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close this bookEnvironmental Handbook Volume II: Agriculture, Mining/Energy, Trade/Industry (GTZ, 1995, 736 p.)
close this folderTrade and industry
Open this folder and view contents44. Nitrogenous fertilisers (raw materials, ammonia and urea production)
Open this folder and view contents45. Nitrogenous fertilisers (starting materials and end products)
Open this folder and view contents46. Cement and lime, gypsum
Open this folder and view contents47. Ceramics - Fine, utilitarian and industrial
Open this folder and view contents48. Glass
Open this folder and view contents49. Iron and steel
Open this folder and view contents50. Non-ferrous metals
Open this folder and view contents51. Mechanical engineering, workshops, shipyards
Open this folder and view contents52. Agro-industry
Open this folder and view contents53. Slaughterhouses and meat processing
Open this folder and view contents54. Mills handling cereal crops
Open this folder and view contents55. Vegetable oils and fats
Open this folder and view contents56. Sugar
Open this folder and view contents57. Timber, sawmills, wood processing and wood products
Open this folder and view contents58. Pulp and paper
Open this folder and view contents59. Textile processing

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)


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



Cement and lime, gypsum


Direct discharger g/m3

Sample type

Indirect discharger** g/m3



NOx nitrous oxide grill preheater



NOx nitrous oxide cyclone preheater


and exhaust gas heat utilisation


NOx nitrous oxide cyclone preheater


without exhaust gas heat utilisation


NOx nitrous oxide grill preheater


SOx sulphur oxide as SO2










Filterable solids




Total suspended solids





Chemical oxygen demand
































Cyanides (*)




















































May be formed in reduced burning


Chemical Oxygen Demand


Law applicable in the German state of Baden-Wberg


Total Suspended Solids Technical Instructions on Air Quality Control


Two hour mixed sample


Administrative Regulation


Random sample


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)







Exhaust gas /flue gas


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]


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





Direct discharger g/m3

Sample type

Indirect discharger** g/m3



Sulphur dioxide as SO2


at a mass flow < 10 kg/h


Sulphur dioxide as SO2


at a mass flow > 10 kg/h


Nitrous oxide NOx










Filterable solids




Total suspended solids





Chemical oxygen demand
































Cyanides (*)



















































May be formed in reduced burning


Chemical Oxygen Demand


Law applicable in the German state of Baden-Wberg


Total Suspended Solids Technical Instructions on Air Quality Control


Two hour mixed sample


Administrative Regulation


Random sample


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)






Work- place

Exhaust gas /flue gas


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]


Oil-fired mg/Nm3

Gas-fired mg/Nm3

Pot furnaces



Tanks with recuperative heat recovery



Day tanks



Horseshoe flame tanks with regenerative heat recovery



Cross-burner tanks with regenerative heat recovery



Values attainable for electrically heated tanks


The emission values of nitrate-refined tanks must not exceed twice the above-mentioned values.


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


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)



Glass industry


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


Chemical Oxygen Demand


Law applicable in the German state of Baden-Wberg


Total Suspended Solids Technical Instructions on Air Quality Control


Two hour mixed sample


Administrative Regulation


Random sample


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)






Work- place

Waste gas/ Flue gas


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 form. The last three substances must be removed from the wastewater using appropriate physical and chemical treatment processes.

The top gas can be used as a fuel for heating purposes within the works, in view of its high carbon monoxide content due to the reducing atmosphere in the blast furnace, though this will inevitably result in the formation of carbon dioxide, with its climatic implications.

Excessive levels of sulphur dioxide and nitrous oxide gases can be reduced by flue gas desulphurisation and denitrification.

Carbon monoxide concentrations in the workplace pose a particular problem. Where top gas pipes are not perfectly leakproof there is a danger of poisoning with possible fatal consequences for workers present at the furnace throat. Close attention must also be paid to CO concentrations by carrying out measurements and ensuring that protective breathing equipment is worn during repair and maintenance work on shut-down blast furnaces or gas cleaning systems.

Protective equipment for blast furnace workers includes fireproof clothing, breathing equipment and ear protectors, depending on where they are working; protective helmets and safety footwear must be worn in all areas.

Noise in blast furnace plants comes mainly from the combustion air fans and the charging process; also there is the noise generated upon changeover from blast to heating operation. Suitable abatement measures include silencers, enclosure of the furnace throat or encapsulation of all valves and shields. The noise level from the blast furnace plant is in the range of 110 to 125 dB(A); the level of background noise in the immediate vicinity may be 75 to 80 dB(A). Possible noise reduction measures should be selected as early as the blast furnace planning phase. Their effect can be determined by advance calculation, taking care to ascertain the significance of the emission sources (plant sections and operating processes). One should preferably begin by damping or eliminating occurrences and noise sources which arise only periodically.

2.3 Direct-reduction plants

Direct reduction plants function according to a variety of methods, e.g. with shaft furnaces or rotary tube furnaces which are similar to blast furnaces. In the former, the top gas is scrubbed and then enriched with natural gas and used for heating; in the latter, the gas is not used unless steel and rolling mills are available for this purpose. If this is the case, the gas should be burnt provided the CO content is sufficiently high. The waste gas flow is cleaned by mass force separators (dust chambers) for preliminary separation and then by fabric filters. Sulphur dioxide emissions may occur in the solids reduction process, depending on the sulphur content of the coal used.

2.4 Crude steel production

Excessive carbon content impeding further processing of the pig iron and substances influencing the quality of crude steel, such as silicon, phosphorus or sulphur, are either expelled in gaseous form or slagged during the steel production. The following emissions occur in the steel works:

- waste gases and dust containing components with potential environmental relevance: CO, NOx, SO2, F, Cd, Cr, Cu, Hg, Mn, Ni, Pb, Si, Tl, V, Zn ammonia, phenol, hydrogen sulphide and cyanide compounds may occur, depending on the process.
- dust from waste gas cleaning
- slag

In the steel works dust is formed mainly due to the top-blowing or through-blowing with oxygen necessary for oxidation. The solids content of the waste gases from the oxygen converter is between 5 and 50 g/m3. They contain finely dispersed evaporation products of iron oxides and primary anoxide ("brown fume"); also sulphur and phosphorous compounds, fluorine compounds and, where fluxing agent is used, silicon tetrafluoride.

Specific dust masses are approximately as follows:

- electric furnace: 2 - 5 kg dust per tonne crude steel
- bottom blowing converter oxygen bottom metallurgy (OBM) 5 - 10 kg dust per tonne crude steel
- top blowing converter (LD and LDAC process) 15 - 20 kg dust per tonne crude steel

Gases occurring in addition to carbon monoxide include inorganic fluorine compounds with the addition of fluorspar, also small quantities of sulphur dioxide and nitrous oxides, nitrous oxide formation being significantly higher in electric furnaces than in the blowing converter.

A technical solution exists for the collection and cleaning of the process gases from the converter. A fixed or lowerable hood over the converter prevents the intake of large quantities of infiltrated air or the escape of converter gases. The gas is subsequently dedusted by a wet or dry process. Wet dedusting takes place in a two-stage operation by a combined wet scrubber and wet electrostatic precipitator. For dry dedusting, dry electrostatic precipitators are used, designed to resist internal pressures up to 2 bar (due to risk of deflagration). The clean gas concentrations are under 50 mg/m3 dust and under 500 mg/m3 sulphur dioxide. A value of under 400 mg/m3 nitrous oxide cannot be continuously maintained. Maintenance of the separation equipment is important in order to achieve an adequate continuous level of separation. Dry dedusting is advantageous as the yielded dust can be returned to the converter after hot briquetting.

Transfer, charging and mixing processes produce random dust emissions which may pose a considerable nuisance for the neighbourhood. Clean gas contents of 10 mg/m3 can be maintained by a waste gas collection system with a collection rate of 90% and a downstream separator using fabric filters or horizontal electrostatic precipitators.

Proposals for the use of a process-dependent control and instrumentation system for reducing specific waste gas quantities must be examined with respect to system requirements such as robustness, error detection ability and ease of maintenance.

Since waste gas collection is difficult with Siemens-Martin furnaces while the furnace is in operation, the solution is to convert to electric furnaces. In addition to lead and zinc, chromium, nickel and vanadium occur in the dust if electric furnaces are used to produce fine steels. Certain chromium compounds in the form of breathable dusts have proved to be carcinogenic.

A full doghouse enclosure is necessary to achieve 95% collection of the waste gases occurring with electric furnaces during charging, smelting and casting. Fabric filters permitting clean gas dust concentrations of under 20 mg/m3 are used for dust separation.

When the converter is in operation, large amounts of carbon monoxide are produced which should be transferred for controlled burning in a torch or in a boiler with energy conversion, so as to avoid excessive air burdens (immissions). A potential source of polyhalogenated dibenzodioxin and furan emissions (though not currently thought to pose a major risk) is the recycling of iron scrap in electric steelmaking plants. Large quantities of iron scrap contaminated with halogen compounds and the operating conditions give rise to the formation of these substances. Initial random sample checks yielded emission concentrations of the order of a few nanograms. A comprehensive measuring programme is being prepared. Careful selection and preliminary sorting of iron scrap is currently a practicable way of minimising carcinogenic emissions. Processes for separating health-endangering dioxins and furans are currently being developed. Current trials of activated charcoal adsorption filters and their separation capabilities are being followed with close interest.

The wastewater from wet dedusting is clarified in a hydrocyclone or settling tank and recirculated. The separated sludge is dewatered by a vacuum drum filter and returned to the blast furnace via the sintering plant. Attention must be paid to the zinc content of the sludge upon recycling. Slag produced in steel works is used in road construction or processed into fertilisers.

Loud noise is generated in converting steel works by high-powered fans and dedusting systems and in electric furnaces by the arcing and transformer. Noise levels in electric steelmaking plants without noise reduction measures is between 117 and 132 dB(A), and around 100 dB(A) with noise reduction.

Noise reduction measures can include:

- arc soundproofing
- smaller apertures in the furnace shell
- encapsulation of the furnace
- acoustic separation of the furnace bay from adjacent bays
- increasing the soundproofing of bay walls
- silencers on air intakes and outlets
- slow-running cooling air fans
- enclosure of individual systems
- avoiding free-fall of scrap upon loading and charging.

Very high peak noise levels can occur during smelting, especially with wet scrap. Highly automated modern plants have control rooms which provide effective protection against noise at the workplace. The protective measures mentioned under 2.2 also apply to workplaces in steelworks.

2.5 Steel forming

The following emissions and residues occur with forming (shaping) of crude steel into rolled steel:

- oily rolling scale
- waste gases from the furnace
- oily wastewater
- wastewater from the waste gas cleaning

During the production of steel plate, the following are produced:

- oily wastewater
- waste air from the pickling baths
- spent pickling solutions
- sulphuric and hydrochloric acid
- or nitric and hydrofluoric acids
- mixtures

The most prolific residue produced in hot rolling mills is rolling scale. The specific mass is 20 to 70 kg/t finished steel. Scale comprises mainly iron oxides (70 - 75) and can therefore be utilised in the blast furnace. Finer components must first be sintered or pelletised. Oily scale with a small percentage of oil from the machinery lubricants can be freed of oil by combustion or by alkaline wet scrubbing. To avoid polluting the subsoil with oil, oily scale should not be dumped.

Wastewater is produced in the hot rolling mill by

- transport of the scale to the wastewater treatment system
- alkaline washing of the oily scale.

The scale-water mixture is separated in settling tanks and gravel filters (sometimes with the addition of flocculation agents). Floating rolling oil and grease is skimmed off and the settled or filtered scale is dewatered and transferred to the sintering plant. The clarified wastewater is recirculated.

The alkaline scrubbing water from the scale scrubber contains an oil emulsion which must be broken down with chemicals. The water contains oil and chemical residues. It should be transferred to a biological filter plant. The recovered oil can be processed and in certain cases re-utilised in the rolling mill.

In the cold rolling mill the steel plate is descaled in a pickling bath before further processing. Hence, no solid waste (scale) is produced in the actual cold rolling process.

With cold rolling, wastewater occurs due to contamination of water with rolling oils (mineral oils, palm oil) and from the pickling. The rolled down plates are once more pickled with acid and electrolytically degreased prior to tinning or galvanising.

Wastewater treatment requirements in rolling mills depend on the type and extent of recycling and the quality of the receiving body of water. Regular monitoring of wastewater values is necessary.

The oil-water emulsions produced by the cold rolling process must be chemically treated (flocculation with ferrous salt and lime). The oily sludge must be incinerated and the ashes transferred to the sintering plant. Oil separated from the emulsion can be used for secondary lubrication purposes.

To protect soil and groundwater from unwanted discharges, a waste disposal and re-utilisation record should always be kept for emulsions, mixtures of mineral oil products and mineral oil sludges.

Spent steel pickling agents contain mainly ferrous salts. These can be separated and sold (for production of pigments, precipitation agents for clarification processes, sulphuric acid). The remaining pickling agent must be neutralised with lime milk. The resulting hydroxide sludges are placed in drying beds or preferably dewatered with filter presses. Before dumping, the leachability and stability of these residues must be checked to ensure they are suitable for final dumping. If the solids content exceeds 40%, the residues should be taken to the sintering plant.

The acid pickling water must be neutralised and the coagulated hydroxide sludges separated in clarifying tanks. The clarified wastewater can be re-used (must be neutralised with acid); sludges must be placed in a suitable, sealed dump.

Special hoods are used to eliminate oil mist in rolling mills; it is separated by a mechanical preliminary separator combined with a downstream electrostatic precipitator.

The effective noise level generated by hot and cold rolling mills is 95 - 110 dB(A). In a rolling mill the noise level, e.g. 5 metres from the open bar steel train, is 106 dB(A) and in a pipe steel rolling mill, near the tube straightening machine, as much as 124 dB(A).

To protect workplaces from noise, the plant is extensively automated and provided with appropriate control rooms. These can be well insulated against noise. Ear protection should be worn at workplaces with high levels of noise.

2.6 Foundry and forging operations

Smelting takes place in cupola furnaces (shaft furnaces) and electric melting furnaces. Gaseous emissions from smelting are: carbon monoxide, sulphur dioxide, fluorine compounds and nitrous oxides; those from casting are: phenol (briefly), ammonia, amines, cyanide compounds and aromatic hydrocarbons (traces).

Dust occurs in foundries during e.g. preparation of the moulding sand and core sand, manufacture of sand moulds and cores, in casting, cooling of castings, knocking out moulds and with the surface treatment of parts of moulds, known as fettling. Fabric filters have proved effective for reducing dust emissions. These have permitted the achievement of concentrations of under 10 mg/m3 in the clean gas from sand preparation dedusting systems. Optimum fine dust separation with fabric filters can help reduce toxic emissions, e.g. nickel, during fettling.

Dust occurring in cupola furnaces during smelting is intercepted by wet type dedusters or filtering separators. With cold blast cupola furnaces with smelting capacities below 10 t/h, wet dedusters are increasingly being replaced by fabric filters with preliminary separators. Clean gas dust concentrations of under 20 mg/m3 are being adhered to. Fluorine emissions can also be reduced by dry absorption using hydrated lime.

It is essential to intercept emissions in all operating phases, including blowing and melting-down.

With hot blast cupola furnaces with smelting capacities exceeding 10 t/h, operators have managed to obtain clean gas dust concentrations of 20 mg/m3, with blowing and melting-down as well, using optimised wet type dedusters in combination with primary measures on the cupola furnace. An enclosed forehearth feed bay also contributes to low-emission operation.

The use of induction crucible furnaces is increasing; with these, emissions from the crucible opening are intercepted by an extraction system.

When using electric furnaces, which produce significantly lower dust emissions than cupola furnaces, values of 20 mg/m3 are possible using filtering separators. Additional emissions of hydrochloric acids, soot and traces of organic compounds (possibly dioxins) occur when smelting large amounts of scrap mixed with oil, paints and plastics. A high-performance wet scrubber must be used under these operating conditions.

Highly odorous substances such as formaldehyde, phenols and ammonia occur in foundries for small castings for which moulds are produced according to the cold-box, hot-box or Croning process. In addition to the odour nuisance, these substances are also health hazards. As formaldehyde and high ammonia concentrations are suspected carcinogens, steps must be taken to reduce these. Emissions can be reduced by a counter-current scrubber with a phosphoric acid solution. The scrubbing fluid is recirculated and continuously treated.

Waste gases with inorganic compounds occur during core production, including core sand mixing. The waste gases must be cleaned with a wet scrubber and in particular the amount of amines in the waste gas must be under 5 mg/m3.

The sludge-water mixture resulting from wet dedusting, which may contain substances hazardous to health and the environment such as cadmium, lead and zinc, is neutralised. The precipitated solids are separated from the water by sedimentation. The scrubbing water is recirculated. Before dumping the sediment, which may contain phenols from the moulding sand binders, it must be tested for leachability and treated if necessary. In a suitably modified process, part of the wastewater flow can be evaporated and the circuit largely, closed, thereby considerably reducing the scrubbing water requirement.

The moulds are made of moulding sands with approx. 4 to 10% binder (clays, cement, organic materials, hardenable plastics, soda, water glass etc.). They are usually used once and then broken up. The used sands can be treated and re-used as components in clay-bonded mould production.

The ambient noise levels in foundries can reach 120 dB(A). Noise sources include loading operations, mixing, dedusting systems, fettling bays, sand preparation, conveyors and fans. Noise reduction measures include enclosed hall designs, installation of fans in enclosed rooms and silencers on air intakes and outlets. Machine soundproofing measures are especially necessary in the moulding, core and fettling shops. Measurements made over an 8 hour shift have yielded workplace noise levels of 106 dB(A) in the moulding shop, 99 dB(A) in the core shop and 103 dB(A) in the fettling shop. Principal noise sources affecting workplaces are: jolt moulding machines, vibratory grates, swing conveyors, fettling machines, impact pneumatic tools, grinders, fans, compressors and conveyors.

Appropriate noise protection measures in the workplace include encapsulation of noisy machines, separation of noisy machines from other parts of the shop and avoidance of manually operated machines. Personal ear protection must of course be worn. Monitoring is imperative.

Waste gases are expelled from the furnace in forges. Emissions can be controlled by using gas as a fuel. A forge must be regarded as an industrial installation as regards production of wastewater and waste materials.

The ambient noise level in a forging shop with e.g. 6 hammers (impact energy 0.6 to 1.3 Mpm) is 112 dB(A). The background noise level due to heating furnaces, fans etc. is already 90 to 100 dB(A); to this must be added the pulsating noise of the forging machinery. Forging hammers are louder than mechanical and hydraulic presses. It is important to maintain a safe distance between the forge and purely residential areas. This distance must be calculated and allowed for in the planning where a reasonable noise level cannot be achieved in the near vicinity through noise reduction measures in the works. The maximum noise level in the workplace of a drop hammer (1,500 kg tup weight) is 120 dB(A). That of an electric forging hammer in the workplace (tup weight 275 kg) is 97 dB(A). The interior noise level in forging shops is normally above 90 dB(A).

Possible noise reduction measures include reducing structure-borne noise by modifying the forging force curve, reducing the propagation of the structure-borne noise, encapsulating work room openings, reducing the noise from pneumatic control systems, placing silencers on air relief pipelines and using multiple tube nozzles for descaling. The wearing of personal ear defenders should be obligatory and should be monitored.

Besides noise, forging also produces vibrations. Measures to reduce vibration include the definition, at the planning stage, of suitable foundation designs, with appropriate vibration insulation at the time of installation. Vibrations in the neighbourhood must be below the threshold of perceptibility.

3. Notes on the analysis and evaluation of environmental impacts

Emissions produced by the iron and steel industry require particularly extensive measures and systems for air protection. Above all, dusts containing substances hazardous to health and the environment, such as lead, cadmium, mercury, arsenic and thallium, must be cleaned by high-performance separation systems. Nowadays, not only the primary emission sources, such as sintering plants, but also secondary sources such as blast furnace casting bays can be intercepted and dedusted. In the case of gaseous emissions, attention must be paid primarily to reducing carbon monoxide and sulphur dioxide, as well as nitrous oxides and fluorine compounds.

Monitoring of permissible emissions and the effectiveness of waste gas cleaning systems must be guaranteed by measurements. The dust must also be periodically analysed to detect heavy metals. Emissions must be measured after commissioning the plant to see whether the values assumed in the planning correspond to the reality. If there are discrepancies, new forecasts must be made and further reduction measures implemented if necessary.

Emission and immission standards applicable in Germany are detailed in TA-Luft (Technical Instructions on Air Quality Control) and in the Groeuerungsanlagenverordnung (Ordinance on Large Firing Installations). In the USA, guidelines and standards for the iron and steel industry have been published by the Environmental Protection Agency.

The guidelines adopted by the Association of German Engineers (VDI) contain detailed descriptions for performing emission and immission measurements. Measuring equipment designed for continuous operation must be rigorously examined for robustness, error detection ability and ease of maintenance. Maintenance contracts should be concluded with suppliers. Continuously operating measuring instruments should be employed for measuring dust, sulphur dioxide, fluorine compounds and nitrous oxides (e.g. in the sintering plant and the steel works).

Recycling of water and the use of closed-circuit cooling water systems deliver cost-savings and a high rate of re-use in iron and steel works. Effective water treatment systems are needed for this purpose.

General minimum requirements are laid down in Germany for treated wastewater discharged into receiving bodies of water and for special plants. These parameters must be monitored by measuring equipment at the point of transfer of the cleaned water to the receiving body of water. Cleaning systems for waste gases and water can only satisfy their intended purpose when they are correctly operated, serviced and repaired. The provision of detailed operating, maintenance and repair manuals is imperative.

Practically all processes involve greater or lesser levels of noise. High noise emissions can cause annoyance in the vicinity if reduction and protection measures are inadequate. In Germany, TA-L (Technical Instructions on Noise Abatement) and the guidelines adopted by the Association of German Engineers (VDI) are used for calculating and assessing noise immissions in the neighbourhood. Noise immissions are assessed against immission reference values which are graded according to the type of area to be protected and the periods of noise. Guidelines are also available for assessing noise emissions at the workplace.

As in Germany, works environmental protection officers should be deployed in iron and steel works who are totally independent of the production side. Their task is essentially to work towards the development and introduction of environment-friendly processes. In addition they are entitled and obliged to monitor adherence to statutory regulations and compliance with official directives and conditions in so far as these relate to environmental protection.

The scope and monitoring of working conditions and health protection measures, which vary from one workplace to another, should be set down in a manual. Proposals are detailed in the regulations of the employers' liability insurance association (Berufsgenossenschaft) of the iron & steel industry. Suitably qualified safety officers and a works doctor should be appointed.

4. Interactions with other sectors

The erecting of iron and steel production plants involves land-use which is measured in terms of the works site with adjoining areas and connecting roads. Before erecting production plants, impacts on the local natural order and the geogenic and anthropogenic burdens on the soil and groundwater and on any bodies of surface water must be investigated in the context of the location planning. An adequate distance from the nearest residential zones must also be guaranteed. Details are contained in the environmental brief Planning of Locations for Trade & Industry.

