc.).

The amount of wastewater occurring in connection with wet desulfurization methods having gypsum as a by-product depends mainly on the chloride content of the coal and on the permissible concentration of chloride in the washings. In a typical hard-coal power plant, flue-gas desulfurization processes can yield wastewater in quantities between 20 and 50 l/h per MW of power output.

The high water solubility of calcium chloride (CaCl2) entrained in the wastewater makes it an unprecipitable saline emission.

If no salt is allowed to be discharged into the receiving water, the FGD wastewater can be evaporated to yield dry, water-soluble salts requiring controlled disposal, e.g., in an underground sensitive-waste depot. Since the evaporation process requires high energy inputs, it should be ascertained for such cases whether or not an effluentless method (dry process, spray absorption) would be suitable.

Apart from the aforementioned direct effects, power plants can also have indirect effects on water. Consider, for example, the "acid rain" phenomenon involving the washout of airborne pollutants (SOx, HCl, NOx) from power plants in connection with natural precipitation.

2.3 Soil and groundwater

Thermal power plants can have multifarious impacts on soil and groundwater. The soil quality, for example, can be adversely affected by dust sediment, particularly in the near vicinity of the plant. The seriousness of ground-level pollution depends on the heavy-metal content of the dust. The chemism of the soil can be altered by acidic precipitation (acid rain) characterized mainly by the acid formers SO2 and NOx. Under unfavorable conditions, acidification can pass from the soil to both the groundwater and surface waters. The extent of soil and groundwater pollution does not depend on how much particulate matter and acid formers are contained in the exhaust, but rather on the absolute quantities emitted in the course of a year (total annual emissions) and on the conditions of distribution. Thus, it is important to limit such emissions by separation capacities commensurate with the size of the power plant.

The ground and, even more so, the groundwater in the immediate vicinity of the power plant are threatened by the escape of water-polluting substances, the main sources of which are various weak points in the collection and purification of wastewater, the leakage of oil and oil-containing liquids, and storage areas for oil, coal and residues.

The deposition of residues also has consequences for the soil and, even more so, for the groundwater. Power-generating residues consist primarily of slag, fly ash, remanents from flue-gas desulfurization, and sludge from the treatment of raw water and effluent. The residual quantities depend in part on the processes employed; in general, however, it may be said that, the lower the quality of the coal, the higher the quantity of residues.

Slag and fly ash can be put to various uses (for roadbuilding or as cement aggregate), depending on their composition. To the extent that they cannot be recycled, such substances must be disposed of at suitable dumps (e.g., above groundwater level). In Germany, these matters are regulated by TA-Abfall (Technical Instructions on Waste Management).

Part 1 in Appendix C of the catalogue of particularly sensitive wastes specifies aboveground deposition in the form of a mono-type hazardous waste dump for solid reaction products resulting from the purification of combustion-plant exhaust gases, excluding gypsum; cf. briefs Solid Waste Disposal, Disposal of Hazardous Wastes.

The nature of FGD residues depends on the method employed (cf. Appendix A-3) and may occur in recyclable form, e.g., gypsum. The quantities depend on the sulfur content and the calorific value of the fuel, the degree of desulfurization, and the additives involved. Prior to choosing a particular desulfurization process, it should be ascertained whether or not the respective remanent substances occurring as by-products of the different processes could be marketed in the respective country. This would require a detailed local market analysis, appropriately involving local contractors/consultants. Potential uses for the residues (as building materials) must be investigated; in their absence, it must be clarified whether or not and under which conditions the substances can be safely disposed of.

The following table compares the quantified residues of flue-gas desulfurization in facilities fired with heavy fuel oil and two different types of coal:

Hard coal

Lignite

Heavy fuel oil

Calorific value [kJ/kg]

28 000

10 000

40 000

Sulfur content [weight %]

2.0

2.0

2.0

Degree of desulfurization [%]

85

85

85

SOx in raw gas [kg/MWelh] [mg/m³STP]

14 4 000

38 8 600

9.5 2 850

SOx in treated gas [kg/MWelh] [mg/m³STP]

2.1 600

5.7 1 300

1.4 427

Residual quantities [kg/MWel] (process-dependent)

Hard coal

Lignite

Heavy fuel oil

Gypsum

32

87

22

Sulfite/sulfate

36

97

24

Sulfur

6

16

4

Sulfuric acid

18

50

12

When both fly ash and desulfurization products (gypsum or a sulfite/sulfate mixture) require disposal, it is advisable to mix the products first. A blend of fly ash and desulfurization products can be hardened to stabilize the water-soluble constituents (stabilizate) and reduce their leachability.

Desulfurization processes with useful end products require appropriate treatment of the wastewater. The resultant sludge contains large amounts of heavy metals and therefore should be treated as sensitive waste.

2.4 Human health

Adverse effects of thermal power plants on human health can derive from the direct impact of noxious gases on the organism and/or their indirect impact via the food chain and changes in the environment. Especially in connection with high levels of fine particulates, noxious gases like S2 and NOx can lead to respiratory diseases. SO2 and NOx can have health-impairing effects at concentrations below those cited in the German smog ordinance. The duration of exposure is decisive. Injurious heavy metals (e.g., lead, mercury and cadmium) can enter the food chain and, hence, the human organism by way of drinking water and vegetable and animal products. Climatic changes such as warming and acidification of surface waters, Waldsterben (forest death) caused by acid rain and/or the greenhouse effect of CO2 and other trace gases can have long-term detrimental effects on human health. Similarly important are the effects of climatic changes on agriculture and forestry (and thus on people's standard of living), e.g., large-scale shifts of cultivation to other regions and/or deterioration of crop yields. Hence, the construction and operation of thermal power plants can have both socioeconomic and sociocultural consequences; appropriate preparatory studies, gender-specific and otherwise, are therefore required, and the state of medical services within the project area must be clarified in advance. Early, comprehensive involvement of the concerned sections of the population in the planning and decision-making process can help reduce and avoid points of conflict.

Noise, as an item of emission from thermal power plants, has direct effects on humans and animals. The main sources of noise in a power plant are: the mouth of the smokestack, belt conveyors, fans, motors/engines, transformers, flues, piping and turbines.

At least some of the personnel working in power plants are exposed to a more or less substantial noise nuisance.

Diverse noise-control measures can be introduced to reduce immissions to a tolerable level, whereas the primary goal must be to protect the power plant staff. To the extent possible, power plants should be located an acceptable distance from residential areas, and all appropriate noise-control measures must be applied to the respective sound sources at the planning and construction stages.

Two particularly effective measures are the use of sound absorbers to reduce flow noises and the encapsulation of machines and respective devices to reduce airborne and structure-borne sound levels. Appropriate enclosures constitute an additional means of simultaneously reducing both the emission and immission of noise. Incidentally, enclosures also provide weather protection and are therefore used widely in power plant engineering.

2.5 Landscape

Power plants have substantial spatial requirements. The extent of land consumption is generally higher for coal-fired facilities than for gas- or oil-fueled plants. With regard to siting, cf. environmental briefs on Spatial and Regional Planning, Planning of Locations for Trade and Industry.

The landscape is also affected by construction of the roads needed for delivering operating media and disposing of residues; cf. environmental briefs on railways, roads and waterways. The associated mining activities to obtain coal and, say, limestone (for desulfurization purposes) and for disposing of residues not to be recycled also tend to alter the landscape. In connection with the disposal of residues, priority should be given to landfilling schemes (e.g., in worked-out strip mines) or land reclamation in coastal areas. Both alternatives avoid the need for separate dumping facilities and put the residues to an advantageous use. The residues, of course, should be environmentally benign, either by nature or by reason of appropriate treatment to impart, for example, a low level of leachability. Additionally, it must be ascertained whether or not and which measures (sealing, controlled drainage, conditioning of percolating water) will be required to keep soluble heavy metals and other substances contained in the residues from passing into the groundwater or coastal water (cf. sections 2.1.1 and 2.3).

Moreover, attendant pollution can cause damage to forests, lakes and rivers, resulting in serious permanent changes in the landscape.

3. Notes on the analysis and evaluation of environmental impacts

3.1 Immissions Limits for Air

As already explained in section 2, the decisive atmosphere-specific environmental impact parameter is "ground-level pollution", i.e., the effects of air pollution on humans, animals, plants and inanimate objects. In evaluating the environmental consequences of thermal power plants, air pollution is normally of central interest. With the exception of CO2, the main pollutants are increasingly regulated by the particular immission limits adopted by different countries. In actual practice, concrete projects must attach primary importance to abiding by the applicable standards. In some countries, those standards are even more stringent than those stipulated by Germany's TA-Luft (Technical Instructions on Air Quality Control). To the extent that the relevant standards have not yet been set or have been set too high, recourse should be taken to the long-term standards prescribed by TA-Luft with regard to impairment of human health and, in part, to the protection of vegetation, materials, water bodies, etc. (cf. Appendix A-4).

If in connection with a concrete project the relevant standards will obviously be exceeded by the baseline pollution load or foreseeable developments, then the promotion of thermal power plants must be ruled out from the beginning on environmental grounds. According to TA-Luft, exceptions can be made for new power plants if the additional burden attributable to the planned facility will not exceed 1 % of the long-term immission limits (irrelevance clause).

If an existing power plant contributes considerably toward substantial transgression of the relevant immission limits, the first step to take is to investigate the possibility of its - economically feasible - relocation. If the results of the study indicate retention of the existing site, the annual relevant pollutant concentrations attributable to the power plant must be significantly reduced in absolute terms by appropriate rehabilitation measures. If the contribution of the existing power plant toward the overall pollutive burden does not exceed 1 % of the standard values after rehabilitation, the irrelevance clause may be applied by way of analogy to the exemption provisions for new plants.

Whenever the relevant standards are significantly exceeded, care must be taken to prepare an appropriate sanitation concept for the affected sphere of influence. Such a concept must provide for the reduction of pollution from sources not standing in direct connection with the project of interest.

With regard to the immission limits listed in Appendix A-4, the reader's attention is called to the fact that the particulate, sulfur dioxide and nitrogen oxide values serve as vitally important indicators for the environmental consequences of thermal power plants. The limit values for hydrogen chloride, cadmium and lead gain significance, when those elements are more abundantly present than normal in the fuel. In such cases, all considerations concerning the environmental relevance of the thermal power plant must be made subject to an analysis of the fuel to be used.

As far as German immission limits are concerned, it should be noted that they only come to bear in increasingly rare cases, because steady cuts in pollutant releases have enabled extensive compliance in most areas in recent years. Any requirements exceeding the immediately prophylactic scope are substantiated on the basis of the pollution prevention principle. Pollution limits are not schematically transferable to other situations and other countries, because, for example, the sensitivity of the local vegetation, the prevailing climatic and weather conditions, and the composition of the local soil(s) can be wholely different, hence justifying either more stringent or more lenient standards. Those specified in TA-Luft give due account to the protection of human health. As such, they are more stringent for clean-air areas than for regions in which high levels of baseline pollution already prevail.

3.2 Emission limits for air

As explained in section 3.1, the premier measure for limiting the environmental consequences of thermal power plants is adherence to the pertinent immission limits. Nonetheless, power plant emissions also should be appropriately limited - since an ounce of prevention is better than a pound of cure. As mentioned in section 2, there are a number of tried & tested commercial-scale pollution control technologies, each with its own particular benefits and drawbacks. One frequent drawback is the relatively high cost of efficient technology. The extent to which a less complex and therefore less expensive approach could significantly reduce the adverse environmental impacts of a thermal power plant should be ascertained in advance.

For example, it certainly would make sense to eliminate particulate emissions with a relatively low-cost cyclone instead of a more efficient and accordingly more expensive electrostatic precipitator or fabric filter, particularly since the high cost of the latter could be regarded as prohibitive, with the result that, ultimately, no dust control effect whatsoever is achieved. According to that same line of reasoning, it would be better to install a single-field electrostatic precipitator than none at all on the grounds that a multiple-field unit would be too expensive. Moreover, the use of more elementary processes has the added advantage of simplifying the operation, maintenance and repair of the equipment while offering a higher level of operational reliability.

Appendix A-5 lists the main laws, rules and regulations governing the release of power plant emissions to the air, water and soil in the Federal Republic of Germany.

As a rule of thumb for concrete projects, the emission limits adopted by the developing country or countries in question should be adhered to. In some cases, of course, this could result in transgression of the comparatively strict emission limits prevailing in the Federal Republic of Germany. Depending on the general context, though, that still could be regarded as tolerable. Nevertheless, the pollution prevention principle dictates that every attempt be made to install appropriate emission control technologies, even on a stage-by-stage basis if necessary, e.g., by first installing a cyclone separator and leaving room for the eventual retrofitting of an electrostatic precipitator.

Appendix A-6 summarizes the essential emission limits for airborne pollution from large-scale combustion plant in the Federal Republic of Germany.

As the table shows, the requirements differ according to type of fuel and size of installation (the latter expressed in terms of thermal output), whereas the larger installations generally are expected to satisfy more stringent environmental protection standards.

Other European Countries go by emission limits similar to those applying in Germany, particularly by way of EC Directive 88/609, most notably for SO2. The Japanese and U.S. American emission limits are also comparable, but how stringently they are enforced depends on local circumstances (competent authorities, baseline pollution levels, etc.). Appendix A-6 also lists the emission standards for new, large-scale coal-fired power plants in selected countries, along with the corresponding EC standards, for the indicators SOx, NOx and particulate emissions. Also included is a conversion chart for converting SO2 and NOx units from mg/m³STP to ppm or lb/106 BTU.

The limit values prescribed in Appendix A-6 can be achieved at justifiable expense for favorable fuels, i.e., for those with high calorific values and low sulfur contents. For unfavorable fuels, however the stipulation of low emission limits can be rather problematic. For example, according to table 2, it would take a separation efficiency of roughly 98 % to limit the SOx emission level to 400 mg SO2/m³STP for a raw gas concentration of roughly 18 000 mg SO2/m³STP. For such fuels, however, stipulation of an 85 - 95 % degree of desulfurization corresponding to the justifiable techno-economic expenditures would be more advantageous.

In some countries, the only available fuels are of such inferior quality that the emission levels listed in Appendix A-6 cannot be adhered to, and higher levels are therefore permitted.

It would be inappropriate to simply transfer the emission limits of, say, the Federal Republic of Germany to other countries, since identical limitations in combination with inferior fuels would call for more sophisticated purification technology than that required in Germany. To maintain a like level of expenditures, one must work from the given emission levels and automatically arrive at higher limit values. It should be noted in that connection, that some of the fuel used in the Federal Republic of Germany does not meet standard German specifications.

From the standpoint of environmental protection, emission limits serve merely as expedients denoting a certain state of technological development under a certain set of boundary conditions. The primary purpose of environmental protection, however, must be to protect human health, the vegetation, water bodies, etc. In other words, the primary objective of such provisions is to comply with the immission limits (cf. section 3.1). The factors governing ground-level pollution were discussed in section 2.

3.3 Monitoring of pollution levels

As a rule, it takes very sensitive instruments to accurately measure pollutant concentrations, since the levels in question can be situated several orders of magnitude below the emission concentrations. Still, certain conclusions can be drawn concerning past pollution by studying the proposed site and its surroundings. The baseline pollution level will be all the higher, of course, if other power plants and/or emission-intensive industries are located in the near vicinity or if the proposed site borders on a major traffic artery. A conflict of purposes could arise in that cogeneration, for example, as its high efficiency and accordingly low emission levels requires a nearby consumer, normally some form of industrial enterprise. If the consumer is characterized by relatively high emissions, the correspondingly high baseline pollution level could partially or even entirely counteract the environmental merits of cogeneration.

With regard to emission measurement, care should be taken to ensure that the scope of supply for the power plant includes instruments for measuring dust, SOx and NOx emissions. Such pollutants are relatively easy to monitor with the aid of mobile local instruments applied to flues or breeching. The requisite gas analyzers operate according to different principles. Differentiation is made between photometric and physicochemical measuring processes.

Photometric processes operate on a purely physical basis (nondispersive infrared process, nondispersive ultraviolet process), while the physico-chemical processes are based on a chemical reaction. Such instruments offer resolutions extending to 1 ppm.

Particulate concentration levels are monitored primarily by physical techniques, e.g., using graphimetric and radiometric instruments.

3.4 Emission limits for wastewater/effluent

In the Federal Republic of Germany, effluent from water treatment and cooling systems is subject to discharge limitations pursuant to section 7a Wasserhaushaltsgesetz - WHG (Federal Water Act) and Appendix 31 of the Rahmen-Abwasser VWV General Administrative Framework Regulation on Wastewater as listed in table 3.

Table 3 - Discharge limitations for effluent from water treatment and cooling systems
Closed-loop systems of:


Power plants

Industrial processes

Other steam-generating sources



Random sample



Settleable solids

mg/l

0.3

0.3

0.3

Available chlorine

mg/l

-

0.3

-

Hydrazine

mg/l

-

-

5.0

2-hour composite sample

Chemical oxygen demand

(COD)

mg/l

30

40

-

Phosphorus (Ptot)

mg/l

3

5

8

Vanadium

mg/l

-

-

3

Iron

mg/l

-

-

7

Source: Rahmen-Abwasser VWV (General Administrative Framework Regulation on Wastewater), Appendix 31 (Aug. 13, 1983)

To the extent that a flue-gas desulfurizing system produces wastewater, the minimum discharge requirements put forth in Appendix 47 of the General Administrative Framework Regulation on Wastewater as per section 7a Federal Water Act dating from Sept. 8, 1989, shall apply (cf. Appendix A-4).

The discharge of effluents other than those described in section 2.2 is governed by additional appendices to the General Administrative Framework Regulation as per section 7a of the Federal Water Act; its Appendix 49, for example, applies to oily wastewater.

The above requirements are in line with the stringent provisions of the German Federal Water Act, which stresses the importance of prevention and prescribes limits based on the hazard levels of the respective substances. Moreover, the Abwasserabgabengesetz (Wastewater Charges Act) rewards users who satisfy the requirements of section 7a, WHG (75 % lower wastewater charge) or who maintain existing facilities at least 20% below the prescribed limits (setting off the cost of investment against the past three years' wastewater charges.

For a concrete project, the type and nature of tolerable water pollution naturally depends on the size, quality and manner of utilization of the receiving water. Weak, sensitive recipient bodies must be analyzed in any case. Particularly in tropical countries, the water flow rate can vary widely on a seasonable basis - a fact that must be given due consideration. In that connection, consideration must be given to either relocating the plant or, as discussed in section 2.2, installing a dry cooling tower. Apart from the pollution load, the tolerable thermal load on the receiving body must be critically examined for each concrete project. According to the recommendation of the German Ler working group on water LAWA, the maximum temperature increase of a receiving body in a temperate climate zone should not exceed 3 K.

3.5 Noise

Depending on the local situation, the noise immission requirements for power plants can differ widely. According to the TA-L (Technical Instructions on Noise Abatement) in the Federal Republic of Germany, the following noise immission limits (guide values) should be complied with:

day dB (A)

night dB (A)

areas containing only nonresidential buildings areas containing primarily nonresidential buildings areas containing nonresidential and residential buildings areas containing primarily residential buildings areas containing exclusively residential buildings areas containing health resorts, hospitals, nursing homes

70 65 60 55 50 45

70 50 45 40 35 35

The concrete-case values also depend on the baseline noise-immission levels.

As a rule, power plants should be located as far as possible from residential areas. According to the North-Rhine/Westphalian spacing ordinance Abstandserla/I>, a distance of 800 m or more means that the power plant can be expected to cause no impairment. In a number of German cities, power plants are situated much closer to residential areas, particularly in the case of cogenerating facilities, since the district heat produced by the power plant suffers substantial transmission losses with increasing distance to the consumer heat sinks.

The distance between a power plant and the nearest residential area depends primarily on the noise immission levels encountered at the points of interest, i.e., where the noise is measured. Noise immissions from the boiler and turbine plant can be substantially reduced by the application of noise control measures to the fae.

The delivery of fuel and process materials and the hauling away of residues (incl. the loading and unloading of trucks, railroad cars, barges, etc.) contribute substantially to the overall noise pollution levels from a power plant. For a coal-fired plant, the noise caused by the coaling system must also be allowed for. Consequently, delivery and removal activities, as well as operation of the coaling system, often have to be restricted to the daytime hours.

4. Interaction with other sectors

Power plants release certain pollutants into the air, water and soil. If a substantial number of small individual industrial furnaces with relatively poor pollution characteristics can be replaced by a single central thermal power plant, or if such a plant is able to provide process heat as well as electricity to industrial enterprises, the resultant gain in efficiency and environment-friendly technology can yield a relative improvement in the overall emission/immission situation. Within that context, cogeneration appears as a favorable option, as long as the plant can be located in an industrial zone or integrated into an industrial complex with adequately large heat demand.

Power plants require diverse operating media. The relevant interaction with other industrial sectors is particularly pronounced in the case of coal-fired power plants. The sectors of essential relevance include mining, of course, as the coal source, and the nonmetallic minerals industry as a supplier of lime products for flue-gas desulfurization. If gas is used as fuel, the power plant will interact closely with the natural gas industry, and oil-fueled plants depend on oil producers, refineries and petroleum-product storage and transport firms. Reciprocity between a thermal power station and such other sectors involves the entire system catena, e.g., from the mining of the fuel to the disposal of residues (cf. section 5). Additionally, the power plant's water consumption must be viewed in context with the public water supply system, if both are competing for the same scarce water resources.

Relations with yet other industrial sectors can be entered into in connection with the disposal of residues. Fly ash and slag, for example, can serve as aggregates in the cement industry, and a number of byproducts from flue-gas desulfurization (gypsum, stabilizate and compounds of sulfur) can be useful in the cement, plaster or chemical industry (e.g., as fertilizer), depending on their properties and degree of purity. Such connections can help reduce the exploitation of natural resources like gypsum. Fly ash and desulfurization products (gypsum, sulfite, sulfate) can also be used in the construction of roads and dams or as fillers for purposes of recultivation (backfilling of mines).

5. Summary assessment of environmental relevance

As explained in sections 2 and 3, thermal power plants have negative environmental impacts in the form of emissions extending from particulates, noxious gases (SOx, NOx, CO, CO2, HCl, HF,...) and waste heat to noise pollution. Diverse measures such as appropriate siting, the use of efficient, environment-friendly technologies (cogeneration, i.e., the combined generation of heat and power) and the avoidance or reduction of noxious emissions can substantially alleviate such negative environmental consequences. Nonetheless, it is not always possible to limit the environmental consequences to an acceptable scale, particularly if inferior fuel is used, the power plant is unusually large, or the surroundings (human population, flora and fauna) are particularly sensitive.

For the purposes of an environmental impact assessment, the entire system catena - from the production and transportation of fuels and chemicals to their in-plant combustion and on to the disposal of residues and the consumption of energy produced in other areas, e.g., a user industry - must be given thorough consideration. Such a holistic approach helps identify additional burdens resulting from, say, transportation of the fuel or residues by truck, as well as reductions ascribable to such aspects as credits granted for the replacement of older, less ecologically sophisticated combustion plant.

Since the primary objective in the erection of an environmentally compatible power plant must be to reduce pollution of the environment, the siting and baseline-pollution evaluation aspects are exceedingly important. However, a conflict of goals can arise by reason of the fact that the positive effects of reduced emissions - thanks to cogeneration, for example - can be partially or entirely negated by the necessity of locating the plant in the near vicinity of an industrial complex in which the pollutant concentrations already have contributed to baseline pollution in the area in question.

Regarding the limitation of particulate, SOx and NOx emissions by thermal power plants, various well-proven commercial-scale techniques are available. Since, for economic reasons, many countries prefer to fuel their power plants with indigenous coal characterized by high ballast and sulfur contents, special attention must be paid to reducing both of those pollutants. Depending on the local boundary conditions and in consideration of the overall situation, every attempt should be made to reduce emissions to below 150 mg/m³STP particulates and/or 2000 mg/m³STP SO2. Technically feasible measures for low-NOx combustion should be incorporated at the planning stage to ensure limitation of NOx emissions. Depending on the type of fuel in question, such pollution-control measures can confine NOx emissions to the 200 - 600 mg/m³STP range (excl. slag tap firing).

In general, priority should be attached to a combination of avoidance and combustion-modification measures, e.g., high efficiency, with favorable effects on CO2 emissions. Secondary measures in the form of post-combustion flue gas clean-up, for example, should remain just what the name implies.

In assessing the environmental compatibility of a thermal power plant, proper monitoring is extremely important, since the best of all emission-control measures can only be as efficient as the attendant monitoring. One suitable approach would be to appoint one or more in-house environmental protection officers.

The following catalogue of criteria should be applied to the planning and evaluation of the environmental relevance of thermal power plants:

- efficiency in the production and ultimate use of electricity and/or heat (subsidized rates?);
- substantiable necessity of the project (size of plant, interaction with other sectors);
- description and analysis of the project and its impacts (technical concept, choice of fuel, emission sources, control systems, safety considerations);
- discussion of siting alternatives and determination of baseline pollution levels and the prospective overall burden at the selected location (ground-level pollution, ambient air pollution, effects on water, soil, flora, fauna, human health, physical and cultural assets);
- ascertainment of the environmental relevance of effects emanating from the anticipated overall burden, plus measures aimed at reducing relevant environmental burdens (siting, avoidance measures, pollution control by pre- and post-combustion measures).

6. References

General

Asian Development Bank: Environmental Guidelines for Selected Industrial and Power Development, Projects, 1987.

Biswas, A.K.; Geping, Q.: Environmental Impact Assessment for Developing Countries, London: Tycooly Publ., Editor: United Nations Univ., Natural Resources and the Environment Series, vol. 19, 1987.

Deutsche Stiftung fernationale Entwicklung (DSE - German Foundation for International Development): Environmental Impact Assessment (EIA) for Development; Proceedings of a joint DSE/UNEP International Seminar in Feldafing, Federal Republic of Germany, April 9 - 12, 1984.

Fleischhauer, M.; Friedrich, R.; Hng, S.; Haugg, A.; M J.; Reuter, A.; Vo A.; Wystrcil, H.-G.: Grundlagen zur Abschung und Bewertung der von Kohlekraftwerken ausgehenden Umweltbelastung in Entwicklungslern, Institut frgiewirtschaft und Rationelle Energieanwendung, Stuttgart, May 1990.

Storm, Bunge: Handbuch der Umweltvertrichkeitspr Berlin: E. Schmidt-Verlag, Umweltprogramm der Vereinten Nationen, Ziele und Grundse der Umweltvertrichkeitspr January 16, 1987.

World Energy Conference: Environmental Effects Arising from Electricity Supply and Utilisation and the Resulting Costs to the Utility, Report 1988, Oct. 1988.

Air Protection

Anton, P.; Elser, R. F.: Problemverschiebungen bei der Umweltpolitik zwischen Luft, Wasser und Boden, VGB-Kongre"Kraftwerke 1985", p. 207 - 211.

Basu, P.; Greenblatt, J.; Wu, S.; Briggs, D.: Effects of Solid Recycle Rate, Bed Density and Sorbent Size on the Sulfur Capture in a Circulating Fluidized Bed Combustor, Proceedings from the 1989 International Conference on Fluidized Bed Combustion, San Francisco, Ca, pp. 701 - 707.

Baum F.: erblick ie Entschwefelungsverfahren, Sonderpublikation der BWK, Staub, Umwelt, p. 7 - 11, 1986.

Berman, I.M., Fluidized bed combustion systems: FBC presents a way to burn coal with minimal SO2 and NOx emissions. Development work is leading into demonstration units by a number of manufacturers, POWER ENGINEERING, November 1982.

Boardman, R.D.; Smoot, L.D.: Prediction of Fuel and Thermal NO in Advanced Combustion Systems, 1989; Joint Symposium on Stationary Combustion NOx Control, March, San Francisco, Ca.

Davids, P.; Haug, N.; Lange, M.; Oels, H.-J. und Schmidt, B.: Luftreinhaltung bei Kraftwerks- und Industriefeuerung, BWK 39, Heft 4, p. 180 - 188, 1987.

EPRI Report, Inorganic and Organic Constituents in Fossil Fuel Combustion Residues, Volume 1: A Critical Review, EPRI EA-5176, Project Z4BS-8, Interim Report, August 1987.

Given, P.H.: An Essay on the Organic Chemistry of Coal, COAL SCIENCE, Volume 3, Edited by Gorbaty, M.L.; Larson, J.W. and Wender, I., pp. 63 - 252, 1984.