Iron and steel works involve large-scale production and require large amounts of raw materials. These include primarily ores, coke and limestone. Generally speaking, to produce 1 tonne of crude steel requires 450 to 500 kg coke and fuel oil, 250 kg lime and 5 m3 water.

In an integrated iron works for example, the specific total energy consumption is some 20 GJ/t crude steel. In an integrated iron works, the sintering plant, blast furnace, coking plant, steel works, rolling mill and power station areas are interconnected as a combined energy system. Thus, the top gas is utilised in all areas, its calorific value enriched with converter gas, coking oven gas or natural gas. Power and steam are supplied by the power station. Boilers are usually operated with gas, e.g. top gas. The burners can be fired with top gas, coking oven gas or fuel oil. External power supplies are used in addition to internally generated power. Waste heat boilers from the steel works contribute to steam production.

A mixed iron works is linked to the following other sectors:

- The raw materials (ores, coal, limestone) must be mined in large quantities in open cast or deep mines. (See environmental briefs Surface Mining and Underground Mining).
- Ores must be dressed (see environmental brief Minerals - Handling and Processing).
- Efficient transport routes (canals, railways or roads) are required for transporting raw materials and products. For environmental protection reasons, transport should mainly be via inland waterways and railways. Whether the location of the iron works is chosen because of where the ore, coal or sales market is situated, high-capacity transport facilities must always be provided.
- Coke of specified quality must be supplied for the blast furnace by a coking plant. Reference should be made to the environmental brief Coking Plants, Coal to-gas Plants, Gas Production and Distribution to assess the environmental impacts associated with coke production.
- In view of the quantities of cooling water needed, an adequate water supply must be available. To avoid the adverse consequences of drawing excessive quantities of water from groundwater or surface water resources, extensive recirculation systems must be provided, internal treatment of wastewater and cooling water. Water consumption must be in harmony with the general water framwork planning.
- The large workforce of a mixed iron works may result in the disorganised development of housing at an insufficient distance from the plant. This can lead to water shortages, unsatisfactory wastewater treatment and disorganised dumps, plus immission burdens affecting the areas of habitation.
- Other sectors directly or indirectly linked to the iron and steel industry are: lime kiln plants, cement works, ferroalloy production plants, power generating plants and slag and dust recycling plants. The above plants and establishments are associated with considerable potential atmospheric burdens. Reference is made to the relevant briefs.
- A general or single-purpose dump is to be provided for non-recyclable residual and waste materials including furnace debris from the metallurgical processes with hazardous pollutants. These should be classified according to criteria of environmentally acceptable final storage (see environmental brief Disposal of Hazardous Waste).

5. Summary assessment of environment relevance

The establishment of iron and steel production plants in areas not previously used for industry will have an impact on the landscape. Environmental damage can be reduced by selecting locations with relatively insensitive landscapes where there is unlikely to be any great effect on the regional productiveness of the natural environment.

The environmental burdens imposed by an iron and steel making plant and related technologies relate to the air, water, soil, flora and fauna, waste, noise and vibration.

Efficient separators are available for reducing dust emissions. Important in this regard is the continuous monitoring of the operation of these separators using suitable measuring equipment. Since a large proportion of the separated dust can be re-utilised in the process, high-performance gas cleaning systems are desirable, not only for environmental protection reasons but also in the interests of economy. Increasing attention is being paid to random dust sources, e.g. from working bays. Tried and tested collection systems are available for this purpose. High dust immissions occur in the vicinity of iron works. Although high grade cleaning of waste gases reduces dust emissions, dust emissions for the iron works as a whole are between 1 and 3 kg/t, depending on the number of installed process stages and the extent of dust reduction from diffuse sources. 1 kg/t should be regarded as an optimum value. Studies should be carried out in all cases to determine whether agriculture in the vicinity of the works is being impaired by contamination over wide areas with phytotoxic and zootoxic heavy metals, especially zinc, copper, chromium, nickel and lead, taking into account long-term deposition and accumulation in the soil. Heavy metals, especially cadmium and mercury, can be injurious to human health through accumulation in the soil and in plants, with increased absorption through the food chain. Conflicts can be avoided or diminished by consulting the affected population groups at an early stage, possibly developing and planning new sources of employment (see also Vol. III, Compendium of Environmental Standards).

As the increased environmental burden poses additional health risks and hazards, e.g. for women and children (during pregnancy etc.), adequate medical care should be provided in the project region.

In some respects air protection measures lead to a shifting of problems, e.g. where separated residues cannot be recycled. A high degree of recycling of the material and energy present in dusts, sludges and gases is a basic requirement for environmental compatibility, and one that can be met. For materials which cannot be recycled, a dumping system must be selected which will enable environmentally acceptable final dumping.

Although technological development in iron works has led to high water consumption, use of water in the plants can be minimised by recycling as much as 80% and through the use of closed cooling circuits. The standards applicable to the cleaning of wastewater contaminated with heavy metals must be raised from the level of the general rules previously applicable in Germany to a truly "state-of-the-art" level.

Noise levels can be minimised by extensive noise reduction measures. However it is also important to ensure an adequate distance between the works site and neighbouring areas of habitation.

Possible ways of preventing adverse environmental impacts through state-of-the-art emission reductions in old plants include (in the process engineering area) replacing old converter techniques for steel production with low-emission converters and electric furnaces and introducing continuous casting in approximately final dimension form. In the waste gas and air purification area, the use of multistage separators, fine dust separators and the interception of diffuse emission sources is also possible in old plants. Increased recycling of residues and water will help reduce the environmental burdens imposed by old plants. Secondary noise reduction measures are more difficult to implement than primary measures.

6. References

Statutory provisions, regulations

Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft) dated 27.02.1986, GMBl (joint ministerial circular). 1986, Ausgabe p, S.95.

Zweite Allgemeine Verwaltungsvorschrift zum Abfallgesetz (TA-Abfall) Teil 1: Technische Anleitung zur Lagerung, chemisch-physikalischen, biologischen Behandlung, Verbrennung und Ablagerung von besonders chungs-beden Abfen, Gemeinsames Ministerialblatt (joint ministerial circular) Nr. 8, p. 139 - 214 dated March 12, 1991.

24. Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer (Eisen- und Stahlerzeugung), GMBl (joint ministerial circular). 1982, p. 297.

Deutsche Forschungsgemeinschaft: Liste maximaler Arbeitsplatzkonzentrationen (MAK-Wert-Liste), 1990, Mitteilung XXVI, Bundesarbeitsblatt 12.1990, p. 35.

DIN 4301 (April 1981): Eisenhchlacke und Metallhchlacke im Bauwesen.

EC Council Directives of 12 May 1986 on the protection of workers from the risks related to exposure to noise at work - 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): Effluent Guidelines for Iron and Steel

Manufacturing (CFR 420); Iron and Steel Development Document (Volumens I - VIII); Regulations on Standards of Performance for New Stationary Sources (40 CFR 60).

Hinweise f Einleiten von Abwasser in eine ntliche Klnlage, Arbeitsblatt A115 (January 1983) der Abwassertechnischen Vereinigung e.V., St. Augustin.

Lschutz an Hochofen- und Sinteranlagen, herausgegeben vom Minister feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen, Dorf, 1982.

Lschutz an Elektrostahlwerken, herausgegeben vom Minister feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen, Dorf, 1982.

Technische Anleitung zum Schutz gegen L (TA-L) dated July 16, 1968, zur Allgemeinen Verwaltungsvorschrift enehmigungsbede Anlagen nach § 16 der Gewerbeordnung, leitet nach § 66 des Bundes-Immissionsschutzgesetzes dated 15.03.1974, Beilage BAnz. No. 137.

Unfallverhvorschriften, Hauptverband der gewerblichen Berufsgenossenschaften, Bonn u.a. UVV-L, VBG 121 dated 01.01.1990.

VDI-Richtlinie 2288, Blatt 1: Auswurfbegrenzung, Kupolofen-Betrieb, September 1971.

VDI-Richtlinie 2288, Blatt 2: Anleitung fubauswurfmessungen an Kupol, August 1971.

VDI-Richtlinie 3465: Auswurfbegrenzung, Stahlwerksbetrieb, Elektrolichtbo-gen, January 1978.

VDI-Richtlinie 3887: Emissionsminderung, Giereien, in Vorbereitung.

VDI-Richtlinie 2058, Blatt 1: Beurteilung von Arbeitsl in der Nachbarschaft, September 1985.

VDI-Richtlinie 2561: Die Gesamtemission von Gesenk- und Freiformschmieden und Maahmen zu ihrer Minderung (L), July 1968.

VDI-Richtlinie 2560: Perscher Schallschutz, December 1983.

VDI-Richtlinie 3572, Blatt 2: Emissionskennwerte technischer Schallquellen; Umformmaschinen, Schmiedepressen, October 1986.

VDI-Richtlinie 2262: Staubbekfung am Arbeitsplatz, December 1973.

VDI-Richtlinie 3929: Erfassen luftfremder Stoffe (Entwurf), March 1990.

VDI-Richtlinie 2058, Blatt 3: Beurteilung von L am Arbeitsplatz unter Berhtigung unterschiedlicher Tgkeiten, April 1981.

Verordnung rbeitssten (Arbeitsstenverordnung ArbStV) dated 20.03.75, BGBl I (Federal Law Gazette I), p. 729, 15: Schutz gegen L.

Dreizehnte Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes (Verordnung roeuerungsanlagen - 13. BImSchV) dated 22.06.83, BGBI (Federal Law Gazette), Teil I, p. 719.

Verordnung zur Bestimmung von Abfen nach § 2 Abs. 2 des Abfallgesetzes dated April 3, 1990, BGBl I (Federal Law Gazette I), p. 614.

Verordnung zur Bestimmung von Reststoffen nach § 2 Abs. 3 des Abfallgesetzes dated April 3, 1990, BGBl I (Federal Law Gazette I), p. 631.

Verordnung as Einsammeln und Befrn sowie ie erwachung von Abfen und Reststoffen dated April 3, 1990, BGBl I (Federal Law Gazette I), p. 648.

Verordnung efliche Stoffe (Gefahrstoffverordnung GefStoffV) dated 26. August 1986, BGBl I (Federal Law Gazette I), p. 1470 in the version dated. August 23, 1990, BGBl I, p. 790.

Scientific / technical papers

Abwassertechnische Vereinigung: Lehr- und Handbuch der Abwassertechnik, Band VI, Industrieabwer mit anorganischen Inhaltsstoffen, Verlag fhitektur und technische Wissenschaften, Berlin 1985.

Aichinger, H.M., Borgsschulte, B., Britz, H., Held, B., Meyer, O., Strohschein, H.: Stand des primnergiesparenden Konvertereinsatzes in der Bundesrepublik Deutschland, Stahl u. Eisen 108, 1988, No. 13, p. 645 - 654.

Anonym: Die neue Entstaubungsanlage im Oxygenstahlwerk Beeckerwerth der Thyssen Stahl AG, Stahl u. Eisen 110, 1990, No. 4, p. 137.

Baum, J.P., Gerhardt, J.W.: Abgasreinigungsanlagen in der Eisen- und Stahlindustrie und ihre Kosten. in: Stand und Entwicklung der Anlagentechnik im Eisenhesen, Haus der Technik-Verntlichung No. 369, Essen.

Bogdandy, L., Nieder, W., Schmidt, G., Schroer, U.: Die Schmelzreduktion von Eisenerz nach dem Corex-Verfahren im kraftwirtschaftlichen Verbund, Stahl u. Eisen 109, 1989, No. 9, p. 445 - 452.

Buckel, M., Kersting, K., Kister, H., L H.: Neue Entwicklungen bei der Sinterherstellung, Stahl u. Eisen 110, 1990, No. 2, p. 43 - 51.

Direktreduktion von Eisenerz, Verlag Stahleisen mbH, Dorf, 1976.

Dreyhaupt, F.J.: Handbuch fissionsschutzbeauftragte, Verlag T Rheinland, Cologne, 1981.

Fischer, B., R H., D, W., Nagels, Gl., Knorre, H.: Entgiftung cyanidhaltigen Gichtgaswaschwassers von Hoch, Zeitschrift fser- und Abwasser-Forschung 14, 1981, No. 5/6, p. 210 - 217.

Fleischer, G.: Abfallvermeidung in der Metallindustrie, EF-Verlag frgie- u. Umwelttechnik GmbH, Berlin, 1989.

Geiseler, J., Drissen, P., Treppenschuh, H.: Metallurgische Verwertung von Stauben und Schlen der Stahlindustrie, Stahl u. Eisen 109, 1989, No. 7, p. 359 -365.

Gemeinfaiche Darstellung des Eisenhesens, Verlag Stahleisen mbH, Dorf, 1971.

Grebe, K., Gr, G., Lehmk H.J., Schmauch, H.: Die Metallurgie der Direktreduktion von Heststoffen nach dem Inmetco-Verfahren, Stahl u. Eisen 110, 1990, No. 7, p. 99 - 106.

Grher, K., de Haas, H., Mohnkern, H., Ulrich, K., Kahnwald, H.: Staubunterdr in Hochofengieallen, Stahl u. Eisen 111, 1991, No. 3, p. 51 - 56.

Haering, H.U.; Polthier, K.: Gerchemission und Lminderung von Gesenkschmieden, Stahl u. Eisen 108, 1988, No. 4, p. 179 - 184.

Haering, H.U.; Mrs, K.H.; Neugebauer, G.; Polthier, K.: Lminderung durch Einhausung von Lichtbogen, Stahl u. Eisen 109, 1989, No. 7, p. 343 -349.

Haucke, M., Theobold, W.: Behandlung und Aufbereitung von Sten und Schlen in der Stahlindustrie, Gewerschutz-Wasser-Abwasser, Aachen, Bd. 21, 1976, p. 511 - 54.

Kaas, W.: Handhabung von Walzzunderschlamm, Stahl u. Eisen 101, 1981, p. 963 -965.

Krumm, W., Fett, N., Pen, H,. Strohschein, H.: Optimierung der Energieverteilung im integrierten Herk, Stahl u. Eisen 108, 1988, No. 22, p. 1097 - 1106.

K., Haucke, M.: Erfahrungen bei der Behandlung und Verwertung von Stahlwerkssten and -schlen, Stahl u. Eisen 101, 1981, p. 701 - 705.

Lange, M., Minimierung der Dioxin- und Furanemissionen aus Abfall -verbrennungsanlagen, T32, 1991, No. 3, p. E35 - E40.

Lemission und Lminderung an Elektrolichtbogen, Verbesserung des Gesundheitsschutzes f Belegschaft. Bericht No. 809 des Betriebs -forschungsinstituts Dorf.

Lquellen der Eisen- und Metallindustrie, Ed.: Berufsgenossenschaftliches Institut fmbekfung, Mainz, 1973.

Meinck, F.; Stooff, H.; Kohlsch H.: Industrie-Abwer, Stuttgart, Gustav Fischer Verlag, 1968, 4. Aufl.

Ministerium feit, Gesundheit und Soziales des Landes NW: Luftreinhalteplan Ruhrgebiet West, 1. Fortschreibung, 1984 - 1988, Dorf, 1985.

Philipp, J.A. et al: Umweltschutz in der Stahlindustrie, Entwicklungsstand -Anforderungen - Grenzen, Stahl u. Eisen 107, 1987, No. 11, p. 507 - 514.

Philipp, J.A., Maas, H.: Abfallwirtschaft in einem Herk, Stahl u. Eisen 104, 1984, p. 403 - 407.

Rat von Sachverstigen feltfragen: Umweltgutachten 1987, Verlag W. Kohlhammer GmbH, Stuttgart.

Rat von Sachverstigen feltfragen: Sondergutachten Altlasten 1989, Sondergutachten Abfallwirtschaft 1990, Verlag Metzler-Poeschel, Stuttgart.

Reichelt, W.; Kapellner, W.; Steffen, R.: Endabmessungsnahe Herstellung von Flachprodukten, Stahl u. Eisen 108, 1988, No. 9, p. 409 - 417.

Schallschutz in Giereien, Teil 1: Beschreibung von Giereien und Zusammenstellung von vorhandenen Erkenntnissen as Gerchemissions- und Immissionsverhalten, Studie des T Rheinland im Auftrag des Ministers feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen, Dorf, 1983.

Schmidt, H.: Schalltechnisches Taschenbuch, VDI-Verlag, Dorf, 1984.

Steffen, R., L H.: Stand der Direktreduktion von Eisenerzen zu Eisenschwamm, Stahl u. Eisen 108, 1988. No. 7, p. 339 - 343.

Umweltbundesamt [German Federal Environmental Agency]: Altanlagereport 1986, Umweltbundesamt Berlin, 1986.

Umweltbundesamt [German Federal Environmental Agency]: Jahresbericht 1988, 1989 und 1990, Umweltbundesamt Berlin.

Umweltbundesamt [German Federal Environmental Agency]: Checklisten zur Prder Umwelterheblichkeit raumbedeutsamer Vorhaben "Metallverarbeitende Industrie". UBA-FB 87-039, Werbung und Vertrieb Verlag, Berlin 1988.

VDI-Kommission Reinhaltung der Luft: Schwermetalle in der Umwelt, Dorf, 1984.

Vigder, I.: Wasserkreisle f Stahlindustrie, Stahl u. Eisen 103, 1983, p. 1195 -1197.

Wischmann, G.: Gerchemission von Schmiedepressen und Mchkeiten zur Lminderung, Schriftenreihe der Bundesanstalt feitsschutz [German Federal Institute for Occupational Health and Safety], Dortmund, 1984, Heft Fb 393.

1. Scope

Since the non-ferrous metals sector covers a multitude of individual products, charge materials, fuels and processes, this brief can only deal with a few examples of the principal industrial non-ferrous metals. Environmental impacts and protection measures in the production and processing of aluminium, copper, lead and zinc are dealt with as representative of the large number of other non-ferrous metals as well.

The non-ferrous metals sector comprises the subdivisions:

- smelting of appropriately pretreated primary raw metals to produce metals
- processing recycling material in secondary smelting plants, and
- processing of metals to produce standard commercial billets and blanks.

2. Environmental impacts and protective measures

The following deals primarily with the environmental factors arising in the application of current standard processes. For projects using pyrometallurgical processes these are primarily air protection measures; slags are also produced which, depending on their composition, can be a danger to soil, water and living things. In hydrometallurgical treatment processes, measures to protect water and soil predominate.

Since most processes generate noise, the possibility of noise pollution occurring both in the work-place and in the neighbourhood must be taken into account.

Non-ferrous metal production plants occupy a considerable amount of space to accommodate the works site with adjoining areas and connecting roads.

Different quantities of energy are required depending on the production process. The choice of location partly depends on the availability of sufficient low-cost electricity, e.g. in the case of aluminium production. An encapsulated furnace producing aluminium by igneous electrolysis, with a current load of 200 kA and d.c. voltage of 4.2 V requires approximately 13 kWh/kg aluminium. Zinc production with the stages of roasting, leaching, neutralization, leachate cleaning and electrolysis requires 4 kWh/kg zinc. Values for copper production are somewhat higher. Energy requirements of secondary smelting plants are considerably lower: 20% of the primary smelting energy requirement with 100% scrap copper, around 40% with 100% scrap zinc and 10% with 100% scrap aluminium.

2.1 Aluminium extraction

The Bayer process is used almost exclusively for producing aluminium oxide, the charge material for primary aluminium smelting plants. Bauxite is treated with soda lye under pressure and heat in autoclaves to produce aluminium hydroxide and red mud. The latter is separated, washed and filtered, and may be recyclable or may have to be dumped. After sedimentation and filtration, the aluminium hydroxide is converted to aluminium oxide (alumina) by fluidized bed calcination at around 1100°C.

Large quantities of red mud (1 - 2 t/d Al2O3) are produced. Depending on its composition and the situation in the country in question, it should be used for extracting aluminium oxide and iron, producing flocculation agents for wastewater cleaning or the manufacture of building materials. Red mud which cannot be further processed must be dumped. Where it is stored on a dump, special requirements must be met in respect of sealing and treatment of percolation water. Dumping should be on a single-purpose dump subject to continuous supervision.

A considerable amount of fine dust may be produced upon loading, unloading and transport of fine-grained materials (bauxite, alumina) unless enclosed conveyor systems and suitable storage facilities are provided. Waste gas from the calcination furnaces contains dust with an aluminium oxide content which is deposited in dry filters and recirculated. Dust emissions in cleaned waste gas are under 50 mg/m3.

The process most commonly used for extracting pure aluminium is igneous electrolysis. Aluminium oxide at approximately 950°C is dissolved in a molten mixture of aluminium fluoride and cryolite and separated by direct current into pure aluminium and oxygen. The liquid aluminium is periodically drawn off and cast.

The following emissions and raw materials occur with the extraction of pure aluminium:

- primary alumina dust during storage, transport and charging;
- primary dust during anode production (petroleum coke etc.);
- volatile binding agents, fluorine from anode residues in the waste gas from the anode burning kilns;
- fluorides (dust and gaseous form) in the pot waste gas containing CO/CO2; hydrogen fluoride gas is highly corrosive, harmful to health and the environment (also affects plant growth);
- used cathodes, containing fluoride;
- furnace breakage materials with fluoride components;
- wastewater.

The following individual protection measures are necessary:

Fine dust: Use of enclosed conveying systems (e.g. pneumatic conveyors).

Anode production: Extraction of dust and gaseous emissions, electrostatic waste gas cleaning, wet-chemical fluorine separation. Use of fabric filters permits clean gas dust concentrations of under 20 mg/m3 and fluorine contents of under 1 mg/m3.

Pots: Pot encapsulation with anode gas extraction and waste gas cleaning, wet chemical fluorine recycling or combined dedusting and dry absorption in the Al2O3 fluidized bed with direct recirculation. Wet chemical separation with water recirculation produces a sludge which, after drying, can only be partly returned to the process. Dry absorption and return of the filter dust to the process is preferable as this relieves the burden on the water circuit. Clean gas dust contents of under 30 mg/m3 and fluorine compounds of under 1 mg/m3 are obtained with encased, centrally controlled, large-capacity furnaces with computerised waste gas regulation and dry absorption with fabric filter.

Cell house: Shop air extraction and cleaning is compulsory with non-encased furnaces. Can be retrofitted.

Cathode and furnace Dumping only on specially protected, single-purpose breakage: dumps Cryolite, used as a fluxing agent for the electrolysis, can be obtained by processing (fluorine recycling).

Wastewater: The discharge of wastewater from aluminium oxide production and aluminium smelting must satisfy the requirements laid down under the generally recognised standards regarding chemical oxygen demand for aluminium and fluorides.

With respect to noise, a distinction is made between noise emissions affecting the neighbourhood and those affecting the workplace. Emission from main noise sources can be restricted by encapsulation and by means of silencers on air intakes and outlets. A noise reduction plan should be prepared during the planning phase.

2.2 Heavy metal ore smelting

The composition of the concentrates or raw materials is crucial for the applicable smelting process and thus also for the nature and quantity of the environmental pollutants arising. Sulphidic ore concentrates are thus mostly smelted by pyrometallurgical processes, whilst hydrometallurgical processes are employed for oxidic, sulphidic-oxidic and complex ores.

Combined processes are also used in which, for instance, material roasted by a pyrometallurgical process undergoes further treatment by hydrometallurgy. The charge material is ore enriched by beneficiation.

· Pyrometallurgical process stages

Roasting: Partial or total desulphurization (dead roasting) of the charge material;

Sinter roasting: Roasting of sulphur with admission of air (conversion of sulphides to metal oxides and SO2 gas) with simultaneous agglomeration of the roasted material for use in shaft furnaces;

Rolling: Metal oxide enrichment by controlled volatilization (Zn);

Smelting: Separation of gangue (slags): production of high grade metal sulphides (Cu2S) by partial combustion of the sulphur content and reduction of metal oxides (PbO, ZnO) under coke combustion with air admission;

Fuming: Conversion of metal sulphide to metal in a converter;

Pyrometallurgical Cleaning molten metal of oxygen, sulphur, impurities refining: and tramp metals by intermetallic precipitation, slagging and/or volatilization;

Slag cleaning: Thermal processing of slags to extract metal components.

Numerous emissions and residual materials occur with the above processes:

- Waste gases of various origins
- Primary dust from the charge material,
- Dusts from volatilized metals, including lead, zinc, arsenic, tin, cadmium, mercury, selenium, tellurium and their compounds (condensed after cooling),
- gaseous materials including SO2, HCl, HF, CO, CO2;
- Wastewater from coolant circuits and waste gas scrubbing;
- Final slags with residual metal contents, sulphates, sulphides; possibility of polychlorinated dibenzo-dioxins and -furans with chlorinating methods (e.g. copper roast leaching process);
- Furnace breakage materials, containing arsenic, lead, cadmium, mercury and cyanide.

For protective measures to be effective, it is essential that all emissions, including diffuse emissions of gas and dust, be efficiently intercepted at their points of origin. Diffuse emissions can be intercepted by hoods, covers or encapsulation, also by constructional measures such as encasement of conveyor belts or enclosed bays. Roasting furnaces should not be outdoor installations.

Dust: Waste gases are normally dedusted in dry filter systems (cyclones, electrostatic precipitators, fabric filters). Dedusting efficiency of up to 99.9% is possible, but depends on the permissible solid or pollutant content. Dusts can also be separated with fabric filters in lead smelting plants. Good separation efficiency is particularly important for the environment because waste gas from smelting contains toxic substances such as arsenic, antimony and lead in the form of fine dust. High-performance filtering separators have proved effective for fine dust separation.

Dust recycling for enriching and recovering metals. Separate pyrometallurgical or hydrometallurgical processing of tramp metals, for example As, Cd. Fabric filters are the principal method of dust separation. Clean gas dust contents of 10 mg/m3 can be obtained. Best values are around 1 mg/m3, e.g. in lead smelting plants.

SO2 gas: Removed by waste gas scrubbing followed by neutralization. SO2 concentrations in waste gas of over 3.5% are suitable for sulphuric acid production. In certain circumstances liquid SO2, gypsum or elementary sulphur can be produced as a possible preliminary stage for industrial usage. Wet chemical waste gas cleaning processes are used for lower SO2 concentrations. Only limited SO2 concentrations and overall quantities may be discharged via chimneys.

Oil mists: If oil mists are present in the waste gases from shaft furnaces on account of the charge material, waste gases must undergo thermal afterburning.

Final slags/ Slags and furnace breakage material should be stored furnace breakage: in a specially protected single-purpose dump, since toxic and water-polluting substances such as heavy
metals may be released through leaching and weathering. Depending on residual metal content and
concentrations of other substances such as sulphides, sulphates, dioxins and furans, may possibly be used for road construction or reprocessing, or may have to be discarded.

Wastewater: Wastewater from waste gas scrubbing and slag granulation is polluted with heavy metals. Dissolved and undissolved metallic compounds in communal treatment plants lead to excessive metal concentrations in sewage sludges, restricting or preventing agricultural use.

Measures for reducing pollutant loads include minimizing wastewater volumetric flow by recirculation, recycling of treated wastewater and separating wastewater requiring treatment from that not requiring treatment. Extremely high standards must be applied to the discharge of wastewater with metal compounds toxic to humans and the ecosystem. State-of-the-art wastewater treatment systems include selective ion exchangers, microfiltration systems, reversal osmosis and thermal concentration processes. Production-specific concentrations of cadmium, mercury, lead, zinc, arsenic, copper, nickel and chromium should be limited.

Significant waste gas and emission reductions are achieved by combining several process steps in modern processes such as the flash cyclone reactor and the flash smelting method. Trials in a copper smelting plant and a lead smelting plant yielded reductions of 75%.

· Hydrometallurgical processes

Charge materials are oxidic ores, pretreated sulphidic ore concentrates which can be hydrometallurgically treated, or sulphidic concentrates which undergo oxidizing leaching. Hydrometallurgy processes also include extraction and refinement electrolysis.

Leaching: Treatment and lixiviation of the metals to be recovered, e.g. with dilute sulphuric acid for zinc production. For dump leaching in the case of very low-grade ores (bottom sealing necessary for soil and ground water protection);

Enrichment: Concentration of weak solutions by fluid extraction, using an organic solvent with simultaneous leachate cleaning.

Cleaning: Separation of accompanying substances and impurities by solids-fluid extraction and/or precipitation (hydroxide or sulphide precipitation, cementation);

Extraction: Electrolytic metal deposition with insoluble anodes (e.g. with Zn, Cu);

Refining: Electrolytic metal deposition with soluble anodes (e.g. with Cu, Pb).

The following environmentally relevant emissions and substances may be produced with the above processes:

Wastewater: Greater or lesser quantities of zootoxic and phytotoxic heavy metal components may be present in the wastewater, depending on the charge materials.

Leachate residues: Leachate residues contain metallic compounds harmful to the environment.

Waste gases: Sulphuric acid mists are produced in the extraction electrolysis; metal-containing vapours, e.g. in crude copper anode furnaces; organic solvents, e.g. xerosin, during liquid extraction in the enrichment process.

Anode sludge: This sludge contains metals and metal compounds, e.g. gold, silver, lead, tin, arsenic, antimony.

Spent electrolyte: The electrolyte contains dissolved metallic compounds of iron, nickel, zinc, arsenic and cobalt.

The following individual protection measures are necessary:

Wastewater: The wastewater volume must be reduced by appropriate measures, e.g. recirculation, recycling. Wastewater containing heavy metal pollutants must be treated by state-of-the-art methods. Wastewater contaminated with e.g. cadmium and mercury must be channelled and treated separately.

For wastewater treatment, especially low production-specific concentrations are to be stipulated, with residual concentrations of under 1 mg/l Cd and under 0.1 mg/l Hg to be achieved. Suitable processes include ion exchange, ultrafiltration and electrolysis.

Leachate residues: Residues must be converted by washing and neutralization processes to form compounds suitable for final dumping. Where technically possible, solvent residues are to be eliminated.

Waste gases: Permissible work-place concentrations for sulphuric acid mist can be achieved by appropriate room air ducting and, where necessary, waste air scrubbing.

By equipping a crude copper anode furnace with fabric filters, it was possible to separate gaseous metallic compounds to clean gas concentrations of 0.001 mg cadmium/m3, 0.05 mg lead/m3 and 1.9 mg/arsenic/m3. With liquid extraction using organic solvents, precautions must be taken against combustion and explosion and for fire fighting.

Anode sludge/ Special hydrometallurgical or pyrometallurgical electrolyte: measures are to be employed for the phased recovery of useful materials and the extraction of tramp metals; e.g. electrolytic deposition of arsenic and antimony or precipitation of nickel, iron or cobalt.

The extraction of zinc from zinc blende or galmei inevitably yields 3 to 4 kg cadmium per tonne of zinc as an alloy element in crude zinc or in the form of residues. Cadmium is extracted in primary zinc smelting plants by dry and wet absorption processes. The generally preferred wet processes and electrolytic cadmium extraction result in no direct production of cadmium dusts. The waste gases resulting from the smelting of cadmium to produce commercial formats can be introduced to the air for roasting, in order to achieve total waste gas cleaning.

Due to the toxic effects of cadmium, strict requirements must be imposed on work-place hygiene and waste air and water cleaning. In heavy metal ore smelting operations, main noise sources are wherever possible to be restricted by encapsulation and by means of silencers on air intakes and outlets. A noise reduction plan should be prepared at the project planning stage. In the case of operations generating high levels of noise, one should preferably begin by damping or eliminating occurrences and noise sources which arise only periodically.

To protect work-places from noise, installations should be extensively automated and equipped with appropriate control rooms. Protective equipment includes fireproof clothing, breathing equipment and ear protectors, depending on where they are working; protective helmets and safety footwear must be worn in all areas.

Measures for safety in the work-place and to protect the soil of the works site include all precautions to prevent the discharge of water-polluting substances. Special attention is to be paid to installations for producing, handling and using water-polluting substances. Relevant precautions include storage tanks with leakproof drip trays, overfilling safeguards, sealed and impermeable floor surfaces and leak testing, and these should be set forth in a manual.

2.3 Secondary smelting plants

Secondary smelting plants process mainly recycling material (shredder scrap, cables, batteries etc.), heavily contaminated mixed scrap, production scrap with alloy constituents that are difficult to remove, also slags, dross and other metalliferous residues. Predominantly pyrometallurgical processes are employed for metal recovery.

Environmental burdens stem mainly from impurities and pollutants present in the charge material, e.g. oil, paint, plastics, solvents or salts.

Special characteristics of the emissions and substances and requisite safeguards are as follows:

· Aluminium scrap melting plants

Salt slags: Aluminium scrap is usually melted down in rotary or hearth type furnaces under a layer of liquid salt to prevent ingress of air. The salt absorbs impurities present in the scrap and occurring during the melt-down process and produces salt slag (0.5 t/t Al).

Dumping these salt slags seriously pollutes the dump percolation water, therefore salt slag should be processed and returned to the melting process.

Waste gases: The molten aluminium is refined in converters using chlorine gas. The waste gases contain dusts, gaseous chlorine and fluorine compounds and chlorine gas; they may also contain organic substances which, depending on the operating conditions, may include traces of especially environmentally hazardous materials such as polychlorinated dibenzo-dioxins and -furans. Adequate separation of the dusts and inorganic compounds is achieved by dry absorption and fabric filters. Emissions of organic substances can be minimized by scrap sorting and cleaning or by special thermal afterburning of the waste gases.

· Copper scrap melting plants

Dust: When melting down copper-bearing residues, the interception and dry separation of emissions produced on charging and running-off are particularly important. Where oil mist occurs due to the impurity of the copper scrap, waste gases must undergo thermal afterburning before dust separation. For ecological and economic reasons, melting down should take place in a converter with top lances in a shop with waste air collection and cleaning rather than in shaft furnaces.

· Lead scrap melting plants

Waste gases: When recycling scrap batteries, PVC residues may give rise to gaseous inorganic chlorine compounds which are absorbed in the dust and in the slag.

Depending on the operating conditions, small quantities of polychlorinated dibenzo-dioxins and -furans may be present in the waste gases when recycling scrap cables. Emissions of health-endangering dioxins and furans can be restricted by careful sorting of scrap lead, scrap batteries and cables. Trials are in progress on activated-charcoal-based equipment for separation of these substances. Cleaning of scrap batteries results in varying quantities of battery acid (sulphuric acid) entering the washing water. The washing water is contaminated with lead, antimony, cadmium, arsenic and zinc. Separate interception and treatment is necessary.

2.4 Non-ferrous metal semifinishing works

In semifinishing works, the main problems of maintaining clean air stem from the upstream format foundries. These use large amounts of defined scrap in addition to primary metal which may call for pyrometallurgical smelting refining (e.g. with chlorine gas compounds in the case of Al).

Oily and plastic-coated scrap produces soot, oil mist, chlorine- and fluorine-bearing acid mist and similar substances on being melted down. Formation of polyhalogenated dibenzo-dioxins and -furans cannot be ruled out. For this reason scrap should be precleaned in fuming furnaces with afterburning chambers; depending on the permissible level of purity, waste gases are to be cleaned in electrostatic precipitators and/or gas scrubbers.

Waste gas from melting furnaces can contain metal oxides, volatile metalliferous vapours and halogen compounds which must be separated in dust filters or waste gas scrubbers. Through process automation and the use of additional reactors, even low-capacity secondary smelting plants (2,400 t/a) can achieve low clean gas emission values, e.g. 5 mg/m3 dust, less than 1 mg/m3 fluorine compounds, by chemisorption combined with cyclone and fabric filter. Separation efficiency for chlorine compounds can be as high as 98%.

Cooling bays for gas-emitting dross and slag are also to be connected to centralized waste air extraction systems.

Alkaline or acid solutions should be used for degreasing, cleaning and pickling metal surfaces. Organic solvents containing halogens should be avoided. Flushing water and used pickling and washing liquids are to be treated in neutralization plants.

Sludge residues are either pyrometallurgically processed in a smelting plant or, if they contain no pollutants, dumped. Vapours from heated pickling and rinsing baths must be extracted, precipitated by gas scrubbers and neutralized. Polluted waste must be placed on protected dumps with collection of percolation water.

As non-ferrous metal semifinishing plants are frequently situated close to residential zones, consideration must be given to noise reduction measures and the necessary distance.

3. Notes on the analysis and evaluation of environmental impacts

Non-ferrous metal industrial operations using thermochemical or pyrometallurgical processes produce considerable quantities of waste gases laden with environmentally harmful substances. Air protection measures must therefore be a priority.

The following examples illustrate the possible pollutant content of the waste gases:

- aluminium smelting plant, toxic fluorine components in the anode gas raw gas approx. 10 kg F/t Al
- copper smelting plant, sulphur dioxide in the waste gas raw gas approx. 2.6 t SO2/t Cu

The values indicate that even in regions with low levels of existing pollution, waste gases from metal smelting plants must on no account be discharged uncleaned. Wet and dry processes are available for cleaning, dry processes being preferred for ecological and economic reasons.

Continuous monitoring involving measurements to verify the effectiveness of the separation systems is necessary both after erection of the plant and during its operation. Detailed descriptions for carrying out emission and immission measurements are contained in the guidelines of the German Association of Engineers VDI. In Germany the obligatory emission and immission values are detailed in TA-Luft (Technical Instructions on Air Quality Control).

In plants using hydrometallurgical processes, to reduce environmentally harmful substances to a minimum, intermediate products and residues must undergo repeated chemical treatment, filtration, electrolytic precipitation or scrubbing with subsequent neutralization. Wastewater from gas scrubbing or pickling plants may only be returned to receiving bodies of water once it has been chemically neutralized and freed of solids. Guideline values for permitted pollutant concentrations must be established for discharging wastewater in accordance with the state of art. Reference values may be obtained from the regulations in force in Germany. In every case care must be taken to ensure that drinking water and other water resources are not impaired. Analytical processes have been defined under German DIN standards to determine pollutant concentrations in wastewater; in Germany these are detailed in Allgemeine Verwaltungsvorschriften [General Administrative Regulations]. Routine measurements are also to be carried out to monitor the efficiency of water treatment and clarification plants. The scope of measurements and the inspection and maintenance intervals of wastewater - and waste gas - cleaning systems must be defined in an operating manual.

Contaminated material is to be stored in such a way as to prevent soil and groundwater contamination. Where possible, single-purpose dumps should be established, with sealing and percolation water collection and treatment systems which satisfy stringent requirements.

As in Germany, works environmental protection officers should be deployed in non-ferrous metal works who are totally independent of the production side. They are obliged to monitor adherence to the regulations.

In addition to monitoring external pollutant discharge, internal work-places must also be inspected for pollutant concentrations, noise and safety. Suitably qualified safety officers and a works doctor should be appointed for these purposes.

4. Interaction with other sectors

Normal annual production capacities of newer non-ferrous metal smelting plants are between 50,000 and 100,000 t. Allowance must be made for future capacity expansions. Due to the quantity of land occupied and the environmental pollution involved, projects cannot be considered in isolation. As early as the initial location selection phase, existing prior pollution of air, water and soil must be taken into account, making adequate allowance for the additional burdens imposed by such an industrial complex. As early as the planning phase, and when defining permissible immissions, effects on the environment must be considered from the point of view of community development. Adequate distancing from the nearest residential zones is to be guaranteed. Further details are contained in the environmental brief Planning of Locations for Trade and Industry.

Raw materials for smelting plants have to be extracted in large quantities from underground or surface mines. The environmental briefs on mining provide information on the environmental impacts. Efficient transport routes are necessary for transporting charge materials and products. Details are contained in the briefs Road Traffic, Railways and Railway Operation and Shipping.

A special secondary effect of the use of electrolytic processes is that their profitability, and particularly that of an aluminium smelting plant depends on the availability of cheap electricity. Additional pollution results from the erection or extension of power stations and the associated construction, particularly of hydraulic engineering works (see environmental briefs Thermal Power Stations and Power Transmission and Distribution).

A single-purpose dump must be established for non-recyclable products and waste, including slag and furnace breakage material (see environmental brief on Disposal of Hazardous Waste and Volume III, Compendium of Environmental Standards).

5. Summary assessment of environmental relevance

Processes and raw materials utilized in non-ferrous metal smelting plants for extracting aluminium, copper, lead and zinc, and also refining and smelting plants for further processing, produce emissions and raw materials which can pollute the environment. Of special significance are heavy metals which endanger health and in some cases are carcinogenic. In many countries this concerns especially the poorer sections of the population who are particularly at risk due to malnutrition and illness. The same of course applies to metal smelting plants other than those mentioned here.

Environmental damage can be reduced by selecting locations with relatively insensitive landscapes where there is unlikely to be any great effect on the regional productiveness of the natural environment. It is also necessary to exclude regions that are already heavily burdened with high existing or background levels of fluorine compounds and heavy metals. In this regard it should be noted that anthropogenic heavy metals are often more readily plant-available than lithogenic or pedogenic heavy metals.

Pyrometallurgical processes cause mainly air pollution in the form of gases, mists and dusts which must be minimized in gas scrubbers or returned for further processing. Apart from the ecological benefit, this form of emission reduction has the economic benefit of recovering valuable metals or producing sulphuric acids. Similar conditions exist for secondary smelting plants but with the additional problem of polluted charge materials. Depending on the operating conditions, halogen-bearing pollutants combined with organic materials are a particular potential source of polyhalogenated dioxin and furan emissions (waste gas emission concentrations of the order of nanograms).

Emissions and residues from hydrometallurgical processes on the other hand can pollute wastewater and dumps. Recycling of water in the circulation system is very important. Though it is state-of-the-art practice to recirculate liquid process materials such as acids, alkalies or solvents by regeneration, thereby reducing residues, these must be subsequently processed and the waste products neutralized in more or less costly stages to recover valuable metals and/or extract pollutants. Checks must be made in every case to determine whether pollution of groundwater or surface water is possible due to the storage or emission of primary, intermediate or end products. Pollutant yield and hence the necessary outlay for pollutant reduction is significantly lower in the case of semifinishing works.

A survey should be conducted in every case to determine whether agricultural use of the land in the vicinity of the works will be impaired by large-area pollution with phytotoxic and zootoxic heavy metals, especially zinc, copper, chromium, nickel and lead, taking into account long-term deposition, accumulation and reactivity in the soil. The environmental risk resulting from heavy metals in the soil must be distinguished according to the form of bonding of their elements which in turn depends on their origin.

Heavy metals, especially cadmium, can be injurious to human health through accumulation in the soil and in plants, with increased absorption through the food chain, leading in particular to kidney damage. Preliminary calculations of the expected additional environmental burdens are necessary for assessing these indirect effects via the air - soil - food chain. As a precaution, it is advisable to restrict agriculture in the immediate vicinity. Conflicts can be avoided or diminished by consulting the affected population groups at an early stage, possibly developing and planning new sources of employment. The question as to whether the increased environmental pollution poses additional health risks and hazards, e.g. for women and children (during pregnancy etc.) should be investigated, and adequate medical care provided. In addition to the pollution burdens, attention must also be paid to the noise emitted by the plant machinery. Depending on the plant design, noise levels as high as 125 dB(A) may be emitted. Noise levels can be minimized by noise reduction measures which are to be specified in a noise reduction plan. The wearing of personal ear protection must be obligatory in workplaces with noise levels in excess of 85 dB(A) and must be monitored.

For environmental protection measures to be effective, it is vital that personnel should be made sensitive to the issues and receive appropriate training. Although the smelting industry already has a range of proven methods and processes at its disposal for effective pollution control, their application can be excessively cost-intensive where pollutant emissions are too low for improvements to be economic but too high to be ecologically harmless. In these cases, bearing in mind the long-term effects of heavy metal pollution, one must give considerable weight to the needs of environmental protection, even putting this before the profitability of the individual plant.

The emphasis of current development work is towards totally enclosed circuits in the production system. The aim is to enclose the circuit to prevent harmful effects on the biosphere through ever better utilization of charge material, production of pure intermediate and end products without recourse to dumping, with improved emission protection and recycling of separated dusts and solids.

6. References

Statutory provisions, regulations

Abwassertechnische Vereinigung (ATV): Arbeitsblatt R 115, Hinweise f Einleiten von Abwasser in eine ntliche Abwasseranlage, January 1983.

Allgemeine Verwaltungsvorschrift zur derung der allgemeinen Rahmenverwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer. GMBl (joint ministerial circular). No. 37, 1989, p. 798.

Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft) dated 27.02.1986, GMBl (joint ministerial circular). 1986, Ausgabe A, p. 95.

Zweite Allgemeine Verwaltungsvorschrift zum Abfallgesetz (TA-Abfall) Teil 1: Technische Anleitung zur Lagerung, chemisch-physikalischen, biologischen Behandlung, Verbrennung und Ablagerung von besonders chungsbeden Abfen, vom M 1991, GMBl (joint ministerial circular). No. 8, p. 139.

39. Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwer in Gewer (Nichteisenmetallherstellung). GMBl (joint ministerial circular). No. 22, 1984, p. 350 - 351.

Deutsche Forschungsgemeinschaft: Liste maximaler Arbeitsplatzkonzentrationen (MAK-Wert-Liste), 1990, Mitteilung XXVI, Bundesarbeitsblatt 12, 1990, p. 35.

Environmental Protection Agency (EPA): Effluent Guidelines and Standards for Non-Ferrous-Metals, 40 CfR 421.

GVBl. des Landes Hessen, Teil 1, 31.03.1982.

Ministerium feit, Gesundheit und Soziales des Landes Nordrhein-Westfalen: Umweltprobleme durch Schwermetalle im Raum Stollberg, 1975, Dorf.

5. Novelle zum Wasserhaushaltsgesetz: Mindestanforderungen nach § 7a, BGBl. I (Federal Law Gazette I), p. 1529.

Technische Anleitung zum Schutz gegen L (TA-L) vom 16.07.1968, Beilage BAnz. (Supplement to the Federal Law Gazette) No. 137.

Unfallverhvorschriften: Hauptverband der gewerblichen Berufsgenossen-schaften, Bonn u.a. UVV-L, VBG 121 of 01.01.1990.