Gra, H.: Anthropogene Beeinflussung des Klimas, VGB Kraftwerkstechnik 69, Heft 11, November 1983.

Haji-Javad, M.; Heinisch, M.; Hetschel, M.; Hutter, F.; Ludwig, H.: Konzeption eines Steinkohlekraftwerks aus umweltfreundlichen Komponenten, Forschungsbericht BMFT-FB-T 85 - 065.

Haer, G.; Fuchs, P.: Verfahren und Anlagen zur kombinierten SO2-/NOx-Minderung, Sonderpublikation der BWK, Staub, Umwelt, p. 21 - 27, 1986.

Kalmbach, S.; Kropp, L.: Umweltrelevante Stoffe, Umweltmagazin, p. 53 - 55, May 1987.

Kanij, J.B.W.: The Emission of Polycyclic Aromatic Hydrocarbons by Coal-fired Power Stations in the Netherlands, Kema Scientific & Technical Reports 5, 1987.

Krolewski, H.: Maahmen zur Luftreinhaltung bei Kraftwerken und ihre Auswirkungen auf Wasser und Abfall, VGB Kraftwerkstechnik 65, Heft 9, pp. 801 - 806, 1985.

Leckner, B.; Amand, L.E.: Emissions from a Circulating and a Stationary Fluidized Bed Boiler: A Comparison, Proceedings from the 1987 International Conference on Fluidized Bed Combustion, Boston, Ma, Vol. 2, pp. 891 - 897.

Lee, Y.Y.; Hiltunen, M.: The Conversion of Fuel-Nitrogen to NOx in Circulating Fluidized Bed Combustion, 1989 Joint Symposium on Stationary Combustion NOx Control, March, San Francisco. Ca.

Leithner, R.: Einfluunterschiedlicher WSF-Systeme auf Auslegung, Konstruktion und Betriebsweise der Dampferzeuger, VGB Kraftwerkstechnik 69, July 1989.

Natusch, D.F.S.: Final Report: Formation and Transformation of Particulate Polycyclic Organic Matter Emitted from Coal-fired Plants and Shale Oil Reporting, U.S. DOE Contract DOE-AC02-78EV04960, University of Colorado, April 1984.

Natusch, K.; Ratdjczak, W.: Meechnik zur erwachung des Betriebsverhaltens von Rauchgasreinigungsanlagen. Sonderpublikation der BWK, Staub, Umwelt, p. 29 - 34, 1986.

Perhac, R.M.: Environmental Effects of Nitrogen Oxides, 1989 Joint Symposium on Stationary Combustion NOx Control, March, San Francisco, Ca.

Smith, R.C.: The Trace Element Chemistry of Coal During Combustion and the Emission from Coal-fired Plants, Prog. Energy Combustion Science, 6 (1) pp. 53 - 119, 1980.

US EPA Report: Preliminary Environmental Assessment of Coal Fired Fluidized Bed Combustion Systems, EPA Report No. 600-7-77-05, May 1977.

US EPA Report: The Hydrogen Chloride and Hydrogen Fluoride Emission Factors of NAPAP (National Acid Precipitation Assessment Program) Emission Inventory, US EPA Report No. 600/7-85/041, October 1981.

US EPA Report: Locating and Estimating Air Emissions for Sources of Polycyclic Organic Matter, EPA 450/4-84-007P, September 1987.

Vernon, Jan L.; Soud, Hermine N.: FGD Installations on Coal-fired Plants, IEA Coal Research, EACR/22, London, April 1990.

Weber E.; HK.: ersicht auchgasseitige Verfahren zur Stickoxidminderung, Sonderpublikation der BWK, Staub, Umwelt, p. 12 - 16, 1986.

Yeh, H.; Newton, G.J.; Henderson, T.R.; Hobbs, C.H.; Wachtner, J.K.: Physical and Chemical Characterization of the Process Stream for a Commercial Scale Fluidized Combustion Boiler, Environmental Science & Technology, Vol. 22, July 1988.

Residues

Hackl, A.: Vom Rohstoff bis zum Sonderabfall, Entsorgungspraxis 3, p. 81 - 83, 1987.

Pietrzeniuk, H.-J.: Rnde bei der Verbrennung: Flugaschen, Filterste und REA-Gips, Umwelt Nr. 6, p. 455 - 458, 1986.

Verwertungskonzept f Reststoffe aus Kohlekraftwerken, VGB Kraftwerkstechnik 66, Nr. 4, p. 377/385, 1986.

Wastewater / Effluent

Burfmann, F.: Betriebserfahrung mit der Abwasseraufbereitung hinter einer Rauchgasreinigungsanlage, VBG Kraftswerkstechnik 66, 1986 H. 9, p. 866 - 871.

Heitmann, H.G.: Chemische Behandlung von Abwern aus Kraftwerken, BWK 38, Nr. 11, p. 499 - 509, 1986.

Ludwig, H.: Abwasserbehandlung, BWK Bd. 437, 1985, Nr. 9, p. 343 - 351.

Neumann, J.C. und Hofmann, G.: Behandlung und Aufarbeitung von Abwern aus Rauchgaswhen, BWK Bd. 437, 1985, Nr. 9, p. 352 - 355.

Sieth, I.: Abwasser aus Rauchgasreinigungsanlagen, Techn. Mitt. 78., Jahrg. 1985, H. 1/2, p. 71 - 73.

Laws, Directives

Wastewater Charges Act (Abwasserabgabengesetz dated Nov. 6, 1990; Federal Law Gazette, BGBl. I, p. 2432).

First General Administrative Provision Pertaining to the Federal Immission Control Law (Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionschutzgesetz) Technical Instructions on Air Quality Control (Technische Anleitung zur Reinhaltung der Luft - TA-Luft) dated February 27, 1986, joint ministerial circular (GMBl. Gemeinsames Ministerial-Blatt p. 95, ber. p. 202).

Deutsches Umweltrecht, WLB, Verlag Technik GmbH, Berlin, 1991.

Act on the Prevention of Harmful Effects on the Environment Caused by Air Pollution, Noise, Vibration and Similar Phenomena (Gesetz zum Schutz vor schichen Umwelteinwirkungen durch Luftverunreinigungen, Gerche, Erschngen und liche Vorge) Federal Immission Control Act (Bundes-Immissionsschutzgesetz - BlmSchG) as amended and promulgated on May 14, 1990 (Federal Law Gazette BGBl. I, p. 880).

Waste Avoidance and Waste Management Act (Gesetz ie Vermeidung und Entsorgung von Abfen (Abfallgesetz - AbfG) dated August 27, 1986 (Federal Law Gazette BGBl. I, p. 1410, ber. p. 1501).

Act on the regulation of matters relating to water resources (Gesetz zur Ordnung des Wasserhaushalts; Wasserhaushaltsgesetz - WHG) dated September 23, 1986 (Federal Law Gazette BGBl. I. p. 1529).

Lbekfung 81, Entwicklung - Stand - Tendenzen, Umweltbundesamt (German Federal Environmental Agency), (Ed.), Berlin 1981.

General Administrative Framework Regulation on Minimum Requirements for the Discharge of Wastewater into Waters (Rahmen-Abwasser-Verwaltungsvorschrift) with Annexes 31 and 47 to section 7a WHG, dated November 25, 1992.

VDI guideline 2113 (12/76): Emission control, supplement units for solid fuels fired boilers.

Vernon, Jan L.: Emission Standards for Coal-fired Plants: Air Pollutant Control Policies, IEACR/11, IEA Coal Research, London, August 1988.

Verordnung zur Durchf des Bundesimmissionsschutzgesetzes (Stll-Verordnung, Ordinance for the Implementation of the Federal Immission Control Act = Hazardous Incident Ordinance), with
- Erster Allgemeiner Verwaltungsvorschrift zur Stll-Verordnung (first general administrative provision on the hazardous incident ordinance) and
- Zweiter Allgemeiner Verwaltungsvorschrift zur Stll-Verordnung (second general administrative provision on the hazardous incident ordinance).

Vierte Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes (fourth ordinance for the implementation of the Federal Immission Control Law) Verordnung enehmigungsbede Anlagen - 4. BImSchV (ordinance on installations subject to licensing) dated July 24, 1985 (Federal Law Gazette BGBl. I, p. 1586).

Zweites Gesetz zur derung des Bundes-Immissionsschutzgesetzes (second law amending the Federal Immission Control Act) dated October 4, 1985 (Federal Law Gazette BGBl. I. p. 1950).

Second General Administrative Provision on the Waste Avoidance and Management Act (Zweite allgemeine Verwaltungsvorschrift zum Abfallgesetz) Technical Instructions on Waste Management (TA-Abfall), Part 1: Technical Instructions on the storage, chemical, physical and biological treatment, incineration and storage of waste requiring particular supervision (Technische Anleitung zur Lagerung, chemisch/ physikalischen, biologischen Behandlung, Verbrennung und Ablagerung von besonders chungsbeden Abfen) dated March 12, 1991.

7. Appendices

A-1 Flow diagram of energetically and environmentally relevant materials in a thermal power plant
A-2 Schematic diagram of a thermal power plant equipped with various flue-gas cleaning systems
A-3 Details of various desulfurization processes
A-4 Immission limits standards as per the German TA-Luft
A-5 German laws and regulations governing the limitation of emissions from thermal power plants
A-6 Emission limits for air pollutants from large firing installations (³ 50 MW) in Germany; emission limits for new, large-scale, coal-fired power plants in various countries, plus pertinent EC and World Bank standards; conversion chart for SO2 and NOx emissions
A-7 Minimum requirements as per German Federal Water Act (WHG) section 7a
Appendix 47: Scrubbing of flue gases from combustion plant, Sept. 8, 1989

Appendix A-1 - Flow diagram of energetically and environmentally relevant materials in a thermal power plant


Flow diagram of energetically and environmentally relevant materials in a thermal power plant

Appendix A-2 - Schematic diagram of a thermal power plant equipped with various flue-gas cleaning systems


Schematic diagram of a thermal power plant equipped with various flue-gas cleaning systems

Appendix A-3 - Details of various desulfurization processes

In-boiler desulfurization techniques are employed for solid fuels, e.g., in fluidized-bed combustion systems. The SO2 forming in the flue gas combines with lime or limestone injected into the combustion system. Desulfurization therefore takes place simultaneously with fuel combustion at roughly 850°C. That relatively low combustion temperature helps limit NOx emissions to 200 - 400 mg/m³STP. The degree of desulfurization ranges between 80 % and 90 %. Fluidized-bed combustion systems, which only can be used in new power plants, operate according to either the stationary or the circulating principle, with the latter achieving the lower emission levels under otherwise identical boundary conditions.

Dry additive processes can be applied to coal-fueled, grate- and dust-fired boilers. At a temperature below 1000°C, a pulverized lime product, e.g., slaked lime, is injected into the flue gas at a point above the combustion chamber, where it reacts with the SO2 and precipitates. The requisite equipment is retrofittable and can remove 60 - 80 % of the sulfur from the flue gas.

The residual product from fluidized-bed combustion and dry additive processes - a mixture of coal ash, CaO or other unreacted additive, and various calcium salts (CdSO4, CaCl2, CaF2) - is separated out in a downstream dust precipitator. In each case, it should be ascertained whether or not the residue can be put to some practical use, perhaps in the building materials industry (usually somewhat problematic due to the mixed salts), or will instead require safe disposal.

There are three basic types of flue-gas desulfurization processes:

- wet processes
- spray-dryer processes
- dry processes.

The wet process using limestone, lime or slaked lime as the additive and producing gypsum as a reaction product is the most widely employed commercial-scale alternative. It has yielded the largest worldwide empirical potential and is used in the majority of facilities. Appropriately processed via drying and pelletizing, for example, the gypsum can be used by the building materials industry, mixed with fly ash and landfilled, or used for land reclamation purposes in coastal areas (cf. section 2.5).

In the spray-dryer process, the sorbent (lime or slaked lime) is sprayed as an aqueous solution into an absorber at 60 - 70°C. As the water introduced with the suspension evaporates, the additive reacts with any SO2 present to produce a fine-grained reaction mixture that precipitates out in downstream particulate removal equipment. Consisting of various calcium salts (CaSO4, CaSO3, CaCl2, CaF), excess sorbent and residual fly ash, the reaction product can either be landfilled or used for land reclamation purposes. Potential preteatment requirements for the residue and additional measures for preventing groundwater or coastal-water contamination due to leaching are dealt with in section 2.5.

Other flue-gas desulfurization techniques, most notably dry processes using activated charcoal and regenerative processes involving sodium sulfite as the sorbent and sulfur dioxide as an intermediate product capable of further processing into sulfuric acid or sulfur, have become widely accepted in some areas and can be used for various other specific situations. As a rule, however, such processes are more elaborate and expensive than the limestone/gypsum techniques, and they impose particularly stringent standards on the quality of the end products, for which a corresponding market, e.g., the chemical industry, is needed.

Assuming otherwise identical constraints, the quantities of residue produced derive in descending order from the dry sorbent, spray drying, scrubbing with gypsum, and scrubbing with sulfuric acid or sulfur (cf. section 2.3).

Appendix A-4 - Immission limits as per the German TA-Luft

Pollutant



IW 1

IW 2

-

Suspended particles

mg/m³


0.15

0.30

-

Lead and inorganic lead compounds as components of the suspended particles indicated as Pb

µg/m³


2.0

-

-

Cadmium and inorganic cadmium compounds and components of the suspended particles indicated as Cd

µg/m³


0.04

-

-

Hydrochloric acid indicated as Cl

mg/m³


0.10

0.20

-

Carbon monoxide

mg/m³


10.0

30.0

-

Sulfur dioxide

mg/m³


0.14

0.40

-

Nitrogen

mg/m³


0.08

0.20

The above table lists the immission limits for the prevention of health hazards as prescribed by the German TA-Luft, (Technical Instructions on Air Quality Control). The values IW1 and IW2 are the short-term and long-term limits, respectively. In assessing the environmental compatibility of a thermal power plant, its IW2-value (continuous operation), for which TA-Luft specifies a monitoring period of one year, is significant.

As protection against substantial detriment and nuisance attributable to particulate precipitation, TA-Luft prescribes the following limits referred to as deposition values.

Pollutant

IW 1

IW 2

Particulate deposition

g/(m²d)

0.35

0.65

Lead

mg/(m²d)

0.25

-

Cadmium

µg/(m²d)

5.0

-

Thallium

µg/(m²d)

10.0

-

Fluorine

µg/(m²d)

1.0

3.0

The inorganic compounds in the above table are regarded as particulate constituents, with fluorine HF and the inorganic gaseous fluorine compounds counting as F.

Relatively little information is available on the combined, so-called synergistic, effects of pollution and on the interaction of atmospheric pollutants.

The toxicological effects of the various pollutants are listed in the Compendium of Environmental Standards.

The main effects of the most important pollutants are essentially as follows:

- Lead inhibits various globular metabolic enzymes in humans and other mammals, causing disruption of the oxygen balance and tidal volume. Sustained intake of less than 1 mg Pb/d has injurious effects. For plants, which take in lead primarily from the soil as opposed to the air, lead is only mildly toxic, the tendency being to lower the quality, but not the quantity, of the produce.
- Cadmium, a freely soluble metallic element, is resorbed into the digestive tract and stored in the liver and kidneys of humans and other mammals. Like its various compounds, cadmium has carcinogenic properties. In Asia, the so-called Itai-Itai and Aua-Aua syndromes were found to have been caused by Cd-polluted rice. Even low concentrations of cadmium in the soil can cause extensive damage to plants. Plants assimilate cadmium through their roots as well as their leaves and branches. Apart from reducing yields, cadmium contamination is hazardous to human health in that it enters the food chain as a cumulative toxin.
- Carbon monoxide, with its affinity for hemoglobin, the protein pigment responsible for the transport of oxygen, is toxic to humans and other vertebrates. Ingested exclusively by inhalation, carbon monoxide is odorless, colorless, tasteless and otherwise imperceptible to the senses. CO is nontoxic to plants, because it rapidly oxidizes to form CO2, which plants need for photosynthesis.
- Sulfur dioxide causes corneal clouding, respiratory distress, inflammation of the respiratory tract, irritation of the eyes, disorientation, pulmonary edema, bronchitis and cardiovascular insufficiency in humans and other mammals.

Sulfur dioxide exposure causes both direct damage to the aboveground parts of plants and indirect damage primarily by way of soil acidification.

- Nitrogen oxides resulting from combustion processes occur in the atmosphere mainly as nitrogen monoxide NO and nitrogen dioxide NO2. The preferred generic term is nitrous gases (NOx)

Inhaled by a human or animal, an NOx gas enters the lungs and irritates the mucous membranes. While NO2 leads to pulmonary edema, NO affects the central nervous system.

In a photochemical smog situation, nitrogen oxides and hydrocarbons combine to form nitrate compounds that cause irritation of the eyes and mucous membranes.

All nitrous gases are toxic to plants, as evidenced by brown to brownish-black leaf margins and spots. The poisoning process culminates in dry withering of the damaged cells.

Compared to nitrogen monoxide NO, nitrogen dioxide NO2 is substantially more toxic. For plants and animals, NO2 is less hazardous than for human beings. Atmospheric NO oxidizes to NO2; consequently, NO is prevalent in the near vicinity of combustion plants and is gradually supplanted by NO2 with increasing distance from the source.

Appendix A-5 - German laws and regulations governing the limitation of emissions from thermal power plants

- Federal Immission Control Act (Bundes-Immissionsschutzgesetz) (BImSchG)

· Ordinance on Large Firing Installations (Groeuerungsanlagenverordnung) (GFAVO)
· Technical Instructions on Air Quality Control (Technische Anleitung zur Reinhaltung der Luft) (TA-Luft)
· Technical Instructions on Noise Abatement (Technische Anleitung zum Schutz gegen L) (TA-L)
· Hazardous Incident Ordinance (Stllverordnung)

- Resolution of the Conference of Ministers for the Environment concerning mandatory dynamization of the Ordinance on Large Firing Installations with regard to nitrogen oxide emissions (Beschluder Umweltministerkonferenz) (UMK)
- Federal Water Act (Wasserhaushaltsgesetz) (WHG)

· General Administrative Framework Regulations on... Wastewater (Rahmen-Abwasser-Verwaltungsvorschrift), Annexes 31, 47 to section 7a (AbWVwV)
· Provisions governing the handling of substances constituting a hazard to water (section 199) (AbWVwV)

- Ordinance on the industrial sources of wastewater (Abwasserherkunftsverordnung) (AbWHerkV)
- Waste Avoidance and Waste Management Act (Abfallgesetz) (AbfG)

· Technical Instructions on the storage, chemical, physical and biological treatment, incineration and storage of waste requiring particular supervision (TA-Abfall)

Appendix A-6 - Emission limits for air pollutants from large firing

Installations (³ 50 MW) in Germany



Data stated in mg/m³STP, dry base











Type of fuel

MW*

Dust


Nox (as NO2)

SOx (as SO2)

CO

HCl

HF






Solid

£ 300 >300

50 50


400 200

2000 (400)1) 400

250 250

200 100

30 15






Liquid

£ 300 >300

50 50


300 150

1700 400

175 175

30 30

5 5






Gas

£ 300 >300

5 5


200 100

35 (100)2) 35 (5)3)

100 100






* MW = megawatt thermal output
1) for fluidized-bed combustion
2) coke oven gas
3) liquid petroleum gas

2 and NOx Emissions"Appendix A-6 - SO2 and NOx Emissions

Conversion Chart



To: (Multiply by) (r)



















To convert






















From ¯


mg/


ppm

ppm

g/GJ

g/GJ

g/GJ

lb/106 Btu



lb/106 Btu

lb/106 Btu











NOx

SO2

CoalA

ilOilB

GasC

CoalA



OilB

GasC









mg/m³



1

0.487

0.350

0.350

0.280

0.270

8.14 x 10-4



6.51 x 10-4

6.28 x 10-4









ppm Nox



2.05

1

0.718

0.575

0.554

1.67 x 10-3



1.34 x 10-3

1.29 x 10-3









ppm SO2



2.86

1

1.00

0.801

0.771

2.33 x 10-3



1.86 x 10-3

1.79 x 10-3









CoalA

2.86


1.39

1.00

1

2.33 x 10-3











g/GJ

OilB

3.57


1.74

1.25

1



2.33 x 10-3









GasC

3.70


1.80

1.30

1



2.33 x 10-3









CoalA

1230


598

430

430

1











lb/106 Btu

OilB

1540


748

538

430



1









GasC

1590


775

557

430



1









A:- Coal:- Flue Gas dry 6 % excess O2: Assumes 350 Nm³/GJ - ref IEA Paper 1986.
B:- Oil:- Flue Gas dry 3 % excess O2: Assumes 280 Nm³/GJ - ref IEA Paper 1986.
C:- Gas:- Flue Gas dry 3 % excess O2: Assumes 270 Nm³/GJ - ref IEA Paper 1986.

Appendix A-6 - Emission limits for new, large-scale, coal-fired power plants in various countries, plus pertinent EC and World Bank standards

Appendix A-6 Emission limits for new, large-scale, coal-fired power plants in various countries, plus pertinent EC and World Bank Standards

Country

SO2 emissions [mg/m³]

Size of plant

NOx emissions [mg/m³]

Size of plant

CO emissions [mg/m³]

Size of plant

Dust emissions [mg/m³]

Size of plant

EC

400

> 500 MWt

650

> 50 MWt

50

> 500 MWt

World Bank

500 t/d or 50 µg/m³ additional immission over slight prior SO2 burden (£ 50 µg/m³) 100 t/d or 10 µg/m³ additional immission over high prior SO2 burden (> 100 µg/m³)


858 (780 for lignite)

100 (150 in rural areas and when immission < 260 µg/m³ beyond power plant perimeter)


Australia

200

800

> 30 MWt

1000

80

-

Austria

80 % (sep. efficiency)

> 200 MWt

800

> 50 MWt

250

> 2 MWt

50

> 50 MWt

Belgium

400

> 300 MWt

200

> 100 MWt

50

> 50 MWt

Canada

740

740

125

Denmark

860

> 50 MWt

1150

> 50 MWt

57

> 5 MWt

Finland

140

> 150 MWt

200

> 300 MWt

57

> 50 MWt

France

1700 - 3400

(regional)

130

> 9.3 MWt

Germany

400

> 300 MWt

200

> 300 MWt

250

> 50 MWt

50

> 5 MWt

Great Britain

90 % (sep. efficiency)

> 700 MWt

760

> 700 MWt

97

> 700 MWt

India

height of stack > 500 MWt: 275 m > 200 < 500 MWt: 200 m < 200 MWt: (equation)


no limits


150 (350 for plants with < 200 MWt in unprotected areas)


Italy

400

> 100 MWt

650

> 100 MWt

50

> 100 MWt

Japan

plant-specific


411

> 70000 m³/h

50

> 200000 m³/h

New Zealand

125 - 500

> 5 MWt

Netherlands

400

> 300 MWt

400

> 300 MWt

50

Spain

2400

200

> 200 MWt

Sweden

290

430

35

USA

740

> 29 MWt

740

> 29 MWt

37

> 73 MWt

/.../ The minimum size of plant to which the relevant limit applies is stated in MWt; the volumetric flue-gas flow is stated in m³STP/h









Appendix A-7 - Minimum requirements as per German Federal water act (WHG*), section 7a

Appendix 47: Scrubbing of flue gases from combustion plant, Sept. 8, 1989

COD

Filterable substances4)

Fluoride

Sulfate

Sulfite

Lead

Cadmium

Chromium

Copper

Nickel

Mercury

Zinc

Sulfide

Accepted engineering practice





State of the art









General

805)

30

30

20000

20

0.1

0.05

0.5

0.5

0.5

0.05

1

0.2

1506)

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

mg/l

Hard-coal

1

power plants (pollutant concentr., mg/kg chloride)

see above

3.8 mg/kg

1.8 mg/kg

18 mg/kg

8 mg/kg

18 mg/kg

1.8 mg/kg

36 mg/kg

7.2 mg/kg

Lignite power plants with chloride contents up to 0.05 weight % (pollutant concentr., g/h)7)

see above

0.2 g/h

0.1 g/h

1 g/h

1 g/h

1 g/h

0.1 g/h

2 g/h

0.4 g/h

* WHG = Wasserhaushaltsgesetz
4) via quicklime
5) via limestone
6) pollutant concentration in g/h per 300 MW installed electrical output
7) after subtraction of the prior COD pollutant concentration introduced with the service water

1. Scope

Adequate power supply systems constitute an essential part of any country's technical infrastructure. Such systems comprise facilities for the generation, transmission and distribution of electricity.

This brief deals with the planning, construction and operation of all technical facilities required for transmitting and distributing electric power.

Transmission is understood as the conveyance of electrical energy from its place of generation to its place of use. Power transmission is characterized by the conveyance of electric power over comparatively long distances with the aid of high-voltage and medium-voltage systems. Depending on the relative locations of the power generating facilities and the power consumers, many different forms of landscape and vegetation can be affected.

Distribution is understood as the delivery of electric power from the bulk power source to the consumer. As a rule, this involves relatively short distances within populated areas by way of medium-voltage and low-voltage systems.

The technical facilities required for transmitting and distributing electric power comprise mainly:

- overhead power lines
- cables
- transformer and switching stations.

2. Environmental impacts and protective measures

Direct effects on the environment result from the erection and operation of such facilities, with the extent and intensity of the impacts depending substantially on the physical circumstances and the project planning.

This section describes and illuminates the direct and indirect effects of power transmitting equipment on the natural environment, i.e.:

- resources (water, soil, air) and
- ecological systems (flora and fauna, interlinked biotopes)

as well as on humans, i.e.:

- their health and safety, occupational and otherwise,
- their socioeconomic and sociocultural circumstances, as well as
- their visual perceptions.

2.1 Consequences for the natural environment

· Soil, water and air

In wooded areas, the erection and safe operation of overhead power lines necessitate the maintenance of unobstructed lanes, the widths of which vary between 25 and 100 meters, depending on the size of the transmission line. Paved or unpaved access roads may be needed for installing and inspecting the lines and towers. That, in turn, entails the permanent destruction of forest; due to the loss of its original vegetation, the disturbed soil is at least temporarily unprotected and exposed to the climatic effects of heat, frost and rain, all of which promote erosion. Soil compaction resulting from project-site motor vehicle traffic intensifies the soil's susceptibility to erosion. Afterward, the affected area is only conditionally suitable for other forms of utilization. Any strip of land that cannot be used for forestry purposes due to its being located along a right of way (danger of grounding) should be greenbelted in order to combat erosion. The use of space-saving components helps reduce the space requirement quite substantially.

The erection of towers and tower footings on steep slopes demands detailed knowledge of the subsoil situation. Any mistake made in planning and executing the work can seriously impair the stability of the slope and lead to slip erosion.

The construction of switching and transforming stations permanently occupies certain areas and jeopardizes the soil and groundwater through the potential leakage of coolants and insulants (mineral oil or other liquids possibly containing toxic polychlorinated biphenyls - PCB) in large quantities from such components as transformers, capacitors, ground-fault neutralizers and underground cables.

Suitable collecting troughs/separators must be provided to prevent contamination of the groundwater and soil.

· Flora and fauna

Due to the machines involved, the erection phase of power transmission lines and switch plant imposes stress on - and causes potentially permanent damage to - the surrounding flora and fauna.

The clearing of lanes in wooded areas modifies the microclimate by admitting more insolation and wind, thus altering the temperature distribution. Such changes can disrupt the local ecosystem.

Depending on the attitude of the transmission route, such lanes can seriously enhance the windslash incidence in the adjacent woods.

Frequently, fire and herbicides are used to create lanes and keep them clear of vegetation. Since such practices are very damaging to both flora and fauna, they should be dispensed with to the greatest possible extent.

Due consideration should also be given to the danger of dissecting biotopes into small "islands" that are not likely to survive beyond the medium term.

Overhead power lines are a fourfold hazard for birds:

- they debase breeding grounds;
- birds (particularly night-flying species) can fly into the wires;
- birds can be killed by simultaneously contacting two wires or a wire and the tower (medium-voltage lines);
- the "magnetic compass" effect can interfere with their navigating system.

In Germany, the populations of several species of large birds have been substantially decimated; some 70 % of all white storks are lost to electrocution.

In extremely rare cases, a short circuit or other defect in a transformer or switchgear has been known to cause a fire with resultant destruction of the surrounding flora and fauna.

The roads and lanes established to enable the erection and maintenance of overhead power lines can have the same environmental consequences as other traffic routes, in particular opening-up effects (cf. environmental briefs Transport and Traffic Planning, Road Building).