VDI-Richtlinie 2262: Staubbekfung am Arbeitsplatz, December 1973.

VDI-Richtlinie 2285: Auswurfbegrenzung, Bleih December 1975.

VDI-Richtlinie 2058, Blatt 3: Beurteilung von L am Arbeitsplatz unter Berhtigung unterschiedlicher Tgkeiten, April 1981.

VDI-Richtlinie 2560: Perscher Schallschutz, December 1983.

VDI-Richtlinie 2058, Blatt 1: Beurteilung von Arbeitsl in der Nachbarschaft, September 1985.

VDI-Richtlinie 2102: Emissionsminderung, Kupferschrotthund Kupferraffinierien, Entwurf February 1985.

VDI-Richtlinie 2286: Emissionsminderung, Aluminiumschmelzflulektrolyse, Entwurf January 1987.

VDI-Richtlinie 3929: Erfassen luftfremder Stoffe, Entwurf March 1990.

VDI-Richtlinie 2310: Bler 30 und 31: Maximale Immissionswerte fi (Blatt 30) und Zink (Blatt 31) zum Schutze der landwirtschaftlichen Nutztiere, July 1991.

VDI-Richtlinie 3792, Blatt 3: Messen der Immissions-Wirkdosis von Blei in Pflanzen, April 1991.

Verordnung rbeitssten (Arbeitsstenverordnung - ArbStV) of 20.03.75, BGBl. I (Federal Law Gazette I), p. 729, 15 Schutz gegen L.

Verordnung efliche Stoffe, Gefahrstoffverordnung (GefStoffV) of 26. August 1986, BGBl. I (Federal Law Gazette I), p. 1470, in the version dated 23. August 1990, BGBl. I, p. 790.

Verordnung zur Bestimmung von Abfen nach § 2 Abs. 2 des Abfallgesetzes of April 3 1990, BGBl. I (Federal Law Gazette I), p. 614.

Verordnung zur Bestimmung von Reststoffen nach § 2 Abs. 3 des Abfallgesetzes of April 3, 1990, BGBl. I (Federal Law Gazette I), p. 631.

Verordnung as Einsammeln und Befrn sowie ie erwachung von Abfen und Reststoffen of April 3, 1990, BGBl. I (Federal Law Gazette I), p. 648.

Verordnung nlagen zum Lagern, Abfund Umschlagen wassergefdender Stoffe und die Zulassung von Fachbetrieben.

Scientific/technical papers

Bureau of Mines, Washington 1973, Control of Sulfur Oxide Emissions in Copper, Lead and Zinc Smelting.

Buann, H.: Stand und Entwicklung des Kupferrecyclings in: Fleischer, G., Abfallvermeidung in der Metallindustrie, p. 159 - 166, Ef Verlag frgie und Umwelttechnik, Berlin 1989.

Corwin, T.K. et al: International Technology for the Nonferrous Smelting Industry, Noyes Data Corporation, Park Ridge NJ, 1982.

Dengler, H.: Behandlung schwermetallhaltiger Abwer in: UTZ Materialien, 1989; Zentrum felttechnik beim Battelle-Institut Frankfurt am Main.

Deutsche Gesellschaft fhnische Zusammenarbeit (GTZ), Dornier-Studie: Erstellung eines Kataloges von Emissions- und Immissionsstandards, October 1984.

Gesellschaft Deutscher Metallh und Bergleute, Hauptversammlungsvortr, Stuttgart 1972, Umweltschutz in der Metallhndustrie.

Gr, Machelet, B., Podlesak, W.: Kontrolle der Schwermetallbelastung landwirtschaftlich genutzer B in der DDR.

Hartinger, L.: Taschenbuch der Abwasserbehandlung f metallverarbeitende Industrie, Carl Hauser Verlag, Munich 1976.

Kirchner, G.: Die Bedeutung von Sekundluminium f Aluminium-Versorgung in: Fleischer, G., Abfallvermeidung in der Metallindustrie, p. 173-179, Ef Verlag frgie und Umwelttechnik, Berlin 1989.

Kloke, A.: Orientierungsdaten ferierbare Gesamtgehalte einiger Elemente in Kulturb, Mitt. VDULFA 1980, p. 1 - 3 and 9 - 11.

Koch, C.T., Seeberger, J.: ologische Mwertung, Verlag C.F. M Karlsruhe, 1984.

Landtag Nordrhein-Westfalen: Plenarprotokoll 11/28 of 03.05.1991.

Lquellen der Eisen- und Metallindustrie: Berufsgenossenschaftliches Institut fmbekfung, Mainz 1973.

Merz, E.: Minimierung der Belastung durch Metalle und Metalloide, Vortrag im VDI-Kolloquium "Krebserzeugende Stoffe in der Umwelt", 23.04.1991. Mannheim, VDI-Bericht in Vorbereitung.

Miehlich, G., Lux, W.: Eintrag und Verfeit luftbr Schwermetalle und Metalloide in B, VDI-Berichte No. 837, 1990, p. 27 - 51.

Persche Mitteilungen: Wirtschaftsvereinigung Metall e.V., Dorf, 1991.

Rademacher, K.D., Ko K.D.: Wassergefdende Stoffe, Springer Verlag, Berlin 1986.

Riss, A. et. al: Schwermetalle in B and Graufwuchs in der Umgebung einer Kupferhn Brixlegg/Tirol, VDI-Berichte 837, 1990, p. 209-223.

Rack, von A.: Integrierter Umweltschutz - die Aufgabe der Zukunft, Erzmetall, 44 (1991), No. 2, p. 67 - 74.

Spona, K., Radtke, U.: Blei-, Cadmium- und Zinkbelastung von B im Emissionsgebiet einer Zinkhn Duisburg, VDI-Berichte 837, 1990, p. 165 - 183.

Ullmanns Enzyklope der technischen Chemie, 4. Auflage, Band 6 (Umweltschutz), Band 7 (Aluminium), Band 8 (Blei), Band 15 (Kupfer), Band 24 (Zink) - 1974/1983.

Umweltbundesamt [German Federal Environmental Agency] Berlin, April 1978: Stand der Technik bei PrimAluminiumh

Umweltbundesamt [German Federal Environmental Agency] Berlin, March 1980: Richtlinien fssionsminderung in NE-Metallindustrien, incl. ausfhe Bibliographie.

Umweltbundesamt [German Federal Environmental Agency], Berlin, March 1983, R. Fischer: Maahmen und Einrichtungen zur Reinhaltung der Luft bei NE-Metallhund Umschmelzwerken.

Umweltbundesamt [German Federal Environmental Agency] Berlin, 1986: Altanlagenreport 1986, p. 59 - 73.

Umweltbundesamt [German Federal Environmental Agency] Berlin: Jahresberichte 1986, 1987, 1990.

Umweltbundesamt [German Federal Environmental Agency] Berlin, 1989: Luftreinhaltung '88, Tendenzen - Probleme - Lgen, Erich Schmidt Verlag.

Umweltbundesamt Vienna: Montanwerk Brixlegg - Wirkungen auf die Umwelt, 1990.

VDI-Kommission Reinhaltung der Luft: Schwermetalle in der Umwelt, Dorf, 1984.

VDI-Berichte 837, 1990, p. 593 - 612.

Verein Deutscher Ingenieure, Bericht 203, 1979, Schwermetalle als Luftverunreinigung - Blei, Zink, Cadmium.

Williams, Roy E.: Waste Production and Disposal in Mining, Milling and Metallurgical Industries,

Miller Freeman Publ., San Francisco, 1975.

1. Scope

The different branches of mechanical engineering are concerned with the machining and processing of ferrous and non-ferrous metals. This covers the whole range of production processes, which can be subdivided as follows:


Metal cutting

* drilling

* milling

* turning

* planing

* broaching

* sawing

* filing

* honing

* grinding

* lapping

* sandblasting

* chiselling


Non-cutting processes

Thermal bonding

* oxy-acetylene welding

* electric welding

* inert-gas-shielded welding

* submerged arc welding

* build-up welding

Thermal cutting

* oxy-acetylene cutting

* plasma cutting


* forging

* deep drawing

* bending


* punching

* cutting

* shearing

* nibbling


* riveting

* adhesive bonding

* soldering

Surface treatment

* surface cleaning

* degreasing

* pickling

* surface coating

* phosphating

* chromatizing

* electroplating

* enamelling

*hot-dip galvanizing

* anodizing

* painting, lacquering

* surface annealing

The raw materials used in these processes may have high environmental pollution potential (e.g. heavy metals), and hazardous production materials may be used (e.g. cleaning agents containing chlorinated hydrocarbons). At the same time, vapours, heat and noise are generated, together with various waste products and wastewater, leading to adverse effects on the environment and on man, especially in enclosed areas.

In shipyards, the main process is welding. This is made additionally hazardous by the fact that welders working on bulkheads often have to work in enclosed areas, which further aggravates the health risks discussed below.

2. Environmental impacts and protective measures

A product undergoes numerous production stages in the course of the metalworking process. The environmental impacts of these stages affect the workplace and hence the people working there. They also affect the air, water and soil.

Due to their proximity to the point of origin, it is the workforce who are most seriously exposed to the production hazards. In highly industrialised countries this is the subject of comprehensive worker protection rules. The workplace hazards are listed below, taking as examples the most important and environmentally relevant machining processes. This is followed by a description of the wider environmental effects including the problems of waste disposal.

2.1 Potential hazards of selected operations

2.1.1 Metal cutting

Machining processes such as drilling, milling, turning, cutting, honing, grinding etc. make use of oils and oil preparations for lubricating and cooling tools and workpieces, to prevent overheating and possible melting of the workpiece and tool. Oils are dosed by spraying or pouring systems at rates of up to 100 litre/min. in order to dissipate heat. The spraying of moving and sometimes very hot tools and workpieces produces vapours containing droplets known as aerosols.

Metalworking techniques require appropriate coolants which must combine several different properties (non-foaming, corrosion-inhibiting, non-decomposing etc.).

Such a wide range of properties can only be achieved through the addition of varying quantities of chemical additives. These are added to the coolants in the form of non-water- miscible cutting oils or water-miscible concentrates.

More than 300 individual substances are used as coolant components. The following table divides these into substance groups by areas of application.

Substance group

Reason for use


Mineral oil

Lubrication effect

Hydrocarbons with different boiling ranges; fatty oil; esters

Polar additives

Enhanced lubrication properties

Natural fats and oils of synthetic esters

EP additives

To prevent micro-welds between metal surfaces at high pressures and temperatures

Sulphurized fats and oils, compounds containing phosphorous, compounds containing chlorine

Anti-corrosion additives

To prevent rusting of metal surfaces

Alkano-amines, sulphonates, organic boron compounds, sodium nitrite

Anti-misting additives

To prevent breakdown of the oil and thus generate less mist

High molecular substances

Anti-ageing additives

To prevent reactions within the coolant

Organic sulphides, zinc dithiophosphates, aromatic amines

Solid lubricants

To improve lubrication

Graphites, molybdenum sulphides, ammonium molybdenum


To combine oils with water

Surfactants, petroleum sulphonates, alkali soaps, amine soaps


To prevent foaming

Silicon polymers, tributyl phosphate


To prevent formation of bacteria/fungus

Formaldehyde, phenol, formaldehyde derivatives, cathon MW

A significant increase in certain occupational diseases has occurred parallel with the introduction of the coolants which are now commonplace. According to scientific findings, diseases of the skin and respiratory tracts and cancer may occur.

Where coolant use is unavoidable, mist extraction as close as possible to the point of origin or encapsulation is necessary. Consistent use must be made of personal protection measures such as the wearing of protective clothing and the use of special skin protection substances. Factories should produce skin protection plans.

Bacteria which can have severe effects on health can occur due to the organic nature of coolants. Bacteria formation is promoted by warm/hot ambient temperatures. Anti-bacterial additives are introduced to counter this. Timely replacement of coolants avoids the need for high doses of anti-bacterial additives, which also represent a health hazard. However, this increases the total quantity of waste to be disposed of. Proper storage of "spent" coolants and subsequent separation of emulsified oils and greases, and also of metal compounds and other components, is imperative.

Safety data sheets informing of the danger of coolants and instructions for use should be displayed in the national language(s). It is important that staff are aware of the long-term dangers of coolants; a particular difficulty here being the often creamy, pleasant smelling and seemingly harmless nature of coolants.

No generally applicable limit values exist for coolants in the breathing air. The only guide is the relevant MAK values9) for the individual substances. The management should find out which are the most environment-friendly coolants and ensure that these are procured.

9) The term MAK (maximum allowable concentration) in Germany refers to the maximum possible concentration of a substance in the air of the workplace, in the form of gas, vapour or suspended matter.

2.1.2 Cleaning and degreasing of workpieces

For subsequent surface treatment, adhesive or thermal bonding etc., workpieces have to be freed of substances such as oils, fats, resin, wax, cellulose, rubber or plastics. Solvents are widely used for this purpose. Workpieces can be degreased and cleaned by various methods, for instance by cold, hot and/or vapour degreasing or combined processes.

Cold cleaning frequently involves the use at room temperature in open baths of solvent mixtures whose precise composition is not known to the user. Mixed with air, the vapours of these solvents or solvent mixtures can be explosive. Most solvents represent a health hazard for man.

Solvents are classified as organic compounds such as hydrocarbons, halogenated hydrocarbons, ethers (diethyl-ether, tetrohydrofuran, dioxan), ketones (acetones, methylethylketone) and organic alkalis (sodium hydroxide solution, ammonia) and acids (hydrochloric acid, nitric acid, sulphuric acid).

The most important halogenated hydrocarbons are chlorinated hydrocarbons (CHCs), such as tri-, tetra-, perchloroethylene, dichloromethane, tetrachloroethane etc.10) On account of their grease-dissolving properties and high volatility, CHCs are used in almost every branch of metal working as cleaning agents in cold cleaners and in hot degreasing. The high volatility ensures quick drying after cleaning, but also means it is necessary to monitor solvent concentrations in the workplace. Through skin contact and inhalation, CHCs can damage mucous membranes, central nervous system, liver, kidneys and lungs.

10) The best known are CFCs (chlorofluorocarbons) used in other application e.g. as refrigerants. CFCs are partially responsible for the destruction of the vital ozone layer in the atmosphere. CFCs and carbon tetrachlorides and certain other chlorinated hydrocarbons are banned in Germany under the CFC halogen prohibition directive of 6 May 1991 and the chloro-aliphatic compounds directive.

In addition, most solvents are inflammable and represent a particular pollution hazard for water.

Alternative processes use alkaline aqueous solutions (with surfactants and other washing components in varying concentrations) or water (high-pressure cleaning).

Apart from the need for worker protection, it should be remembered that practically all solvents seriously pollute the environment. Particular problems in this regard include damage due to solvent evaporation, soil and groundwater pollution and the difficulties of disposing of used solvents and solvent sludges.

Foremost among modern methods of alleviating the problems of disposal are primary measures to prevent wastewater occurring in the first place, rather than subsequently treating highly contaminated bath and flushing water before it enters the drainage system. Membrane filtration and ion exchange processes can be used to regenerate process baths and extend their useful life. Similarly, flushing water can be used several times over with continuous dirt and oil separation (recycling via ion exchangers, emulsion cracking and cascade flushing techniques). Resulting wastewater quantities and pollutant loads are reduced. One might also attempt to process and reuse solvents in a closed solvent circuit. This technique is rarely successful in the case of reprocessing surfactants, so the improvement of their biodegradability is an important factor. Management should optimize selection of solvents based on technical and environmental factors11).

11) Only wastewater experts can definitively optimise the choice of solvents. Information is available in: Dagmar Minkwitz, "Ersatzstoffe fogenkohlenwasserstoffe bei der Entfettung und Reinigung in industriellen Prozessen" (serial publication of the Bundesanstalt feitsschutz (German Federal Institute for Occupational Safety and Health) GA 38) Dortmund, Bremerhaven 1991 (Wirtschaftsverlag NW) ISBN-3-89429-086-2. See also "Zeitschrift Oberflentechnik, Bezugsquellennachweis f Oberflentechnik mit Trendchten und Tabellen, Munich, 4th edition 1991) (Seibt Verlag), ISBN 3-922948-70-7.

The following precautions should be taken where degreasing is carried out with organic solvents:

- do not use substances which are unknown;
- use enclosed equipment where possible;
- ensure effective ventilation and aeration of work rooms;
- ensure good extraction at the workplace;
- avoid skin contact;
- use protective equipment;
- as solvents are heavier than air, they force the breathing air out of trenches, cellars, containers and depressions in the ground; suffocation can be avoided by means of floor openings and ventilation;
- use only non-combustible washing vessels with self-closing covers for cleaning small parts with inflammable solvents;
- keep only quantities of flammable solvents at the workplace as are required for the work and store in suitable containers with effectively sealed covers;
- avoid electrostatic charges;
- in operating manuals indicate the solvents used, limitations on use and safety precautions, instruct personnel;
- secure and lock installations when not in use;
- avoid hand-spraying of degreasing agents with spray guns;
- avoid blow-drying with compressed air of surfaces which have been treated with chlorinated solvents;
- with open degreasing equipment, note the quantities of solvent displaced on immersion of the workpiece and dimension the system accordingly;
- workpieces should leave the system free of solvents.

2.1.3 Painting

Most spray paints and brush paints contain considerable quantities of hydrocarbon and chlorinated hydrocarbon solvents (spray paints as much as 90%, normally 50 - 70%) which evaporate on spraying and drying. Paints also contain finely dispersed pigments. Some of these are highly toxic. Depending on the application, paints may have to satisfy a wide range of quality requirements. Available paint systems are accordingly diverse.

There are three possible ways of avoiding solvent emissions from painting installations; these can be used separately or in combination:

- use of low-solvent paints

"High solids" paints, water soluble paints and dispersion paints have been developed for this purpose. A further alternative is solvent-free powder paint, for which new applications are constantly being found.

- use of high-performance application methods

Solvent emissions depend not only on the paint formulation but also on the application method. An important evaluation criterion is the application efficiency factor, which is defined as the ratio of paint remaining on the product to the total quantity of paint used. Lower efficiency means higher paint consumption and thus higher solvent emission. Application efficiency is primarily determined by the process and by the form of the parts to be painted.

The following application efficiency values can be taken as guidelines for the painting of large surface areas by various methods:

- compressed air spraying 65%
- "airless" spraying 80%
- powder painting 98% (with recycling of spraying loss)
- electrostatic spraying 95%
- dipping, flooding 90%
- rolling, pouring approx. 100%
- brush, roller application 98%

The choice of application method depends on certain quality requirements, e.g. coating thickness, surface roughness etc. and is hence closely related to the purpose of the painted object.

The various levels of waste gas resulting from the different methods can be greatly reduced by enclosing the application zone and additionally by air circulation. This will reduce the outlay on waste gas cleaning.

- collection and cleaning of waste gas (with solvent recycling).

2.1.4 Electroplating

To obtain different surface properties (surface refining), workpieces are electroplated with chromium, zinc, tin, copper, cadmium, lead or brass. For this the selected metallic coating is deposited from an electrolyte solution in an electro-chemical process. To enable the metal coatings to be applied, workpieces must be cleaned and degreased.

Where cold cleaning and degreasing are carried out, the hazards from cold cleaners must be taken into account (see 2.1.2). The boil-off technique is also used for rough cleaning. Strong alkalines such as sodium or potassium hydroxide solutions are used for this purpose. These alkalines can damage eyes, skin and respiratory tracts if splashed or given off as mist or dust. An electrolytic process is often used for subsequent fine cleaning. Electrolytes are often alkaline solutions (5% sodium hydroxide solution) or cyanidic salts. Apart from the dangers posed by the boil-off technique, extraction ventilation is necessary in view of the large quantities of hydrogen produced, so as to avoid reaching the explosibility limit of the air-hydrogen mixture. Safety in the workplace is increased by installing gas warning devices.

Pickling degreasers and pickles are used to remove oxidation layers and casting or rolling scale from metal surfaces. These are acids (sodium hydroxide solution for aluminium) such as sulphuric, hydrochloric, phosphoric, hydrofluoric or nitric acid which attack and dissolve the workpiece surface. The main health hazards are skin diseases; dangerous vapours and gases can be inhaled in the case of inadequate extraction. Especially dangerous are nitrous gases which can occur when using nitric acids, also fluorine compounds from hydrofluoric acid and hydrogen chloride from hydrochloric acid.

Cyanides are used for cleaning in salt baths (fluorides), pickling (removal of thin surface films), with chemical and electrolytic polishing or burnishing, and also with surface coating and thermo-chemical hardening processes. These can cause hydrocyanic poisoning as well as skin diseases when solutions containing cyanide come into contact with acids. Therefore baths containing acids and cyanide must be covered and separated by partitions. Containers and equipment are to be clearly marked to prevent carry-over of substances which can mutually react. In all cases one should check to determine whether cyanide can be replaced by substances less hazardous to health.

The actual electroplating of the workpiece can be done in countless different process variants and stages. Materials posing just about every conceivable danger can be used in electroplating. The dangerous properties result both from the main components of the bath fluid and from different additives such as emulsifiers, foam inhibitors and wetting agents.

Strong aerosols can occur during bath filling and further preparation. Dangerous substances may enter the breathing air due to the production of gas (hydrogen) during the electrolytic process.

The main hazards with coatings are skin complaints and in particular allergies due to nickel and chromates. If consumed, both nickel and chromates can be carcinogenic. Nickel in fluid particle form is subject to a TRK value12) 4 of 0.05 mg/m³ breathing air.

12) TRK value: German technical directive on concentration of carcinogenic substances

2.1.5 Welding

Welding is the joining of materials using heat and/or force, with or without the use of welding fillers (anti-oxidation substances).

The individual processes most commonly used are gas welding, arc welding and inert gas shielded welding.

Polluting factors in welding workshops are:

- chemicals in the generated gases, vapours and dusts
- high temperatures (approx. 3,200°C - 10,000°C)
- radiation (ultraviolet radiation): eye damage, severe inflammation of unprotected skin;

infrared radiation: can penetrate the vitreous body of the eye, reaching the retina and causing cataracts)

- noise (up to 110 dB(A))

Diverse hazards occur depending on the fuels, inert gases, filler materials, workpiece coatings etc. in use. The following table summarizes the pollutants occurring with the different welding methods. The carcinogenic and mutagenic elements chrome and nickel are especially relevant. Certain hazardous elements are detectable in welding fumes in concentrations of over 1% and can lead to health damage. Clinical and epidemiological investigations indicate a frequent occurrence amongst welders of chronic bronchitis and increased impairment of the respiratory tracts.

Pollutants occurring in various welding processes include:



Welding process

MAK * mg/m3



Welding of lead or lead-coated workpieces




Cr2/ 3

Welding with alloyed electrodes, Cr Ni steel




Cadmium-coated workpieces



Carbon monoxide


Welding with basic coated electrodes, gas flame



Carbon dioxide


Gas welding with coated electrodes, inert gas





Welding of copper, copper-coated workpieces




Mn O

Welding of workpieces containing Mn, all electrodes





Welding of Cr Ni steel, alloyed electrodes




Welding in confined spaces, trenches, tanks





Welding of zinc, galvanized workpieces, zinc paint





Welding of aluminium, almost all types of electrodes

Arc welding




Welding of steels, all electrodes

Plasma arc welding




Welding with basic and alloyed electrodes

Arc welding




Welding with coated electrodes

Arc welding



Na2 OH

Welding with coated electrodes

Arc welding


Oxygen (ozone)


Strong UV radiation

Plasma arc welding




Welding with coated electrodes

Arc welding




Welding workpieces containing vanadium

Arc welding


* MAK: maximum allowable concentration

The welding of metals with anti-corrosion coatings may also have adverse toxicological consequences. Pollutants may be released depending on the type of coating.

Alkyl resins: acrolein, butyric acid
Phenolic resins: phenols, formaldehyde
Polyurethane: isocyanates, hydrogen cyanide
Epoxy resins: phenols, formaldehyde, hydrogen cyanide.

Although the inert gases carbon dioxide, argon and helium are not toxic, in poorly ventilated rooms they can displace the breathing air and under extreme conditions cause suffocation. Ozone may be produced during arc welding. Even low concentrations (0.1 parts per million (ppm)) of ozone can cause irritation to the eyes and upper respiratory tracts and in the event of exposure to 5-10 ppm over several minutes, pulmonary oedema.

At high temperatures nitrogen oxides are formed and emitted from the nitrogen and oxygen in the air on the periphery of the welding flame. Nitrogen oxides are highly toxic and, after a relatively long asymptomatic period, can lead to radical lung changes, pulmonary oedema and death. If the workpiece has been degreased with solvents containing chlorine and not properly dried, phosgene may be produced during welding. Phosgene is highly toxic and can also cause pulmonary oedema after a long asymptomatic period.

Since the welding of plastics is not yet widespread in many countries, it is not dealt with here. It must be pointed out however that the hazards for man and the environment are also considerable with the welding of plastics. Protective measures and special disposal procedures are necessary to guard against the release of solvents and other waste gases containing pollutants.

2.1.6 Soldering

Soldering is the thermal joining of two materials using a material (solder) whose melting point is below that of the workpiece.

If the solder melts above 450°C the process is termed "hard soldering or brazing" and at lower temperatures "soft soldering". Apart from additional hazards due to the base material binders, the hazards involved in soldering are mainly associated with the flux and the solder.

The composition of a flux depends on the base material, the solder and the intended use. More than 300 different types of flux are currently available, all of which contain aggressive chemicals. Soldering paste usually contains colophonium, talc and salmiac, while soldering fluid contains zinc chloride or tin chloride. Chlorine and chlorine compounds cause irritation of the respiratory tracts and the skin and, in high concentrations, lung damage. Fluxes also frequently contain fluorine compounds (irritation of the respiratory tracts, burns). Fluxes often contain substances responsible for allergies. These are mainly colophonium and hydrazine. Hydrazine is additionally classed as carcinogenic.

Tin-based solders containing lead are used for soft soldering and silver solder containing cadmium for hard soldering. Flux vapours carry metal particles which can be inhaled.

Environmental protection measures to combat the emission of liberated gases and component substances of solders and fluxes include the installation of extractor systems with downstream separator filters (cyclone method). This method may also be used to contain the environmental impact of the production stage discussed in the next section.

2.1.7 Grinding

Grinding is the cutting of a workpiece with a geometrically undefined cutting process.

Grinding processes are characterised by high temperatures, workpiece removal and abrasive wear. In addition to noise, the health hazards from grinding are principally emissions from abraded dust or particles from the abrasive tool, workpiece and any coating, and - in the case of wet grinding - from coolants. There is an attendant risk of health disorders especially affecting the skin and respiratory tracts. Additives in coolants and the metal dusts produced (e.g. from chromium, cobalt, nickel or beryllium) can result in allergies. These metals may also be carcinogenic. The following table shows the potential pollutant sources when grinding metals.

Potential pollutant sources in the grinding of metals

Material-dependent Process-dependent

Grinding tool Formation of superfine dust with

- abrasive material - profiling and dressing of containing zircon grinding discs
- lead chloride, antimony - tool grinding sulphide in separating - fettling, due to adhering cutting in stationary operation mould residues
- additives in grinding - manual grinding, usually belts containing fluorine carried out without extraction ventilation

Coolant - coarse grinding additives, with respect to - use of magnesite binders toxicity, carcinogenicity and mutual reactivity

Material containing Combustion and pyrolysis

- more than 80% %/wt. products which can occur nickel (e.g. depositing with the thermal decomposition of materials) rubber or synthetic resin
- less than 80% %/wt. nickel (e.g. high grade corrosion-resistant steel)
- Lead (e.g. in automatic Accumulation of heavy metals and steel) superfine particles in coolant
- Cobalt (e.g. hard metal, co- due to inadequate filtration alloys) or overuse
- Beryllium (e.g. Ni Be alloys)

Atomization of coolant and thus also of additives, reaction products, dissolved heavy metals and superfine, non-separated particles.

Protective measures include environment-oriented selection of grinding tools, coolant and - where possible - materials, extraction of the abraded materials and personal breathing and hearing protection.

2.2 Mechanical engineering and operation of workshops and shipyards

Special environmental problems which are not found elsewhere arise in mechanical engineering, in workshops and in shipyards. This is because the work is not carried out in one location alone, and because pollutants are diffused and vaporised throughout the site. Estimation of their environmental relevance is difficult due to their often low concentration and they frequently seem harmless, so it is not easy to communicate the problem to workers and managers. Therefore environmental training measures should be taken into account as early as the planning phase. Much depends on the attitude in the workplace, the choice of working equipment and materials and the observance of worker protection measures. Planning must additionally include early integration of technical environmental protection measures (filter systems, wastewater collection installations, cleaning installations etc.).

2.2.1 Waste air

Environmentally relevant waste air flows can be released into the environment through forced ventilation (e.g. fan systems) and/or random emission13) from diverse areas of the site.

13) Emissions are defined as air impurities (gases, dusts), noise, radiation (heat, radioactivity etc.), vibration and similar phenomena given off to the environment by a (fixed or mobile) system.

These include emissions from:

- production extractor systems
- workplace extractor systems
- room air extraction
- production processes
- mechanical cutting
- thermal joining and parting (welding, cutting)
- joining (e.g. bonding, soldering)
- surface treatment (cleaning, coating, hardening and tempering)
- drying

Emissions into the air can be divided into:

- coarse and fine dust
- aerosols
- organic and inorganic gases and vapours

Harmful components of the waste air are essentially:

- organic solvents and halogenated hydrocarbons from metal cutting (coolants), cleaning, degreasing, bonding and painting of workpieces in the form of gases, vapours and aerosols
- dusts from the mechanical processing of materials

Whether or not cleaning of the waste air is an absolute necessity depends e.g. on the solvents in use, the presence of other contaminating operations, weather conditions etc., also therefore on ambient factors. Long-term risks for man and the environment may be posed even by relatively small workshops.

In the interests of worker protection, room air pollutants occurring in the production process must not exceed certain MAK values14). Where necessary work should be carried out in enclosed equipment. Efficient aeration and ventilation must be guaranteed, or pollutants must be extracted at the point of origin. Extracted flows of (pollutant) substances are to be cleaned by suitable processes before being expelled to the environment.

14) in Germany

Possible processes are:

· Dust separation:

Dust is a mixture of particles of different grain size, particle size depending very much on the process. Various processes are used for dust separation. These are classified as follows:

A: inertia separators (cyclone, "multiclone", mechanical separator)
B: wet type separators (scrubbers, wet separators)
C: electrical separators (dry and wet electrostatic filters)
D: filtering separators (fabric filters, cloth filters, bag filters, vibratory sheet filters and tubular filters).

· Aerosol separation:

Waste gases containing droplets are also termed aerosols and hence distinguished from dust-laden waste gases. Droplets can be separated using the same physical principles as for dust. The greater adhesion of the separated droplets compared with dust however rules out use of the principal dust separators such as electrostatic filters and filtering separators. Only wet separators, i.e. scrubbers and wet type electrostatic filters are suitable without modification for separating aerosols.

· Separation of vaporous or gaseous substances:

The principal methods for reducing emissions of gaseous inorganic and organic substances are absorption, adsorption and thermal processes. With absorption the gaseous air pollutant is absorbed by a washing fluid. Absorption is either physical or chemical, depending on whether the absorption is based exclusively on the solubility of the gas, or whether additional chemical reactions occur in the liquid phase. Absorption processes, and also thermal and catalytic processes, are used particularly for reducing levels of organic substances.

Water-soluble organic substances, e.g. methanol, ethanol, isopropanol and acetone can be effectively separated from waste gases through absorption by means of scrubbers. The contaminated washing fluid can normally be regenerated by fractionation15).

15) Fractionation is the separation of fluid mixtures by repeated distillation.

Separation of large amounts of solvents is done by the condensation process. Recently, biological processes such as biofilters or biowashers have also become popular for cleaning waste gases with highly odorous components and/or solvents.

Adsorption is the attachment or accumulation of foreign molecules on the surface of a solid (adsorbent). Regeneration of laden adsorbents is normally done by desorption of the adsorbed substances in the gas or liquid phase (so-called desorption phase), i.e. by reversal of the adsorption process. As the desorption phase (usually a gas) contains the substance removed from the waste gas in an enriched concentration, recycling or reprocessing is possible. Solvent recycling is an especially important area of application for the adsorption process. Adsorbents are mostly activated carbons.

The residual substances yielded by the separation of the solid and gaseous waste gas pollutants (filter dusts, scrubbing water residues etc.) are normally hazardous materials and must be disposed of as special waste (giving rise to waste problems). The price of solving emission problems is often soil and water contamination, and land may become so contaminated it will eventually have to be rehabilitated (see also the environmental brief Disposal of Hazardous Waste).

2.2.2 Wastewater

In mechanical engineering, the recycling of process materials from wastewater is frequently only possible with disproportionate technical effort or not at all, because of the low concentrations involved. Concentrated liquid and spent process and production materials can and must be collected and disposed of as (hazardous) waste.

Wastewater is returned to natural bodies of water (lakes, streams, rivers, sea) after preliminary and final cleaning. There, any inorganic pollutants will lead to poisoning and deposits. Organic impurities may also be toxic and/or non-degradable. Degradable, non-toxic waste substances damage the environment by initiating excessive growth (eutrophication) of bacteria and minute life forms (algae, fungi) due to the nutrient supply. In combination with cell metabolism, this results in high oxygen consumption and finally to phenomena such as the "overturning" of the water (anoxic waters).

Heavy metals mostly enter the wastewater as metal salts produced by chemical reaction of the metals with the acids. The acidic pH value which prevails in heat treating and pickling shops promotes the solubility of the heavy metals in wastewater and hinders their removal.

Heat treating and pickling shops rinse workpieces in fresh water prior to further processes. After use, pickling fluids also contain heavy metals. In electroplating operations, rinsing water contains cyanide and is polluted with the heavy metals which are used (depending on the type of surface finishing).

Halogenated hydrocarbons are insoluble in water. They mainly enter the wastewater via rinsing water after degreasing in surface treatment plants and when cleaning engines and other objects in motor vehicle and general workshops by the use of cold cleaners and pickling agents. Further emission sources are coolant carry-overs and losses, workpiece rinsing and workshop floor cleaning.

Organic solvents can enter the wastewater via absorption and spray cleaning processes. Mineral oils occur with the cleaning of workpieces and floors and degreasing, and through losses during processing. Emission sources are repair, motor vehicle, factory and maintenance workshops. In surface treatment workshops they occur in the form of the workpiece anti-corrosion and rust-protection oils used in preliminary cleaning.

Acids and alkalis enter the wastewater in pickling shops and heat treatment shops in connection with degreasing. Other wastewater burdens occur due to nitrogen (ammonium) and phosphor compounds (phosphates from pickling shops).

Wastewater can be cleaned by chemical, physical and biological processes or a combination of these. Three-stage purification of industrial wastewater is now generally considered the state of the art.

Only organic and non-toxic wastewater impurities can be removed biologically. Tests in the laboratory will determine whether or not the components contained in the wastewater inhibit biodegradability.

With biological processes a distinction is made between aerobes (with oxygen) and anaerobes (without oxygen). With high burdens (chemical oxygen demand (COD) in excess of 15,000 mg/l), anaerobic processes are used for preliminary cleaning before aerobes carry out the final cleaning, since otherwise the oxygen supply costs are excessive.

High-performance biological processes with high pollutant decomposition rates are now available to build small but nevertheless efficient systems. Newly developed processes are achieving success in the biological neutralisation of organic pollutants previously considered non-biodegradable, e.g. CHCs, by optimising the living conditions for special bacteria.

Flocculation/precipitation processes can be used to remove heavy metals from wastewater, also sedimentation processes in the case of undissolved wastewater. Chemical oxidation and precipitation processes can be used for the removal and de-toxification of cyanide.

Emulsions originating from the use of coolants can be separated by the membrane filtration process in conductive wastewater (approx. 90%) and concentrate.

Ultrafiltration is used with electrostatic immersion painting for the separation of solid paint residues. This is increasingly replacing simple sedimentation with the separation of undissolved pollutants in wastewater because it is more efficient, though more costly. Wastewater containing acids and alkalines must pass through neutralization systems. Ion exchange systems cannot selectively remove metals but are highly suitable for cleaning water carried in a circuit and recycling raw materials. For recycling pure raw materials, the different waters must be carried and used separately.

2.2.3 Waste matter

Waste matters generated by these plants can be divided into three groups:

A. Residues of the used raw materials. These include both ferrous and non-ferrous (NF) waste (scrap/chips and swarf) which may be highly contaminated with coolant, cutting oil and leaked lubricating oil.

B. Waste from process residues resulting from the processing of semifinished products and auxiliary materials. Metalliferous residues are e.g. burnt slag from torch cutting, metal sludges, used salt and acid baths from electroplating or pickling shops.

C. Non-metalliferous waste can be paint and adhesive residues, oil and oily waste, organic acids, alkalis and concentrates. Finally, waste may also be produced by wastewater and waste air cleaning processes. These include purification sludges from the works’ own sewage treatment plant plus dusts and sludges from the cleaning of waste air and extraction flows in the form of filter residues.

Nearly all waste in the second and third groups can be regarded as hazardous waste. They demand special monitoring and special disposal methods. Waste from the first group should mostly be recycled. Separate collection of scrap types (structural steel, alloyed steel, NF metals) in different containers is important for simple and comprehensive recycling.

In order to reduce scrap quantities with torch cutting and punching, care must be taken to achieve a systematic geometrical arrangement of contours on the sheet metal. Recycling should be considered where there are high concentrations of costly raw materials in liquid or sludge waste. To reduce waste further, fluids should where possible be cleaned with filters or baths regenerated.

2.2.4 Soil

The effects on the soil can be problematic in terms of both quality (e.g. toxicity or persistence) and quantity (e.g. acidification or leaching). Airborne emissions are normally small in quantity, therefore the main causes of pollution are the discharging of residual and waste materials (filter dusts, washer and scrubber residues, purification sludges) and improper handling of auxiliary materials. Of the large number of chemical substances used in metal processing, only a few substance groups have to be regarded as representing a soil hazard and thus in general also a groundwater hazard:

- anions (chlorides, sulphates, ammonium, nitrates, cyanides etc., produced e.g. in heat treatment and pickling shops)
- heavy metals (lead, cadmium, chromium, copper, nickel, zinc, tin etc.).
- solvents (halogenated and pure hydrocarbons)
- other oil-containing substances

The areas in which contamination occur are:

- all production stages using the named substances
- storage of new and used chemicals
- transport, loading and unloading on the works site (containers, tanks, pipelines, extraction system)
- cleaning and repair processes.

To protect against contamination in these areas, the ground must be "sealed" (i.e. provided with a protective layer to prevent penetration of the materials into the ground, or with pollutant collection devices, e.g. containment basins). Insufficient attention is often paid to the storage of hazardous materials. This can result in severe environmental pollution with long term consequences, also and in particular for third parties (e.g. due to groundwater pollution). Containers and pipelines used for transporting the materials are to be regularly checked for leaks. Care must be taken to ensure an efficient flow of work and materials, with clear rules on the depositing and disposal of waste/residues (see environmental brief Disposal of Hazardous Waste, also the reference literature).

2.2.5 Noise

Deafness and loss of productivity result from noise pollution above a certain level. A noise level in the workplace of around 85 dB(A) or higher for the greater part of the working shift, over a number of years, is regarded as detrimental to hearing16).

16) It is as harmful to be exposed constantly to a uniformly low noise level as to a higher one for a short time.

For comparison: Leaves blown by a light wind emit a noise level of 25 to 35 dB(A); normal conversation is between 40 and 60 dB(A). Note also that the medium and higher frequencies between 1,000 and 6,000 Hz are the most damaging.

When considering noise immissions17), a distinction must be made between the direct effect on workers at the workplace and the indirect effect due to radiation and immission in the environment. In assessing noise therefore, three aspects, each requiring different reduction measures must be considered.

17) The term immission is the effect of air impurities, radiation (e.g. thermal radiation) on man, animals, plants and property.

A. Noise origination
B. Noise propagation

· Noise transmission (propagation of sound waves in different media, e.g. transmission of machine vibrations to foundations);

· Noise radiation (stimulation of air vibrations by solid-body vibrations - loudspeaker diaphragm principle).

During operations in this sector, noise is generated by machinery, by hammering, nailing, or chipping, by internal transportation processes, impact upon depositing or lifting of semifinished products, air and gas movements, fan outlets, pneumatic components, cutting torches etc.

A fan, e.g. with 50 kW, 970 rpm and a diameter of 1,800 mm, without noise damping produces a noise level of 100 dB(A). A compressed air jet produces a noise level of 108 dB(A) with an air pressure of 5 atmospheres. Welding and cutting generate noise levels of up to 101 dB(A) and pneumatic riveters and chippers produce between 100 and 130 dB(A). Manual grinders develop up to 106 dB(A). Metal band saws develop up to 106 dB(A). Turning generates between 80 and 107 dB(A). Screw presses produce noise levels up to 103 dB(A).

Noise pollution in the neighbourhood of a factory is mainly caused by radiation through the walls of the production sheds and buildings and by outward blowing fans.

Structural measures to reduce noise should therefore be taken into account as early as the planning phase (noise-absorbing walls, choice of windows, type of building materials etc.). The expected noise conditions cannot be determined simply by adding together the known noise levels of the planned machines and processes. Due to interaction and the different damping and reflection circumstances, only on-site measurements can yield accurate data on noise conditions. The maintenance of adequate distances reduces the effect on the neighbourhood.

With regard to noise protection, a distinction is made between primary and secondary measures. Active primary measures signify the use of machines constructed according to low-noise principles. For example, sheet metal forming can be made quieter by replacing impact methods with hydraulic pressing. Priority should be given to the implementation of active primary measures.

Active secondary measures are sound insulation (prevention of propagation by obstacles) and sound absorption (absorption of sound energy and its conversion to heat). A distinction is made between structure-borne and airborne noise:

- Insulation of airborne noise is achieved by partition walls, full or partial enclosure, cladding or screening.
- Insulation of structure-borne noise can be achieved by machine feet of elastic material which prevent the transfer of vibrations.
- Absorption of airborne noise over large areas can be achieved with sound-absorbing cladding material of foam or glass fibre matting. Silencers should be fitted to reduce noise at gas and air outlets. Composite silencers combining an absorber and a resonator should be provided for dust-laden gases.
- Absorption of structure-borne noise damping is achieved by means of soundproof coverings in the form of foam rubber mats on sheet metal or in sandwich form (metal - covering - metal).

Passive noise protection signifies all equipment and measures for preventing the immission of noise and vibration to the environment and the human ear. These include personal ear protection, noise protection for control rooms, noise-insulated cabins etc.

Workers must wear ear protection in the workplace where noise levels are higher than 90 dB(A). Such workplaces must display suitable warning signs; the observance of protective measures must be monitored.

Proven methods of reducing noise immissions include the use of soundproof walls or partitions and increasing the distance between industrial buildings and residential areas. With uninhibited propagation the acoustic power level is reduced by 3 (house wall) or 6 (point source of noise) dB(A) by doubling the distance.

3. Notes on the analysis and evaluation of environmental impacts

This section describes underlying reference material which, unless otherwise indicated, refers to the situation prevailing in Germany. Obviously these rules cannot be applied wholesale to other countries without modification. The material is intended at least to serve as a reference where no national regulations are available. The INFOTERRA National Focus Points of the UNEP are a valuable source of information. These contain environmental information records for the member state in question. The reference service is free of charge. The Environmental Guidelines of the World Bank are an important source of application-related information, e.g. for dust emissions, waste matter and wastewater.

The Catalogue of Environmental Standards (Vol. III of this Environmental Handbook) also deserves special mention. This lists standards and limits for assessment purposes.

Regulations on the protection of persons from danger and injury in the workplace (worker safety, industrial medicine) are contained in the Unfallverhvorschriften der Berufsgenossenschaften (accident prevention regulations of the employers’ liability insurance associations) and in their other publications such as "Sicherheitsregeln" (safety regulations) and "Richtlinien" (guidelines). Also worthy of note are the Occupational Health and Safety Guidelines of the World Bank and the Encyclopedia of Occupational Health and Safety of the International Labour Organisation (ILO).

3.1 Air

TA-Luft (Technical Instructions on Air Quality Control) regulates the technical standards concerning pollutant emissions and immissions for installations subject to licensing.

The guidelines on maximum immission concentrations (MIK) published by the Association of German Engineers (VDI) lay down limits for certain air pollution levels. These are defined as the concentrations in the ground-level open-air atmosphere or in dust and the quantities precipitated on the land below which man, animals, plants and property are guaranteed to be safe according to the present level of scientific knowledge (see also reference to MAK values).

Also of importance are the EC Directives on sulphur dioxide and suspended particulates, lead and nitrogen dioxide (EC Directives 80/779/EWG, 82/884/EWG, 85/203/EWG), also the WHO Air Quality Guidelines for 28 chemicals on the basis of toxicological findings.

3.2 Wastewater

Discharge conditions for wastewater are laid down in the Wasserhaushaltsgesetz (Federal Water Act), the Abwasserangabengesetz (Wastewater Charges Act) and the associated Verwaltungsvorschriften (administrative regulations). These prescribe limits of individual pollutants for different sectors.

Annex 40 currently applies to metalworking and processing with direct discharge (discharge into bodies of water). This gives details of the maximum concentrations for COD18), BOD19), heavy metals, hydrocarbons, ammonium, phosphorous and halogenated hydrocarbons.

18) COD: Chemical Oxygen Demand
19) BOD: Biological Oxygen Demand

The limits for indirect discharge (discharge into waste-water purification plants) for COD and substances classified as non-hazardous are less strict. The limits for indirect discharge are detailed in the ATV work sheet Arbeitsblatt A 115 according to sectors. This work sheet is currently being adapted to the new wastewater management regulations.

For their projects the World Bank stipulates that the temperature of discharged wastewater must be no more than 3°C higher than that of the receiving body of water. If the temperature of the receiving body is 28°C or less, the temperature of the discharged wastewater must be no more than 5°C above that of the receiving water.