· Minimization and avoidance measures

The aforementioned impacts can be minimized or avoided by heeding the following points in connection with the planning and erection of overhead power lines:

- consider possible alternatives to new construction, e.g., conversion or more efficient/multiple utilization of existing lines;
- adjoin overhead lines to existing traffic routes and pipelines;
- adapt the right of way to existing landscape structures, i.e., avoid such exposed locations as hilltops and domes, ridges, razorbacks, etc.;
- significantly reduce the consumption of landscape and forest by installing high towers to permit greater spans between towers, thus traversing larger areas;
- avoid nature preserves and other protected areas, biologically and/or ecologically significant regions and recreation areas;
- use insulation sleeving, shrouding covers, perching and nesting platforms on towers for MV and LV lines as protection for birds;
- allow for the future installation of additional lines, i.e., for multiple use of the transmission route (multiple-circuit lines);
- significantly reduce space requirements by choosing suitable tower types (latticed steel, steel-pipe/concrete/wood) and configurations (size and arrangement of line-supporting cross-arms) and by using trefoil insulated LV and MV conductors;
- reduce the ground-area-requirement by using cables instead of overhead lines, even though the cable route also has to be kept free of tree growth (The use of cables can be problematic, however, for economic and technical reasons attributable to the high cost of investment and the need for highly qualified maintenance personnel.);
- minimize the danger of soil and groundwater pollution by performing routine safety inspections of pole impregnating facilities and by either replacing tar-base impregnants with more environmentally appropriate (salt-base) agents or opting for vacuum- or high-pressure impregnated wood;
- prevent soil erosion by mulching and greenbelting to cover all exposed ground. In climate zones with rainy seasons, this should be done at the beginning of the rainy season in order to prevent sheet erosion;
- modify and strengthen existing lines to save energy and additional cables;
- restock working areas under forest-traversing spans.

2.2 Human health, occupational safety and accident prevention

· Accidents

The primary cause of accidents imperiling human life and limb (electrocution, serious burns) is inadvertent contact with live components, possibly in inadequately protected facilities, and the secondary cause is fire resulting from short circuits.

The danger of accidents is most acute when:

- technical specifications relevant to safety measures are disregarded in the planning and erection of plant and equipment (use of low-quality components, inadequate sizing, negligent execution, nonobservance of safety clearances), so that the finished facilities are inherently unsafe;
- the operating personnel has not received sufficient training in connection with safety measures and their observance;
- the local populace has not been properly educated with regard to electrical hazards, which can lead to such misbehavior as climbing up on towers, trespassing on switching stations, lack of lightning conductors, illegal tapping of electricity, etc.

In the past, and to a certain extent even today, the use of polychlorinated biphenyls (PCB, askarel/chlophen) as flame-retarding dielectric liquids in transformers and capacitors has constituted a health hazard in its own right. PCBs are very toxic. They accumulate in the food chain, cause chronic disorders and are carcinogenic. Moreover, their incineration (due to, say, exposure to an accidental fire) produces highly toxic dioxins and furans.

With but few exceptions (e.g., for electric plants in underground mines), the use of PCB in electrical plants is now generally prohibited in many countries.

Tar-base impregnants for wooden poles constitute a health hazard in that they can cause skin ailments.

Such risks can be substantially reduced or even completely avoided by:

- choosing plant components of the proper type and size,
- precluding unauthorized access to electrical plant and installing anti-climbing guards on high-voltage towers,
- reducing the danger of fire by using noncombustible dielectric liquids or dry transformers and refractory partitions,
- avoiding the use of dielectric liquids containing PCBs and of coolants in new installations; ensuring proper disposal and replacement of old transformers and the like,
- providing the operating personnel with appropriate safety clothing and suitable tools and test instruments,
- ensuring that the operating personnel receives the proper, duly qualified training,
- educating the local populace about the dangers of electrical installations.

· Effects of electric and magnetic fields on human health

According to information derived from prolonged observations and experiments in numerous countries, the electric and magnetic fields around power transmission and distribution facilities (exhibiting frequencies between 50 and 60 Hz) have no harmful effects on human health.

According to a WHO publication dealing with the effects of magnetic fields on human health, field strengths below 0.4 mT at 50 - 60 Hz induce no detectable biological reaction. The magnetic fields acting on the ground below overhead lines develop a maximum field strength of 0.055 mT for the above frequencies.

· Noise nuisance

Substation and distribution-system transformers generate a monotonous buzzing sound that can be annoying in residential areas. The use of quiet-running transformers and/or appropriate structural measures (incl. adequate distances) can avoid such problems.

2.3 Optical impairment of the landscape

Overhead power lines amount to an optical disturbance. The extent of disturbance depends on:

- the size, type and general configuration of the lines and towers,
- the concentration of overhead lines within a given area,
- the transmission route and/or visibility of the lines, i.e., how well the right of way has been accommodated to the landscape (color, "low profile"),
- the location (undeveloped/developed land, population density, industrial/residential areas, etc.).

The recreational value of landscapes and affected areas is diminished by the optical impairment.

The aforementioned preventive measures apply in equal measure to the avoidance of optical impairment.

2.4 Socioeconomic and sociocultural impacts

Any direct consequences the installation and operation of power transmission and distribution facilities may have on the socioeconomic and sociocultural environment are of minor significance. Radio and television reception, for example, can be substantially disturbed by corona discharges [luminous discharge along undersized and/or improperly arranged conductors (bundle-conductor lines)].

Indirect consequences derive from the purpose of such facilities, namely to improve living conditions by supplying electricity to a region or center. Access to electricity increases comfort and convenience in private life (e.g., time saved and work facilitated) and in the public domain. In combination with other technical infrastructural measures, it can initiate or stimulate economic activities aimed at creating new jobs (i.e., reducing unemployment) or rationalizing production processes6).

6) The negative environmental effects of power generation can be aggravated by excessive demand resulting from artificially low (submarginal) supply tariffs.

On the other hand, past experience has shown that electrification and other forms of regional development can lead to a loss of traditional ways of life, modes of behavior, cultural peculiarities and sociocultural ties and structures. Moreover, it can have a whirlpool effect on neighboring regions, giving rise to emigration and new congested areas.

3. Notes on the analysis and evaluation of environmental impacts and on occupational safety standards

Numerous different authorities, associations, public and private bodies both corporate and individual must be involved in defining the rights of way and the locations of substations. The process must include appropriate consideration of environmental interests.

Suitable structural measures (e.g., to prevent erosion) and technical measures (e.g., to prevent the escape of transformer oil) must be taken to avoid pollution of the soil and/or water.

Optical impairment of the landscape is unavoidable but should be minimized. The extent of impairment depends both on how the land is used (work - recreation) and on its optical complexity. The right of way can be visually assessed with the aid of a computer.

Detriment to flora and fauna must be appraised with a view to the protection of endangered species and in consideration of local, national and international standards and regulations. Determination of the local and regional significance of biotopes must be based on a large-scale survey in which suitable measures for the protection of birds are included.

Internationally recognized and harmonized, detailed standards on safety clearances, protective measures against contact with and entry to, in addition to working on, live systems [e.g., the German Standards DIN 0800, DIN 0848, DIN 57106, Association of German Electrical Engineers' VDE guideline 0106, accident prevention provisions and implementing instructions for electrical equipment and operating equipment issued by the Verband gewerblicher Berufsgenossenschaften ("Elektrische Anlagen und Betriebsmittel" - VBG 4)] should be consulted in connection with the planning of power transmission and distribution facilities.

The use of PCB in closed systems (transformers, capacitors, etc.) has been prohibited in the EC since 1985, although the continued operation of existing PCB-filled equipment is permitted for the duration of its service life. In the interest of environmental protection, however, such equipment should be replaced and properly disposed of (sodium-base dechlorination of the oil). Its incineration would produce dioxins!

4. Interaction with other sectors

The planning and installation of power transmission and distribution systems depend on decisions deriving from higher-level (national, regional) planning processes devoted to regional development, general energy development, town and country planning, general power supply measures, etc. (cf. corresponding environmental briefs).

There is a direct connection to the power generating sector (cf. environmental brief Thermal Power Stations). As soon as power transmission is correlated to a particular power source, the environmental impacts of the latter, i.e., of power generation, demand consideration; high transmission losses also have environmental consequences in that they necessitate the generation of additional power.

The rights of way for transmission lines are extensively determined by the relative locations of the power plant and the power consumers. Particularly valuable biotopes and landscapes must be protected by routing such rights of way around them.

Coordination with existing or still-to-be-installed technical infrastructure (roads, railways, waterways, other supply lines, etc.) is not only possible but even necessary for, say, crossing airports, waterways, roads, etc. and for the parallel routing of power transmission and telecommunication lines - all in order to ensure the safe, reliable operation of all facilities concerned.

With regard to the reprocessing and disposal of transformer oil (with or without PCB content), please refer to the environmental brief Disposal of Hazardous Waste.

5. Summary assessment of environmental relevance

The aforementioned environmental impacts and their consequences are evaluated below, and potential means of minimization and avoidance are proposed.

Landscape consumption in the form of pressure on natural resources (soil, vegetation) and destruction of landscape is generally unavoidable, though adequate attention to environmental concerns at the planning stage can at least diminish its consequences.

Appropriate structural measures can be adopted to reduce, but not eliminate, the hazard for birds posed by overhead power lines.

The danger of accidents for humans emanating from transmission and distribution installations can be reduced by strict adherence to existing, recognized rules, regulations and standards. Relevant training and sensitization are crucial in this area.

The emissions (noise, corona conduction) of power transmission and distribution installations can be reduced to negligible levels by appropriate technical means. The use of liquids containing PCBs in transformer substations still constitutes a substantial hazard potential in that such liquids are liable to escape to the environment as a result of equipment malfunction or accident (leakage, fire). Consequently, the use of components and equipment containing PCBs should be globally prohibited, and existing equipment should be replaced.

Compared to other means of energy conveyance (road, rail, water, pipeline) the transmission of electricity involves a modest, though by no means negligible, risk. Whenever new facilities for transmitting and distributing electric power are deemed absolutely necessary (e.g., if there is no possibility of opting for noncentralized power generation), appropriate low-impact approaches should be sought out.

The easiest and most effective way to minimize or completely avoid harmful environmental impacts is to conscientiously allow for environmental concerns from the planning stage on.

6. References

Algermissen, W.; L W.; KB.: SF6-isolierte Lasttrennschalteranlagen, Eine Technik f Netzstation von morgen, Elektrizitwirtschaft, 1988, Heft 16/17.

Asian Development Bank: Environmental Guidelines for Selected Industrial and Power Development Projects; Manila 1988.

Biegelmeier, G.: Wirkungen des elektrischen Stromes auf den menschlichen Kr, etz., 1987, Heft 12.

Borris, D., v.: Umweltbelastungen durch Transport: Speicherung und Verteilung von Energie, Energie und Umwelt, Heft. 7/8, Bundesforschungsanstalt fdeskunde und Raumplanung, Bonn, 1984.

Deutscher Bund felschutz, Landesverband Baden-Wberg e.V. (Ed.): Verdrahtung der Landschaft: Auswirkungen auf die Vogelwelt, ologie der V, Sonderheft 1980, Band 2, 1980.

Deutsches Institut fmung e.V.: DIN 18005, Noise abatement in town planning, 1982.

Dreiser, Rolf: Ursachen und Folgen von Arbeitsunfen in Elektrizitversorgungsunternehmen, Elektrizitwirtschaft, 1983, Heft 13.

Fanger, U.; Weiland, H.: Entscheidungskriterien bei Projekten der llichen Elektrifizierung aus sozio-omischer und entwicklungspolitischer Sicht. Kurzgutachten im Auftrag des BMZ, Arnold-Bergstraesser-Institut, Freiburg, 1984.

FINNIDA: Guidelines for Environmental Impact Assessment in Development Assistance; Draft 1989.

Gro Markus: Graphische Datenverarbeitung in der Freileitungsplanung - Innovative Methoden mittels Sichtbarkeitsanalyse, Elektrizitwirtschaft, 1990, Heft 6.

Haubrich, H.J.: Biologische Wirkung elektromagnetischer 50-Hz-Felder auf den Menschen, Elektrizitwirtschaft, 1986, Heft 16/17.

Haubrich, H.-J.; Dickers, K.; Lange, G.: Influenzwirkung auf Personen und Fahrzeuge im elektrischen 50-Hz-Feld, Elektrizitwirtschaft, 1990, Heft 6.

Jarass, L.: Hochspannungsleitung geplant - was is zu beachten?

Jarass, L.: Auswirkungen einer Dezentralisierung der Stromversorgung auf das Verbund- und Verteilungsnetz, in: Bodenbelastung durch Fleninanspruchnahme von Infrastrukturmaahmen, Bundesforschungsanstalt fdeskunde und Raumordnung (German Federal Research Institute for Regional Geography and Regional Planning (Ed.)), Bonn, 1989.

Jarass, L., Obermaier, G.M.: Raumordnungsgerechte Ausf von Hochspannungsleitungen, Energie und Umwelt, Heft 7/8, Bundesforschungsanstalt fdeskunde und Raumplanung (German Federal Research Institute for Regional Geography and Regional Planning (Ed)), Bonn, 1984.

Pflaum, E.: Entwicklung der Lprinzipien von Hochspannungs-Leistungsschaltern, etz., 1988, Heft 9.

Rat von Sachverstigen feltfragen: Sondergutachten M 1981, Energie und Umwelt, Verlag W. Kohlhammer GmbH, 1981.

Rauhaut, A.: PCB-Bilanz, etz., Bd. 104, Heft 23, 1983.

Sander, R.: Biologische Wirkungen magnetischer 50-Hz-Felder, Medizinisch-technischer Bericht, Elektrizitwirtschaft, Bd. 82, Heft 26, Institut zur Erforschung elektrischer Unfe der Berufsgenossenschaft der Feinmechanik und Elektrotechnik, Cologne, 1982.

Sauer, E. u.a.: Energietransport, -speicherung und -verteilung, Handbuchreihe Energie, Bd. 11, Cologne.

Schemmann, B.: Vakuum-Leistungsschalter in Ortsnetz-Verteilerstationen, etz., 1987, Heft 16.

Silny, J.: Der Mensch in energietechnischen Feldern, Elektrizitwirtschaft, Jg. 84, Heft 7, 1984.

Soldner, K., Gollmer, G.: Probleme mit PCB-gef Transformatoren, Elektrizitwirtschaft, Jg. 82, Heft 17/18, 1982.

Theml, Horst: Schutz gegen gefliche Krstr- Anordnung von Betgungselementen in der N bersgeflicher Teile, Elektrizitwirtschaft, 1982, Heft 25.

Umweltbundesamt (German Federal Environmental Agency): Ersatzstoffe fKondensatoren, Transformatoren und als Hydraulikfleiten im Untertagebergbau verwendete Polychlorierte Biphenyle, Berlin 1986.

Umweltbundesamt: (German Federal Environmental Agency): Lbekfung 1988, Berlin, 1989.

United States Agency for International Development: Environmental Design Considerations for Rural Development Projects; Washington 1980.

VDEW: Begriffsbestimmungen in der Energiewirtschaft - Teil 4, Begriffsbestimmungen der Elektrizitagung und -verteilung, 4. Ausgabe, Frankfurt 1979.

VDEW: PCB oder Askarel, VDEW zum Thema Askarel Elektrizitwirtschaft, Jg. 82, Heft 17/18, 1982.

VDEW: Vogelschutz an Freileitungen, 1986.

WHO: Environmental health criteria, Magnetic fields, Dec. 1985.

Zahn, B.: Weiterentwicklung SF6-gasisolierter Schaltanlagen, etz., 1988, Heft 9.

(-): ANSI (American National Standards Institute) Standards.

(-): DIN VDE - Vorschriften zur Errichtung und Betrieb von elektrischen Anlagen (Standards relating to the erection and operation of electrical installations)

(-): Htzulige Gerchwerte fnsformatoren, Technische Angaben Trafo-Union, 1982.

(-): IEC (International Electrotechnical Commission) Publications.

1. Scope

In addition to finite deposits of fossil and mineral fuels such as oil, gas, coal and uranium, the earth also offers various natural, auto-regenerative - or renewable - sources of energy that derive from sun insolation, geothermal activity and gravitational forces.

Theoretically, the global supply of energy from such renewable sources by far exceeds the earth's present total energy demand. The supply of energy is subject in part to pronounced technical and economic utility limitations, e.g., the disparity between the temporal/spatial demand for energy and the actually available supply of renewable energies, and the latter's modest power density compared to conventional energy vehicles.

The main renewable energy (RE) sources are:

1. Insolation, i.e., the direct radiant energy of the sun (made useful by collectors, solar cells, etc.)

2. Energy obtained from biomass; biochemical energy of photosynthetic products; made useful by

- burning (of wood, straw, etc.)
- gasification (of wood, etc.)
- anaerobic digestion (= biogas)
- alcoholic fermentation

3. The kinetic energy of wind

4. The kinetic energy of moving water:

- low-pressure systems
- high-pressure systems
- micro-hydropower plants
- tides, waves, ocean currents

5. Miscellaneous

- geothermal energy
- thermal energy deriving from differences in seawater temperature
- osmotic energy deriving from concentration gradients between saltwater and freshwater.

With a view to the proper and adequate sizing and, hence, limitation of the environmental consequences of renewable energy systems, the energy consumers' options for the conservation and rational use of energy should always be given full consideration, whereas boundary conditions in the form of prices, tariffs, etc. are major factors.

The environmental impacts resulting from utilization of the following renewable sources of energy are dealt with in this brief:

- solar energy (heat and photovoltaics)
- energy from biomass
- wind energy
- hydropower
- geothermal energy.

To the extent deemed relevant, other renewable sources of energy are dealt with in other briefs.

With regard to the general environmental consequences of energy systems and to the supradisciplinary aspects to be considered in connection with the planning of energy policy and energy economics projects, the reader is referred to the environmental brief Overall Energy Planning.

2. Environmental impacts and protective measures

The utilization of energy, no matter what the source, is bound to have certain environmental consequences (land consumption, pollution,...) that need to be identified and evaluated, preferably in advance.

2.1 Solar energy

The use of solar energy via collectors or photovoltaic systems places no immediate material burden on the environment. However, the collector system can be expected to contain a heat transfer medium (fluid), the escape of which could result in pollution. The acceptable media include such readily degradable substances as propylene glycols. Noxious additives serving as preservatives should be replaced by less harmful alternatives (carboxylic acid).

The use of solar cookers involves the danger of blinding, and solar energy collected by solar cells and stored in batteries demands proper handling and appropriate disposal of the spent batteries. The materials used for the battery case, as well as the hydrochloric acid and lead contents, can be recycled in suitable facilities.

Land consumption for small-scale systems can be avoided by installing them on roofs and facades. Well-considered integration can prevent optical/aesthetic impairment, and annoying reflections can be diminished by lumenizing and/or delustering.

With the exception of reduced reflections, no such measures can be applied to large-area systems. Consequently, optical/aesthetic expectations may stand in conflict with other natural surface potentials (soils for agricultural production, protection of species and biotopes; unless, of course, the site in question is located in the desert).

Depending on the local situation, the shading and altered albedo resulting from large-scale installations can affect the flora, fauna and microclimate (evaporation rates, airflow, temperature).

Solar cells and various collectors have a substantial space requirement relative to the amount of energy produced (per 100 MW: ~ 1 km² for solar cells and ~ 3 km² for solar-thermal power plants, compared to ~ 0.4 km² for hard-coal power plants).

Additional environmental impacts derive from the manufacture of materials used in the production of collectors and solar cells. Steel, copper and aluminum, all of which are used frequently, cause environmental problems in the form of emissions, i.e., particulates, fluorine compounds, solid and liquid waste and high levels of energy consumption, particularly for aluminum.

Some rare and toxic metals such as cadmium, arsenic, selenium and gallium used in solar cells are mildly pollutive at the processing stage (wastewater, exhaust gases). These substances are characterized by high chemical stability, and the environmental risk remains confined to the production site. Thus, adequate monitoring and safety measures can minimize the risk; cf. environmental brief Non-ferrous Metals.

2.2 Biomass energy

Used as a substitute for metal, cement, plastic and diverse other raw materials, biomass can help reduce the energy expenditures for processing and manufacturing such materials.

In the present context, however, our interest in biomass is limited to its being a source of energy.

Significant utilization of biomass presupposes that the biomass cycle of growth and extraction remains essentially intact, i.e., that the biomass source (a forest, perhaps), is always allowed to adequately regenerate.

2.2.1 Burning

The burning of biomass (wood, straw, dung, etc.) liberates pollutants -

- from the fuel and the combustion air
- or which form as a result of incomplete combustion [CO, tar, soot and hydrocarbons, including carcinogenic polycyclic aromatic hydrocarbons (PAH)].

The main cause of emission problems with biomass is incomplete combustion. The following measures can help achieve complete combustion:

Combustion plant

- sufficiently large incinerator
- sufficiently hot combustion chamber

Those conditions are inherently satisfied by systems equipped with prefiring chambers or for bottom firing.

Fuel conditions

- use of dry fuel (< 20 % wood moisture).

Mode of operation

- full-load operation
- uniform fuel supply.

The exhaust gases, particularly in the case of straw, contain large amounts of solid particulates; large-scale systems therefore should include appropriate cyclone separators or filters.

On a country-specific basis, biomass can cover as much as 90 % of the overall demand for energy. As a rule, wood, dung and straw are burned in open fires from which the aforementioned pollutants escape and can be inhaled by the users (primarily women and children).

This can amount to a formidable health hazard, particularly because of the carcinogenicity of polycyclic hydrocarbons. In addition, respiratory ailments can also result from such exposure.

The use of stoves with some form of chimney substantially reduces the indoor smoke nuisance and improves the combustion efficiency, thereby reducing fuel consumption and, hence, emission levels.

The use of straw and dung as fuel can lead to conflicts concerning agricultural production and the sustenance of soil fertility due to loss of nitrogen and reduced humification, because what has been burned cannot be returned to the soil. In some climate zones, using the ashes as fertilizer can cause a dust-evolution problem.

From an ecological standpoint, the use of scrap wood and various forms of wood residue calls for a somewhat sophisticated frame of reference: while tending felling can be both ecologically compatible and advisable, the safe extent of wood removal from forests and plantations depends on the climate, the soil conditions and the vegetation. The removal of wood residue impacts the nutrient cycle, humification, microflora and microfauna. This applies as well to large-scale stump-grubbing, which also makes the ground more susceptible to erosion.

Long-term natural wood production does not satisfy the "firewood criteria" of easy, short-term availability. Agroforestry projects involving certain harmonized plant species in certain spatial arrangements designed to make the individual species and combinations serve different functions (shading, soil amelioration, shelterbelting, improvement of water regimen, mulching, fuel, food/fodder, starting material), are able to more quickly satisfy fuel requirements by reason of brief rotation periods. Such - noncentralized - configurations facilitate the gathering of wood while abating environmental burdens in connection with road transport and helping to bridge over fuel shortages.

Intensive (energy farming) techniques based on fast-growing combustibles treated with high doses of pesticides and fertilizers can pollute, i.e., eutrophize, surface waters due to nutrient loading, possibly in combination with erosion, a loss of diversity, and health hazards emanating from residual pesticides. The use of machines on sensitive ground (marginal soils) can induce erosion; cf. environmental brief Forestry.

Large-scale felling of trees (= land clearing) affects the water economy and microclimate, is harmful to flora and fauna, and can cause erosion, the extent of which depends on the type of soil, the climate and the angle of slope.

If cleared land is not appropriately reafforested, or if the soil is overused for a prolonged period, both the soil and the water regimen may sustain irreversible damage.

Any attempt to substantially expand fuelwood production without integrating the effort into the general agricultural scheme can generate conflicts over space requirements for food production; cf. corresponding environmental briefs on agriculture, such as Plant Production, Forestry etc.

2.2.2 Gasification

As a rule, any gas extracted from biomass by such means as pyrolysis is used as fuel, either for heating purposes or for driving gas-fueled power generators.

While the environmental effects of fuel extraction from biomass are dealt with in section 2.2.1, additional ecological impacts can derive from:

- carburetion (accidents, deflagration);
- the gas itself (accidents, fire, poisoning due to leaks);
- wastewater from gas scrubbing;
- carbonization residue (ash, tar);
- combustion emissions (exhaust, cooling water, lubricant).

Generator gas obtained from large plants (as opposed to small wood gasifiers, e.g., for tractors) should be cleaned and dedusted prior to use. The wastewater from gas scrubbing can be expected to contain ammonia, phenols, perhaps even cyanides and potentially carcinogenic polycyclic aromatic hydrocarbons (PAH). Consequently, they cannot be disposed of freely. To the extent possible, the incidental tars and oils should be returned to the gasification process. In addition to the mechanical extraction of solids, e.g., in a settling basin, the effluent can be put through a biological clarifying plant in which phenols are digested by suitable strains of bacteria.

Solid residue from the gasification process is usually heavily polluted and therefore problematic with regard to its disposal. The harmful-substance contents require case-by-case determination, because they vary according to the raw material in question and the process employed.

The exhaust from generator gas combustion may also require treatment, depending on the quantity involved and its pollutive load. It is likely to contain oxides of nitrogen, PAH's, carbon monoxide or soot (plus negligible amounts of sulfur dioxide). The NOx and hydrocarbon contents can be extensively decomposed with the aid of catalytic converters.

2.2.3 Biogas

Biogas resulting from anaerobic bacterial fermentation of biomass consists primarily of methane (principal component), carbon dioxide, carbon monoxide and small amounts of hydrogen sulfide. Small biogas plants provide fuel for cooking, lighting, etc., while large-scale facilities can produce enough biogas for fueling gas motors.

Accidents can occur when a slurry pit or a fixed-dome digester has to be entered for cleaning (danger of asphyxiation).

Since hydrogen sulfide has toxic effects of humans, corrodes materials, and forms sulfur dioxide in the combustion process, its removal should be given due consideration. However, the precleaning process is rather complicated and generates end products with a pollutive potential. The chemicals used for cleaning biogas (e.g., iron oxide), as well as their reaction products (mixture of iron oxide and sulfur) demand proper storage, use and subsequent disposal.

Whereas biogas often requires interim storage, appropriate pertinent safety standards must be heeded (danger of poisoning, fire, explosion); cf. environmental brief Petroleum and Natural Gas.

The raw material may contain toxic heavy metals that are prejudicial to health. While such constituents (deriving from polluted soil) remain unaffected by the digestion process they nevertheless should be monitored (tested for). And while the digestion process does not kill off all pathogens and worm ova, the digested sludge nonetheless counts as safe and benign from the standpoint of epidemic control. Used improperly, its high nitrogen content can emburden both surface water and groundwater. Thus, the use of biosludge as a fertilizer must be properly timed (availability for plants), effected with suitable equipment, and applied in accordance with the soil's nutrient reserves.

Considering methane's relevance as a greenhouse gas, its collection and combustion is ecologically advantageous as long as it is being generated by anaerobic digestive processes.

2.2.4 Biofuels

Various technical processes are available for deriving oil and alcohol from biomass and using them as substitutes for conventional fuels.

The cultivation of biomass as a raw material for obtaining fuel by alcoholic fermentation (e.g., of sugar cane) or by extracting oil from soybeans stands in direct competition with foodstuff farming. Large monocultures involving high levels of fertilization and pesticide spraying have environmental impacts of the kind discussed in section 2.2.1; cf. environmental brief Plant Protection.

The following environmental loads result from the production of ethanol and oil:

- exhaust gases deriving from the provision of process energy (e.g., distillation, burning or refining of crude oil) - cf. section 2.2.1;
- carbon dioxide as a product of fermentation;
- nontoxic but very pollutive organic sludge and wastewater (slops) from ethanol production, all containing large amounts of nitrogen-phosphorus and potassium components.

The slops, or distiller's wash, can serve as a fertilizer or fodder additive. If it contains enough residual sugar or starch, it is suitable for fermentation, i.e., biodigestion.

The biogas yield can serve as a substitute for part of the conventional process energy, while the organic substances remaining in the effluent must be decomposed in a clarifying plant.

The production of alcohol is very energy-intensive.

The use of ethyl alcohol (ethanol) as a fuel additive in internal-combustion engines produces relatively low pollution in the form of NOx, CO, soot and simple hydrocarbons, but is accompanied by certain aldehydes, some of which are carcinogenic.