3.3 Waste matter

The definition of waste types according to Section 2 of the Abfallgesetz (Waste Avoidance and Waste Management Act) for the metal working and processing industry is contained in the Verordnung zur Bestimmung von Abfen (Regulation on Waste Definition). A further designation of waste types according to code numbers is contained in the publication on waste types of the German state working group on waste Landesarbeitsgemeinschaft Abfall (LAGA). Of relevance here are waste groups 35 (metal waste), 51 (oxides, hydroxides, salts) with electrolytic sludges, 52 (acids, alkalis, concentrates) with waste from surface treatment, 54 (mineral oil products) and 55 (organic solvents, paints, lacquers, adhesives, cements and resins). For electroplating and painting, refer to the regulation on waste identification Abfallnachweis-Verordnung. For motor vehicle and general workshops, see the regulation on waste oil Altrordnung.

For the use and handling of special waste, refer to the three-volume edition of "The Safe Disposal of Hazardous Wastes" and the manual "Techniques for Assessing Industrial Hazards", both published by the World Bank; also the environmental brief Disposal of Hazardous Waste.

3.4 Noise

Accident prevention regulations are published by the employers’ liability insurance associations or Berufsgenossenschaften, and these deal with the protection of workers from noise in the workplace. The noise protection and information sheets of the Hauptverband der gewerblichen Berufsgenossenschaften, are important publications in this regard. The Association of German Engineers (VDI) has issued numerous regulations and directives concerning noise in the workplace, the impact of noise on the environment and noise protection measures. Guidelines on noise protection for installations subject to licensing (according to the implementing ordinance of the Federal Immission Control Act) and neighbourhood immission guidelines are contained in TA-L (Technical Instructions on Noise Abatement).

4. Interaction with other sectors

Mechanical engineering and the production of semifinished products for machinery in other sectors represent a highly diversified capital goods industry, so there is often close interaction with other sectors. Interaction is not necessarily regional, on account of the high specific added value, therefore interacting environmental problems do not occur generally but rather in individual cases.

With mechanical engineering works, workshops and shipyards of a certain size, attention must be paid to the effects on infrastructural sectors. In this regard see the environmental briefs Spatial and Regional Planning, Planning of Locations for Trade and Industry, Overall Energy Planning, Water Framework Planning, Urban Water Supply, Rural Water Supply, Wastewater Disposal, Solid Waste Disposal, Transport and Traffic Planning, Road Building and Maintenance - Building of Rural Roads, Road Traffic, Railways and Railway Operation, Inland Ports, Shipping on Inland Waterways, Ports and Harbours - Harbour Works and Operations, Shipping, River and Canal Engineering.

There may also be an interaction with sectors covered in the following environmental briefs Surface Mining, Underground Mining, Minerals - Handling and Processing, Power Transmission and Distribution, Iron and Steel and Non-ferrous Metals.

5. Summary assessment of environmental relevance

The aim of this environmental brief has been to summarize the environmental relevance of mechanical engineering works, workshops and shipyards. Detailed investigations are to be made in each specific case as to the possible environmental hazards. Even small environmental problems which appear at the outset to be of marginal importance can, in certain contexts, result in failed projects or serious damage. Countermeasures must be integrated into the planning and execution at an early stage. From the point of view of environmental protection, mechanical engineering should involve a combination of precautionary measures and appropriate management decisions. Therefore training in environmental protection must be given high priority in every project. Workers should be trained in occupational safety and environmental protection. The management should be familiar with and apply additional precautionary measures (knowledge of suitable pollutant disposal methods or plant optimization with a view to environmental protection, e.g. choice of paints/solvents with low pollutant contents).

An important further precondition of applied environmental protection is the existence of effective waste disposal facilities, especially for problematic hazardous waste. Technical staff must also be on hand, e.g. to maintain filtration and wastewater treatment plants, the erecting and operation of which are described in the present brief.

6. References

Abwassertechnische Vereinigung (ATV) (Ed.): Lehr- und Handbuch der Abwassertechnik, Bd. I - VI, Ernst Verlag, Berlin, various years.

Abwassertechnische Vereinigung (ATV) (Ed.) Arbeitsblatt A 115, Hinweise f Einleiten von Abwasser in eine ntliche Abwasseranlage, draft of 22.03.1990.

40. Anhang zur Allgemeinen Rahmen-Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer, GMBI. (joint ministerial circular) 1989, Nr. 25, p. 517 ff.

Batstone R. et al.: The Safe Disposal of Hazardous Wastes, The Special Needs and Problems of Developing Countries, Vol. I, II, III, World-Bank Technical Paper No. 93, Washington, 1989.

Brauer, H.: "Die Adsorptionstechnik - ein Gebiet mit Zukunft", Chem.-Ing.-Tech. 57, (1985), Nr. 8, p. 650 - 663.

Deutsche Forschungsgemeinschaft (DFG) (Ed.): Kmierstoffe, Liste von Komponenten, in: Toxikologisch-Arbeitsmedizinische Begr von MAK-Werten, Weinheim 1983.

DIN 45635: Gerchmessungen an Maschinen.

EC Council Directive on sulphur dioxide and suspended particulates, lead and nitrogen dioxide (EC Directive 80/779/EWG, 82/884/EWG and 85/203/EWG).

Fischer, H. et al.: "Galvanotechnik", in: Ullmanns Enzyklope der technischen Chemie, Band 12, p. 137 - 203, 76th year.

Geretzki, P.: "Erkrankungen durch Kmierstoffe in der Metallindustrie", in: Dermatosen 31, 1983, Nr. 1, p. 10 - 14.

Gesetz bgaben f Einleiten von Abwasser in Gewer (Abwasserabgabengesetz -AbwAG, BGBl. I (Federal Law Gazette I), p. 2432, 1990).

Gesetz zur Ordnung des Wasserhaushalts (Wasserhaushaltsgesetz - WHG, BGBl. I (Federal Law Gazette I), p. 205, 1990).

Gewerbliche Berufsgenossenschaften, Unfallverhvorschriften: VBG 7, VBG 15, VBG 23, VBG 24, VBG 57, VBG 113.

Hser, M., et al.: Kmiermittelbestandteile und ihre gesundheitliche Wirkung", in: ZbC. Arbeitsmed., 35, 1985, Nr. 6, p. 176 - 181.

Hartinger, H.: Handbuch der Abwasser- und Recyclingtechnik f metallverarbeitende Industrie, Munich, Vienna, 2. Auflage 1991 (Carl Hanser Verlag) ISBN 3-446-15615-1.

Hauptverband der gewerbliche Berufsgenossenschaften e.V.:

ZH 1/81 Merkblatt fliche chemische Stoffe

ZH 1/194 Merkblatt forkohlenwasserstoffe

ZH 1/425 Kaltreiniger-Merkblatt

ZH 1/562 Sicherheitsregeln fagen zum Reinigen von Werkstmit Litteln (Littel-Reinigungsanlagen)

ZH 1/566 Merkblatt flosionsschutzmaahmen an Littelreinigungsanlage

Other ZH 1 publications.

Hauptverband der gewerblichen Berufsgenossenschaften e.V.: Lschutz-Arbeitsbler und Lschutz-Informationsbler.

Koenigs, M.: "Schweierfahren, Gefdungen und Schutzmaahmen", BAD-intern 2/83.

K, W., et al.: Schadstoffe beim Schleifvorgang, Schriftenreihe des Bundesanstalt feitsschutz, Forschungsbericht 427, Dortmund 1985.

Air Quality Guidelines for Europe, WHO regional publications European series: No. 23/1987.

Mahler, W., Zimmermann, K.F.: "Aktuelle Hinweise zur Einhaltung der verschten Arbeitssicherheits-und Umweltschutzbestimmungen beim Verarbeiten cadmiumhaltiger Hartlote", in: Schwein und Schneiden, 1986.

Mannheim: "Sicherheitsmaahmen bei der Verwendung von Halogen-Kohlenwasserstoffen bei der Metallentfettung", in: sicher ist sicher 7/8, 1983, p. 333 - 338.

Maschinenbau- und Kleineisenindustrie-Berufsgenossenschaft, Kampf dem Arbeitsl 3, Lminderung friebspraktiker, 1983.

Maschinenbau- und Kleineisenindustrie-Berufsgenossenschaft: Broschmierstoffe", January 1991.

Menig, H.: "Luftreinhaltung durch Adsorption, Absorption und Oxidation", Deutscher Fachschriften Verlag, Wiesbaden 1977.

Ministerium fung, Landwirtschaft, Umwelt und Forsten, Baden-Wberg, Altlasten-Handbuch Teil 1, Stuttgart 1987.

M R.: "Arbeitssituation und gesundheitliche Lage von Schweirn", Forschungsbericht Nr. 252 der Bundesanstalt feitsschutz und Unfallforschung, Dortmund.

Muster-Verordnung nlagen zum Umgang mit wassergefdenden Stoffen und achbetriebe der Lerarbeitsgemeinschaft Wasser (LAWA), draft of 31.08.1990.

Rosenkranz, D., Einsele, G., Harre H.M. (Ed.): in: Bodenschutz-Handbuch, Erich Schmidt Verlag, Berlin 1988.

Sch.: "-Aerosole an industriellen Arbeitsplen", in: Staub RL 44, 1984, Nr. 6, p. 268 - 272.

Seebohum, K.W.: "Beurteilung von Schweirbeitsplen", in: sicher ist sicher - Zeitschrift feitsschutz, 9/85, p. 454.

Szedkowski, D.: "Gesundheitsgefahren durch Littel", in: WBau BG, Mitteilungen 2/1985, p. 25 - 27.

TA-Luft, Technische Anleitung zur Reinhaltung der Luft of 27.02.1986, GMBl. (joint ministerial circular),p. 95 ber. p. 202.

TA-L, Technische Anleitung zum Schutz gegen L of 16.07.1968, annex to Federal Law Gazette (BAnz.) No. 137 of 26.07.1968.

Technica, Ltd.: Techniques for Assessing Industrial Hazards, A Manual, World Bank Technical Papers No. 55, Washington, 1988.

Umweltbundesamt (Federal Environmental Agency (Ed.)): Handbuch Abscheidung gasfger Luftverunreinigungen, Erich Schmidt Verlag, Berlin 1981.

Umweltbundesamt (Federal Environmental Agency (Ed.)): Branchentypische Inventarisierung von Bodenkontaminationen, Forschungsbericht 03001, Berlin 1986.

VDI (Verein Deutscher Ingenieure): VDI-Handbuch Reinhaltung der Luft, Beuth Verlag, Berlin and Cologne.

VDI (Verein Deutscher Ingenieure): Technische Sorptionsverfahren zur Reinhaltung der Luft, VDI-Bericht 253 (1975).

VDI (Verein Deutscher Ingenieure): Abgasreinigung durch Adsorption, Oberflenreaktion und heterogene Katalyse, VDI Richtlinie 3674.

VDI (Verein Deutscher Ingenieure): VDI-Richtlinien zur Gerchmessung, Schallschutz, Schwingungstechnik: 2560, 2564, 2567, 2570, 2571, 2711, 2714, 2720, 3727, 3749, 3731, 3742.

Verordnung ie Herkunftsbereiche von Abwasser of 03.07.1987, BGBl. I (Federal Law Gazette I), p. 1529.

Zschiesche, W., et al.: "Neue Erkenntnisse zur Berufspathologie der Schweir", Arbeitsmed., Sozialmed. Prntivmed. 20 (1985), p. 140 ff.

1. Scope

The agro-industry is based on agricultural and forestry production, and its purpose is to preserve and refine raw produce and to extract and concentrate the valuable constituents. The food industry constitutes the most important sector of the agro-industry.

Many agro-industries have developed from skilled manual production processes and accordingly can be carried out at varying technical levels. The following information, however, applies to small and medium-sized operations. The definition of small and medium-sized operations varies from country to country but a maximum of 100 employees can be taken as an upper limit. There are environmental briefs which focus specifically on a number of agro-industries, particularly large plants.

In no other area are development and environment so closely intertwined as in that of the agro-industry. Unforeseen implications can turn intended impacts on their head, and medium and long-term damage may prove to be of short-term benefit. Nowhere are effects on the biosphere -including human society - so all-embracing as in the agro-industry. And no other sector is so dominated by female employment; all the activities in this sector are of major importance to and have major effects on women. All agro-industry activities depend essentially on the limited time women have available, their extensive responsibility and on limited water and energy resources. This is why the socio-economic parameters and influences are priority issues in agro-industry projects.

A distinction can be made within the agro-industry between primary, secondary and even tertiary processing. Primary processing is basically most suited to small industrial operations, as technical input increases in line with processing complexity.

2. Environmental impacts and protective measures

2.1 The agro-industry generally

As the agro-industry will probably increase the demand for certain commodities, or alternatively push towards different forms of land use and farming, the following environmental impacts in the area of agricultural production should be mentioned:

Problems relating to the direct expansion and intensification of resource usage include impairment of soil fertility, problems of soil losses and sedimentation, problems of desertification and irrigation problems (soil and water salination, fluctuating water table and water pollution), which in turn reduce resource productivity. The problems of fertility losses, desertification, and salination are generally greatest in countries where the population pressure on land is greatest. Here, agriculture expands most markedly in peripheral areas and marginal resources are utilised intensively.

The most successful efforts lie in the promotion of soil-conservation measures: reducing the intensification of soil usage, and introducing programmes for minimum or soil-conservation farming (contour line farming, terrace farming, strip farming, extension of dry and green fallow land), programmes to control flooding and wind erosion and programmes for the improvement of crop rotation. What needs to be examined is the extent to which these measures should be implemented as an alternative or in addition to the establishment of agro-industrial production operations.

The economic and social parameters in place and those sought are decisive factors in the agro-industrial sector generally. The maintenance and promotion of subsistence production and agro-industrial activities without restricting subsistence are major axioms in this respect.

Commodity processing gives rise to environmental impacts on the atmosphere (odours and dust emissions), water (quantity and wastewater), primary energy sources (mainly timber) and the soil.

The following comments are confined to certain branches which have been in the greatest demand in recent years.

2.2 Selected branches

2.2.1 Mills handling cereal crops

Only dry milling is carried out in such plants, thus account must be taken of noise and dust emissions which affect not only the specific operational area but also the area surrounding the mill. Suitable countermeasures are technical installations (extraction, soundproofing) and individual measures (breathing apparatus, hearing protection), priority being given to the first group, since the use of individual safety equipment requires explanatory and supervisory measures.

Surface water quality is impaired in cases where streams and rivers are used for waste disposal, for example. Further usage or controlled dumping are suitable countermeasures (cf. environmental brief Mills Handling Cereal Crops).

2.2.2 Processing of starch sources and root crops

If the biologically polluted wastewater from washing and processing is discharged into surface water untreated, the result can be overfertilization, reduction in the oxygen content and therefore a general impairment of water quality, changes in the micro flora and fauna and, in the medium term, disruption of water biotopes.

Appropriate minimum measures are mechanical separators and aeration ponds in which the biological oxygen demand is reduced to an acceptable level. Since a reduction in the biological pollution of wastewater is associated with improved yield, optimised process technology can also be an economically beneficial environmental measure. Finally, highly polluted wastewater which can normally be avoided where a process is appropriately optimised, can be used as a substrate for biogas production.

2.2.3 Processing of oil-bearing seeds and fruits

In small and medium-sized works, only pressing processes are used for oil extraction, with solvent extraction reserved for large plants (see also the environmental brief Oils and Fats). Oil-bearing fruits are heated directly or with steam or hot water to improve yields. This produces steam emissions and oil-laden wastewater. Wood is often used for energy production, and this can lead to over-use of tree stocks.

Because steam emissions affect mainly operating personnel extraction should take place at the point of production. Once again, process optimisation, the use of better separators and treatment in aeration ponds should be used to reduce wastewater pollution. Consumption of wood or other commercial fuels can be reduced by incinerating the waste produced in the processing operations and also by optimising energy circuits and consumption in the processing plant.

2.2.4 Sugar beet and sugar cane processing

The essential environmentally relevant aspect of beet and cane processing is the energy required for the concentration of the sugar solution. While this requirement can be met in cane processing by burning bagasse, energy consumption in sugar beet processing must be optimised and, if necessary, alternative energy sources must be identified.

Mention should also be made of organically polluted wastewater from purification and condensate.

There is an environmental brief specifically relating to Sugar.

2.2.5 Fruit and vegetable processing

Biologically polluted washing water and the energy requirement for thermal preservation processes are of environmental relevance in this area, and the same comments as in the previous sections apply. Solar driers can also be used, thereby reducing the energy required for the production of top quality dried products quite considerably.

2.2.6 Dairies

As milk and dairy products are ideal breeding grounds for microorganisms, hygiene requirements are relatively stringent, a factor which prompts the use of aggressive cleaning agents. If they are discharged at certain concentrations, the quality of surface water is impaired and micro flora and fauna are affected.

Countermeasures are the sparing use of biodegradable cleaning agents and dilution in tanks.

Mention should also be made of percolating milk in rinsing and washing water as a source of organic pollution.

2.2.7 Processing of semi-luxury goods and spices

The operations having the greatest environmental relevance in the production of semi-luxury goods and spices are fermentation and waste disposal. Fermentation is generally carried out in fixed locations, and the pollutants thereby produced can accumulate in the soil over long periods, damaging micro flora and fauna. The washing operations sometimes carried out after fermentation (e.g. coffee) give rise to biologically polluted wastewater which, if discharged untreated, can impair surface water quality. The impacts of this are restricted to harvest time, and are then found over longer intervals.

Fermentation should be carried out in the immediate vicinity of an abundant supply of running water at appropriately prepared places (cement bases). The heavily polluted wastewater produced must either be suitably diluted before discharge or used for biogas production. As washing water is not generally so heavily polluted, special measures (aeration ponds) are only required in exceptional cases. Spices are often irradiated as a method of preservation, although the consequences of irradiation on human health are as yet unknown.

2.2.8 Plant fibre extraction

In many countries, microbiological retting is practically the only method of plant fibre production in use. It involves the degradation of non-fibrous components by a microbiological process and is carried out by immersing the raw material either in a slow flow of water or in specially prepared tanks, whereupon the retting is spontaneously initiated. Since this process and the subsequent fibre washing require large quantities of water, these installations are always built close to abundant supplies of running water. In these circumstances, the water exchange required once the retting process is complete is no problem (except perhaps for any dissolving pesticides used during farming).

The retting process is associated with a certain odour nuisance which cannot be avoided at reasonable cost. The only remedy is not to site these plants close to residential areas and to take account of prevailing wind directions.

Because fibre production is a low-input technology in every respect, negative environmental effects can only be avoided by selecting a suitable site and making use of what nature has provided.

2.2.9 Tanneries

Of all the agro-industries tanneries harbour the greatest risk potential for the environment. This is due on the one hand to the considerable odour nuisance and on the other to the dyes and other chemicals (particularly chromium compounds) used in the tanning process which complicate the wastewater treatment operation. And there is also biological pollution. Besides a substantial impairment of the quality of the nearby surface waters, an enrichment of the hazardous substances in the soil, and possibly also in the groundwater must also be expected.

The elimination of odours at source is only possible if the tanning is carried out in enclosed rooms and any air escaping is cleaned in technically sophisticated filter systems. The nuisance can be limited indirectly by concentrating plants of this kind on sites a suitable distance from residential areas. This would also create the conditions essential for the relatively complex process of multistage wastewater treatment, which is essential in this industry but which is really too costly for an individual small plant (see also the environmental guidelines of the World Bank).

2.3 Socio-economic impacts

The overwhelming majority of jobs in the agro-industry call for little in the way of qualifications and most workers are women. However, as mechanisation and machine-based jobs increase, the proportion of male workers rises - as do monotony and isolation of the individual working processes, and the risk of accidents. The extent to which the employment of women leads to changes in their own food production needs to be examined. The jobs are of poor quality in ergonomic terms, and nuisances in the form of dust, damp, smells and noise may attain levels which can affect the health of employees, constituting a considerable risk to women in particular. Because different types of jobs are done by the two sexes, qualification and training programmes must be established at an early stage, with the emphasis on female employment. These programmes should take account of the overall form of production and lifestyle of female employees and their families.

3. Notes on the analysis and evaluation of environmental impacts

The environmental impacts in the agro-industry can be assessed in terms of space, time and in relation to various resources and employees.

In the "agro-industry" sector assessments are based directly or indirectly on the following test criteria:

- impacts on employees in the factory
- impacts on people living near the factory
- environmental changes due to the emissions from the factory
- environmental changes caused indirectly by the factory (e.g. change in the quantity of water or extra energy required).

Short-, medium- and long-term impacts and likewise direct and indirect impacts must be considered in the light of these test criteria.

The evaluation involves comparing the project with other possible projects, and also considers the economic, ecological and social costs involved.

The evaluation of effects on health faces the problem of the frequent lack of national limits or recommended values for individual substances, and this is further complicated where a number of substances are emitted at the same time, thereby increasing their impact due to synergistic effects. One initial approach to this problem area may be provided by publications of international organisations such as the World Health Organisation (WHO) (see in this regard Volume III, Compendium of Environmental Standards.

4. Interaction with other sectors

There are close links with the plant and animal production sector which supplies the raw materials, and with the marketing sector, not forgetting the metal and mechanical engineering industries which manufacture the processing equipment, and the packaging materials industry.

Other factors in the equation are veterinary services, livestock farming, irrigation and health and nutrition. Projects in the field of the economy and also infrastructural measures, particularly in the rural hydraulic engineering sector, are significant issues in the assessment of agro-industrial projects, while cross-sectoral concepts of general resource management, location planning and regional planning must not be forgotten.

5. Summary assessment of environmental relevance

Agro-industries often serve as pilot projects for more general industrialisation, and must therefore be examined very closely in terms of their direct and indirect impacts on the food supply and economic prospects of the country concerned, its general environmental conditions, and the lives of its female population in particular.

Agro-industrial projects are extremely important to a country's independent development and this is closely allied to general subsistence production.

Direct environmental pollution from small and medium-sized agro-industrial factories on an individual level is relatively slight in the short-term, but the more general effects can be quite considerable.

One exception to this is tanneries because of the chemicals used -which are problematic in environmental terms - and the odour nuisance.

All factories which use water as the extraction, cleaning and transport medium produce wastewater which is biologically polluted to varying degrees, and this generally requires treatment in aeration ponds or treatment plants. Noise and dust emissions are normally restricted in terms of the area affected, and therefore affect primarily the employees themselves.

6. References

Bundesimmissionsschutzgesetz BImSchG of 15.03.1974.

Environmental Guidelines, The World Bank, Environment Department.

TA-Luft 27.02.1986.

TA-L 1968.

Verwaltungsvorschriften to § 7a WHG, Mindestanforderungen an das Einleiten von Schmutz- bzw. Abwasser in Gewer.

1. Scope

This sector embraces slaughterhouses, meat-processing plants and animal carcass disposal plants.