Motors fueled by alcohol alone should be specially tuned and optimized in order to minimize harmful emissions. Catalytic converters, for example, reduce the aldehyde emission levels to that of gasoline engines. Compared to gasoline/petrol, ethyl alcohol contains practically no carcinogenic polycyclic hydrocarbons.

Like alcohol, biomass-base oil for diesel engines gives off no sulfur or lead but some amounts of soot, simple hydrocarbons and particulate emissions. Soot filters are conditionally suitable for cleaning the exhaust gases.

2.3 Wind energy

Even large wind power plants have modest environmental impacts. Their material and space requirements are also relatively modest. The manufacture of some steel and plastic components, however, does involve certain environmental problems.

The following substantial environmental problems arise in connection with their operation:

- noise;
- landscape impairment;
- danger of accidents due to rotor-blade detachment;
- electromagnetic interference;
- negative effects on fauna, birds in particular.

How much noise is produced depends on how fast the propellor is rotating. The faster the speed of rotation, the louder the noise.

Old aerogenerators have been known to produce sound intensities on the order of 130 dB(A). Small wind generators tend to make more "wind" noise than running noise. New facilities have aerodynamically optimized blades and encapsulated generators-cum-transmissions that minimize the noise nuisance. Nevertheless, a minimum distance of roughly 100 meters should be maintained between wind generators and residential areas. There is, of course, always the possibility that the safe clearances designated at the planning stage will eventually be transgressed by uncontrolled settlement (squatting).

Impairment of the landscape is unavoidable. The degree of impairment depends on local circumstances, including the intensity of wind-power utilization. Wind parks do more to impair the landscape than individual plants. Especially large aerogenerators with metal motors tend to disrupt natural electromagnetic fields and interfere with radio reception. Modern wind power plants have fiberglass rotor blades and therefore cause no such interference.

The danger of accidents attributable to rotor-blade detachment can be minimized, if not precluded, by routine inspections and maintenance, plus adherence to the appropriate safety clearances.

2.4 Hydropower

Hydropower is the by far the most important renewable source of energy. The incidental reservoirs often serve other, additional purposes such as irrigation and the supply of drinking water.

The harnessing of hydropower entails substantial intervention in the environment (land consumption, altered hydrological regimen, etc.). Due to the importance of hydraulic engineering with respect to the environment, and with deference to the vast experience that has been accumulated in connection with such facilities, a separate brief has been devoted to that sector.

2.5 Geothermal energy

Geothermal sources of energy include:

- warm and hot water in deep-reaching joint systems of crystalline rock formations or deep-lying groundwater stories within expansive sedimentary basins,
- hot-water and steam occurring deep within structurally disturbed zones or in regions marked by current or recent volcanic activity,
- exploitation of geothermal energy according to the dry hot rock process (DHR technology presently under development).

DHR technology aims to establish artificial heat-exchange surfaces in hot rock (with temperatures > 200°C) from which geothermal energy can then be extracted by pumping water into and back out of the artificial hot-rock joint system. Despite substantial research funding to date, however, the method's economic feasibility has not yet been established.

The environmental impacts of exploiting geothermal energy depend on the concrete situation. Environmental burdens can result from entrained pollutants (various salts, sulfur compounds, arsenic, boron) and gases in the geothermal fluids. In modern geothermal facilities the spent (cooled-down) fluids and their entrained pollutants are pumped back into the ground, preferably to a point below the pay zone of the occurrence, while the incidental gases are released to the atmosphere.

The extraction of geothermal fluids, particularly in dry-climate regions, can negatively influence near-surface groundwater stories and, hence, their utilization (potable water, irrigation) by causing the groundwater table to recede (phreatic decline).

Sustained use of a particular geothermal reservoir can lead to gradual and extensive subsidence and frequent consequential damage to railroads, highways, power transmission lines and, particularly, the pipelines through which the geothermal fluids are pumped from the wells to the power plant/user. The local hydrological situation can be substantially influenced and modified by attendant phenomena such as the diversion of streams and rivers or even the formation of lakes in ground depressions.

The space requirements of geothermal installations (wells, pipelines) are quite modest - so much so that such facilities hardly interfere with agricultural utilization of the surrounding land.

The drilling of wells in a geothermal field is somewhat hazardous in that unforeseen eruptions of steam can occur without notice and then take weeks or even months to get under control. In the meantime, the environment may have become substantially contaminated by impurities in the steam.

3. Notes on the analysis and evaluation of environmental impacts

The main environmental consequences of renewable energy systems are the consumption of land area and the loss of plant and animal species and biotopes. Biomass utilization also involves solid waste, wastewater and air pollution.

The environmental consequences of renewable energy systems can be limited in quantity, but normally require qualitative analysis with due regard for avoidance effects (e.g., CO2 emissions) in comparison with nonrenewable energy sources. To evaluate the environmental impacts of any such system, one must begin with an analysis of the biotic (flora and fauna) and abiotic (water, soil, air) ecological factors. For the biotic domain, mapping and charting activities are necessary. For the abiotic range, water, air and soil samples should be analyzed according to standard techniques such as those described in DIN/EN and ISO standards, NIOSH standards, guidelines of the Association of German Engineers VDI, WHO recommendations, etc.).

The evaluation of environmental consequences is a deficitary matter in that, for example, no limit values can be quoted for the loss of animal species, biotopes, etc. Nor do any generally recognized standards of evaluation exist - quantitative or otherwise - for landscape impairment. The criteria need not always be as unequivocally quantifiable as "rarity" (e.g., as defined by international conventions within the pollutants' sphere of influence); it is also difficult to attach a particular value to consumed land area with allowance for alternative uses. For the abiotic domain, though, certain limit values and recommendations can be enlisted in connection with various types of pollution (wastewater, exhaust, noise).

To the extent available, effect-specific reference/limit values should be consulted for evaluating immissions (airborne pollutants, noise,...) as a means of anticipating the sensitivity (reaction) of existing and planned forms of utilization (housing, farming) to the projected impairment.

For all forms of renewable energy utilization, the importance of immissions and pollutant levels increases along with the size of the project.

In connection with the extraction of energy from biomass, any solid substances that are re-utilized instead of being treated as waste count as a positive effect that must be given due consideration.

4. Interaction with other sectors

If a planned renewable energy system will involve material emissions, the local prior load must be determined in advance of the project's implementation (e.g., condition of recipient water in conjunction with wastewater-producing processes).

In addition to the effects of renewable energy utilization listed in section 2, such secondary effects are also important. Apart from the project's consequences for the basic needs of certain sections of the population, its possible impacts on agriculture, water supplies, transportation and diverse aftereffects must also be accounted for (whereas allowance must be made for the fact that improving the supply of energy to or within a given region can have practically identical consequences for the sectors in question):

- The loss of farmland alters the food market structure and/or necessitates the agricultural utilization of formerly more or less "virgin" areas. For additional information, the reader is referred to the environmental briefs on agriculture (e.g., Plant Production).
- Any more intensive use of water resources naturally involves higher rates of water consumption, larger volumes of wastewater and, hence, changes in the water regimen. That, in turn, affects the soil, the microclimate, the composition of the microsystem, and the hygienic situation (salinization, spread of pathogens; cf. environmental briefs Rural Water Supply, Rural Hydraulic Engineering Large-scale Hydraulic Engineering, Water Framework Planning.
- Increased traffic due to transportation in connection with large-scale renewable energy applications (or simply attributable to an improved energy supply situation) necessitates more and better traffic infrastructure. Its provision, in turn, has primary and secondary development effects; cf. environmental briefs Road Traffic, Transport and Traffic Planning. The general environmental impacts of renewable energy exploitation systems are discussed in the environmental brief Overall Energy Planning.

5. Summary assessment of environmental relevance

This environmental brief summarizes the environmental consequences of renewable energy sources. Such consequences include gaseous and liquid emissions, solid wastes, noise evolution, use of sensitive materials, land consumption and other forms of impairment.

The renewable-energy utilization options involving little or no replacement or decomposition of material (solar, wind) and, hence, fewer direct consequences for the environment are deserving of preferential treatment.

The fact that long-term sustained use of renewable energy sources can fit neatly into the natural biochemical and energy cycles produces a situation in which combustion and digestion processes (wood, straw, biogas, alcohol), unlike those involving fossil fuels, add no carbon dioxide to the atmosphere, because the amount emitted is offset by the incorporation of equal amounts into the regeneration of biomass. In other words, biomass enables the CO2 - neutral generation of energy.

On the other hand, again unlike fossil fuels, the continuous renewal process of biomass as an energy vehicle ties up land area, i.e., soil, that otherwise could be put to some other or additional use, e.g., for agricultural production or agroforestry.

Land consumption is unavoidable. Accordingly, valuable ecosystems must be protected - instead of simply being exploited as a renewable source of energy.

As long as the requisite facilities are properly maintained and serviced by skilled specialists, and as long as the operating personnel is well-trained, the use of renewable energy sources poses little danger of accidents.

Like most finite sources of energy, the majority of renewable energy sources can be exploited both on a large, centralized scale as well as through small, noncentralized facilities. Some renewable sources of energy (e.g., solar cells, solar collectors, biogas, wind power) are inherently suited to noncentralized forms of energy generation, particularly in connection with energy supply and development strategies for rural, village-level and regional development projects involving little or no transport costs. Such constellations help minimize energy conveyance losses and avoid such secondary environmental problems emanating from the socioeconomic ramifications of centralized development strategies as urbanization, rural-urban drift and their consequential effects; cf. environmental briefs Spatial and Regional Planning, Overall Energy Planning, Planning of Locations for Trade and Industry.

6. References

AKN Reddy: Rural Technology, Bangalore, 1980.

Albrecht, Buchholz, Deppe u.a.: Nachwachsende Rohstoffe, Bochum, 1986.

Bonnet, D. u.a.: Nutzung regenerativer Energien, Handbuchreihe Energie, Bd. 13, Cologne, 1988.

Bundesgesundheitsamt (German Federal Health Office): Vom Umgang mit Holzschutzmitteln, Berlin.

Bundesminister fschung und Technologie (German Federal Minister of Research and Technology) (Ed.): Expertenkolloquium "Nachwachsende Rohstoffe, Band 1 und 2, 1986.

EC-Council Directives relating to clean-air standards.

Edelmann, Fawre, Seiler, Woschitz (Ed.): Biogas-Handbuch, Aarau, 1984.

Fleischhauer, W.: Neue Technologien zum Schutz der Umwelt, Essen, 1984.

Fort, V.: Environmental Soundness, Proceedings of a Workshop on Energy, Forestry and Environment, Bureau for Africa, Agency for International Development, 1982.

Gadgil, M.: Hills, dams and forests; Some field observations from the Western Ghats, AKN Reddy, 1980.

Gieseler, G., Rauschenberger, H., Schnell, C.: Umweltauswirkungen neuer Energiesysteme, Dornier System/Bayerisches Staatsministerium fdesentwicklung und Umwelt, March 1982.

Hartje, V.J.: Umwelt- und Ressourcenschutz in der Entwicklungshilfe: Beispiele zum erleben? Frankfurt, New York, 1982.

Kannan, K.P.: Ecological and socio-economic consequences of water-control projects in the Kuttanad region of Kerala, AKN Reddy, 1980.

Kaupp, A. und Goss, J.R.: Small-scale Gas Producer-engine Systems, Braunschweig, Wiesbaden, 1984.

Kleemann, M.; Meli M.: Regenerative Energiequellen, Berlin 1988.

Lehner, G. und Honstetter, K.: Solartechnik, Ullmanns Encyklope der technischen Chemie, Band 21, Vienna, 1982.

Menrad, H.; K, A.: Alkoholkraftstoffe, Vienna, 1982.

Meier, P.: Energy Systems Analysis for Developing Countries, Berlin, 1984.

Montalembert, de, M.R.: The forestry/fuelwood problem in Africa and its environmental consequences, Proceedings of a Workshop on Energy, Forestry and Environment, Bureau for Africa, Agency for International Development, 1982.

Osterwind, D., Renn, O. und Vo A.: Sanfte Energieversorgung, J 1984.

Porst, J.: Holz-Zyklus Kenia - Zusammenfassung der Studien des Beijer-Instituts, Berichte fE/GTZ, 1984.

Porst, J.: erwachung eines chinesischen Reisspelzengasgenerators in Mali, Berichte fE/GTZ, 1986 und 1987.

Rat von Sachverstigen feltfragen: Energie und Umwelt, Sondergutachten, Stuttgart, 1981.

Ripke, M. und Schmit, G.: Erschlieng und Nutzung alternativer Energiequellen in Entwicklungslern, Cologne, 1982.

Sorensen, B.: Renewable Energy, London, 1979.

UNESCO: Programme on Man and the Biosphere; Ecological effects of energy utilization in urban and industrial systems, Bad Nauheim, 1973.

Umweltbundesamt (Federal Environmental Agency (Ed.)): Lbekfung 1988, Berlin, 1989.

VDI - Richtlinien - Maximale Immissions-Werte.

Weih, H.; Engelhorn, H.: We und Strom aus Sonnenenergie, Altlueim, 1990.

WHO (World Health Organization): Environmental Health Criteria, Geneva.

1. Scope

Worldwide demand for synthetic nitrogenous fertilisers currently stands at some 80 million tonnes per year. Practically the sole source of nitrogen for all synthetic nitrogenous fertilisers is ammonia - chemical formula NH3 - which has a characteristic pungent odour, is gaseous under ambient conditions and liquid at -33°C under atmospheric pressure.

Since 1913, ammonia has been produced on a large scale from atmospheric nitrogen and hydrogen by catalytic synthesis.

Naturally occurring hydrocarbons are converted with steam at high temperatures to produce hydrogen.

Cn Hm +2nH2 O = (m/2+2n) H2 + nCO2 (endothermic)

The following raw materials are used in ammonia synthesis gas production:

- pit coal
- lignite
- peat
- non-volatile hydrocarbon residues
- light petrol
- natural gas and other gases.

For economic reasons the electrolytic disintegration of water to produce hydrogen can only play a minor role in ammonia synthesis.

The synthesis gas produced is in all cases converted directly into ammonia:

3 H2 + N2 = 2 NH3

As ammonia in liquefied gas form is only suitable for direct fertilisation under certain circumstances, and only at a considerable cost, some or all of the ammonia produced is processed in situ to produce urea or other nitrogenous fertilisers. Only a few production plants are totally export-oriented.

In this section of the brief, only the synthetic manufacture of urea from ammonia and carbon dioxide (CO2) - which occurs as a by-product of hydrocarbon reforming - will be considered.

Normal current production capacities ranges from approximately 400 to 2,000 t of NH3/day and 600 to 3,000 t of urea/day.

Sites are not selected on the basis of any specific criteria; some plants are both raw material oriented and consumer and transport oriented.

The environmental impact of the production plants derives from waste gases, wastewater, waste heat, dust, solid residues and from noise, transport routes, space requirements (pressure on space) and general industrialisation phenomena.

We will not consider in this brief the impact on the environment from noise, transport, space requirement and other general industrialisation phenomena; this subject is dealt with in the environmental brief Planning of Locations for Trade and Industry.

We examine in the following the process materials, intermediate products, by-products and waste products which arise in the production processes and the measures required to dispose of waste, to prevent any harmful impact on the environment and to keep within prescribed limits.

2. Environmental impacts and protective measures

2.1 Ammonia synthesis gas production (ASGP)

2.1.1 ASGP from light hydrocarbons

Because it is economical, the catalytic steam reforming of light hydrocarbons, such as natural gas, petroleum-associated gas, LPG, light petrol and other gases containing H2, and hydrocarbons such as coke oven and refinery gas, has become generally accepted.

Some 80% of all ammonia synthesis gas plants use this highly endothermic process which can be illustrated - taking methane reforming as an example - by the following molecular formula:

CH4 + 1.39 H2O + 1.45 AIR = CO2 + 2.26 (H3 + N)

In the initial stage of this process, light hydrocarbons are catalytically reformed with steam at temperatures of between 750°C and 800°C with the addition of heat (primary reforming) and, in a second autothermic stage, with air at approx. 1,000°C (secondary reforming); depending on pressure and temperature determined equilibrium conditions, this produces a mixture of H2, CO, CO2, N, CH4 and traces of Ar. The nitrogen required for ammonia synthesis is introduced into the system by the air used for autothermic conversion in the secondary reformer. The carbon monoxide (CO) which forms is then converted catalytically into H2 and CO2 (usually in two stages) with steam at 300°C to 450°C.


Figure 1 - Ammonia Production from Light Hydrocarbons

Before catalytic reforming, sulphur, chlorine and other compounds, which toxify the catalysts, must be removed, and this is performed in a single or multi-stage gas purification process.

Once the carbon monoxide from the reforming gases has been converted to hydrogen, the carbon dioxide is separated by chemical or physical scrubbing, from which a CO2 stream can also be produced for urea synthesis.

The purity of the H2/N mixture necessary for ammonia synthesis is obtained by a fine purification stage following CO2 removal.

In most plants, the primary reformer is heated with the process raw material.

Thanks to the intensive utilisation of waste heat, almost all known processes involved in ammonia synthesis work autonomously, i.e. steam for heating and power from an external source is required or must be produced by an auxiliary boiler only at start-up. The total energy requirement of modern autonomous plants is less than 29 GJ/t NH3.

· Waste streams, pollutants and protective measures:

(a) Waste gases

- Carbon dioxide (CO2):

It occurs at a concentration of around 98.5 % by volume, is used in full or in part as a raw material for urea synthesis and can be released into the atmosphere untreated as in practice the only impurities contained are H2, N2 and CH4.

- Flue gases from the primary reformer and steam boilers:

If the heating medium contains too much sulphur, it may undergo a purification process to keep SO2 values in the flue gases to within admissible levels. Primary measures to reduce the NOx emission can be taken in the primary reformer. Flue gases are released into the atmosphere through a chimney so as to comply with the values of the TA-Luft [Technical Instructions on Air Quality Control] valid in Germany, for example.

- Other waste gases:

All other waste gases formed in the plant contain combustible components and are fed into the plant’s heating gas system. If there is any unscheduled stoppage, process gases (H2, CH4, CO, CO2, NH3, N2, steam) have to be burnt in a flare as a temporary measure so that only flue gases are released into the atmosphere.

(b) Wastewater

- Process condensate: is generally reprocessed and used as boiler feedwater.
- Blow-down water from steam generators: does not contain any toxic components and can be discharged untreated or fed into the cooling water circuit.
- Blow-down water from cooling water circuits: is to be treated before disposal depending on the degree of concentration and the content of corrosion inhibitors, hardness stabilisers and biocides.
- Wastewater from demineralisation plants for boiler feedwater conditioning: can be drained following a neutralisation stage.
- Spent lye from CO2 scrubbing:

In normal operation, no waste streams are produced. Wash water is to be treated in the same way as wastewater from demineralisation plant or cooling water circuits. (On the general subject of wastewater, see also the environmental brief on Wastewater Disposal).

(c) Solids

- Sludges: The purification of blow-down water from cooling circuits can produce sludge residues which then need to be dumped by a method appropriate to their composition.
- Spent catalysts and purification masses:

The useful life of catalysts used in ammonia production plants ranges from about 2 to 8 years depending on the particular use and method of operation. When the activity of catalysts falls below a predetermined level, they are replaced by new active ones. Most catalysts contain notable quantities of oxides and sulphides of the heavy metals Co, Ni, Mo, Cu, Zn and Fe, which are insoluble in water, while spent sulphur purification masses consist in the main only of water-soluble oxides and sulphides of Zn or Fe, and chlorine purification masses of NaCl/Na2O on Al2O3. Some of these waste products are recovered by the manufacturers for reprocessing or are passed on to smelting works for metal recycling. Otherwise, they have to be dumped by a method appropriate to their composition; for example, the water-soluble HT conversion catalyst containing Cr must be dumped so that no soil or water pollution is possible.

(On the general subject of waste, see also the Environmental Briefs Solid Waste Disposal and Disposal of Hazardous Waste).

2.1.2 ASGP from heavy residual oils

The residual oils containing sulphur and heavy metals produced in crude oil processing should today no longer be burnt untreated for reasons of environmental protection. They can however be successfully used for the production of ammonia synthesis gas.

The residues are gasified by partial oxidation with oxygen from an air separation plant - in which the nitrogen required for ammonia synthesis is also produced - according to the following simplified molecular formula:

Cn Hm + n/2 O2 = n CO + m/2 H2

The hydrogen required for ammonia synthesis is produced by further conversion with steam and disintegration of contaminants - such as H2S, COS, CNS, HCN, soot and metal residues - formed due to the raw material composition and the particular process conditions.

As the process generally consumes a large amount of energy, there is intensive waste heat utilisation and all combustible by-products and waste products formed are used internally for reasons of economy.


Figure 2 - Ammonia Production from Heavy Residue Oils

· Waste streams, pollutants and safety measures

Solid residues, such as ash and salts, and also liquid and gaseous by-products and waste products are formed during the process due to raw material composition and the gasification and purification processes.

Numerous processes are available for waste reprocessing and pollutant disposal, thus plants of this kind can even operate within the strict environmental regulations of the Federal Republic of Germany. Generally, the details given in section 2.1.1 apply to the reprocessing of the corresponding waste gases, wastewater and solid residues.

The following are also produced:

- H2S as a conversion product of the sulphur contained in the raw material. Elementary sulphur is produced with a 98% yield by the Claus process (a 99% yield can even be achieved by means of additional stages); alternatively a 98% yield can likewise be obtained by wet catalysis of sulphuric acid.
- Process water contaminated with the metals contained in the raw material, such as Ni, V, Co etc., and the water-soluble compounds formed in the gasification process from other elements present in the raw material, such as H2S, CNS, HCN, As, NH3, Cl, MeOH etc. Before it can be discharged into drains, this wastewater must be purified by means of appropriate purification processes and biodegradation. In most cases provision must be made for a demetallisation stage, the heavy metals deriving from this being transported to special dumps or to special works where the metal is recovered.

2.1.3 ASGP from solid fuels

A crude gas consisting of H2, CO, CO2 and CH4 is produced with steam at temperatures of over 1200°C and by the partial oxidation of hard coal, lignite, coke, peat etc., with oxygen from an air separation plant in which the nitrogen required for ammonia synthesis is also produced.

As with the partial oxidation of liquid hydrocarbons (section 2.1.2), the impurities in the crude gas are largely determined by the raw material composition and process conditions (pressure and temperature), the sulphur in the raw material being present almost exclusively in the form of H2S. In the subsequent purification and conditioning stages, which in principle correspond to the operations involved in the reprocessing of heavy oil residues (section 2.1.2), pure hydrogen is extracted and this is used for ammonia synthesis with the oxygen from the air separation process.

On a large scale, the following methods of solid gasification have proved successful:

- moving bed process,
- fluidised bed process and
- entrained bed process.

Feed and storage installations for the fuel and also conditioning stages tailored to the particular gasification process used, are always found upstream of the gasification process.

As the overall process consumes a great deal of energy, there is intensive waste heat utilisation.

· Waste streams, pollutants and protective measures

In all processes, solid residues such as ash, slag and salts are produced, as are also liquid and gaseous by-products and waste products, in quantities and of compositions which are determined by the raw material composition and the gasification and gas purification processes.

A large number of processes can be used for waste recycling and pollutant disposal, thus plants of this kind can operate within the strict environmental regulations of the Federal Republic of Germany applicable in the energy supply sector.

The type and reprocessing of waste gases, wastewater and solid residues conform in principle to the provisions of sections 2.1.1 and 2.1.2.


Figure 3 - Ammonia Production from Solid Fuels

In addition the following are formed:

- Dust, formed during fuel transport, storage and reprocessing. The problem of dust can however be controlled effectively by the implementation of measures which are commonplace in coal power stations and which have proved to be highly successful in overcoming the dust problem.
- Leakage water from the fuel store. Any harmful effects can be avoided by drainage and/or by covering the ground water area with an impermeable layer of clay.
- In many processes wastewater containing ammonia, phenol, cyanide and tar is formed, but there are also processes which can be used to separate these contaminants and recover them to a technically pure level.
- Ash and/or slag from the gasifiers. It is essential to check in each individual case whether this can be recycled, e.g. in the construction industry, and to determine what form of dumping is appropriate.

2.1.4 Water electrolysis and air separation

The feed product is fully demineralised water; this is produced in ion exchangers and mixed bed filters. Water electrolysis consumes a great deal of power and is thus an option only where cheap excess energy is available or where other raw materials are in short supply. The nitrogen required for NH3 synthesis is obtained by air separation. In electrolysis, very pure oxygen, suitable for a large number of technical applications, is formed, whereas in air separation only an oxygen-enriched spent air flow is generated which is normally released into the atmosphere.

· Waste streams

Only wastewater from the demineralisation plant and blow-down water from the cooling water circuit are continuously formed; they must be treated as described in section 2.1.1. The precious metal catalyst for the removal of residual oxygen from the synthesis gas is only replaced at intervals of several years and can be returned to the manufacturer for reprocessing.


Figure 4 - Ammonia Production by Water Electrolysis

2.2 Ammonia synthesis and storage

Very pure hydrogen and nitrogen are converted catalytically in an exothermic process to ammonia at pressures of over 100 bar and temperatures of around 350°C - 550°C.

3 H2 + N2 = 2 NH3

The conversion is not complete due to the equilibrium conditions. The ammonia formed is condensed by cooling (air, cooling water, cold) and released from the process in liquid form. Any gases not converted remain in a recycle. This results in an accumulation of inert components (CH4, Ar, He) which must then be removed from the process by a continuous stream of purge gas. The purge gas stream, together with the flash gases from the ammonia produced, can be used as heating gas in the synthesis gas production plant, in which case NH3, H2, N2 and Ar can first be separated in recovery plants.

The liquid ammonia goes either directly into processing plants or into a storage tank, storage taking place under pressure but at ambient temperature or slightly lower, or alternatively at atmospheric pressure and at a temperature of around -33°C.

· Waste streams, pollutants and protective measures

In normal operation, the plant does not release any pollutants into the environment. The continuously formed waste gas streams are processed internally or in the synthesis gas production plant.

No problems arise with the disposal of the catalyst, consisting of iron with small quantities of Al2O3, K2O, MgO, CaO and SiO2, an operation which takes place at intervals of around 5 to 10 years (e.g. smelting, road-building).

As ammonia fumes are highly irritant and the liquid is caustic and causes freezing, appropriate safety precautions - particularly during storage - need to be taken, such as double-shell tanks, collecting basins and water spray curtains.

2.3 Urea synthesis and granulation

Urea is produced from ammonia and the carbon dioxide which is a by-product of ammonia synthesis gas production from hydrocarbons, in a 2-stage process at pressures of 140 to 250 bar.

1st stage: Ammonia carbamate synthesis (exothermic)

2NH3 +CO2 = NH2 - CO - ONH4

2nd stage: Thermal carbamate decomposition to urea (endothermic)

NH2 - CO - ONH4 - CO(NH2 )2 + H2O

The urea is present in the form of an aqueous solution in a concentration of some 70 to 80%, from which a pumpable melt is extracted for further processing by the vacuum evaporation of the solution water.

It is then processed to granular urea fertiliser either by prilling in towers using a countercurrent of cold air or by fusion granulation on rotary plates or other cooled installations and by the fluidization technique.

The granular product is then poured directly into bags and/or stored temporarily in warehouses as bulk product.

· Waste streams, pollutants and protective measures

(a) Waste gases:

- Waste gases from synthesis contain only CO2 and air, together with traces of the gases dissolved in the ammonia: H2, CH4, Ar, as all waste gases have to be scrubbed before they are released into the atmosphere.
- Waste gases from prilling towers or granulation installations always carry a certain amount of product dust with them, the release of which must be contained by filtration to prevent "overfertilisation" of the environment with the repercussions this has on soil and water quality.

(b) Wastewater:

- Wastewater derives mainly from the gas scrubbing operations and contains NH3, CO2 and urea. All wastewater is recycled in the process itself, to keep the addition of water to the process as low as possible and to minimise raw material and product losses. The wastewater which does arise can be simply biologically purified.

(c) Solids:

- Residue produced during waste gas dust extraction, which is practically pure product, is returned to the process.


Figure 5 - Urea Production and Granulation

3. Notes on analysis and evaluation of environmental impacts

In the fertiliser production plants described here, environmental impacts, in the form of emission into the atmosphere, watercourses and soil, as well as noise emissions, may be anticipated. However, there are process stages for all production plants which can be implemented to contain this impact.