To date no standard project types have gained prevalence for slaughterhouses, particularly in terms of size, as each project is dependent on a a number of factors, such as:

- regional population density;
- specific consumption (kg/person and year);
- animal stocks in the region, catchment area;
- distance from nearest slaughterhouse;
- export potential, restrictions;
- eating habits;
- religious constraints.

Nor is there a standard size of meat-processing plant, as their design is also influenced by these same factors.

Animal carcass disposal plants (ADP) process dead animals, confiscated carcasses (where the meat or organs of slaughtered animals is found to be unfit for human consumption), blood, bones etc., the end products of which are - depending on the raw material - technical fats and meat meal, bone meal, blood meal etc., used for fodder and in some cases as fertilizer. Project size is determined primarily by the capacity of the neighbouring slaughterhouse.

For reasons of hygiene, cattle are hung for slaughter. The slaughter line feed system is manual in small operations and mechanical in plants with a medium or large line capacity.

Different processes are used in the bleeding stage, for example, since animals must be hung for bleeding to comply with EC Guidelines, but laid flat ("bleeding with the neck pointing to Mecca") in accordance with the dictates of Islam. (Sheep and camel slaughter similar to cattle slaughter).

Pigs can be slaughtered either hung or lying. A number of processes have been developed for the scalding and skinning of pig carcasses (scalding tank and depilation machines, production line systems where the animals are suspended or laid flat) depending on line capacity. Ritual slaughter is carried out for export.

Sheep are hung for slaughter and a number of methods are used for bleeding.

Because of the large number of different meat and sausage products, a wide range of processing stages20) are required. However, the following can be regarded as basic operations for all products:

20) for the processing of raw products and by-products.

carcass splitting - grinding of meat - seasoning - filling of natural or synthetic skins with sausage meat - heat treatment - cooling - dispatch - long-life meat products - tinned food.

The various processes used in the manufacture of meat and sausage products depend on the particular meat and sausage products in question, with processing carried out within different temperature ranges:

- uncooked sausage process temperature approx. 14 -28°C
- cooked sausage process temperature approx. 50 - 80°C
- tinned meat and sausage products process temperature approx. 80 -121°C

In animal carcass disposal plants, the material used and the waste material is largely processed by the pressing process following heating.

The extraction process is rarely used today because of the residues it leaves in the meal.

Fig. 1 - Flow chart of slaughterhouse

Fig. 2 - Flow chart of slaughter procedure

Fig. 3 - Flow chart of a meat product factory

Fig. 4 - Flow chart of ADP press installation

2. Environmental impacts and protective measures

Meat industry facilities cause environmental impacts due to:

- wastewater;
- spent air/waste gases;
- noise;
- animal waste;
- waste heat;
- residues in the end product;
- waste.

German regulations relating to environmental pollution caused by meat processing are taken as the reference in the following as they have also gained acceptance as the international standard.

Table 1 - Environmental impacts from meat industry plants

Type of plant



Waste gases



Waste heat

Fattening and breeding operations Slaughterhouses Recycling plant Meat-product factories







2.1 Water pollution

Water consumption and the degree of contamination of the wastewater arising from the process depend on a number of factors, and are determined principally by the following:

- species of animal;
- type and capacity of plant;
- intensity of cleaning of carcasses and
- working accommodation during the process.

The following values apply for slaughterhouses (average values):

- cattle 600 - 800 l/animal
- swine 300 - 500 l/animal
- sheep 200 - 300 l/animal.

Water consumption in meat-product factories is largely product dependent. Wastewater pollution is higher, for example, in plants producing mainly cooked sausage and tinned products than in those which, for example, produce only uncooked sausage (salami). Consumption is around 10 - 15 m3 per tonne of sausage and meat products.

Water consumption in ADPs is relatively low. The quantity of wastewater produced depends on the quantity processed, as some 65% of the raw material must be evaporated. On average, the wastewater level is approximately 1 m3/t raw material.

The degree of water pollution in the meat-processing industry is extremely high, particularly in slaughterhouses and ADPs. In Germany, the following minimum requirements on the discharge of dirt or wastewater into watercourses must be observed by the meat industry to prevent water pollution.

Table 2 - Degree of pollution of wastewater


BOD5 valuemg/l

Causes and factors of influence

Slaughterhouses Meat-product factories ADPs

approx. 4,000 approx. 10,000 approx. 10,000

Some blood, content of stomach and intestinal tract, urine, liquid manure, animal waste etc. Animal waste, type of processing (boiling and steaming of raw material and end product) Type and quality of the raw material

Table 3 - Minimum requirements for wastewater disposal in water


Matter which can be removed by settling3)


COD2) 4)

Slaughterhouses and meat-processing plants ADPs

< 0.3 ml/l < 0.5 ml/l

< 35 ml/l < 40 ml/l

< 160 ml/l < 30 ml/l


1) BOD5 = Biochemical oxygen demand over a 5-day period, with oxygen consumption determined in this period (g O2/l wastewater at T = 20°C)

2) COD = Chemical oxygen demand in the reaction with KMnO4 or K2Cr2O7 as the oxidation agent (mg O2/l wastewater)

3) Random sample

4) 2hr mixed sample

Slaughter costs are increased because of increased investment costs and running costs for wastewater treatment in relatively expensive treatment plants. Consequently animals may be slaughtered outside instead of inside slaughterhouses and thus no comprehensive check on hygiene conditions can be guaranteed.

After eliminating solids by mechanical purification, pond systems or the seepage of wastewater into the ground can be considered a substitute for biological treatment systems, provided that this does not pollute the groundwater mains or groundwater collection installations used for the drinking water supply.

The following can help slaughterhouses and meat-product factories reduce their wastewater pollution and dispose of their effluent correctly:

- better understanding of environmental issues by personnel;
- installation of technical facilities for improved separation of blood from the wastewater system;
- removal of waste of coarser consistency from production area floors before wet cleaning;
- fitting of sludge buckets in floor drains;
- fitting of wastewater screens to separate solids from the wastewater (these solids have a high protein content and can be passed on to ADPs);
- installation of sludge trap and fat separator;
- flotation plants (mechanical flotation treatment);
- supplementary biological clarification as a second treatment stage following mechanical treatment in plants which discharge their wastewater directly into surface water.

Wastewater from ADPs has to be sterilised.

2.2 Air pollution

Emissions occur primarily in the form of air discharged from the following areas:

Table 4 - Emissions from outgoing air


Source area

Slaughterhouses Meat-product factories ADPs

Stalling, possibly also storage, confiscated meat Processing, smoke (cooking plant) Delivery, processing

To reduce the smell nuisance, slaughterhouses in Germany must, wherever possible, be sited at a distance of at least approx. 350 m from the nearest residential building.

Odours arise due to the odour of the animals themselves and changes to organic materials. As all smells arising in slaughterhouses are biodegradable, bio-scrubbers and biofilters can be used to reduce smells, as can adsorption and absorption processes.

Table 5 - Immission values (IVs) (TA-Luft [Technical Instructions on Air Quality Control])


IV 1 continuous operation

IV 2

Airborne dust (regardless of dust content) Lead and inorganic lead compounds as components of airborne dust -expressed as Pb -Cadmium and inorganic cadmium compounds as components of airborne dust -expressed as Cd -Chlorine Hydrogen chloride - expressed as Cl -Carbon monoxide Sulphur dioxide Nitrogen dioxide

0.15 2.0 0.04 10.0 0.10 10 0.14 0.08

0.30 mg/m3 - µg/m3 - µg/m3 0.30 mg/m3 0.20 mg/m3 30.00 mg/m3 0.40 mg/m3 0.20 mg/m3

Waste gas from meat-product factories can be treated in a number of ways, including:

- post-combustion;
- condensation;
- absorption - adsorption;
- electrical separators for particulate substances in conjunction with the above processes.

The emission reference value is the total carbon in the organic compounds.

In new continuously operating plants, emission values can be contained with technical installations so that:

- the established immission values (see Table 5) are not exceeded, and
- as experience has shown, no odour nuisance occurs where the chimney is of the correct height for gas disposal.

The installation of ventilation and air-extraction systems, waste gas systems etc. incurs high investment costs and this in turn can lead to high slaughterhouse fees which users cannot afford.

The following values are recommended to reduce substances which cause odours in ADPs:

- thermal post-combustion: 20 mg/m3 carbon in the combustible substances.
- other post-treatment systems:

The total frequency of odour assessments of emitted spent air, measured by the olfactometry process with 50% negative evaluations (ADP odour not perceivable) must produce a dilution factor of 100. A solids emission value of 75 mg/m3 can be observed in the air emitted from meal, conveyor and storage systems. The air emitted from heating and air purification systems must be removed through a chimney of an appropriate height.

Odour emissions can be generally reduced or prevented by:

- designing enclosed working and production areas with windows which cannot be opened;
- closed process circuits;
- fitting of air locks;
- preventing any accumulation of materials which could result in the development of odours;
- spent air systems with appropriate air treatment, as shown in Table 6.

Table 6 - Reduction of odour emission due to spent air treatment



Slaughterhouses Meat-product factories (Smoking installations) ADPs

Biofilters, waste gas scrubbing, active carbons Post-combustion, condensation, absorption, adsorption Wet scrubbing (multi-stage), heat treatment, biological treatment, earth filters, biological scrubbers

2.3 Noise

Potential sources of noise in slaughterhouses and/or meat-product factories and ADPs are:

Table 7 - Sources of noise



Meat-product factories


Animal delivery Animal slaughter area Machine and process area Spent air system recooling chamber




As the operations under discussion here are not noise-intensive, technical measures - such as the fitting of sound absorbers etc. - are usually sufficient to comply with local limits/guide values. The possibility of keeping at an adequate distance must be checked first.

It is possible to avoid or reduce noise by:

- installing sound dampers in ventilation systems;
- enclosing machines;
- using sound-barrier walls;
- making allowance for the main wind direction at the design stage in terms of sources of noise.

2.4 Waste and residues

There are two types of waste in the meat-processing industry:

- waste material which can be reused for the manufacture of by-products;
- waste to be destroyed or stored in dumps.

Odour emission in the processing of waste to by-products is reduced by:

- immediate processing of waste;
- cold storage of waste until reprocessing;
- use of closed containers;
- spent air treatment by appropriate installations.

If possible, a wet extraction process should be avoided in ADPs in view of the residues this leaves behind in the end product (animal meal); the pressing process should be used instead.

Waste which goes for further processing, destruction or storage in dumps, should be collected in separate containers (metal, plastic, paper etc.).

Manure should be reprocessed as far as possible for agricultural purposes.

2.5 Waste heat

The operations considered here produce waste heat primarily from:

- boiler house installations;
- cooking and smoking installations;
- open-hearth furnaces (pig slaughter);
- extract cooling (ADP).

State-of-the-art heat recycling plants must be used in new plants, to ensure a lower consumption of primary energy (see also environmental brief Renewable Sources of Energy).

2.6 Industrial safety

The well-being of people employed in the meat-product processing industry is affected in relatively few areas. Noisy machines are used, for example, to saw carcasses into pieces (approx. 90 dB(A)) and to grind meat with cutter mixers (approx. 80-90 dB(A)), and so here appropriate hearing protection is to be worn.

ADP personnel is exposed to odours for a short time when the raw material is delivered, but suitable ventilation and air-extraction systems can reduce this problem, with protective mouth masks recommended in some cases.

2.7 Location planning

Modern slaughterhouse sites are divided by a fence into a clean and an unclean zone, each of which has its own entrances and exits.

The unclean zone houses all activities where cleanliness is not an issue, such as the cattle market, stabling, transport of waste, confiscated carcasses, preliminary clarification, middens etc.

The clean zone is for all areas where hygiene is a major consideration, such as the slaughter plant, cold chambers, cutting plants, dispatch etc.

When designing slaughterhouses, the siting of the clean zone must be analysed and specified appropriately for hygiene reasons in terms of wind direction and emissions from existing or planned works or factories.

3. Notes on the analysis and evaluation of environmental impacts

Limits and approximate values are specified for wastewater and air pollution and are laid down in Germany, for example, in the Wasserhaushaltsgesetz [Federal Water Act] and in TA-Luft [Technical Instructions on Air Quality Control] or in the guidelines (Richtlinien) of the Association of German Engineers VDI; they also describe the correct analysis procedure. Constant wastewater and outgoing air control is necessary to conform to these values, and this also involves checking that technical laboratory conditions are adequate. It must also be ensured that suitable numbers of qualified personnel are available for the analysis work.

The adverse effect of noise on nearby utilities can be reduced by keeping appropriate distances; in Germany, for example, a distance of 350 m from the nearest residential building must be observed. Within the plant, hearing protection must be provided for personnel at noise-intensive workplaces and the wearing thereof checked. Values for the maximum admissible noise nuisance at the workplace are included, in Germany for example, in the Arbeitsstenverordnung [Ordinance on Workplaces].

Waste recycling produces, in the main, odour emissions, but this nuisance can be minimised in the neighbourhood by appropriately designed operating procedures (immediate processing, cold storage, closed containers) and adequate plant distances.

Appropriate dumping facilities must be guaranteed for waste.

The possibility of any residues remaining in the end product must be ruled out by an appropriate choice of process; end products must be controlled by continuous analysis. In new installations, waste heat is returned to the process.

If there are no national provisions, analyses should be carried out to define the preconditions for protecting the population from pollution, e.g. in the form of groundwater pollution, the storage of waste and the associated risk of disease. This applies correspondingly to industrial safety.

Factors of a socio-economic nature must also be analysed, with due consideration given to employment opportunity issues and working conditions, differentiated by sex, and an examination of sources of income for women etc.

4. Interaction with other sectors

Raw material procurement for the meat industry - in this case live animals - and the waste and by-products arising from animal slaughter and the meat-processing industry, give rise to a range of interactions within this sector of industry.

The following special recycling facilities are therefore provided for waste and by-products from slaughterhouses and meat-processing plants, as shown below.

Table 8 - Waste recycling potential

By-products and waste product

Secondary industry



Blood Technical blood Hair Manure Content of intestines Skins, pelts Bones (not fit for human consumption) Bones (fit for human consumption) Hoofs Suet

Blood reprocessing ADP Brush processing -- -- Tanneries Leather industry Fat production Fat production ADP Fat production

Plasma Blood meal Brush/paint brush hair Compost Biogas Leather Technical fats Bone meal Fat gelatine Hoof meal Technical oils (acid free) Edible fat

Food industry Animal fodder General Fertilizers Energy Leather items Soap industry Animal fodder Food industry Fodder Lubricants Food industry

Since slaughterhouses are provided for the general supply of meat and to serve meat-processing factories for the production of meat and sausage goods, and since the by-products and waste constitute the raw material base for these secondary processing plants, there are close links between the businesses in this sector.

The following environmental briefs provide more detailed information about the surveying, evaluation and reduction of environmental impact caused by the meat-processing industry:

· Wastewater Disposal
· Solid Waste Disposal
· Livestock Farming
· Veterinary Services
· Planning of Locations for Trade and Industry

5. Summary assessment of environmental relevance

The main environmental impact from slaughterhouses and meat-processing plants derives from wastewater, as the pollutant waste load produced in the process is absolutely enormous. If this wastewater (effluent) is discharged into receiving bodies, a fee should be charged, based on the pollutant load.

In addition to the wastewater, serious environmental implications (e.g. odour) can be caused if the critical areas/plants are not maintained as required and waste storage or removal is not carried out with due care.

Unless they are subsidised, slaughterhouses are financed solely by slaughter fees paid by users. The fees are higher the greater the investment and maintenance costs.

The provision of state-of-the-art slaughterhouses can therefore lead to increased meat prices.

In the light of these factors, there is a risk that animals will not be slaughtered in municipal slaughterhouses under veterinary control, but unregulated outside the slaughterhouse (e.g. on the road side) to avoid slaughterhouse fees.

A further crucial point which must be considered when designing such plants, is the availability of technically trained personnel.

Correct plant operation with due allowance made for environmental imperatives can only be guaranteed if the technical installations are correctly designed and the following conditions are met:

- availability of adequately trained personnel;
- understanding of environmental protection constraints;
- implementation of preventive maintenance;
- adequate spare part supply.

6. References

ArbStV § 15 - Schutz gegen L

ATV-Arbeitsblatt A 107, Hinweise f Ableiten von Schlachthofabwasser in ein ntliches Kanalnetz

Bundes-Immissionsschutzgesetz BImSchG of 15.03.1974

Zweite Durchfsverordnung zum Vieh- u. Fleischgesetz (VFIG), amended on 20.08.1979

Vierte Durchfsverordnung zum Vieh- u. Fleischgesetz (VFIG), amended on 10.11.82

Sechste Durchfsverordnung zum Vieh- u. Fleischgesetz (VFIG), newly issued on 16.12.1986

Siebente Durchfsverordnung zum Vieh- u. Fleischgesetz (VFIG), in the version of 10.11.1982

EC Directive of 15 July 1980 relating to the quality of water intended for human consumption

Fleischhygienegesetz in der Fassung der Bekanntmachung of 24.02.1987 - BGBl. I (Federal Law Gazette I), p.549 - FIHG

Gesetz en Verkehr mit Vieh und Fleisch (Vieh- und Fleischgesetz - VFIG) of 25.04.1951 - BGBl. I (Federal Law Gazette I), p.272, in the revised version of 21.03.1977 - BGBl. I, p.l477, most recently amended on 10.06.1985 - BGBl. I, p.953

Gesetz ie Beseitigung von Tierkrn, Tierkrteilen und tierischen Erzeugnissen (Tierkrbeseitigungsgesetz - TierKBG) of 02.09.1975, BGBl. I (Federal Law Gazette I), p.2313 and 2610

Gesetz ie Neuorganisation der Marktordnungsstellen of 23.06.1976 - BGBl. I (Federal Law Gazette I), p.1608

Handelsklassengesetz of 05.12.1968 - BGBl. I, p.1303 in der Fassung der Wiederlautbarung of 23.11.1972 - BGBl. I (Federal Law Gazette I), p.2201

Council Directive No. 64/433/EEC of 26 June 1964 on health problems affecting Intra-Community trade in fresh meat, in the version of the Council amendment directive no. 83/90/EEC of February 07 1983 (Official Journal of the European Communities L 59 of March 05 1983, p.10), last amended by the Council Directive no. 88/288/EEC of May 03 1988 (Official Journal of the European Communities L 124, p.29)

TA-Luft of 27.02.1986

TA-L - Genehmigungspflichtige Anlagen in accordance with § 16 of the Gewerbeordnung

VDI-Richtlinie 2590 Auswurfbegrenzung, Anlagen zur Tierkrbeseitigung

VDI-Richtlinien der Luftreinhaltung, Nr. 2595, Blatt 1 Emissionsminderung bei Rheranlagen

VDI-Richtlinien der Luftreinhaltung, Nr. 25965, Emissionsminderung bei Schlachth

Verordnung esetzliche Handelsklassen fweinehten, coordinated with Verordnung of 18.12.1986, valid from 01.04.1987

Verordnung esetzliche Handelsklassen faffleisch of 27.01.1971, BGBl. I (Federal Law Gazette I), p.77 - in the version of the amendment of 11.11.1977 - BGBl. I, p. 2139

Verordnung esetzliche Handelsklassen fdfleisch, coordinated with Verordnung of 13.11.1982, valid from 01.01.1983

Verordnung ie hygienischen Anforderungen und amtlichen Untersuchungen beim Verkehr mit Fleisch (Fleischhygiene-Verordnung - FIHV of 30.10.1986, BGBl. I (Federal Law Gazette I), p. 1678)

Allgemeine Verwaltungsvorschrift ie Durchf der amtlichen Untersuchungen nach dem Fleischhygienegesetz (VwVFIHG) of 11.12.1986 - B Anz. (Federal Gazette) Nr. 238a of 23.12.1986

Verwaltungsvorschrift on § 7a WHG, Mindestanforderungen an das Einleiten von Schmutz- bzw. Abwasser in Gewer.

1. Scope

The sector embraces mills handling cereal crops, including warehousing for raw materials and end products, and also animal feed production and seed dressing, operations which are almost always linked to the cereal processing complex.

The only milling industries to be considered in the study are those involved in manufacturing end products for human consumption from raw materials imported or grown in rural areas, with animal feed simply a by-product.

Below, the environmentally relevant factors of noise, dust, process water and pesticides are considered.

The sector concerned can be divided essentially into four parts:

- storage, drying and seed dressing,
- flour mills,
- hulling mills,
- heat treatment.

Projects for the drying and storage of locally grown cereal and for seed conditioning have been given a boost recently and have been priority now that it is realised that raw materials for food need to be protected from spoilage and perishing due to climatic conditions, pests etc. and that better seed increases production.

Modern industrial mills have an integrated silo and warehouse capacity for the raw material to be processed and the end products and by-products manufactured. Depending on the site, ownership and the general purpose of the plants, drying and seed cleaning plants may be incorporated. By-products are often recycled as animal feed components.

2. Environmental impacts and protective measures

Given the processing techniques employed today, it may generally be assumed that large volumes of air are required to produce milled and hulled products (flour, wholemeal products, flakes, grains etc.), in addition to power for cleaning, hulling, grinding (milling) and the transport of intermediate and end products.

This air is used mainly for vertical and horizontal transfer inside the milling or hulling system and for dust extraction from the processing units and the entire mill complex. Furthermore, under certain climatic conditions cool air is required to ventilate power plant and processing machinery as well as the entire building complex.

Industrial wastewater is produced only in the cereal washing department in the mill industry, and even then only where granular or wholemeal products are to be produced. The modern mill industry makes particular use of a dry cleaning process which separates out impurities by means of screens and weighing sorters. If the plant also produces bulgur and parboiled rice, process water with a low starch content is produced.

The wastewater from waste-recycling power generating plants, particularly that from rice husk gasification for the production of lean gas for gas-engine powered plants, has a phenol content of over 0.03 mg/l. When husks are burnt to produce steam, a residual quantity of 18% ash in relation to the quantity input must be disposed of. The same applies to gas plants.

It can therefore generally be stated that the environmental impacts of the mill operation lie in the following areas:

- dust emission,
- noise nuisance,
- hazard of dust explosions and fires,
- odour nuisance to a limited degree,
- hazard of toxic gas,
- recycling of residual substances and waste disposal,
- process water.

2.1 Cereal storage and handling

2.1.1 Port and transshipment silos, mill silos

Storage installations of this kind are used for the storage and transshipment of cereal for import and export. They are found in all major ports where imported cereals (wheat, maize, rice, millet etc.) as well as raw products and semi-finished products for the food and animal feed industry are put into store for intermediate storage, and from which the domestic industry is supplied with raw materials or goods for export are shipped (maize, rice, millet, tapioca etc.).

The following table shows the dust content of the service air from the various mill sections and admissible emission values in Germany.