In Germany, the TA-Luft [Technical Instructions on Air Quality Control] is the main instrument as regards air quality. Pollutant limit values relating to specific plants and substances are listed in the Allgemeine Verwaltungsvorschrift zum Bundesimmissionsschutzgesetz [General Administrative Regulations pertaining to the Federal Immission Control Act] of 27.02.1986. It also contains a series of Richtlinien des Vereins Deutscher Ingenieure (VDI-Richtlinien - guidelines of the Association of German Engineers) regarding process and gas purification techniques and emission measurement techniques, which must be complied with. There are similar provisions in other countries, e.g. the Clean Air Act in the USA or its Swiss equivalent, the Luftreinhalteverordnung.

In countries which do not have their own regulations, reference is frequently made to the TA-Luft or other foreign regulations at the planning stage.

Most atmospheric pollution in such plants derives from SO2 in the waste gas. Under TA-Luft, a sulphur emission level of 3% down to 0.5%, depending on plant size, must not be exceeded in sulphur extraction plants. Not all purification processes achieve this, but they are nonetheless used where less stringent regulations are in force.

In wet catalysis for sulphuric acid extraction, a minimum conversion level of 97.5% must be complied with. Sulphur trioxide emissions in the waste gas must not exceed 60 mg/m3 under constant gas conditions, and must not exceed 120 mg/m3 otherwise.

Limits which can also be adhered to are established in TA-Luft for NOx emissions in furnace flue gas streams - tube furnaces, steam generators, booster heaters.

Dust emissions from UREA fertiliser production facilities are restricted to 50 mg/m3, while the free ammonia content in waste gases must not exceed 35 mg/m3. The dust load is measured gravimetrically with filter head equipment and the free ammonia is determined by titration.

The wastewater treatment processes used are subject to local regulations. In Germany, the Wasserhaushaltsgesetz (WHG) [Federal Water Act] applies, with its associated Verwaltungsvorschrift [Administrative Regulation] relating to minimum requirements for the disposal of wastewater in drains. In fertiliser production plants, the associated 44. Verwaltungsvorschrift [44th Administrative Regulation] can be observed.

In the extreme case of wastewater treatment, no wastewater is produced, merely combustion residues which are finally disposed of on special dumps where no leaching can occur, or concentrated residual solutions which require disposal in deep wells, for example, may be formed.

The catalyst and purification mass residues, most of which are formed at intervals of two years or more, do not cause any problem in terms of quantity and, as already stated, are passed on to smelting works for metal recycling or must be dumped as special waste.

With regard to the ash and slag from solid-fuel ammonia production, the possibility of recycling or dumping has to be examined in each individual case.

The TA-L [Technical Instructions on Noise Abatement] which is the comparable administrative regulation for noise protection, specifies immission values which are graded by location and time for areas, based on a variety of uses. The determining criterion is that of total impact level. Noise protection measures must be taken into account at planning stage as they are costly if implemented at a later date. In site planning, therefore, adequate distances from protected property, such as residential housing development, and a shortening of this distance must be prevented.

In Germany the TRgA 9007) for limiting the maximum pollutant concentration at the workplace (MAK/TRK values8)), the Arbeitsstenverordnung [Ordinance on Workplaces] including workshop guidelines for workplace design and the accident prevention regulations Unfallverhvorschriften of the Berufsgenossenschaften (employers' liability insurance associations), as being the body responsible for insuring accidents at work, apply to workplace conditions in terms of pollutant concentration, noise nuisance and industrial safety. Comparable regulations exist in other countries, e.g. in the USSR, with Health Standards for Industrial Concerns (SN 245-71).

7) TRgA - Technische Regeln zur Arbeitsstoffverordnung [technical regulations on the industrial substances decree]

8) MAK - Maximale Arbeitsplatzkonzentration [maximum workplace concentration]

TRK - Technische Richtkonzentration [technical approximate concentration]

4. Interaction with other sectors

In view of the high energy and raw material requirement, ammonia and urea production plants are normally built close to raw material sources or transport routes; these include natural gas and crude oil conveying plants, refineries, pipeline terminals, LNG stores, coal mines, power stations and coking plants - or hydroelectric power stations with high excess energy (for water electrolysis).

Proximity to other fertiliser production facilities is also useful, e.g. NP or NPK fertiliser production.

Less practical, in contrast, are purely consumption-oriented sites if these do not also enjoy favourable conditions for the supply of raw materials or energy (e.g. port installations, power stations).

5. Summary assessment of environmental relevance

In ammonia and urea production plants, mainly gaseous by-products and residues are formed due to the raw materials used, together with wastewater, waste heat and spent catalysts resulting from the processes used. Moreover, noise and other industrial influences also occur.

Because of the high energy requirement for ammonia production, which is about 29 GJ/t of NH3 in modern natural gas fed plants and over 70 GJ/t of NH3 where coal is the raw material, the environmental impact is comparable to that of power stations (cf. environmental brief Thermal Power Stations).

With today’s gas and water purification methods, even the most stringent environmental protection regulations can be complied with, the lowest costs being incurred where natural gas is the raw material, and the highest being incurred for coal - due to its complex composition. In the manufacture of granular urea fertiliser, particular emphasis must be placed on effective dedusting techniques. Likewise, suitable wastewater purification plant and environmentally friendly dumping facilities must be available.

In industrial conurbations, air coolers or dry cooling towers may be required to prevent the environmental pollution which can occur where cooling water is used to deal with waste heat.

The population affected should be involved at the planning phase; likewise, the population resident in the area of the project should have access to medical care.

In the case of new planning measures without any differentiated (state) monitoring system in the environmental field, the aim must be to choose a technique which is best adapted to the particular circumstances.

It is extremely important for plants of this kind to be systematically monitored and maintained to guarantee correct operation - a point which is all too easily ignored. Thus, a works environmental protection officer with appropriate powers must be appointed who will also be responsible for increasing the awareness, and for the education and training of operating personnel with regard to environmental issues.

It may generally be stated that apart from the pollutants due to waste heat and contained in the raw materials, very little environmental impact need be feared from ammonia and urea production provided that environmental protection aspects are taken into account during planning and operation.

6. References

Allgemeine Verwaltungsvorschrift enehmigungsbede Anlagen nach 16 der Gewerbeordnung - GewO; Technische Anleitung zum Schutz gegen L (TA-L), 1968.

Gesetz zur Ordnung des Wasserhaushalts (Wasserhaushaltsgesetz - WHG), 1976.

Gesetz zum Schutz vor schichen Umwelteinwirkungen durch Luftverunreinigungen, Gerche, Erschngen und liche Vorge, BundesImmissionsschutzgesetz - BImSchG, 1985.

Katalog wassergefdender Stoffe, Bekanntmachung des BMI, 1985.

Technische Regeln fnnbare Fleiten - TRbF

TRbF 100 Allgem. Sicherheitsanforderungen

TRbF 110 Lr

TRbF 210 Lr

TRbF 180 Betriebsvorschriften

TRbF 280 Betriebsvorschriften.

1. Allgemeine Verwaltungsvorschrift zum BundesImmissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft), 1986.

1. Allgemeine Verwaltungsvorschrift (VwV) zur Stll-Verordnung (1. Stll-VwV), 1981.

2. Allgemeine Verwaltungsvorschrift zur Stll-Verordnung (2. Stll-VwV), 1982.

4. Verordnung zur Durchf des BundesImmissionsschutzgesetz (Verordnung enehmigungsbede Anlagen - 4. BImSchV), 1985.

9. Verordnung der Bundesregierung zur Durchf des BundesImmissionsschutzgesetzes, (Grundse des Genehmigungsverfahrens - 9. BImSchV), 1980.

12. Verordnung der Bundesregierung zur Durchf des BundesImmissionsschutzgesetzes, (Stll-Verordnung - 12. BImSchV), 1985.

13. Verordnung zur Durchf des BundesImmissionsschutzgesetzes, (Verordnung roeuerungsanlagen - 13. BImSchV), 1983.

Verordnung nlagen zur Lagerung, Abf und Befrung brennbarer Fleiten zu Lande (Verordnung rennbare Fleiten - VbF), 1982.

Verordnungen der Bundesler nlagen zum Lagern, Abfund Umschlagen wassergefdender Stoffe - VAwS.

1. Scope

Nitrogenous fertilisers in the strict sense of the term include the following, which are considered in the context of this environmental brief:

- ammonium nitrate (abbreviation AN)
- calcium-ammonium nitrate (abbreviation CAN)
- ammonium sulphate (abbreviation AS)
- calcium nitrate (abbreviation CN)
- nitrogen solutions (abbreviation N solutions)
- ammonium chloride
- ammonium phosphates.

The nitrogenous fertilisers examined here are produced for agriculture in a granulated or prilled form with the exception of nitrogenous solutions, the use of which requires a system of mixing and distributor stations.

The primary products required for the manufacture of these fertilisers comprise:

- ammonia, covered by the environmental brief Nitrogenous Fertilisers (raw materials, ammonia and urea production)
- nitric acid
- sulphuric acid
- urea
- limestone.

The capacities of individual plants vary considerably; the upper limit for nitric acid, for example, is 2000 t HNO3/day, for sulphuric acid 3000 t H2SO4/day and for ammonium nitrate and calcium-ammonium nitrate 2000 t/day on one line.

2. Environmental impacts and protective measures

With the use of modern processes, environmental impacts can be confined to gaseous emissions in the overwhelming majority of cases. Any liquid emissions produced can usually be avoided by internal recycling, although in a few cases solid waste cannot be avoided, and noise emissions occur with most processes.


Figure 1 - Nitrogenous Fertiliser Production

2.1 Nitric acid production

Industrial production of nitric acid is based on the catalytic oxidation of ammonia and subsequent absorption of the nitric oxides, formed during oxidation, in water. The various processes used in industrial production differ mainly with regard to the pressure used in the burning or absorption stage and the efficiency of the heat recovery system. The acid produced for further processing into fertilisers is an aqueous solution containing up to about 60% HNO3.

· Pollutants produced and counter-measures

The process does not give rise to continuous liquid emission flows. Where liquid ammonia is used, an oily waste is produced intermittently depending on the oil content of the ammonia, which is collected and burnt in a suitable incineration plant. Gaseous emissions are the tail gas containing (NO + NO2) = NOx from the absorption column.

The higher the NO2 content, the more intense the brown colour of the waste gas, as is plain to see for miles around.

While the NOx content in older plants can be several thousand mg NO2/m3, modern facilities are designed for around 400 mg NO2/m3. There are a number of ways of removing nitrogen oxides completely, e.g. catalytic tail gas burning with hydrogen, ammonia or methane.

If neither fresh water nor seawater can be used as cooling water, blow-down water from the cooling water recycle arises which, in compliance with local provisions, cannot always be discharged directly as wastewater because of its increased salt concentration and other additives. In this case, it is conditioned in the wastewater treatment plant together with the other wastewater flows in the works. The residues must then be taken to a controlled dump or, in the case of biological wastewater purification, can be incinerated. Where fresh water is used for cooling purposes, the heat transferred to the river or lake must be taken into account; if necessary, measures are to be taken to cool it before it is discharged.

2.2 Sulphuric acid production

Today sulphuric acid is produced on an industrial scale almost exclusively using the contact process in which gases containing sulphur dioxide are channelled through a vanadium catalyst. The gases containing sulphur dioxide required as the primary product for sulphuric acid production come mainly from:

- the burning of elemental sulphur,
- roaster gases from pyrite,
- roaster gases from sulphide ores of non-ferrous metals.

A modern sulphuric acid plant can be identified by optimum use of the reaction heat in the individual process stages. Most surplus steam is used for energy production, and in some plants, the low-temperature energy produced in the acid coolers is already being utilised.

The SO3 formed in catalytic SO2 oxidation is absorbed in 98% to 99% sulphuric acid, which yields H2SO4 in a reaction with water.

· Pollutants produced and counter-measures

There are no process-specific liquid emissions if sulphuric acid is produced by sulphur oxidation.

The tail gas from sulphuric acid facilities contains SO2 and SO3.

For sulphuric acid facilities, emissions of sulphur trioxide in the waste gas, at constant gas conditions, are limited to maximum 60 mg/m3. Moreover, the emissions can be further reduced by the use of the peracidox process, a fifth tray stage (5th catalyst level) or equivalent measures.

Where roasters are installed upstream, small quantities of contaminated sulphuric acid are produced in the form of washing acid, which, if it does not contain any harmful pollutants, can be concentrated and used, for example, in a fertiliser plant. If it contains harmful pollutants from the raw materials which have not been removed by the waste gas plant upstream, the acid must be neutralised and the residue dumped.

The slag may, depending on the feedstock analysis and possibly following an intermediate stage in which elements of any value are extracted, be passed to the steel industry or dumped. The remarks made in section 2.1 apply with regard to the cooling water problem.

In Germany, pure liquid sulphur is used almost exclusively. In the rare cases in which the sulphur contains arsenic or selenium, purification is essential and filtration residues must be dumped with care. Where the dumps are in the open, it must be ensured that the sulphurous acid formed by oxidation of the sulphur in the atmosphere does not percolate into the ground water with rainwater.

2.3 Ammonium nitrate production

Along with urea, ammonium nitrate is one of the most frequently used nitrogenous fertilisers worldwide. It is mainly produced by the neutralisation of 45 - 65% nitric acid with ammonia.

Ammonium nitrate is also a by-product of the nitrophosphate process in which NP or NPK fertilisers are made by the nitric acid decomposition of crude phosphates. The neutralisation reaction yields 95 to 97% solutions of ammonium nitrate.

The solution is processed further to obtain a marketable product by granulating or, after concentrating further to 99.5%, by prilling.

· Pollutants produced and counter-measures

Where the prilling process is used, the prilling tower in the dry part of the plant can give rise to serious emission problems, as the relatively large quantities of discharged air are extremely costly to purify. In time, ammonium nitrate dust kills vegetation in the surrounding area. Such problems can be dealt with far more easily in granulation installations. Thus, this aspect should be studied in depth before any new investment is made and before any decision is taken on the process to be used.

With granulation, the process gas flows must be purified in effective wet scrubbers before they are discharged into the atmosphere. The installation should be fitted with a dust extraction system to ensure the safety of operating personnel.

Waste fumes from neutralisation and evaporation also must be scrubbed if they are to be discharged into the atmosphere as vapour. The preferred solution is the condensation of purified fumes, which yields condensates polluted with ammonium nitrate and ammonia, some of which can be used as process water for an adjoining nitric acid plant. Condensate which contains small amounts of impurities can be fed through an ion exchanger installation and reprocessed to boiler feed water.

2.4 Calcium-ammonium nitrate production

While the ammonium nitrate considered in section 2.3 has an N content of 33.5 - 34.5%, the nitrogen content of calcium-ammonium nitrate is 20.5 - 28%, and EC regulations do not permit a nitrogen content of over 28%. The nitrogen content is reduced by the addition of crushed limestone. With the exception of this addition of crushed limestone and mixing with the ammonium nitrate melt immediately before the prilling or granulation process, calcium-ammonium nitrate is made in the same way as ammonium nitrate. For this reason, the comments made in section 2.3 regarding pollutants and counter-measures apply here too but, in addition, because of the crushing plant for the lime, increased noise emissions must be anticipated. An effective dedusting unit is to be provided for the crushing process. Where there is a constant electricity supply and the plant is maintained to West European standards, continuous dust removal to less than 50 mg/m³ can be achieved.

2.5 Ammonium sulphate

In view of the popularity of more highly concentrated nitrogenous fertilisers, the consumption of ammonium sulphate with just 20.5% N is constantly declining and now, worldwide, accounts for just 6% of nitrogenous fertiliser consumption. The strong physiologically acidic effect of this fertiliser is also to blame for the decline in its use.

The main industrial-scale production methods are:

- from coke-oven or coal gasification;
- from ammonia and sulphuric acid;
- as a by-product of organic syntheses, e.g. caprolactam manufacture;
- from gypsum, either from natural deposits or as a by-product of other processes, by reaction with ammonia and carbon dioxide.

2.5.1 Production from coke-oven or coal gasification

In both dry distillation and pressure gasification, some of the nitrogen in the coal forms ammonia. This ammonia is also found in the aqueous and carbon dioxide-rich condensate produced when the gas is cooled. The gas condensate also contains tar, phenols, pyridins, hydrogen sulphide, hydrocyanic acid etc., which cause serious problems when it comes to ammonia recovery and wastewater purification. When the tar has been separated and the phenols

removed, the volatile components of the gas condensate are stripped in a column by steam injection. The fumes from the stripper are scrubbed with sulphuric acid in coking plants, and the acidic gases remaining after sulphuric acid scrubbing are either processed to sulphur in a Claus plant or converted directly to sulphuric acid in a wet catalysis installation. Fume burning could well be an option for consideration where only small quantities are produced, but this must be in line with sulphur emission regulations.

The wastewater must undergo a biological treatment as it contains various sulphur compounds, phenol and other organic compounds.

· Pollutants produced and counter-measures

The problems arising from ammonia production have already been examined in the previous section and should be the topic of a separate study - on coal. The dust needs to be removed from waste gases produced by ammonium sulphate drying before they can be discharged into the atmosphere, as otherwise they lead to overfertilization with the associated negative consequences for soil and water quality.

2.5.2 Production from ammonia and sulphuric acid

Neutralisation and crystallisation are carried out under vacuum or at atmospheric pressure. Crystallised ammonium sulphate is removed from the resulting mash in centrifuges and then dried.

· Pollutants produced and counter-measures

The fumes produced by the exothermic reaction of sulphuric acid and ammonia, in particular the ammonia in the waste gas which can cause caustic burns to man, animals and plants, may contain impurities depending on the process used, and should be fed though a scrubber before being discharged into the atmosphere.

Dedusting systems are needed to remove the dust content from drying plant waste gases before they are released into the atmosphere.

2.5.3 As a by-product

Ammonium sulphate is obtained from the liquid waste of some organic processes, e.g. the production of caprolactam or acrylonitrile which yields a dilute ammonium sulphate solution, by evaporation, crystallization, centrifuging and drying.

For information on pollutants and counter-measures, see section 2.5.2.

2.5.4 Production from gypsum, ammonia and CO2

The feedstock is finely ground natural gypsum or anhydrite, or alternatively calcium sulphate - a by-product, for example, of phosphoric acid production - which is converted with ammonia and carbon dioxide. The calcium carbonate obtained from the reaction is filtered off and the ammonium sulphate solution evaporated, crystallised and treated as described in section 2.5.3.

· Pollutants produced and counter-measures

In principle, the same factors as stated in 2.5.2 need to be considered. Where natural gypsum is used, there is the added nuisance of noise from the grinding plant. The details given in 2.4 apply with regard to the dust produced in the grinding process.

2.6 Calcium nitrate production

Ca(NO3)2 is produced either directly via the reaction of nitric acid with limestone or, alternatively, produced as a by-product of the nitrophosphate process.

In direct manufacture, limestone is dissolved in dilute nitric acid and granulated or prilled after evaporation of the dilute calcium nitrate solution.

In the nitrophosphate process, in which crude phosphate is decomposed with nitric acid, the calcium nitrate is crystallised by cooling, separated and, after appropriate treatment, granulated or prilled.

· Pollutants produced and counter-measures

In direct manufacture, the dissolution process yields gases which contain NOx and need to be extracted and absorbed, mainly to protect the health of operating personnel, although the gases are also responsible for corrosion of equipment and buildings.

Either appropriate precautions have to be taken at the design stage, or a scrubber installation is to be provided to reduce the pollutant content of the fumes produced during evaporation. Any purification stage installed after dissolving generates a moist waste which - depending on its composition - can be used in other plants or must be dumped.

Dust-laden gases must be cleaned before discharge into the atmosphere. Any washing solutions produced by these cleaning operations are to be concentrated and recirculated.

2.7 Production of nitrogen solutions

The following are used as liquid nitrogenous fertilisers:

- liquid ammonia;
- aqueous ammonia solutions (e.g. 25%);
- solutions which contain free ammonia together with either ammonium nitrate or urea, or both;
- solutions of ammonium nitrate or urea, or both.

Liquid ammonia is used directly as a fertiliser principally in the United States, where it is injected 15 - 25 cm deep into the soil with special equipment.

Where applied in this way, storage, transport and transfer equipment are the basic essentials, and the precautionary measures stated in the first section with regard to ammonia are to be observed.

These same precautionary measures are also to be taken in a somewhat diluted form for other nitrogenous solutions containing free ammonia.

The long-term implications - especially on soil microorganisms and the humus layer - should be examined for the particular soil type concerned before liquid ammonia or nitrogenous solutions containing free ammonia are used.

2.8 Ammonium chloride production

This salt, which - at 26% N - has a somewhat higher nitrogen content than ammonium sulphate, is not used alone as a nitrogenous fertiliser in Germany. Its main areas of use are China, Japan and India, principally in rice paddies as an alternative to ammonium sulphate, which decomposes into toxic sulphides where rice is attacked by fungus. The use of ammonium chloride is now on the decline as soils become overchlorinated if chloride is used for prolonged periods.

By far the largest share of ammonium chloride made for use as fertiliser is produced in solvay plants modified for soda production. After separating the sodium bicarbonate, ammonium chloride is crystallised out of the remaining solution by additional process stages, thus obviating the need for the usual ammonia recovery with its attendant yield of relatively useless calcium chloride, and instead ammonium chloride fertiliser is obtained as a by-product.

· Environmental impacts and counter-measures

As facilities of this kind yield ammonium chloride as a by-product of soda manufacture, the main measures applicable are those relating to soda works. The additional equipment required for ammonium chloride production must be fitted with efficient dedusting systems, especially for waste gases from driers.

2.9 Ammonium bicarbonate

To complete the picture, mention must also be made of this nitrogenous fertiliser, which is only produced and used in China. According to statistics, of the 11.1 million tonnes made in China in 1983, 6.4 million tonnes went to the fertiliser market in the form of ammonium bicarbonate. The reason for this one-off development lies in the rapid establishment of nitrogenous fertiliser production from 1960 on, with the creation of a large number of small facilities for ammonia production using carbon gasification. The CO2 obtained as a by-product is used directly for neutralisation of the ammonia produced.

Please refer to the section on ammonia synthesis using coal gasification for information on environmental impacts and counter-measures.

2.10 Transport, storage and bagging of solid fertilisers

Because they are water soluble, and in view of their hygroscopicity, fertilisers must be stored in bulk goods stores which are roofed and enclosed on all sides and then transferred to a bagging and transfer station in the immediate vicinity for dispatch. The delivery, removal and transfer points are to be of an as dust-tight as possible design, and - as in production plants - at critical points, where enclosure is not feasible, dust-laden waste gases must be collected and transferred to a dedusting installation.

3. Notes on the analysis and evaluation of environmental impacts

The basic regulations to be considered for this environmental brief are found, in Germany, in the 1. Allgemeinen Verwaltungsvorschrift [1st General Administrative Regulation] to the Bundes-Immissionsschutzgesetz [Federal Immission Control Act] (Technische Anleitung zur Reinhaltung der Luft [Technical Instructions on Air Quality Control] - TA-Luft) of 27.02.1986.

It is often the case in countries without firm regulations that the relevant German provisions are used when designing such facilities.

The NOx emission for new nitric acid facilities is now restricted to 0.45 mg/m3, expressed as nitrogen dioxide, and waste gases must be colourless before discharge. NOx is determined analytically by titration or photometry.

In sulphuric acid plants, sulphur trioxide emissions in waste gas, at constant gas conditions, are restricted to 60 mg/m3 maximum. The sulphur dioxide content of the tail gas is determined by the conversion level, which must be at least 99.6% in the double-contact process, with a minimum sulphur dioxide volume content of 8% in the input gas and at constant gas conditions. Furthermore, emissions are to be further reduced by the use of the peracidox process, a fifth tray stage or equivalent measures. Sulphur dioxide can be determined iodometrically, titrimetrically, gravimetrically or colorimetrically. For continuous measurement, recording analyzers are used, working on the basis of optical absorption in the infrared or ultraviolet spectral range or the electrical conductivity of the sulphur dioxide.

For fertiliser plants, dust emissions from granulation and drying installations for multinutrient fertilisers with an ammonium nitrate content of over 50% or a sulphate content of over 10% are restricted to 75 mg/m3 maximum. This category includes, for example, the following fertilisers: ammonium nitrate, calcium-ammonium nitrate and ammonium sulphate. For other fertiliser plants, the dust emission is to be kept at no more than 50 mg/m3. Operating licenses set values of 35 mg/m3 maximum for the free ammonia content of waste gases. Dust is analyzed gravimetrically with filter head equipment. Compliance with sampling technique rules is of utmost importance for the reliability of analyses and thus compliance with statutory limits. Free ammonia is determined by titration.

4. Interaction with other sectors

Today, it is frequently the case that complexes are not confined solely to the production of nitrogenous fertilisers but make NP and NPK fertilisers, too. In this case, the sulphuric acid obtained is used for phosphoric acid production. The phosphoric acid is then neutralised with ammonia to ammonium phosphates which are processed in granulation operations to DAP fertilisers or, after adding potassium salts and micronutrients as necessary, to NPK fertilisers. This sort of combined economic management is characterised by a high level of flexibility with regard to fertiliser type. Furthermore, individual plants, including any ammonia synthesis upstream, can have increased capacities and thus manufacture their products economically; finally, a complex of this kind is self-sufficient in electricity because of the extra energy provided by the sulphuric acid installation. A further possibility is that of using the MKrocess or a modern variation of it to reconvert into sulphuric acid the gypsum produced in the phosphoric acid plant, which in many instances represents a major dumping problem.

The slag from a roaster plant can be a raw material for non-ferrous metal and/or steel works.

Use of the nitrophosphate process obviates the need for sulphuric acid, in which case calcium nitrate is a by-product that can be converted to ammonium nitrate and fertiliser lime or calcium-ammonium nitrate where cheap carbon dioxide is available, e.g. from an adjoining ammonia synthesis plant.

The special variant of the solvay process for soda production practised in the Far East, of which ammonium chloride is a by-product, has already been mentioned.

For high-capacity nitrogenous fertiliser facilities, having ammonia synthesis close by is always worthwhile unless the plant enjoys an excellent transport infrastructure (e.g. ports and harbours, cf. environmental brief) and can also conclude favourable long-term supply contracts.

References are given in the relevant environmental briefs.

5. Summary assessment of environmental relevance

In nitrogenous fertiliser production facilities, the implications for the environment concern in the main gaseous waste (dust, ammonia, nitrous gases, sulphur dioxide), and noise, plus, in the case of roaster installations, process-specific by-products and residues.

Nitric acid installations can be operated such that gaseous emissions are practically colourless, i.e. NOx-free, by the use of catalytic tail gas treatment where the NOx design value is not sufficient.

In sulphuric acid plants, the officially prescribed emission values listed in section 3 are to be further reduced by the installation of a fifth tray stage, the use of the peracidox process or equivalent measures. Where roasters are installed upstream, the slag, if it cannot be further used, must be dumped, the washing acid neutralised and residues dumped if further utilisation is not possible in view of the impurities they contain.

In plants for the production of salt, prilled or granulated fertilisers, an efficient dedusting system is of prime importance. This requires the separate treatment of the individual waste gas flows in specific dedusting installations. As stated, liquid waste from gas scrubbers is returned to the process. With modern technology, the harm to the environment can be kept low in the processes described here.

On the process management side of such plants, all waste gas purification installations must be systematically monitored and maintained. In particular, regular maintenance - which includes the cleaning of machines, motors and plant - is a major determining factor in the operating efficiency of such systems. Another important factor is the timely provision of the necessary spare parts. Monitoring also includes regular analyses by an efficient laboratory so that appropriate measures can be taken promptly when values drift out of the permitted range. Works environmental safety officers should also be appointed; they should have the appropriate powers and should be responsible for the training and upgrading of personnel and for raising their awareness with regard to environmental matters.

Retention basins are also to be provided so that, if there should be any process incident resulting in an unforeseen production of wastewater, the plant does not have to be immediately shut down.

Although the dusts and gases produced are fertilizing substances, attention must be paid to compliance with prescribed emissions as, in the long-term, excessive immissions can be harmful to plant crops or trees in the surrounding area.

The affected population should be involved at the planning stage, and access to medical care must be guaranteed.

6. References

Abfallbeseitigungsgesetz, 04.03.1982.

31. Abwasser VwV Wasseraufbereitung, Kteme, 13.09.1983.

American National Standards Institute Safety Requirements for storage and handling of anhydrous ammonia, ANSI K 61.1., 1972.

1. Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft), 27.02.1986.

44. Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer, Herstellung von mineralischen Dtteln aur Kali, 44. Abwasser VwV, 05.09.1984.

Arbeitssten-Richtlinien (ASR).

The relevant accident prevention regulations of the employers' liability insurance associations (Berufsgenossenschaften) relating to the handling of hazardous materials.

Gesetz zur Ordnung des Wasserhaushalts, Wasserhaushaltsgesetz, 16.10.1976.

Gesetz zum Schutz vor schichen Umwelteinwirkungen durch Luftverunreinigungen, Gerche, Erschngen und liche Vorge, Bundes-Immissionsschutzgesetz BImSchG, 04.10.85, and the associated enforcement ordinances and general administrative provisions.

Katalog wassergefdender Stoffe, German Federal Ministry of the Interior (BMI) publication, 01.03.1985.

Merkbler Gefliche Arbeitsstoffe (codes of practice for hazardous materials), e.g.:

Blatt S 24 Nitrogen dioxide (Stickstoffdioxyd)

Blatt S 33 Nitrogen oxide (Stickstoffoxyd)

Blatt S 03 Nitric acid (Salpeterse)

Blatt A 64 Ammonium nitrate (Ammoniumnitrat)

Blatt A 59 Ammonia solution (Ammoniaklg)

etc.

Technische Anleitung zum Schutz gegen L (TA-L), 16.07.1968.

Technische Regeln zur Arbeitstoffverordnung TRgA 511, Ammoniumnitrat, September 1983.

TRgA 951 Ausnahmeempfehlung nach 12 Abs.2 in Verbindung mit Anhang II, Nr. 11 of the ArbStoffV f Lagerung von Ammoniumnitrat und ammoniumnitrathaltigen Zubereitungen, October 1982.

Ullmanns Enzyclope der technischen Chemie, 4. Auflage.

VDI guidelines, e.g.:

VDI-2066 Staubmesssungen in strden Gasen, pages 1 (10.75), 2 (6.81), 4 (5.80)

VDI-2456 Messung gasfger Emissionen; Messen der Summe von Stickstoffmonoxyd und Stickstoffdioxyd, pages 1 + 2 (12.73).

Messen von Stickstoffmonoxyd, Infrarot-absorptionsger URAS, UNOR, BECKMANN, Modell 315, page 3 (4.75).

Messen von Stickstoffdioxydgehalten, Ultraviolettabsorptionsger-LIMAS G, page 4 (5.76).

Analytische Bestimmung der Summe von Stickstoffmonoxyd und Stickstoffdioxid, Natriumsalicylatverfahren, page 8 (11.83).

VDI-2298 Emissionsminderung in Schwefelseanlagen.

Verordnung efliche Arbeitsstoffe, Arbeitsstoffverordnung - Arbstoff V., 11.02.1982.

Verordnung rbeitssten, Arbeitsstenverordnung, ArbSt V, 01.08.1983.

1. Scope

Companies in the cement, lime and gypsum industries produce mainly powdery products which are mouldable when water is added to them and set after a certain reaction time. The following production stages are required to manufacture the products:

- Extraction: Transport, crushing, dosing of additives, storage, dressing of the raw materials;
- Burning;
- Storage and crushing of the burnt products;
- Addition of additives: e.g. gypsum in the case of cement or water in the case of lime;
- Packing and dispatch

In the cement industry there are essentially two production processes which are used to dress and burn the raw material, the so-called wet process and the dry process. In most cases the raw material consists of a mixture of limestone and clay in the ratio of approximately 4:1.

- In the wet process the raw material is ground, with the addition of water, to form a sludge which contains 35-40% water. During burning the water evaporates. The amount of energy required for this is 100% greater than in the dry process. Because of the conditions of the wet process the specific waste gas flow rate is higher. New furnaces for the wet process are now only being constructed for extreme raw material conditions, whilst older plants are being converted increasingly to the energy-saving dry process.
- In the dry process the raw material is crushed whilst being dried, preheated by the counterflow process in a heat-exchanger by the hot kiln waste gases and in most cases burnt in a rotary kiln at the required sintering temperature of approx. 1400°C. Some of the modern plants have capacities of over 5000 t/day, whilst the capacity of the wet kilns rarely exceeds 1000 t/day. Shaft kilns are only used occasionally in special cases where market or raw material conditions dictate, and for the most part their capacity is less than 200 t/day.

In the lime industry both shaft and rotary kilns are used for burning the limestone, the combustion temperature being 850-1000°C. In some cases ring kiln and similar internally developed shaft kiln processes are still used. Compared with the cement industry the capacities of the lime kiln plants are lower, rarely above 1000 t/day. Small producers with simple shaft kilns having a capacity of only a few tonnes per annum are commonly found in many countries.

Gypsum is dewatered at temperatures of 200 - 300°C max. and converted from dihydrate to hemihydrate. Direct current rotary kilns, calcining mills or calciners and boilers are used for burning. The capacities of modern gypsum works are between 600 and 1100 t/day, but some of the plants still have relatively low capacities.

Anhydrite accompanied by gypsum is found in nearly all gypsum deposits. Anhydrite is an anhydrous form of calcium sulphate (CaSO4) which, after crushing and classifying, can sometimes be used as a quick binding agent without prior thermal treatment.

2. Environmental impacts and protective measures

2.1 Air

2.1.1 Waste gases/flue gases

No waste gases are produced in the extraction and crushing of cement, lime and gypsum raw materials (principally limestone, gypsum and anhydrite), processes which are mainly carried out in the quarries.

The cement raw materials are frequently dried during dressing and crushing so that the moisture produced can be driven off as harmless water vapour. During the burning of the raw materials for cement production, calcium carbonate is converted to calcium oxide when the carbon dioxide (CO2) contained in the limestone is driven off. Sulphur compounds (mostly in the form of SO2) and nitrous oxides (NOx) may also be contained in the waste gas. Chlorine and fluorine gas and vapour emissions are prevented in the normal process by the fact that these impurities are deposited in the burnt product.

Water vapour and CO2 emissions are process-related, whilst the occurrence of sulphur compounds can be greatly reduced by the use of suitable raw materials and fuels and control of the burning process. Up to certain limits, sulphur components are bound by the cement clinker during burning. Only under extraordinary operating conditions, e.g. where there is an excess of sulphur in the raw material and fuel, or in the case of reducing burning, will there be occasional short-term emissions of appreciable quantities of SO2.

The flame temperature at which cement is manufactured may be as high as 1800°C, with the result that more nitrous oxides are formed by oxidation of the atmospheric nitrogen than in lime burning.

The NOx values of 1300 - 1800 mg/Nm3h permitted in the waste gas in Germany (TA-Luft - Technical Instructions on Air Quality Control - Table 1) will probably become subject to more stringent requirements in the next few years. At the present time, possible ways of reducing the NOx values are the subject of large-scale trials, and there currently appear to be four potential methods:

- non-catalytic combustion;
- plants with activated carbon filters;
- optimisation of the burning operation;
- conversion of plants to a two-stage calcining installation (oxidising, reducing).

These processes require different levels of investment and they all presuppose continuous operational monitoring.

In the cement industry oils, solvents, paint residues, old tyres or other combustible waste materials are frequently used as additional fuels. Some of these waste products introduce contaminants which are normally bound by the clinker and do not reach the waste gas. If such fuels are used, the process must be monitored by special safety inspections to prevent the emission of additional contaminants.

In lime burning, which takes place in much smaller plants than in cement production, CO2 is also emitted with the flue gas, but the quantity of waste gas is much smaller than in cement works because of the size of the plant and because of the lower combustion temperatures in the process.

In lime slaking calcium carbonate is converted to calcium hydroxide with the addition of water, some of the water added being discharged again as water vapour, since the process is exothermic. However, this water vapour is harmless.

In gypsum burning water vapour and small quantities of flue gas are discharged into the atmosphere. Since the combustion temperatures of 300-400°C are not very high, and since in most cases the mass flows are very low, these burning plants only cause slight environmental pollution.

Anhydrite from natural deposits is only crushed before use, but anhydrite from phosphoric acid production must be dried before further use, in which case water vapour will be given off. However, this anhydrite is rarely suitable for industrial use, because it is often toxic.

2.1.2 Dust

During the extraction and further processing of cement, lime and gypsum dust is produced in various stages of the work due to process conditions. In the case of cement this dust is a mixture of limestone, calcium oxide, cement minerals, and sometimes even completely burnt cement, whilst in the case of gypsum the dust contains anhydrite and mainly calcium sulphate. With the exception of the pure CaO dust, which is produced during lime burning, the dust is harmless, but on the other hand it does give rise to considerable nuisance. In the case of the individual production units and conveying installations of a cement works 6-12 m3 of spent air and waste gas per kg of material have to be extracted and dedusted. The major sources of dust in a plant include:

- crushing and mixing of the raw material;
- burning of the cement;
- crushing of the cement (clinker + gypsum);
- slaking of the lime.

The proper use of high-performance extraction plants and dedusting installations, such as electrostatic separators, fabric and gravel bed filters, and often cyclones used in conjunction with these, is essential, otherwise correct process management cannot be guaranteed, costs due to machinery wear rise disproportionately and high dust levels impair working conditions, simultaneously causing loss of production.

The separated dusts are mainly recycled, provided no enrichment of heavy metal components such thallium is expected in the waste gas. Only under unfavourable raw material and fuel conditions will it perhaps be necessary to separate and eject partial quantities of the dust because of the excessive concentration of detrimental components in the product, e.g. alkaline chlorides. Occasionally the use of these dusts is possible in other branches of industry. If the dusts are dumped, the groundwater protection requirements must be met due to the water solubility of individual components.

In lime production the quantity of dust produced is smaller because a powdery product is only involved during the slaking, packing and loading of the lime. In the gypsum and anhydrite industry the amount of dust produced is also small.

High quality filters (electrostatic or fabric filters) now make it possible to achieve a dust concentration of less than 25 mg/Nm3 in the spent air in the cement, lime and gypsum industry. At present, values of below 25 mg/Nm3 are being discussed by the European authorities for new plants, whereas the German TA-Luft (Technical Instructions on Air Quality Control) still requires 50 mg/Nm3.

2.2 Noise

Cement works emit far higher noise levels than lime and gypsum works, but the latter also have production areas giving off considerable noise.

In the extraction of raw materials, noise and associated vibrations may occur as a result of blasting, but such noise emissions can be substantially reduced by means of suitable ignition processes. Moreover, the machines used for mining can be soundproofed to such an extent that they meet the requirements of the German TA-L (Technical Instructions on Noise Abatement).

During dressing, noise pollution is liable to occur e.g. through the use of rebound crushers and mills for the crushing of hard materials. These crushing installations and the adjoining dressing installations can be enclosed in such a way as to protect the environment from oppressive noise. The noise generated by the majority of rock- and cement-crushing plants is so intense that they have to be installed in soundproofed premises in which personnel cannot work on a permanent basis.

Burning plants require numerous large fans which generate extremely penetrating noise, with the result that noise protection measures, e.g. in the form of enclosures, are also necessary.

In order to avoid nuisance, plants in the lime, gypsum and particularly the cement industries must be erected at least 500 metres from residential areas. The immissions values for nearby residential areas should not exceed 50 to 60 dB(A) during the day, and 35-45 dB(A) at night.

2.3 Water

In the vicinity of pits in the German cement, lime and gypsum industry the wastewater may contain up to 0.05 ml/l of total suspended solids. To avoid exceeding this value the pit water produced must be discharged via stilling basins. Water used for washing limestone must always be discharged via sedimentation ponds, and the surface water produced in the area surrounding the pits must be discharged separately.

Some cement and lime works are major water consumers, but because of the process involved they cause no water pollution. In cement works approximately 0.6 m3 of water per tonne of cement is required to cool the machines. Most of this water is in circulation, thus only the water losses need be made up. In plants involved in the drying process, water is also used for cooling the kiln exhaust gases, resulting in a calculated net consumption of approx. 0.4 - 0.6 m3 of water/t of cement. In plants using the wet process an additional 1 m3 of water/t of cement or so is required for the sludge milling. This water is discharged again by evaporation.

In the lime industry water is required for slaking burnt lime (approx. 0.33 m3/t of lime). Some lime works consume an additional 1 m3 or so of water per tonne of lime for washing the raw limestone when extremely pure qualities are required. After use, this washing water is fed to settling basins or settling ponds where the fine particles are deposited and the residual water evaporated or partially re-used.

The gypsum industry requires relatively little water because the processes take place at low temperatures, with the result that no cooling energy is required. In plasterboard production, water is added to the raw gypsum and remains in the product to set the gypsum (conversion of hemihydrate to dihydrate).

Water demand can be reduced by increasing the proportion of circulating water or by minimising the water losses.

In dry areas the cooling water demand can be reduced by installing special electrostatic precipitators which are operational at higher exhaust gas temperatures.

Any sanitary water produced must be discharged and disposed of separately.

2.4 Soils

In the area surrounding cement, lime and gypsum works the soils may be impaired by falling dust where the dedusting plants are inadequately maintained.

Although potentially environmentally relevant trace elements can be introduced into the cement production process by special raw material components such as iron ore and, more recently, by the increased use of combustible waste materials, these hazardous substances are almost completely absorbed by the cement clinker in the molten state, chemically bonded and therefore rendered harmless. To rule out the possibility of adverse effects when using special raw material components or waste products from other industries as fuel from the outset, analyses must be carried out te detect environmentally relevant trace elements such as lead (Pb), cadmium (Cd), tellurium (Tl), mercury (Hg) and zinc (Zn), which are deposited in the filter dusts. If necessary, technical measures such as dust separation must be applied to prevent the accumulation of hazardous substances in the process.

2.5 Workplace

Numerous machines generating noise levels of 90 dB(A) are still operated in cement, lime and gypsum works, even with the present state of the art. Noise levels can generally be reduced by means of static devices. Permanent workplaces inside the plants, e.g. control platforms, must be soundproofed, but if continuous noise levels of 85 dB(A) are still produced, hearing protection must be made available. At noise levels in excess of 90 dB(A) this protection must compulsorily be worn to avoid hearing impairment. Even where personnel remain in high-noise process areas for short periods, hearing protection is recommended.

In exceptional cases, e.g. during repair work or when rectifying faults, personnel may be exposed to high temperatures and higher levels of noise and dust for long periods, and suitable protective devices and protective clothing must be provided for these tasks. Moreover, work in the danger area must be restricted and supervised.

2.6 Ecosystems

Cement, lime and gypsum works require raw materials close to the surface, thus interference with the surrounding landscape cannot be avoided in the extraction of raw materials. The environmental effects of extraction are described in the environmental brief Surface Mining.

When selecting locations for cement, lime and gypsum works, due consideration must be given to the environmental aspects. In the case of locations in areas previously used for agriculture, possibilities for alternative employment must be examined, particularly for affected women. Besides complying with the regulations concerning waste gases, dust, noise and water, the conditions as regards the building land, integration in the landscape, and the infrastructure of the location must also be examined. Infrastructural considerations include, amongst other things, the recruitment and housing of employees, transport systems and traffic density and the existing and planned industrialisation of the area.

Since the environmental impact is not limited to the factory area, the local population, including women and children in particular, should be given access to medical care.

In cement production approximately 1.6 t of raw material per tonne of cement and additional quantities of gypsum are required, bringing the total raw material requirement to approximately 1.65 tonnes. In lime production the raw material requirement of approx. 1.8 t per tonne of finished product is about 10% higher than for cement production. In calculating this raw material requirement, the over-burden, which varies considerably from deposit to deposit, is not taken into account. In Germany most of the gypsum requirement could now be covered by the gypsum produced in flue gas desulphurisation plants, so that producing this raw material would no longer affect the landscape.

It is advisable to build up financial reserves for the subsequent recultivation of a quarry, even while the quarry is operational.

3. Notes on the analysis and evaluation of environmental impacts

Limit values for exhaust gas, dust and water have been formulated for dischargers of wastewater in the provisions of TA-Luft and TA-L (Technical Instructions on Air Quality Control and Technical Instructions on Noise Abatement), in the Guidelines adopted by the Association of German Engineers (VDI) and in the administrative regulations specific to the various industries. Similar values are being adopted by most European countries. The US regulations published by the Environmental Protection Agency (EPA) are frequently more stringent than the German regulations, particularly in California.

For countries without their own environmental protection laws, these values must be examined and adapted in the individual case, taking the prevailing environmental conditions into consideration. In exceptional cases, particularly for rehabilitation of plants, special regulations must be established, but new plants should conform to the European standard values for environmental protection.

The Compendium of Environmental Standards offers advice on assessing environmental relevance for individual substances.

Table 1 - Limitation of hazardous substances under TA-Luft (Technical Instructions on Air Quality Control) and the 17th Administrative Regulation according to § 7a of the Federal Water Act

Air

Water





Cement and lime, gypsum

mg/Nm3

Direct discharger g/m3

Sample type

Indirect discharger** g/m3



Dust

50



NOx nitrous oxide grill preheater

NOx

1.500



NOx nitrous oxide cyclone preheater

NOx



and exhaust gas heat utilisation

1.300



NOx nitrous oxide cyclone preheater

NOx



without exhaust gas heat utilisation

1.800



NOx nitrous oxide grill preheater

NOx



SOx sulphur oxide as SO2

SOx

400



Fluorides

F

5

50



Chlorine

Cl

30



Filterable solids

100

1)

1



Total suspended solids

TSS

0.5

2)

1



Chemical oxygen demand

COD

80



Antimony

Sb

5



Arsenic

As

1



Lead

Pb

5

0.50

2)

2



Cadmium

Cd

0.2

0.07

2)

0.5



Chromium

Cr

5

0.10

2)

2



Cobalt

Co

1

0.10

2)



Cyanides (*)

-CN

5

0.2



Copper

Cu

5

0.10

2)

2



Manganese

Mn

5



Nickel

Ni

1

0.10

2)

3



Palladium

Pd

5



Platinum

Pt

5



Mercury

Hg

5



Rhodium

Rh

0.2

0.05



Selenium

Se

1



Tellurium

Te

1



Thallium

Tl

5



Vanadium

V

0.2



Zinc

Zn

2.00

2)



Tin

Sn

5



*

May be formed in reduced burning

COD

Chemical Oxygen Demand

**

Law applicable in the German state of Baden-Wberg

TSS TA-Luft

Total Suspended Solids Technical Instructions on Air Quality Control

1)

Two hour mixed sample

VwV

Administrative Regulation

2)

Random sample

WHG

Federal Water Act

In developing countries dust emissions of 100 mg/Nm3 of exhaust gas or spent air should on no account be exceeded. Higher dust emissions will cause both internal and external environmental burdens.

Similarly, wastewater disposal should meet the minimum requirements imposed by the regulations laying down limits for dischargers of wastewater into receiving bodies of water.

The noise problem is underrated in many countries, but constant noise can lead to permanent damage. Here too, therefore, the prescribed noise limits must be adhered to in the workplace and in the surrounding residential areas (Section 2.2), and encroachment on residential areas must be prohibited.

All parameters must be regularly checked by means of internal audits, for which purpose training must be given and personnel generally sensitised to environmental matters if necessary.

The use of land by the cement, lime and gypsum industry must be kept within definable limits by forward-looking and detailed planning covering the areas of mining, recultivation and water management. The high costs often mean that there is no money available for recultivation of pits, often resulting in direct or consequential damage that may be difficult to repair (see environmental brief Surface Mining)

3.1 Inspection and maintenance of environmental protection installations

A control centre independent of the production process must be established to comply with existing environmental protection regulations. The responsible personnel must be enabled to perform and monitor all inspection functions including measurements relating to environmental protection in the works. They should be available for consultation on investments and take charge of negotiations with environmental protection authorities. Moreover, this department is responsible for ensuring that all environmental protection installations are regularly maintained and upgraded. This internal environmental department is also responsible for staff training.

4. Interaction with other sectors

Cement production may touch on other project areas, particularly where additional raw material components are used. For example, use is made of materials produced in lime works with inadequate lime content, other waste materials such as crystallised calcium carbonate from the chemical industry or ferrous residues from sulphuric acid production. Up to 5% gypsum per tonne of cement is required to control the rate of setting in the cement, and a major proportion of this gypsum requirement is now met in Europe by gypsum from flue gas desulphurisation plants. Up to 85% of fly ashes from power station dedusters and slags can also be added to the clinker to produce cement varieties with special properties.

Because of the high temperatures and comparatively long holding times of the materials in the relevant areas, cement kilns in particular are ideal for disposing of combustible waste. This possibility is increasingly important in countries where large quantities of vegetable waste with high potential energy, such as rice chaff, are produced in the region.

In the cement, lime and gypsum industry, secondary activities such as quarries, fuel stores, workshops etc. also exert environmental impact.

Table 2 - Environmental impacts of adjacent project areas - cement, lime and gypsum

Interacting project areas

Nature of intensification of impact

Environmental briefs

Extraction/storage of raw materials and fuels

- Landscape impairment - Pollution of bodies of water - Waste storage in former pits

Surface Mining Planning of Locations for Trade and Industry Urban Water Supply Rural Water Supply

Disposal of solid and liquid waste

- Discharge of deposited solids e.g. filter dusts - Pollution of bodies of water by wastewaters

Solid Waste Disposal Disposal of Hazardous Waste

Maintenance of workshops and transport facilities

- Risks of handling water pollutants (e.g. solvents) - Impacts of transport and traffic (noise, link roads)

Mechanical Engineering, Workshops Road Building and Maintenance Planning of Locations for Trade and Industry

5. Summary assessment of environmental relevance

The environmental impacts of cement, lime and gypsum works are caused by exhaust gas, dust, noise and water. The following table assigns values to the individual process stages as regards the environmental burden which they impose.

Table 3 - Environmental impact of process stages (cement/lime/gypsum)

Process

Air


Noise

Water1)

Soil

Work-place


Exhaust gas /flue gas

Dust





Extraction Precrushing Rough milling/mixing Burning Cement milling Lime slaking Packing Loading

1 1 2 3 1 2 1 1

1 1 3 3 3 3 2 2

2 3 4 3 4 2 1 1

2 1 2 2 2 3 1 1

3 1 2 2 2 3 1 1

2 2 3 3 2 2 1 1

Key: 1 very slight; 2 slight; 3 moderate; 4 considerable
1) dry process only

Proven technologies have been available for a good many years to reduce pollutant loads. In new plants for the cement industry in the industrialised countries, the costs of environmental protection measures, in the widest sense of the term, already account for as much as 20% of the total investment cost, and in the future this proportion will increase still further.

The more sophisticated the dedusting method, the greater the importance of systematic monitoring and maintenance for the continuing reliability and efficiency of the plants. Besides dedusting plants, changes in burning technology are becoming increasingly important for reducing NOx values.

Catering for the needs of the environment when planning and erecting cement, lime and gypsum works can also save money. The dusts generated are mainly preliminary, intermediate or end products which can reduce the direct production costs if recycled and returned to the process. Reduced ejection of dust also reduces wear on machines, thereby increasing their availability and saving repair costs.

The cement industry is becoming increasingly important as a recycler of waste materials such as food, waste oil or rubber tyres, thereby reducing the need for dumping. The initial fear that this disposal might lead to an increased emission of environmentally relevant trace elements has been allayed by measurements carried out during operation. When the materials are burnt, particular attention must be paid to correct firing, design and monitoring of the plants. Therefore the regulations concerning waste gas emissions and monitoring of such plants have been made more stringent.

The designers of a new plant must consider what environmental protection measures are necessary and appropriate as early as the planning phase. Suitable guidelines must also be established during the planning phase for countries which do not have their own regulations in this area.

Early involvement of neighbouring population groups in the planning and decision-making processes will enable measures to be devised to deal with any problems arising.

6. References

Erste Allgemeine Verwaltungsvorschrift zur Reinhaltung der Luft -TA-Luft - GMBl (joint ministerial circular) Nr. 24.

Allgemeine Verwaltungsvorschriften enehmigungsbede Anlagen nach § 16 der Gewerbeordnung GeWO (technische Anleitung zum Schutz gegen L - TA-L) verschiedene Ausgaben.

Allnoch, G. et. al.: Umweltvertrichkeitsprvon Entwicklungshilfeprojekten - Erstellung eines Kataloges von Emission- und Immissionsstandards, im Auftrag der GTZ Eschborn, 1984.

Betriebswacht, Datenjahresbuch 1991: Berufsgenossenschaft der keramischen und Glasindustrie, Wg.

Emissionsminderung Zementwerke VDI-Richtlinie 2094, Entwurf May 1981.

Entwurf zur Abwasserverordnung, Deutscher Industrie- und Handelstag, Anhang 17, Sept. 21, 1990.

Environmental Protection Agency: New source performance standards - Clean Air Act (USA).

Environmental Assessment Sourcebook Nov. 1990, Worldbank Draft Part 9.3-1 Cement /93-101, Mining and Mineral Processing 31.10.1990.

Funke, G.: Immissionsprognosen fehmigungsverfahren Zement, Kalk, Gips 33, p. 15-23, 1980.

GH.: Grenzen des Umweltschutzes aus der Sicht der Tagebau- und Steinbruchindustrie, Zement, Kalk, Gips 31, p. 252 - 254, 1978.

Gesetz zum Schutze vor Umwelteinwirkungen durch Luftverunreinigungen, Gerche, Erschngen und liche Vorge. Bundesimmissionsschutzgesetz - BImSchG - dated 15.03.1974 - BGBl. I (Federal Law Gazette I), p. 721 - 1193.

Hinz, W.: Umweltschutz und Energiewirtschaft Zement, Kalk, Gips 31, p. 215 - 229, 1979.

Luftreinhalte-Verordnung (LVR) Switzerland, of 16.12.1985, edition of 1 July 1990.

Luftreinhalteplan bei der Basel, February 1990.

Schulze, K.-H.: Immissionsmessungen und ihre Fehlergrenzen Zement, Kalk, Gips 36: p. 7 - 11, 1980.

Technical note on best available technologies not entailing excessive cost for the manufacture of cement: Commission of the European Communities, Report EUR 13005 EN, 1990.

Umweltschutz in der Steine - und Erden-Industrie Zement, Kalk, Gips 31, p. 215 - 229, 1979.

Verein Deutscher Zementwerke: Forschungsbericht der Zementindustrie, Tgkeitsbericht, 1978 - 1981 - VDZ Dorf 1981.

Ditto Tgkeitsbericht 1981 - 1984

Siebzehnte Verordnung zur Durchf des Bundesimmissionsschutzgesetzes 1990, (Verordnung erbrennungsanlagen fe und liche brennbare Stoffe, 17. BImSchV)

Zuke Probleme des Umweltschutzes in der Zementindustrie, Zement, Kalk, Gips 33: p. 1 - 9, 1980.

1. Scope

Fine, industrial and utilitarian ceramics cover the following industrial sectors:

- Ordinary ceramics: tiles, roof-tiles, earthenware, expanded clay, wall tiles and floor slabs, refractory products
- Fine ceramics: earthenware, pottery, fine earthenware, porcelain, electrical porcelain, sanitary products, grinding discs and abrasive wheels
- Technical ceramics

Most ceramics companies are established in the vicinity of clay deposits. (This environmental brief deals only briefly with the extraction of raw materials; for further details refer to the environmental brief Surface Mining. Advice on processing and transportation of raw materials is also given in the relevant environmental brief. The size of ceramic plants and their daily throughputs vary from a few kilograms for technical ceramic plants, normally 10 to 50 t/day for fine ceramics, to as much as 450 t/day in the tile industry. Since many companies operate different types of production, the total output of the works is often higher than the typical daily output of a specific product.

The fine, industrial and utilitarian ceramics industries use all types of clays, kaolins and fireclays (burnt clay), feldspars and sands as a raw material base. The refractory, abrasives and technical ceramics industries also use numerous high-temperature-resistant and abrasion-resistant oxides such as corundum (Al203), zirconium oxide (ZrO2) and silicon carbide (SiC).

Besides using their own, readily available raw materials, many companies are increasingly purchasing ready-processed raw materials, particularly for refractory products, abrasives and technical ceramics, as well as the raw materials required for glazes and frits.

The following process sequence is typical of the production processes in industrial, utilitarian and fine ceramics:

- extraction, processing, forming, drying, partial glazing or enamelling, firing, sorting/packing and transportation.

Execution of the individual process stages varies according to the selected method. Generally speaking, casting, plastic or drying processes are employed, with smooth transitions between the process stages.

Table 1 - Production processes

Casting processes

Plastic processes

Dry pressing processes

- Porcelain - Sanitary products - Electrical porcelain |- Refractory

- Tiles - Roof tiles - Expanded clay - Cleaving tiles - Electrical porcelain - Pottery - Earthenware

- Refractory products - Wall tiles, floor slabs - Pottery - Earthenware tiles - Technical ceramics - Steatite - Abrasive wheels

- In the casting process the raw materials are dosed, wet-ground and poured into plaster moulds as so-called slip. During pressure casting, the slip is shaped to produce the blank under pressure in machines.
- In the plastic process the raw materials are normally prepared in the wet state, mixed and shaped with moisture content of 15 - 20% water.
- In the dry pressing process used in fine ceramics, the raw materials are frequently prepared in the wet state, then dried in a spraying tower to a residual moisture content of 5-7%. In the refractory industry the raw materials are mixed dry and are often processed with pressing moisture content of less than 2%, also using organic and inorganic binding agents.

The moulded products are dried and then fired. They are generally fired in high-power tunnel kilns; special products are fired mainly in individual, hood-type or batch kilns, while fast-burning products are fired in roller hearth kilns of various designs. In many countries, tile products in particular are often fired in self-built single-chamber and ring kilns or in charcoal kiln systems.

Many fine ceramic products are glazed or enamelled before firing.

Depending on the raw materials used, the firing temperatures in industrial, utilitarian and fine ceramics begin at 950°C for some tile products, for example, whereas most fine ceramic products are fired at between 1100°C and 1400°C. Refractory and technical ceramic products have firing temperatures of 1280 to 1900°C. (Pure glaze baking is done at lower temperatures.) The dual firing process is sometimes used for porcelain and very rarely for wall tiles.

Energy consumption depends on the product and the process; in the tile industry, because of the low firing temperatures, it is between 800 and 2100 kJ/kg of manufactured product, but in almost all other areas of industrial, utilitarian and fine ceramics it is on average much higher per manufactured product, and may be as much as 8000 kJ/kg of product.

After firing the products must be sorted and sometimes reworked, which will involve varying labour costs depending on the product.

2. Environmental impacts and protective measures

2.1 Air

2.1.1 Waste gases/flue gases

Hardly any waste gases are produced in the extraction, processing and moulding of ceramic products. Exceptions to this are the demoisturisation in the spraying tower, e.g. during the production of tiles, and the dry crushing plants used in clay processing, where harmless water vapour is given off.

During the glazing process, care must be taken to prevent glazing vapours, some of which contain heavy metals and other toxic substances, being discharged to the environment or being inhaled by personnel. Therefore only glazing plants which are equipped with the necessary extraction and wastewater discharge equipment should be licensed. Operating or maintenance personnel working in this area must be protected by breathing filters. When the glazed products are dried, mainly harmless water vapour is given off.

The amount of flue gas produced during firing depends on the emission of the fired product and on the type of fuel used. Volatile components are sometimes given off from the product mass and from the fuel.

The adverse environmental effects of fluorine emissions from the ceramics industry have come to be recognised as a serious problem, particularly in recent years, in view of the damage occurring in the vicinity of ceramic works (animals and plant diseases). Fluorides are present in all ceramic raw materials and are sometimes emitted in the waste gas during firing. Because of this, fluorine emissions from new plants built in Europe must be less than 5 mg/Nm3.

Because ceramic firing plants operate continuously, residual substances from other sectors such as waste oils or organic components from water treatment plants are sometimes used as fuel additives. Plants which use such materials are subject to special regulations because dangerous oxides may be introduced via these waste substances and re-emitted with the flue gas.

German companies must conform to the following values when burning waste substances:

- Total dust 10 mg/Nm3 max.

Sulphur dioxide 50 mg/Nm3 max.
Cd, Tl, Hg, 0.1 mg/Nm3 (per element)
(cadmium, tellurium, mercury)

Other heavy metals 1 mg/Nm3

Because of these conditions, waste substances cannot be used in the ceramic industry without the installation of additional water-spray separators.

Nitrous oxide emission during firing appears not to be a problem in most plants which are operated at relatively low temperatures, but special solutions must be found for high-temperature firing plants in the refractory industry for denitrifying the waste gases.

No waste gases are generally produced during sorting, packing, internal conveying, processing or refining. Only in very rare cases, e.g. during subsequent colouring or printing, may environmental pollution be caused by waste gases. These problems must be solved on a case-to-case basis.

2.1.2 Dust

Dust presents a latent risk in fine, industrial and utilitarian ceramic plants, particularly for the labour force. Fine quartz dusts < 5 µm may cause silicosis.

Depending on the geological and meteorological conditions, dusts may occur in pits during extraction of the raw materials which can be reduced by wetting and by the use of appropriate extracting and conveying methods. (See environmental brief Surface Mining).

Whilst hardly any dust is produced in the wet medium of the plastic processes, in the preparation, moulding and drying processes a variety of methods can be adopted to minimise dust formation, such as continuous cleaning of the works, concreting and sealing of floors, efficient dedusting systems and wet grinding of porcelain and sanitary products.

Silicosis in the German porcelain and refractory industry, particularly in the case of silicate products, has been successfully minimised by systematic dust control in all working areas, but in many countries it is still a problem. The statutory limits for quartz dusts impose a maximum allowable concentration (MAK) of 0.15 mg/Nm3 of fine dust, and the air may contain no more than 4 mg/Nm3 of fine dust containing more than 1% by weight of quartz.

In Germany according to TA-Luft [Technical Instructions on Air Quality Control] the total dust content must not exceed 50 mg/Nm3 in the waste gas at a mass flow of more than 0.5 kg/h, or 150 mg/Nm3 at a mass flow up to and including 0.5 kg/h.

During firing the dust burden is generally very slight. Dry filters are now frequently installed in kilns, water-spray separators more rarely. Dry absorption systems may create dust, thus care must be taken to ensure that when such systems are used the maximum dust quantity of 50 mg/Nm3 in the flue gas is not exceeded. These plants require regular maintenance to preserve their efficiency (see 3.1).

2.2 Noise

In most production processes in the ceramic industry, noise is emitted but rarely exceeds 85 dB(A) (see 2.5 - Workplace).

During the extraction of raw materials, noise and associated vibrations may occur for a short time as a result of blasting, sometimes causing a serious nuisance to residents living close by. However, such noise can be substantially reduced by means of suitable detonation methods. The machines used for mining can now be soundproofed to such an extent that they meet the noise protection requirements. (See environmental brief Surface Mining).

During dressing, noise pollution is liable to occur e.g. through the use of rebound crushers and mills for the crushing of hard materials. These crushing installations and the adjoining dressing installations can be encapsulated or soundproofed in such a way as to protect the environment from oppressive noise.

During the drying and firing phases, fans are used which may generate noise levels in excess of 85 dB(A). These noise sources must be installed outside permanent workplaces. During special ceramic production processes, e.g. when splitting cleaving tiles and when using sheet metal plates, frames or pallets for internal conveying systems, typical noise problems arise. However, such noise levels can be reduced by taking appropriate measures, e.g. encapsulating permanent workplaces and buffering mobile conveying systems with rubber.

To avoid noise nuisance the immission values for the residential areas located close to the ceramic production centres should not exceed 50 - 60 dB(A) during the day and 35 - 45 dB(A) at night. Housing developments should be sited at least 500 m from a ceramic factory.

2.3 Water

In Germany, ceramic works must comply with the administrative regulations regarding permitted substances in the wastewater.

Works laboratories must be established to monitor the works in question.

Table 2 - Maximum permissible values for direct dischargers according to the 17. VwV of the WHG
[17th Administrative Regulation of the Federal Water Act]

Parameters

Maximum value

Filterable solids from the 2-hour mixed sample Total suspended solids from the random sample Chemical oxygen demand (COD) from the 2-hour mixed sample Lead content from the 2-hour mixed sample Cadmium content from the 2-hour mixed sample

100 ml 0.5 mg/l 80 mg/l 0.5 mg/l 0.07 mg/l

To avoid exceeding the applicable values, the water produced in the area of the pit must be fed through stilling basins, with the addition of sedimenting agents if necessary. The surface water occurring in the area surrounding the pit must be discharged separately.

Fresh water consumption in modern ceramic plants is low because the water required for the process is circulated internally. Some of the water used is driven off again as water vapour in the production of granulates in the spray tower and in the drying of the products. Wastewaters produced contain clay, flux and other ceramic raw materials which are precipitated and returned to the process by internal circulation.

Sanitary water produced in fine, industrial and utilitarian ceramic works must be discharged and disposed of separately.

2.4 Soils

Nowadays old clay pits are frequently used for storing waste products of all kinds, because of their relatively low water permeability. Soil damage may occur due to elutriation and water accumulation in old pits, because when the pit was worked, water management was not normally up to present-day environmental standards.

Soil is rarely impaired by spoil from ceramic works because the waste generated during production is reused in the plant’s own production or in other ceramic works, so that spoil dumps are only formed where the plant is operated inefficiently. Exceptions to this are the small quantities of gypsum produced during porcelain, sanitary and roof tile production, which have to be properly disposed of.

2.5 Workplace

Personnel working in ceramic plants may be endangered or oppressed by noise, dust and heat in certain work areas.

Permanent workplaces near sources of loud noise must be soundproofed. If the noise level is still not less than 85 dB(A) despite soundproofing measures, hearing protection must be made available, and from 90 dB(A) upwards it must be compulsorily worn to prevent resulting hearing impairment. Hearing protection must also be worn by personnel working in high-noise production areas for short periods.

During firing in tunnel, reciprocating, roll-over or bogie hearth kilns, temperature stress on personnel is relatively low in modern plants, but in plants with old single chamber and ring kilns, there may be considerable exposure to heat when the product is inserted and removed. In special cases, e.g. if a tunnel kiln car caves in, work must be carried out for a short time under conditions of extremely high temperature. In this case, strict protective measures, e.g. the wearing of thermal suits, must be complied with. Moreover, such work must only be carried out under appropriate supervision.

In fine ceramic works, particularly in the porcelain and silicate industry (refractory products), personnel may be at risk from continuous exposure to quartz dust. In addition to technical precautions, regular medical check-ups are essential here to ensure that fibrotic changes (changes in the pulmonary alveoli) are detected early, so that the employee in question can be protected from permanent injury through redeployment.

2.6 Ecosystems

When raw materials are extracted the landscape is impaired and there is an alteration to the surface (see environmental brief Surface Mining). Since the raw material requirement per plant is not very high, the individual mining areas are generally also relatively small. Many different types of clay are present in each clay pit, and with the introduction of suitable processing methods even low quality clays have been successfully processed in recent years, thereby reducing the amount of spoil in the vicinity of clay pits.

When selecting a site for a ceramic plant, due consideration must be given to the environmental aspects. In the case of locations in areas previously used for agriculture, possibilities for alternative employment must be examined, particularly for affected women. Besides complying with the regulations concerning waste gases, dust, noise and water, the conditions as regards the building land, integration in the landscape, and the infrastructure of the location must also be examined.

Infrastructural considerations include, amongst other things, the recruitment and housing of employees, transport systems and traffic density and the existing and planned industrialisation of the area.

Since the environmental impact is not limited to the factory area, the local population, including women and children in particular, should be given access to medical care.

Recycling of fine ceramic consumer goods, after use on or in buildings or in the home, is hardly feasible because of the variety of materials and small quantities involved at the points of consumption. On the other hand, in the refractory industry, particularly in steel works, over 30% of the refractory products are recycled.

3. Notes on the analysis and evaluation of environmental impacts

Emission limits for waste gas, dust and water have been formulated in the provisions of the German TA-Luft and TA-L [Technical Instructions on Air Quality Control and Technical Instructions on Noise Abatement], in the guidelines adopted by the Association of German Engineers (VDI) and in the regulations specific to the various industries for dischargers (under the WHG - German Federal Water Act) and MAK (maximum allowable concentration) values have been established by the Berufsgenossenschaft (employers' liability insurance association) of the ceramic and glass industry for avoiding silicosis. These emission limits are being adopted in similar form by most European countries. The US regulations published by the Environmental Protection Agency (EPA) are frequently even more stringent than the German regulations, particularly in California.

For countries without their own environmental protection laws, these values must be examined taking into consideration the prevailing environmental conditions in the individual case and adapted to the particular circumstances. In exceptional cases, particularly for rehabilitation of plants, special regulations must be established, but new plants should conform to the standard values of environmental protection.

The Compendium of Environmental Standards offers advice on assessing environmental relevance for individual substances.

Table 3 - Limitation of hazardous substances under TA-Luft (Technical Instructions on Air Quality Control) and the 17th Administrative Regulation according to § 7a of the German Federal Water Act

Air

Water





Ceramics

mg/Nm3

Direct discharger g/m3

Sample type

Indirect discharger** g/m3



Dust

50



Sulphur dioxide as SO2

SO2



at a mass flow < 10 kg/h

500



Sulphur dioxide as SO2

SO2



at a mass flow > 10 kg/h

1,500



Nitrous oxide NOx

NOX

500



Fluorides

F

5

50



Chlorine

Cl

30



Filterable solids

100

1)

1



Total suspended solids

TSS

0.5

2)

1



Chemical oxygen demand

COD

80



Antimony

Sb

5



Arsenic

As

1



Lead

Pb

5

0.50

2)

2



Cadmium

Cd

0.2

0.07

2)

0.5



Chromium

Cr

5

0.10

2)

2



Cobalt

Co

1

0.10

2)



Cyanides (*)

-CN

5

0.2



Copper

Cu

5

0.10

2)

2



Manganese

Mn

5



Nickel

Ni

1

0.10

2)

3



Palladium

Pd

5



Platinum

Pt

5



Mercury

Hg

5



Rhodium

Rh

0.2

0.05



Selenium

Se

1



Tellurium

Te

1



Thallium

Tl

5



Vanadium

V

0.2



Zinc

Zn

2.00

2)



Tin

Sn

5



May be formed in reduced burning

COD

Chemical Oxygen Demand

**

Law applicable in the German state of Baden-Wberg

TSS TA-Luft

Total Suspended Solids Technical Instructions on Air Quality Control

1)

Two hour mixed sample

VwV

Administrative Regulation

2)

Random sample

WHG

Federal Water Act

When waste materials are used as fuel, the above emission limit values must on no account be exceeded, and regular inspection of the charge material, firing system and process, as well as of the waste gases and dusts, is essential (see 3.1).

It is vital that the dust regulations, based on the maximum allowable concentrations in the workplace, are adhered to, particularly in the porcelain and silicate industry. Non-compliance with these regulations leads to diseases with long-term consequential damage. Intensive dust abatement in all plants and in all sections of plants is imperative in this regard also.

The noise problem is underrated in many countries, but constant noise can lead to permanent damage. Here too, therefore, the prescribed noise limits must be adhered to in the workplace and in the surrounding residential areas, and encroachment on residential areas must be prohibited (see 2.2 and 2.5).

Managers of ceramic production plants must be alerted to the specific risks to employees and must be trained in the use of protective measures so that employees are not exposed to health hazards through ignorance (see 3.1). Suitable training must be given and personnel generally made aware of environmental concerns.

In all plants an internal water circuit must be carefully planned. Treated wastewaters which are discharged into receiving bodies of water are subject to minimum requirements which must be met to avoid damage to the ecosystem in areas close to the works.

All the parameters must be regularly checked by internal audits (see 3.1), and works laboratories must be set up to monitor adherence to the specified values.

3.1 Inspection and maintenance of environmental protection installations

A control centre independent of the production process must be established to comply with existing environmental protection regulations. The responsible personnel must be enabled to perform and monitor all inspection functions including measurements relating to environmental protection in the works. They should be available for consultation on investments and take charge of negotiations with environmental protection authorities. Moreover, this department is responsible for ensuring that all environmental protection installations are regularly maintained and upgraded. This internal environmental department is also responsible for staff training.

4. Interaction with other sectors

In the ceramic industry, interaction between different branches of production is common and is often necessary for a smooth production process. Fine, industrial and utilitarian ceramic works rely on numerous secondary operations, such as extraction plants, fuel stores, workshops and transport systems involving a number of other sectors.

Table 4 - Environmental impacts of adjacent sectors - fine, industrial and utilitarian ceramics

Interacting sectors

Nature of intensification of impact

Environmental briefs

Extraction/storage of raw materials and fuels

- Landscape impairment - Pollution of bodies of water - Waste storage in former pits

Surface Mining Planning of Locations for Trade and Industry Urban Water Supply Rural Water Supply

Disposal of solid and liquid waste

- Discharge of deposited solids e.g. filter dusts - Pollution of bodies of water by wastewaters

Solid Waste Disposal Disposal of Hazardous Waste

Maintenance of workshops and transport facilities

- Risks of handling water pollutants (e.g. solvents) - Impacts of transport and traffic (noise, link roads)

Mechanical Engineering,Workshops Road Building and Maintenance Planning of Locations for Trade and Industry

All ceramic products must be packed, and the packing materials required for this purpose must be disposed of or recycled after use. Environmental impacts can be avoided in this area by making use of modern processes employed in the packaging industry. Moreover, the ceramic industry is highly transport intensive, since tiles, roof tiles, cleaving tiles and refractory products have high bulk weights and therefore require suitable means of transport.

5. Summary assessment of environmental relevance

The individual process stages in the industrial, utilitarian and fine ceramic industry do not generally give rise to severe environmental burdens.

Table 5 - Environmental impact of process stages (ceramics)

Process

Air


Noise

Water1)

Soil

Work- place


Exhaust gas /flue gas

Dust





Extraction Preparation Moulding Glazing Drying Firing Sorting Packing Internal transport Processing/ Refining

1 1 2 3 2 3 1 1 1 1

2 3 2 3 1 1 1 1 1 2

2 3 2 2 2 3 3 1 1 2

3 2 1 3 1 1 1 1 1 2

3 1 1 2 2 2 1 1 1 2

1 2 2 3 1 1 2 1 2 2

Key: 1 very slight; 2 slight; 3 moderate; 4 considerable
1) Depending on composition

Particularly dangerous in the case of free quartz with grain sizes smaller than 5 µm

Moreover, numerous measures to protect employees and the environment have been introduced through modernisation of the technologies applied and by installing protective equipment, e.g.:

- Surface mining: pit problems can be overcome by suitable mining planning, water management and recultivation.
- Internal water circuits and downstream stilling basins minimise the wastewater burden.
- Soundproofing of systems and processes prevents long-term hearing impairment.
- Fluorine and sulphur dioxide emissions are reduced to the required levels in the waste gas by controlling the firing processes or by means of downstream separation systems.
- The risk of silicosis is eliminated in relevant plants by technological improvements and dedusting systems, and is monitored by staff conducting routine preventive checks.

The environmental protection installations required in ceramic works may account for as much as 20% of the total investment costs. To achieve the desired results from the equipment in the long term, its efficiency must be guaranteed by proper maintenance. Improvements in the area of personnel and environmental protection can only be achieved by providing proper information and training.

Early involvement of neighbouring population groups in the planning and decision-making processes will enable measures to be devised to deal with any problems arising.

In countries which have no legal guidelines it should be ascertained as early as the planning stage, based on the raw materials to be used and the process technology applied, what environmental protection measures are necessary and appropriate. Environmental protection equipment provided should be of robust design so that the life of this equipment is appropriate to the overall project and so that simple, low-cost maintenance can be guaranteed.

6. References

Allgemeine Verwaltungsvorschrift enehmigungsbede Anlagen nach §16 der Gewerbeordnung - GewO.: Technische Anleitung zum Schutz gegen L (TA-L), 1985.

Siebzehnte Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer - 17. Abwasser VwV-, GMBL (joint ministerial circular) 1982.

Bauer, H.D., Mayer, P.: Zusammenf staubtechnischer Daten und arbeitsmedizinischer Befunde am Beispiel von Asbesteinwirkungen, Sonderdruck aus "der Kompa91, Nr./1981.

Betriebswacht, Datenjahresbuch 1991: Berufsgenossenschaft der keramischen und Glas- Industrie, Wg.

1. Bundesimmissionsschutzgesetz (BImSchG), 1985.

Entwurf zur Abwasserverordnung Deutscher Industrie- und Handelstag, Anhang 17, Sept. 21, 1990.

Environmental Assessment Sourcebook: Environmental Department, November 1990, Draft, World Bank.

Industrial Minerals and Rocks: 5th Edition 1983.

Mayer, P.: Grenzwerte fest am Arbeitsplatz und in der Umwelt unter besonderer Berhtigung der keramischen und Glas-Industrie "Sprechsaal" 1/80, 1980.

Mining and Mineral Processing: Environmental Department World Bank, October 1990, Draft.

Mineral Commodity Summaries U.S.: Department of the Interior, Bureau of Mines, 1991.

Guidelines of the German Federal Ministry of the Interior (Bundesdesministerium des Inneren) regarding BImSchG -Zugelassene Stellen zur Ermittlung von Luftverunreinigungen im Emissions- und Immissionsbereich nach BImSchG - Guidelines of the Council of the European Community

Schaller, K.H.; Weltle, D.; Schile, R.; Weissflog, S.; Mayer P. und Valentin, H.: Pilotstudie zur Quantifizierung der Bleieinwirkung in der keramischen und Glas-Industrie, Sonderdruck aus "Zentralblatt" Zbl: Arbeitsmed. Bd.31, Nr.11, 1981.

Schlandt, W.: Umweltschutz in der Keramischen Industrie, Beilage zur Keramischen Zeitschrift 36, Nr.10, 1984.

TA-Luft (Technische Anleitung Luft): Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft-), 1986.

Siebzehnte Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes 1990 (Verordnung erbrennungsanlagen fe und liche brennbare Stoffe, 17. BImSchV).

1. Scope

The main raw materials used by the glass industry are sand, lime, dolomite, feldspar, as well as soda, borosilicates and numerous additives which embrace practically the entire periodic system of elements. Its products are a large number of glasses with different properties, many of them further processed after manufacture (Table 1).

Table 1 - Glass products

Container glass

Sheet glass

Utility glass and special glass

- Tall jar - Preserve jar - Medical glass - Packing glass

- Sheet glass (float glass) - Casting glass - Moulding glass - Wire (reinforced) glass

- Optical glasses - Lighting glass - Glass hardware - Laboratory glass - Flasks

Lead crystal and

Mineral fibres

- Bleaching glass - Goblet glass - Television tubes - Glass fibres for optical transmission

- Glass fibres - Mineral fibres - Borosilicate fibres - Ceramic fibres (high-temperature resistant)

In the modern glass industry the raw materials are no longer generally extracted by the companies themselves but are purchased in the desired chemical and physical composition, e.g. in terms of granulation, moisture content, impurity (for the environmental relevance of the extraction of raw materials refer to the environmental brief Surface Mining). The substantial differences between the materials to be dosed and mixed necessitate the use of mixing and processing plants where the mixtures are melted in tank furnaces, more rarely in pot furnaces, or special furnaces. Cupola furnaces are still sometimes used for mineral fibres, and electric melting systems are used for manufacturing ceramic fibres. The flue gases formed during melting are nowadays cooled by regenerative or recuperative plants, thereby reducing the specific fuel consumption.

After melting, the glasses are moulded. Most glasses must then be cooled according to the subsequent application, to avoid glass stresses. Glasses are frequently further processed by thermal, chemical and physical post-treatments, such as clamping, pouring, bending, gluing, welding and grinding. Hollow glassware is frequently decorated. Fibres are drawn, centrifuged, blown or extruded after melting, using a variety of technologies.

The capacities of the individual glass-producing companies vary considerably, and it is often the case that several melting systems with different production programmes are combined in one works. Pot furnaces have a capacity of 3-8 t/day, whilst the tank capacities for special glasses range from 8 to 15 t/day in most cases. In specialist fields, however, the outputs are much higher, e.g. tanks for container glass melt between 180 and 400 t/day, float glass tanks attain melting capacities of between 600 and 1000 t/day.

The melting temperatures of the glass generally range between 1200 and 1500°C, the temperature depending for the most part on the mixture and the product to be manufactured. The amount of energy required to melt 1 kg of glass is between 3700 and 6000 kJ. The capacities and energy consumptions indicated above are average values which depend on the design and operating time of the tank, the production programme and the actual tank load. The specific energy consumption should be reduced by the use of waste fragments wherever possible.

2. Environmental impacts and protective measures

2.1 Air

2.2.1 Waste gases/flue gases

In a glass works waste gases are formed during melting of the glass as a result of combustion of the fuels used. In addition to the combustion residues, such as sulphur dioxide (SO2) and nitrous oxides (NOx), flue gases also contain compound components such as alkalis (Na, K), chlorides (-Cl), fluorides (-F) and sulphates (-SO4).

Sulphur dioxide (SO2)

Sulphur dioxide or SOx emissions, made up of SO2 + SO3, lie within the range of 1100 to 3500 mg/Nm3 of waste gas in the case of regeneratively heated glass tanks within one firing period. Where the chambers are insufficiently scrubbed much higher peak values, as high as 5800 mg/Nm3 of waste gas, are found at the start of the firing change.

Electrically heated or electrically booster-heated tanks can be operated continuously at a lower SOx load (< 500 mg/Nm3). On the other hand, the use of heavy oil with a very high sulphur content (up to 3.7%) gives rise to extremely high emission values. Natural gas, which does not normally contain any sulphur, does not affect the formation of SOx. Some of the sulphur emission is also caused by the addition of sulphate to the mixture.

The currently applicable Technical Instructions on Air Quality Control (TA-Luft 1986) indicates a maximum value for sulphur dioxide of 1800 mg/Nm3 of waste gas, thus in normal glass tanks absorption of the excess sulphur dioxide is required. The sulphur dioxide content can be reduced by feeding magnesium, calcium carbonate and soda into the flue gas. The dusts forming during this process must also be filtered out again.

Nitrous oxides (NOx)

A further environmental problem in glass manufacture is posed by the NOx loads occurring, which can range from 400 to 4000 mg/Nm3 of waste gas. During nitrate refining, i.e. the reduction of the proportion of bubbles or nodules in the glass mass by nitrates, these values are considerably increased. The Nox content depends on the air preheating temperature, the air coefficient (excess air) and the process and type of tank used. NOx content can be reduced using catalysts with ammonia (NH4). This process, which is currently undergoing large-scale trials, promises to reduce NOx content to below 500 mg/Nm3 NOx load.

The NOx limits applicable in Germany (1991) for the different tanks are summarised in Table 2.

Table 2 - Nitrous oxide emissions under applicable version of TA-Luft
[Technical Instructions on Air Quality Control]

Plant

Oil-fired mg/Nm3

Gas-fired mg/Nm3

Pot furnaces

1200

1200

Tanks with recuperative heat recovery

1200

1200

Day tanks

1600

1600

Horseshoe flame tanks with regenerative heat recovery

1800

1800

Cross-burner tanks with regenerative heat recovery

3000

3000

Values attainable for electrically heated tanks

500

The emission values of nitrate-refined tanks must not exceed twice the above-mentioned values.

Fluorine/chlorine

The fluorine contents of the waste gas (calculated as HF) must not exceed certain values since plants and animals can be harmed by fluorine. Fluorides are contained in almost all raw materials used in glass manufacture. Through the addition of waste fragments originally melted with fluorspar to the melting process, the fluorine concentration in the waste gas may exceed 30 mg/Nm3.

The low fluorine limit value prescribed in Germany under TA-Luft 1986 of < 5 mg/Nm3 can only be achieved through systematic selection of raw materials or through additive reactions with calcium and alkali compounds.

Chlorine compounds, which are introduced into the mixture primarily through soda or salt-contaminated raw materials, also cause problems. Measurements have indicated gaseous chloride concentrations of between 40 and 120 mg/Nm3 of waste gas. Problems with gaseous chlorine emissions (HCl) arise mainly in heavy-oil-fired plants. Like sulphur dioxide, chlorides must also be absorbed by calcium or sodium compounds in the mixture.

2.1.2 Dust

One problem area in the glass industry is the dust emission of the glass melting furnaces caused by the high temperatures, and the evaporation of mixture components which sublimate as fine dusts. The dust concentration of different melting tanks without filters is indicated in Table 3.

Table 3 - Dust concentration in the waste gas of glass tanks - Measured values -

Glass type

Firing

Dust in the waste gas1) mg/mg3

Soda-lime glass Soda-lime glass Potassium crystal glass Lead glass Borate glass Borosilicate glass fibres

Natural gas Fuel oil S Natural gas/Fuel oil EL Natural gas/Fuel oil EL Natural gas/Fuel oil EL Natural gas/Fuel oil EL

68 - 280 103 - 356 45 - 402 272 - 1000 120 - 975 1425 - 2425

1) Waste gas in the normal condition, 8% oxygen in the waste gas

The values indicated in the table show that glass furnaces without filter systems have high dust concentrations in the waste gas. The prescribed limits of 50 mg/Nm3 of dust in Germany (TA-Luft 1986) are difficult to achieve without dedusting plants. Electrostatic dust precipitation, fabric dust filters with sorption or wet scrubbing may be used, depending on the type and capacity of the furnace. However, the dedusting systems must also help to reduce fluoride, sulphate and chloride emissions, as well as toxic heavy metals.

Emissions of lead, cadmium, selenium, arsenic, antimony, vanadium and nickel are particularly critical. These environmentally harmful dusts, which are formed primarily during the manufacture of special glasses in the waste gas, can only be separated by dust filters.

2.2 Noise

The noise generated is particularly significant in the glass industry during melting, moulding and cooling and in the chambers of the compressors, whilst hardly any problematic noise loads are generated in the areas of extraction, processing, packing and finishing.

In the furnaces noise levels of up to 110 dB(A) may be reached during melting and in the feeder. The large fans which produce the quantities of air required and the compressors also generate relatively high levels of noise. However, few workplaces are situated in the vicinity of these noise sources. In modern works these workplaces are provided with static noise protection devices. The control systems of the plants can be soundproofed or can be installed outside the noise zone. Hearing protection must be worn for short-term working in these zones.

An extremely critical area in terms of noise emission, which is also affected by high temperatures and oil vapours, is the container glass moulding area with compressed-air-controlled machines; here the noise load generally exceeds 90 dB(A). In recent years improvements have been made with modified air guides. So far, attempts to enclose the machines for soundproofing purposes have been unsuccessful because of the need for regular oil lubrication of the units and cleaning of the moulds. When the glasses are cooled, noise is generated by fans but can be reduced by suitable designs and enclosures.

To avoid noise nuisance, glass works must be erected at least 500 m away from areas of habitation. The distance from residential areas should be such that no more than 50 to 60 dB(A) is immitted during the day, and no more than 35 - 45 dB(A) during the night.

2.3 Water

The total water consumption per tonne of glass produced varies considerably. Circulating systems should be installed so that only small quantities of additional fresh water are required. The main water-consuming areas of a glass works are:

- cooling of the compressors required for generating compressed air
- cooling of the diesel units sometimes used for power generation
- quenching basins for excess glass
- finishing and refining of glass by grinding, drilling etc.

The wastewater produced in these sectors is cooled and reused, but part is also tapped for other functions, such as:

- moistening the mixture for dust prevention
- cooling of flue gases, particularly in EGR dedusting plants
- moistening of lime products for dry sorption filter plants.

The average water consumption in a glass works should be less than 1 m3/t of glass produced. The cooling water of the cutting devices and moulding machines, the compressors, any emergency power diesel generators used and also the water from the quenching basins underneath the production machines may be contaminated by oil. This effluent must be cleaned by oil separators. In Germany, if water is discharged it must meet the minimum requirements regarding discharge of effluent into watercourses (direct dischargers). By virtue of these regulations no more than 0.5 mg/Nm3 of depositable substances may reach the effluent in glass production.

Special disposal arrangements are required for the sewage produced (see the environmental brief Wastewater Disposal).

2.4 Soils

In the area surrounding modern glass works which meet the existing environmental regulations regarding waste gas and dust, are equipped with the necessary cleaning systems and have a suitable internal wastewater circuit and water separator, there is unlikely to be any contamination of the soil or consequent damage to plants or animals.

2.5 Workplace

Employees of glass works may be endangered or oppressed particularly by noise and in certain workplaces by heat. Hardly any dust problems arise in well-maintained glass works, but in special cases, e.g. in the manufacture of special glasses, toxic dusts may pose a health hazard.

In principle no workplace within a plant should be exposed to a continuous noise level in excess of 85 dB(A); at this level hearing protection should be provided, and from 90 dB(A) protection must be worn in all cases. Hearing protection is compulsory in noise-intensive process areas, even when employees remain there only for a short time.

So far it has not been possible, for technical reasons, to enclose glass moulding machines, particularly the noisy container glass machines, or to automate them completely, so that employees must wear hearing protection in these areas. Noise from burner systems, fans and compressors can easily be avoided; firstly there are hardly any workplaces in the vicinity of these machines, and secondly the control units of the machines can be screened against dust, heat and noise. When carrying out maintenance and repair work, employees must wear the prescribed hearing protection and, if necessary, protective clothing.

In the event of stoppage or unexpected breakdown of tanks or faults in the preheating system very high temperatures may occur, since some tanks are operated at temperatures in excess of 1500°C. Work in such emergency situations must be carried out under supervision, and protective devices to facilitate the work, such as thermal protective suits, must be available in all works in case of emergency. Contingency plans must be drawn up and regular drills carried out to ensure rapid, targeted intervention in emergency situations.

According to recent studies, glass and mineral fibres are suspected of having carcinogenic effects. Regular medical examinations should therefore be carried out in glass works to identify any problems arising at an early stage and forestall adverse consequences.

2.6 Ecosystems

Glass works process 70 - 80% natural raw materials (sand, feldspar, dolomite, lime), but these are not generally extracted in the vicinity of the works. About 75% of the natural raw material is quartz sand which nowadays is rarely extracted by the glass works themselves. The soda required is manufactured in Germany synthetically from salt (NaCl) and carbon dioxide, the latter being extracted from limestone. Soda may also be extracted from natural deposits occurring mainly in the USA. Certain of the other raw materials are synthetic or cleaned raw materials such as sodium and boron compounds.

Approximately 1.2 - 1.3 tonnes of raw materials are required to melt one tonne of glass, but the area required for extracting the glass raw materials cannot be determined accurately because the deposits in question are not used exclusively for the glass industry and the extraction levels vary considerably.

If a works carries out its own extraction, the environmental protection aspects must be considered as early as the extraction planning phase, particularly as regards water management and the constant need for recultivation. The extraction and recultivation costs must be added to the raw material costs (see the environmental brief Surface Mining).

When selecting the site of a glass production centre, the environmental factors must also be taken into account. In the case of sites in areas which have so far been used for agricultural purposes alternative sources of income must be examined, particularly for affected women. Besides complying with the applicable regulations regarding waste gas, dust, noise and water, the subsoil conditions, landscaping and infrastructure must also be examined. The infrastructure includes, among other things, recruitment and housing of employees, traffic and transport systems and the existing and planned industrialisation of the area.

Since the environmental impacts are not limited to the works area, the population groups concerned, particularly women and children, should be provided with access to medical care.

The addition of a recycling system for waste glass may on the one hand reduce the energy requirement for glass manufacture and on the other hand substantially relieve pressure on refuse tips. In a similar vein, disposable packaging systems should be replaced by reusable packaging systems.

3. Notes on the analysis and evaluation of environmental impacts

The limits - based on TA-Luft (Technical Instructions on Air Quality Control) and TA-L (Technical Instructions on Noise Abatement) and other regulations - summarised in Table 4 for waste gas, dust and noise are now applicable in Germany and are being adopted in similar form by most European countries. The minimum requirements in Germany regarding treated wastewater discharged into receiving bodies of water are also indicated.

Table 4 - Limitation of hazardous substances under TA-Luft (Technical Instructions on Air Quality Control) and the 17th Administrative Regulation (VwV) according to § 7a of the Federal Water Act (WHG)

Air



Water





Glass industry

mg/Nm3


Direct discharger g/m3

Sample type

Indirect discharger3) g/m3


Dust Sulphur dioxide as SO2 Glass melting furnaces Pot furnaces and day tanks NOx nitrous oxide as NO2 Fluorides Chlorine Filterable solids Total suspended solids Chemical oxygen demand Antimony Arsenic Lead Cadmium Chromium Cobalt CyanideS2) Copper Manganese Nickel Palladium Platinum Mercury Rhodium Selenium Tellurium Thallium Vanadium Zinc Tin

SO2 NOx F CI TSS COD Sb As Pb Cd Cr Co -CN Cu Mn Ni Pd Pt Hg Rh Se Te TI V Zn Sn

50 1800 1100 400-3500 5 30 5 1 5 0.20 5 1 5 5 5 1 5 5 5 0.20 1 1 5 0.20 5

100 0.50 80 0.50 0.07 0.10 0.10 0.10 0.10 2.00

1) 2) 2) 2) 2) 2) 2) 2) 2)

50 1 1 2 0.50 2 0.20 2 3 0.05


*

May be formed in reduced burning

COD

Chemical Oxygen Demand

**

Law applicable in the German state of Baden-Wberg

TSS TA-Luft

Total Suspended Solids Technical Instructions on Air Quality Control

1)

Two hour mixed sample

VwV

Administrative Regulation

2)

Random sample

WHG

Federal Water Act

Glass works, which are generally large-scale plants, produce considerable emissions. In principle a maximum of 1800 mg SO2Nm3 should be established as the mean guideline value for avoiding serious environmental pollution. The NOx emissions must not exceed the currently applicable values, and nitrate refining should be dispensed with because of the high NOx levels generated.

No separate wet or dry sorption plants are required to comply with these relatively high mean values. Accurate control of the tank heating is vital in order to attain the required values.

Fluorine and chlorine emissions which may give rise to direct damage must be kept as low as possible. The values indicated above can be achieved by suitable selection of raw materials and fuels and systematic monitoring of burner operation. A further benefit is that energy consumption can be further reduced by conforming to these guideline values, resulting in greater economy.

The dust emission from glass furnaces should not exceed 50 mg/Nm3. A dedusting plant should always be installed in order to comply with this limit.

It is vital to adhere to the emission limits for toxic dusts (heavy metals) such as cadmium, lead, fluorine, selenium and arsenic; the maximum values specified in TA-Luft must not be exceeded.

For individual substances, the Compendium of Environmental Standards contains notes on evaluating environmental relevance.

It is absolutely essential to comply with the regulations on permissible noise levels, since failure to prevent or protect against noise can result in permanent injury of employees.

To avoid environmental pollution, the limits laid down for direct water dischargers must be observed, particularly regarding heavy metal concentrations in the effluent.

If no national regulations exist, values in line with German or European standards should be established for the erection of new glass works, particularly in areas already suffering from serious environmental pollution. Special regulations must be introduced for plants already in operation. The parameters defined for the principal hazardous substances must in future be regularly monitored and disclosed by the glass works, so that appropriate steps can be taken immediately in the event of nonconformance (see 3.1).

For all practical purposes it may be assumed that in order to comply with the limits indicated all alkali borosilicate, borate, lead and most special glass furnaces must be equipped with dedusting systems. Allowance must be made for these dedusting and sorption systems as early as the planning phase.

In countries with low-cost electricity it is possible to construct glass furnaces of special design which produce far lower emissions and do not require expensive environmental protection equipment. The energy requirement per kg of glass can also be reduced by introducing such melting methods.

3.1 Inspection and maintenance of environmental protection installations

A control centre independent of the production process must be established to comply with existing environmental protection regulations. The responsible personnel must be enabled to perform and monitor all inspection functions including measurements relating to environmental protection in the works. They should be available for consultation on investments and take charge of negotiations with environmental protection authorities. Moreover, this department is responsible for ensuring that all environmental protection installations are regularly maintained and upgraded. This internal environmental department is also responsible for staff training.

4. Interaction with other sectors

Glass works which rely on numerous secondary operations, such as workshops, compressed air generation, fuel stores, galvanisation shops, refining shops, transport and packing departments etc. are also affected by regulations applicable in other sectors.

Because of the relatively high transport costs, container glass factories must be located near their main customers. Modern sheet glass works, on the other hand, can only operate economically with capacities upwards of 600 t/day, thus they supply their products to more distant sales areas and are reliant on good transport facilities.

Table 5 - Environmental impacts of adjacent sectors - Glass -

Interacting sectors

Nature of intensification of impact

Environmental briefs

Extraction/storage of raw materials and fuels

-Landscape impairment - Pollution of bodies of water - Waste storage in former pits

Planning of Locations for Trade and Industry Urban Water Supply Rural Water Supply

Disposal of solid and liquid waste

- Discharge of deposited solids e.g. filter dusts - Pollution of bodies of water by wastewaters

Solid Waste Disposal Disposal of Hazardous Waste

Maintenance of workshops and transport facilities

- Risks of handling water pollutants (e.g. solvents) - Impacts of transport and traffic (noise, link roads)

Mechanical Engineering, Workshops Road Building and Maintenance Planning of Locations for Trade and Industry

5. Summary assessment of environmental relevance

The effects of glass works on the environment and workplace are caused by noise, dust, effluent and flue gases.

Table 6 - Environmental impact of process stages (glass)

Process

Air


Noise

Water

Soil

Work- place


Waste gas/ Flue gas

Dust1)





Dressing Melting Moulding Cooling Sorting Packing Machining/Refining

1 3 2 2 1 1 1

2 3 1 1 1 1 2

2 3 4 3 2 2 2

1 3 2 1 1 1 3

2 3 3 2 1 1 1

2 3 4 2 1 1 2

Key: 1 very slight; 2 slight; 3 moderate; 4 considerable

In some cases technological and processing developments and improvements have already been implemented, e.g.:

- Arsenic and tellurium are now only used as refining agents in exceptional cases.
- Fluorspar is no longer used as a flux.
- The specific outputs of the tanks have been increased with a simultaneous reduction in energy consumption.
- Wastewater circuits have been introduced.
- Numerous noise protection devices have been installed.
- Wet, electric and dry sorption plants have been installed for dust extraction.
- Tank designs and fire management systems have been improved.

Many of the processes so far tested in individual cases are capable of further technical improvement and more economic design, paying particular attention to environmental regulations. The expected costs of environmental protection devices and measures may be as much as 20% of the total investment costs of a glass works.

Proper maintenance is essential to environmentally acceptable operation of the plants. Suitable training must be given and personnel generally made aware of environmental concerns.

Early involvement of neighbouring population groups in the planning and decision-making processes will enable measures to be devised to deal with any problems arising.

In countries which have no legal guidelines it should be ascertained as early as the planning stage, based on the raw materials to be used and the process technology applied, what environmental protection measures are necessary and appropriate. Environmental protection equipment provided should be of robust design so that the life of this equipment is appropriate to the overall project and so that simple, low-cost maintenance can be guaranteed.

6. References

Allgemeine Vewaltungsvorschriften enehmigungsbede Anlagen nach § 16 der Gewerbeordnung 1985.

Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer - 41. AB-Wasser VwV, 1984.

Betriebswacht, Datenjahresbuch 1991, Berufsgenossenschaft der keramischen und Glas-Industrie, Wg.

1. Bundesimmissionsgesetz (BImSchG), 1985.

Entwurf zur Abwasserverordnung: Deutscher Industrie- und Handelstag, Anhang 17, Sept. 21, 1990.

Glass Manufacturing, Effluent Guidelines, World Bank, August 1983.

Guidelines of the Bundesministerium des Inneren [German Federal Ministry of the Interior] regarding the BImSchG, directives of the Council of the European Community.

TA-Luft: Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsgesetz, GMBR 1986 (A).

Siebzehnte Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes 1990 (Verordnung erbrennungsanlagen fe und liche brennbare Stoffe, 17. BImSchV).

Barklage-Hilgefort H.J.: Minderung der NOx-Emission durch feuerungstechnische Maahmen, Glastechnische Berichte 58, Nr. 12, 1985.

Bauer H.D., Mayer Dr. P.: Zusammenf staubmeechnischer Daten und arbeitsmedizinischer Befunde am Beispiel von Asbesteinwirkungen, Sonderdruck aus "Der Kompa 91, Nr. 7 1981.

Bundesverband des Deutschen Flachglashandels e.V., Glasfibel, Vertrieb Kelasa GmbH Cologne, 1983.

Doyle T.J.: Glassmaking Today, An Introduction to Current Practice in Glass Manufacture, Portcullis Press, Redhill, 1979.

Fer H., Feck G.: In Vitro - Studien an kchen Mineralfasern, Sonderdruck, Zbl. Arbeitsmed. Bd. 35, Nr. 5, 1985.

Gebhardt F., Carduck E. und Arnolds J.: Chloremissionen von Glasschmelzwannen, Glastechnische Berichte 51, Aachen 1978.

Gilbert G.: Zur Ausbreitung von Schadstoffen, insbesondere von Stickoxiden in der Atmosph, Glastechnische Berichte 51, Aachen 1978.

Kircher U.: Emissionen von Glasschmelz - Heutiger Stand, Glastechnische Berichte 58, Frankfurt 1985.

Markgraf A.: Abgasentstaubung hinter Glasschmelz mit filternden Abscheidern und vorgeschalteter Sorptionsstufe zur Beseitigung von HF und HCI, Glastechnische Berichte 58, Nr. 12, Stadthaben, 1985.

Mayer P., Bergass: Grenzwerte fest am Arbeitsplatz und in der Umwelt unter besonderer Berhtigung der keramischen und Glas-Industrie, Sprechsaal 2/80, 1980.

Mayer P., Bergass: Glasfaserste und ihr gesundheitlicher Einfluauf den Menschen, Sonderdruck der Zeitschrift, Die Berufsgenossenschaften e.V., Bonn.

Schaller K.H., Weltle D., Schile R., Weissflog S., Mayer P. und Valentin H.: Pilotstudie zur Quantifizierung der Bleieinwirkung in der keramischen und Glas-Industrie, Sonderdruck Zbl. Arbeitmed. Bd 31, Nr. 11, 1981.

Tiessler H.: Zum Einsatz eines Elektro-Entstaubers an einer Spezialglaswanne fali-Borosilikatglas, Glastechnische Berichte 51, Nr. 7, 1978.

Winterhoff G.: Abgasentstaubung periodisch arbeitender Glasschmelz, Glastechnische Berichte 58, Nr. 12, 1985.

1. Scope

This environmental brief covers iron and steel production and processing with the following activities:

- sinter, pellet and sponge-iron production
- pig iron, cast iron and crude steel production (including continuous or strand casting)
- steel forming (hot and cold)
- foundry and forging operations.

The above activities are carried out in an integrated ironworks or sometimes in separate locations.

After delivery and pretreatment of the ore in the ore preparation, sintering and where applicable pelletising plant, pig iron is smelted in the blast furnace with the addition of coke and admixtures; coke supplies the energy and reduces the ore to pig iron. In the converting mill the molten pig iron is refined to form crude steel by top blowing or purging with oxygen and the addition of scrap. Crude steel is also produced from scrap in electric furnaces, sometimes with the addition of pig iron, ore and lime. The crude steel is either continuously cast as blanks or, after casting as slab ingots or blocks in permanent moulds, rolled in the hot rolling mill to form sheets, billets or profiles. Further processing takes place in the cold rolling mills and forges. Continuous casting which already represents 90% of German and 60% of worldwide steel production improves crude steel utilisation by some 10%, saves energy by rolling operations and reduces the production scrap yield in steel and rolling mills per tonne of finished steel by more than 50%.

The direct-reduction process represents an alternative to traditional steel production. With the addition of reduction gas, e.g. from natural gas or coal, sponge iron is produced as a solid, porous product from which crude steel is then refined in the electric furnace, often with the addition of scrap. 90% of sponge iron is produced by the gas-reduction process.

Cast iron smelting takes place in the cupola furnace, with increasing use of induction furnaces.

Moulds and cores are required for the shaped casting of cast iron; these are mostly of sand but frequently contain an organic binding agent.

The following are classified as major units:

sintering plants 20,000 t/day
blast furnaces 12,500 t/day
steel converters 400 t holding capacity
electric furnaces (arc) 250 t holding capacity
cupola furnaces 70 t/h
induction furnaces 30 t/h

In many countries steel is extensively produced from scrap in electric furnaces.

Since iron and steel production is predominantly based on pyrometallurgical processes, air pollution is a primary consideration. In addition to a multitude of gaseous air impurities, dusts play a special role, not only because they occur in large quantities but also due to the fact that the dusts contain some hazardous substances affecting both man and the environment, e.g. heavy metals. Due to the use of coolant water and wet separation methods, problems of maintaining water purity also occur. Continuous casting plants require high specific water quantities from which the wastewater is considerably contaminated with oil. Casting without spray-water cooling relieves the load on water resources.

Metallurgical processes also produce slags which should be recycled wherever possible. Where no effective recycling and final dumping facilities exist, dusts and sludges separated from the waste gas cleaning systems represent potential pollutants of the ground and water environments.

In blast furnace plants and converting mills, also in rolling mills and forging works, noise and vibration protection is of fundamental importance. Foundries produce large amounts of waste from used sand, broken cores and cupola slag.

For reasons of ecology and economy, work is taking place worldwide on process methods which permit the use of coal instead of coke and the extensive use of lump ore instead of sinter or pellets. This would enable coking and sintering plants to be dispensed with as emission sources in a metallurgical plant.

Other developments concern the casting of rolling feed stock in approximately final dimension form. Shortening the process chain permits reductions in energy requirements, residual substances, waste and emissions.

2. Environmental impacts and protective measures

2.1 Sintering / pelletising plants

Sintering plants form lumps of fine ore prior to introduction into the blast furnace and recycling of ferriferous residues (waste materials). Sintering is the traditional method of treating residual and waste materials from the smelting plant. Factors determining the limits include the zinc concentration, because zinc in the sinter contributes in the blast furnace to the formation of scaffolding with impaired gas distribution.

Sintering plants produce the following emissions:

Waste gases and dust containing components with potential environmental relevance:

SO2, NOx, CO2, HF, HCl, As, Pb, Cd, Cu, Hg, Tl, Zn

Of dust components, the heavy metals lead, cadmium, mercury, arsenic and thallium have the greatest environmental relevance where these are present in the charge materials. The relevance of anthropogenic heavy metal emissions is based less on their overall emission rate than in high localised mass flow densities or concentrations. The iron and steel industries are among those industries in whose vicinity the highest immission rates of heavy metals occur in the air and ground.

Dust is separated and returned to the sinter process in gas cleaning systems, normally electrostatic precipitators. In continuous operation the dust content of clean gas is between 75 and 100 mg/m3. Heavy metal, e.g. lead, enrichment in the sinter plant dust is possible with continuous recycling. Dust with heavy concentrations of lead and zinc should be conducted to a zinc and lead recovery system. In the case of stoppages of the sintering belt due to faults, care must be taken to ensure that the gas cleaning system continues to operate at maximum possible separation capacity. In addition to sintering belt dedusting, modern sintering plants also have room dedusting whereby dust-laden waste air from transfer stations, chutes, crushers etc. is cleaned by a hot sieve system.

Depending on the composition of charge materials, inorganic gaseous fluoride and chloride compounds as well as sulphur dioxide and nitrous oxides are emitted. Sulphur dioxide emission can be significantly reduced by using coke with a low sulphur content. The emission of gaseous pollutants can also be reduced by increased lime dosing. This results in problem substances being transferred to the separated dust. Where regional conditions and process engineering do not permit these measures, wet-process desulphurisation systems offer a means of reduction; in this case some problem substances are transferred to the wastewater. On account of the large gas volumes - up to 10 E 6 m3/h - only partial waste gas desulphurisation can take place. For this reason preference should be given to primary measures. Concentrations in cleaned waste gas are around 500 mg/m3 sulphur dioxide.

With respect to noise impact, a distinction is made between the noise immissions of operations to the neighbourhood and the effect on the staff at their work-places. Principal noise sources of the sintering plant include the large fans for drawing air through the sinter cakes, cooling the sinter and dedusting. Crushing and screening stations should be housed in solidly constructed buildings whose walls restrict the propagation of sound. Possible noise reduction measures are silencers in the air supply and discharge pipelines, also the encapsulation of individual units. The acoustic power immission level is used to evaluate the noise radiated to the open air by the plant. The acoustic power level of a noise source is a distance-dependent parameter; for sintering plants without silencers on supply and discharge air pipelines it can be as high as 133 dB(A) and for those with silencers 124 dB(A). With very good acoustic planning and execution an immission level of around 40 dB(A) can be achieved at a distance of 1,000 m from the individual noise sources. If this target cannot be achieved, protection of the residential area adjacent to the sintering plant is only possible by noise protection measures on the propagation path, e.g. a noise abatement wall. Measures for optimising noise protection are to be considered in parallel with the planning of the production unit.

By encapsulation and the separate installation of principal noise sources it is also possible to protect the work places. The typical noise level in the sintering hall is between 83 and 90 dB(A); attention must be paid to the use of personal noise protection because long-term exposure to an acoustic power level in excess of 85 dB(A) results in serious hearing impairment. The wearing of safety helmets and shoes also helps reduce industrial accidents. Staff in work-places particularly exposed to dust, gases, noise and heat are to have regular preventive medical examinations by works doctors.

In pelletising plants, fine ores are mixed with additives and water to form green pellets which are burned in pellet incinerators on travelling grates. The dust-laden waste gases are cleaned in dedusting plants, usually electrostatic precipitators. The filter dust is re-used. Pelletising plants are associated with lower dust and gas emissions than sintering plants. In contrast to sintering, pelletising is mainly performed at the ore mine.

2.2 Blast furnaces

The blast furnace is a countercurrent reactor loaded or charged from the top with layers of feed and coke, the molten pig iron and slag being drawn off from below. Hot air is injected in the opposite direction from the bottom of the furnace. Residual materials (waste) such as oily metal chips and oily rolling scale can be introduced after sintering.

The principal emissions, residues and waste materials are:

- top gas, with the following potentially environmentally relevant components: CO, CO2, SO2, NOx, H2S, HCN, CH4, As, Cd, Hg, Pb, Ti, Zn
- top gas dust (dry) from the gas cleaning plant with high iron contents (35 - 50%)
- slag with the following major components: SiO2, Al2O3, CaO, MgO
- sludge from the waste gas cleaning system
- wastewater from the waste gas cleaning system, with the pollutants: cyanides, phenols, ammonia
- dust from the casting house dedusting system.

The waste gases from the blast furnace are pretreated in mass force separators (dust catchers or cyclones) and, in a second stage, finally cleaned with a high pressure scrubber or wet electrostatic precipitators. Clean gas dust concentrations from 1 to 10 mg/m3 are achieved.

Other dust emissions in the blast furnace area, particular from the burdening process, pig iron desulphurisation and the casting house must also be identified and cleaned.

Dust formation ("brown fume") in the casting house affects not only the neighbourhood but also, to a considerable extent, the workplaces. Efficient casting house dedusting systems which intercept process waste gases and peripheral emissions at the taphole, runners and cut-off points and separate dusts in horizontal electrostatic precipitators can achieve clean gas dust concentrations significantly under 50 mg/m3 (best values 7 and 12 mg/m3 and dust emission factors between 0.020 and 0.028 kg/t pig iron in blast furnace plants with a capacity of 4,000 to 6,000 t/day). As a replacement for the standard collection and cleaning methods, trials are currently in progress with the suppression of "brown fume" through inertisation with nitrogen.

In the dedusting of pig iron desulphurisation, clean gas dust concentrations of 50 mg/m3 are adhered to in both calcium carbide and soda desulphurisation, using radial flow scrubbers or electrostatic precipitators.

The top gas contains between 10 and 30, though possibly as much as 60 g/m3 dust with 35 to 50% iron, i.e. 30 to 80 kg/t pig iron, in older plants 50 to 130 kg/t pig iron. The dust is separated in the dry state in mostly multistage separators, from where it goes to the sintering plant and from there back to the blast furnace.

In view of the zinc and lead content and other factors, the top gas scrubbing water sludge must be disposed of by dumping, unless there is a special hydro-cyclone separation system. With higher concentrations, it should be transferred to a non-ferrous metal works. Recycling in this way would leave the blast furnace process practically free of residues. Dumping involves the risk of leaching and hence penetration of the soil and groundwater by compounds of zinc, lead and other heavy metals. The dump must be permanently and verifiably sealed and the seepage water must be collected and chemically processed. The special requirements imposed on such a dump must be laid down in the project planning stage.

Slag produced by the blast furnace process accounts for roughly 50% of the overall waste materials from pig iron and steel production. This slag is mostly used in road-building. Part of the molten slag is granulated by quenching in water. This so-called slag sand is also used in road-building. Part is used to produce iron slag Portland cement and blast furnace cement. Quenching and granulating releases carbon monoxide and hydrogen sulphide. The wastewater has an alkaline reaction and contains small quantities of sulphide.

Slag heaps sometimes produce seepage water with high levels of dissolved sulphides and strong alkaline reaction, posing a hazard for the groundwater. Slag heaps must be sealed and any seepage water must be treated.

Wastewater is generated by top gas scrubbing and simultaneous wet dedusting. The wastewater is normally clarified in settling tanks and, where necessary, gravel bed filters and recirculated. The wastewater contains suspended matter (dust) and sulphides, cyanides, phenols, ammonia and other substances in dissolved