Table 1 - Pollutants produced and admissible emission values in Germany

Type of mill industry

Dust content of service air

Permissible emission values

Silo installations Drying plants Mills handling cereal crops Hulling mills Seed cleaning

12 to 15 15 to 18 approx.96 6 to 8 8 to 10

g/m3 g/m3 g/m3 g/m3 g/m3

50 mg/m3 50 mg/m3 50 mg/m3 50 mg/m3 50 mg/m3

In storage installations with preliminary cleaning plants and in mills, dust emissions are collected in aspiration pipe systems during cleaning, and separated with the help of cyclones and filters. To achieve the best possible removal of dust from machines and buildings, all equipment handling materials and machinery should be enclosed and fitted with appropriate aspiration connections. The extraction of dust with so-called mass separators or filter separators is described and explained in the guidelines nos. 3676 and 3677 of the Association of German Engineers VDI. The safety measures in these guidelines should be observed.

With the high degree of mechanisation in modern mills, the only workplaces where dust is a problem are the loading and packing operations; here too, extraction devices must be used wherever possible.

All the dust from aspiration systems and cleaning in transshipment silo installations is collected and bagged.

The cleaning waste, which may contain live pests, is to be destroyed immediately.

In mill-cleaning plants, dust waste and granular cleaning waste is treated and added to mill afterproducts (bran) (feed ingredient).

Noise is another environmental problem. The increasing use of high-speed technical equipment and the intensive use of machines in the smallest possible space give rise to an increasing noise nuisance which is becoming a hazard to man.

Precautions must be taken to protect employees and local residents. Structural measures, such as the lining of ceilings and walls with soundproofing materials, must be taken, and vibration isolation materials must be used for machine foundations.

The TA-L [Technical Instructions on Noise Abatement] in Germany lays down, for the various industrial and residential areas and mixed use areas, safety guidelines for immissions which must be observed in the planning and erection of industrial plants.

Personnel must be issued with hearing protection where they are constantly exposed to noise levels of over 70 dB.

Information and training must therefore be provided for personnel, and compliance with safety measures monitored.

People, buildings and the machine stock can be at risk from dust explosions and fires. Following any such explosion, there is a chemical conversion of a dust/air mixture, which accelerates as heat is generated, causing a sudden pressure effect from existing or newly formed gases. Three components constitute the basis for a dust explosion: dust, air (oxygen) and ignition energy; the latter can be in the form of heat or electricity (electrostatic charging).

Silo installations are particularly at risk from dust explosions. Mechanical sparks, pockets of glowing materials, mechanical heating, hot surfaces, welding work, electrostatic discharge sparks and the like are possible ignition sources. They must be eliminated as a safety measure, and the formation of explosive dust concentrations must be prevented, for example by enclosing machines. Structural precautions can also be taken, namely the creation of compression-proof rooms and pressure release and explosion suppressing systems. The following organisational precautions are also effective in terms of fire and explosion safety:

- welding and cutting works only to be carried out during factory shutdowns;
- regular cleaning with dust-explosion-proof equipment;
- training of employees in the handling of fire-fighting equipment and
- information to employees about the causes of dust fires and explosions.

Finally, in the planning phase, provision must be made for taking all the measures required to limit the risk of explosion (cf. in Germany, VDI guideline, 2263 on dust fires and dust explosions - Staubbre und Staubexplosionen).

Gases are most commonly used to protect stocks (pest control) in the silo installations and warehouses, but under certain circumstances sprays and vapours are an option.

The types of pest control agent for cereals currently used and approved in Germany include gaseous insecticides:

- hydrogen phosphide,
- methyl bromide,
- hydrogen cyanide.

In addition to gases, fumigants and sprays can be used for the disinfestation of silos and stores - without any need to include stocks in the treatment.

The following are approved in Germany:

- lindane
- bromophos,
- malathion,
- dichlorvos,
- piperonyl butoxide,
- pyrethrum
- and combinations of these.

The incorrect use of agents for pest control for stock protection purposes can lead to hazardous substances seeping into adjacent production or residential buildings (e.g. hydrogen phosphide). Therefore, particular attention must be paid to the technique of pest control (e.g. silo fumigation using a circulation system).

Specific bans or restrictions on the use of these agents are recorded in the plant pesticide register of the country concerned or may be requested from the registration office for these substances. The manufacturer's instructions must be strictly observed and made available in the local language.

After treatment, waiting periods must be observed to ensure that plant products do not contain higher residue levels than are permissible where they are to be brought into circulation or eaten (cf. environmental brief, Analysis, Diagnosis, Testing and Volume III, Compendium of Environmental Standards (CES)).

Authorised contractors must be employed for the application of agents to protect commodities stored in silos and warehouses; their personnel must be appropriately trained and able to use the special equipment and safety installations.

2.1.2 Cooperative stores and warehouses

Simple storage installations (including raw material stores) are warehouses for bagged commodities or for horizontal storage. Bagged commodities or loose grains are cleaned, stored, ventilated and may also be treated as a pest control measure. Most maize, rice and sorghum harvests are still stored in this way in many countries, with possible storage losses of 15% or more.

Figure 1 - Diagram of a port and transshipment silo installation

Standard warehouses should also have installations for cleaning, ventilation and fumigation.

The risk of dust explosions can be largely avoided in warehouses by a light and open design, although this does not protect against normal types of fires which can occur. Otherwise, the environmental implications are as described in 2.1.1. Pest control in warehouses may take the form of sprays although fumigation is also commonplace.

The safety measures for silo installations described in 2.1.1 are also applicable to warehouses, with the exception of measures against the risk of explosion.

Special precautions must be taken where gases are used for pest control purposes. As bagged commodities cannot be fumigated in airtight areas, gastight fumigation tarpaulins, sealed underneath with sand, are required if this type of pest control is to be used.

2.1.3 Seed cleaning installations

Seed dressing is not considered part of a mill's activities, but in many countries it is one of the services a cooperative storage facility may offer its members.

In using these facilities seed is produced with a higher grade purity thanks to air, screen and specific weight classification. The lower content of other types of grain and the improved growth conditions resulting from chemical treatment improve quality and thus yields per hectare.

The service air from seed cleaning plants contains primary dust. It and the cleaning waste produced (rejected grain, weed seeds etc.) can be used for animal feed production.

Treatment involves the wet or dry application of fungicides and insecticides which - as pesticides - protect the seed and are classified as seed treatment agents. All such treatments approved by the Biologische Bundesanstalt fd- und Forstwirtschaft (Federal Biological Research Centre for Agriculture and Forestry) in Germany are listed in the pesticide register Pflanzenschutzmittel-Verzeichnis (1990).

These plant pesticides are used in seed improvement operations either alone or in combination depending on the purpose of the treatment.

Common pesticides (active ingredients) are:

- anthraquinone,
- bibertanol,
- bendiocarb,
- fuderidazol,
- bromophos,
- lindane,
- carboxin,
- fenfuram etc.

Environmental measures in seed cleaning operations are confined, in terms of aspiration and service air, to keeping the production rooms and the outgoing waste air clean. The filter installations listed in paragraph 2.1.1 and the emission values shown in table 1 are applicable here.

When protecting seeds, appropriate precautions must be taken to protect personnel and, subsequently, users.

The approval regulations of the individual countries must be obeyed as must the manufacturer's recommendations for use (see too Volume III, CES).

Figure 2 - Diagram of a seed cleaning installation

2.1.4 Drying installations

Grain drying is a thermal process in which water is removed from the pre-cleaned damp commodities (cereal, maize, rough rice (paddy), sorghum etc.) by evaporation. Obviously, an adequate supply of heat is essential. The drying of the moist harvested produce is usual in warehousing facilities and the agricultural trade (cooperatives), and mill and silo facilities often have drying installations too. Thus, wherever large quantities of damp grain (moisture content of over 15%) are supplied, rapid drying is called for. Drying installations are used where natural sun drying is not practicable in view of the weather conditions (rainy season). Only dry commodities can be safely stored for prolonged periods without any deterioration in quality.

The service air of drying installations and the preliminary cleaning machines contains coarse to fine particles of dust which need to be separated by means of the dust separators described in paragraph 2.1.1. Drying installations are only used at harvest time, and should preferably be sited close to the (sparsely populated) growing areas. Noise is another problem. Very often mill and silo facilities also have drying installations.

The safety measures listed in 2.1.1 to protect against dust and noise must be taken here too.

Figure 3 - Diagram of a drying installation

2.2 Flour mills (wheat mills)

The purpose of a flour mill is to obtain large quantities of flour which also meet flour product requirements in terms of quality. The by-products and afterproducts (bran, middling and cleaning waste) are recycled in agriculture or in the animal feed industry in the form of feed components. Mills also make wholemeal products.

In some cases, very antiquated washing machines are still used today for cereal cleaning in the wheat mill industry, requiring monitoring of wastewater quantities (up to 1000 l/t), thus safe distances from residential areas must be maintained. In the modern cereal mill, water is only used for conditioning (wetting) the cereal and it is fully absorbed by the grain. Today, the entire cleaning process is carried out by means of air, screening and weight classification. Scouring machines have largely replaced the washing systems, thus no industrial wastewater is now produced.

In conventional mills handling cereal crops, some 5 - 10 cubic metres of air are required per milled tonne. This quantity drops to just 15% where machines working on the circulating air principle are used for cleaning. All service air discharged into the atmosphere must be filtered.

There is also a fire risk due to dust explosions in mills, and mills handling cereal crops as a whole generate noise emissions which have environmental implications for humans.

All safety measures described for cereal storage are appropriate for mills handling cereal crops in all respects. If silo installations are structurally linked to the mill, not only must automatic fire valves be fitted in the interconnecting materials handling equipment, but also the connecting walls between the installations must constitute fire barriers21). A settling tank for organic substances (husks, pieces of stem, fines etc.) must be provided.

21) For this reason, safe distances from populated areas must be maintained.

Figure 4 - Diagram of a wheat mill

2.3 Hulling mills

Hulling mills handle the following cereal types: oats, barley, rice, sorghum and millet, as well as pulses. While hulling mill technology is very different from that used in mills handling cereal crops, the environmental pollution and the resultant safety measures are largely similar in both types of mill.

2.3.1 Rice mills

The process from rough rice (paddy) through to ready-to-use white rice passes from cleaning with air, screening and weighing, dehulling and the polishing process (removal of the aleurone layer) through to sizing. Some countries have their own production from low to medium capacity rice mill facilities (China, Taiwan, Malaysia, Thailand, India and some South American countries).

The environmental pollution from rice mills in these countries is considerable if there are no complete aspiration systems or such systems are not designed to appropriate technical standards. Often, cyclones alone are used for dust separation although they only achieve a separation level of 90 - 95%, with dust emissions standing at 70 to 150 mg/m3 air. Dust filters must be used.

The major disposal problem for rice mills is presented by the rice husks from the production process (20%). One possible means of economically recycling rice husks is that of pyrolysis to produce energy in steam power plants or lean gas for gas-engine plants (see environmental brief Plant Production).

Hot industrial water (approx. 65°C) and saturated steam are used to make parboiled rice (rice precooked in the husk).

Apart from the rice husks, all other by-products are either used locally as animal feed or exported (rice polish/emery flour).

A residue of about 18% ash is produced by rice hull pyrolysis. Ash can be disposed off locally as a soil structure improver and more recently rice hull ash has been used in steel works as an insulant.

Where parboiled rice is produced, organic substances are found in the wastewater, but in such small quantities that their recovery is not economical. Approx. 1 cubic metre of drinking quality water is required per tonne of rough rice (paddy), approximately 30% of which is absorbed by the grain.

Otherwise, the environmental impacts are as described in paragraphs 2.1.1 and 2.2.

The environmental protection measures to be observed for rice mills are listed here in order of priority:

- Dust emission values as applicable in mills handling cereal crops must also be observed in rice mills, i.e. modern aspiration systems with separators and filter installations must be used.
- Noise emissions are a nuisance to the population living in the surrounding area and so the details per sections 2.1.1 and 2.2 apply for this industry.
- The use of biodegradation tanks is recommended for wastewater disposal from parboiling facilities because of the higher starch concentrations.
- Measures must be taken to ensure proper hull disposal. In addition to pyrolysis and soil structure improvement, the hulls can be used in the brick industry, distilleries and possibly for furfurol production. Other uses are technically feasible and should be considered in the light of the particular site.

2.3.2 Hulling and processing of sorghum and millet

The industrial processing of sorghum and millet produces flours with good keeping properties and enables quality to be controlled in the light of the end products to be made. Better quality flours and higher yields are therefore achieved.

The upturn in the fortunes of this new branch of milling has been further enhanced by the possibility of blending this flour with wheat flour (composite flour). This has enabled a number of countries to use local raw materials by producing flours of this kind (blends of up to 20%).

The pollutants produced and safety measures to be taken are based on the data in paragraph 2.2.1.

2.3.3 Pulse hulling

The produce processed in hulling mills includes a range of pulses which are grown in temperate climates as well as the tropics. Pulses such as chickpeas, lentils and local bean varieties are brought onto the market in their hulled/split form or as flour.

The pollutants produced and safety measures to be taken are similar to the substances and measures described in paragraph 2.1.1.

2.4 Location planning

When planning the location of a food industry facility, it must be assumed that medium-sized and large operations will be accommodated. In such mass-production plants where food is processed, manufactured, transported, loaded and unloaded or stored, the following environmental factors must be taken into account, for which detailed information can be found in the relevant environmental briefs:

- An organised transport system is necessary as facilities of this kind turn over substantial quantities of raw materials and finished products (environmental brief and Transport and Traffic Planning).
- When planning larger facilities, a sea/land/sea transshipment facility should also be provided (environmental briefs Inland Ports and Ports and Harbours, Harbour Works and Operations).
- As facilities of this kind run day and night, they must be sited at appropriate distances from residential areas. Dust, and above all noise nuisance, must be prevented (environmental brief Planning of Locations for Trade and Industry).
- There should be a reliable energy supply on site to ensure safe operation of larger plants (environmental brief Overall Energy Planning).
- Furthermore, for safety reasons, they must be sited further from other industrial plants so that in the event of incidents (fire, dust explosion) extensive damage can be avoided.
- A water supply and organised disposal facilities are absolutely essential (environmental brief Water Framework Planning, Wastewater Disposal).

The fundamental factors in site selection (e.g. avoidance of agricultural areas or rare/valuable areas of countryside) are likewise to be found in the environmental brief on Planning of Locations for Trade and Industry.

2.5 Energy from husk waste

The energy requirement of milling plants ranges from 30 to 70 kWh per tonne of end product, and that of rice mills 30 kWh. One economic and environmental objective should be the use of the husks from rice production (approx. 20%) as a source of energy.

Waste gas emissions from the chimneys of steam power plants are becoming an environmental problem due to their ash particle content. When incinerated, a residual quantity of about 18% ash remains.

Where gas is produced from husks, industrial water is used for gas scrubbing to separate tar and dust, and also as cooling water for the gas reactor. This wastewater contains up to 1.6 mg/l phenol. The ash produced by husk pyrolysis must also be disposed of.

All residues from husk burning in the ash disposal section of steam power plants should be collected in its dry form; after cooling and intermediate storage, the ash can be reused by agriculture and industry. Fly ash in the chimney must be separated by scrubbing with dust separators before it enters the waste gas chimney.

Wastewater from gas generators may only be released once it has been neutralised and freed from solids. Venturi scrubbers and biological plant tanks must be used for tar separation.

Even at the planning stage of these power plants, ash disposal, flue gas emission and wastewater disposal must be considered in the light of parallel municipal development.

2.6 Further processing of cleaning waste and mill afterproducts

Normally waste from mills handling cereal crops is immediately milled in hammer mills and then, together with mill afterproducts, supplied to the animal feed industry. Other mill afterproducts are bran and low-grade flour, and from the hulling mill, hull bran.

This industry, often regarded as a secondary operation in mills, produces fodder concentrate for livestock farming, which contains protein, carbohydrate, fats, mineral substances and vitamins as its main blending components.

2.7 Dust disposal

Dust requiring disposal is produced only in the goods inward sections of agricultural trade establishments and cooperatives. This dust actually consists of sandy impurities which are separated when the commodities enter the preliminary cleaning plant, and can, for example, be returned to the supplier.

3. Notes on the analysis and evaluation of environmental impacts

Large quantities of service air are used for transport, separating processes, heat discharge and aspiration in flour and hulling mills where the process technologies comprise milling and sifting techniques and abrasive and centrifugal hulling. This dust-laden air must be treated, making dust removal from air a priority concern.

Furthermore, the noise produced in such installations must of course also be given due consideration.

When planning mill projects, the various national limits must be taken into account at the design stage; if there are no adequate legal provisions, international standards must be applied. The provisions and limits applicable in Germany are quoted below by way of example.

The following legal standards and technical regulations are valid in the Federal Republic of Germany for the area under consideration:

· Bundes-Immissionsschutzgesetz, Neuauflage (New Edition) 1990

TA-Luft, 1986
TA-L, 1986

· VDI-Handbuch Reinhaltung der Luft, Band 6;

VDI 2264, VDI 2263
VDI 3673

· Arbeitsbler der Abwassertechnischen Vereinigung (ATV), November 1980 Issue

· Biologische Bundesanstalt fd- und Forstwirtschaft

Pflanzenschutzmittel-Verzeichnis 1990.

Almost all afterproducts from flour and hulling mills can be recycled in the animal feed industry, are potential sources of energy or can be used as raw products or auxiliary materials in subsequent processing industries (oil mills and breweries, steel industry and foundries).

Emission values for local environmental protection in Germany are those specified in the TA-L (Technical Instructions on Noise Abatement). The guideline of the German Association of Engineers no. 2058 requires noise protection at the workplace, with the issue of personal hearing protection from 85 dB(A) upwards, and the wearing of this protective gear from 90 dB(A). These workplaces should be labelled and compliance with safety measures monitored.

Noise level and air quality measurements in the flour milling industry provide information about environmental impact and the safety measures required to be taken.

Table 2 - Noise levels in mills handling cereal crops

Machine/part of building

Noise level dBA

Frequencies Hz

Separator floor Sifter floor Roller floor Hulling machines Compressors High-pressure ventilators

105 100 105 108 95 100

1000 to 2000 800 to 1200 1500 to 1800 1800 2000 2500

This data shows that not only external noise emissions, but also workplace conditions inside the plant need to be dealt with by effective safety measures22).

22) such as machine enclosures and the wearing of hearing protection.

The Compendium of Environmental Standards provides information on assessment with regard to individual substances.

Where combustible substances are used for drying, only those with a maximum sulphur content of 1.0% are permissible.

4. Interaction with other sectors

Mills handling cereal crops perform numerous additional activities upstream and downstream, for example plant production, transport, and the handling and use of products obtained, e.g. as food. There are therefore a number of connections with other sectors; these are indicated in the text by reference to the relevant environmental briefs.

5. Summary assessment of environmental relevance

Afterproducts resulting from the process or raw materials used, which are in almost all cases used as fodder concentrate components, are produced in flour and hulling mills and in the associated drying and seed cleaning plants which process cereal and tropical grains into food for human consumption. In contrast, rice mills give rise to environmental pollution from the recycling of the husks (steam production).

Dust, which is an ever-present combustible, is a health hazard, potential source of ignition and a danger in the storage and milling industry. Precautions are taken in the form of constant maintenance and monitoring of extractor plants, dust accumulation, with temperature and humidity adjustment as associated preventive measures; personnel must be suitably be trained for this.

The emission guide values applicable for local environmental protection with regard to noise, insofar as they concern the area of production, are binding on the industry and must be observed by measures such as providing safe distances or soundproofing. Inside stores and mill buildings, the noise level is a serious problem for the employees. In the light of all we know about the long-term effects on hearing, due account must be taken of noise protection requirements at the workplace. Personal hearing protection must be issued and its use monitored.

The use of insecticides and pesticides for pest control purposes and seed disinfestation also presents problems since the substances used are highly toxic and health problems can be caused through their uncontrolled use and circulation. Only specially trained personnel using the correct equipment should be employed in these operations.

A certain amount of experience has been acquired in the field of the degradation of organic substances in process water with the help of fermenters, but a degradation tank is recommended where the wastewater is heavily polluted.

Modern mills do not give rise to substantial emissions and residues which pollute wastewater and dumps. Industrial water is only used for conditioning purposes in mills handling cereal crops and is absorbed by the grain. Mill installations with washing plants have to meet minimum requirements for the disposal of organically loaded wastewater. The same applies to industrial wastewater from bulgur or parboiled rice production.

6. References

Abwassertechnische Vereinigung (ATV), Arbeitsblatt A 115, 1980; Hinweise f Einleiten von Abwasser in eine ntliche Abwasseranlage.

Ammermann, K: Ausr von textilen Filtermedien zur Staubabscheidung.

Bartknecht, W: Staubexplosionen (1987), Springer-Verlag.

Berufsgenossenschaft Nahrungsmittel und Gaststen: Staubexplosionen, Mack & Metz GmbH, 68 Mannheim.

Biologische Bundesanstalt fd- und Forstwirtschaft (German Federal Biological Research Centre for Agriculture and Forestry): Pflanzenschutzmittelverzeichnis 1990, Teil 1, 36. Auflage 1990; 6.1 Saatgutbehandlungsmittel, Teil 5, 37. Auflage 1989/90; Vorratsschutz.

DSE (German Foundation for International Development): Mchkeiten, Grenzen und Alternativen des Pflanzenschutzmitteleinsatzes in Entwicklungslern (1987).

DSE (German Foundation for International Development); Zeitschrift: "entwicklung und llicher raum" (1988).

Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz (Technische Anleitung zur Reinhaltung der Luft - TA-Luft), 1986.

FAO: Rice parboiling, Bulletin 56, 1984.

FAO: Rice-husk conversion to energy.

Gerecke, K-H: Vademecum, Teil I - IV (1986), Technische Werte der Getreideverarbeitung und Futtermitteltechnik, Verlag Moritz Schr, Detmold.

GTZ: Aus Abfallbergen Strom f Energieversorgung.

Heiss, Rudolf: Lebensmitteltechnologie (1990), Springer-Verlag.

Ler, F: Staubabscheiden (1988), Georg Thieme Verlag, Stuttgart.

Luh, B S: Rice production and utilization (1980), AVI-Publishing Company, Inc., USA.

Mer, W: Verminderung des Energiebedarfs und Reduzierung der Staubemission bei Trocknungsanlagen.

Pomeranz, Y: Modern Cereal Science and Technology (1987), VGH-Verlagsgesellschaft, Weinheim.

Rohner, A W: Maschinenkunde fler (1986), Versandbuchhandlung DIE MLE, Detmold.

Schr, Flechsig: Das Getreide. 5. Auflage (1986), Verlag Moritz Schr, Detmold.

Technische Anleitung zum Schutz gegen L - TA-L, 1986.

VDI-Handbuch Reinhaltung der Luft, Band 6

VDI-3676, Massenkraftabscheider

VDI-3677, Filternde Abscheider

VDI-3679, Narbeitende Abscheider

VDI-2263, Staubbre, Staubexplosionen

VDI-3673, Druckentlastung von Staubexplosionen

VDI-2057, Einwirkungen von mechanischen Schwingungen auf den Menschen

VDI-2711, Schallschutz durch Kapselung.

1. Scope

This environmental brief discusses the extraction and processing of oils and fats from vegetable sources.

Vegetable oils and fats are used principally for human consumption, but are also used in animal feed, for medicinal purposes and for certain technical applications. They are extracted from a range of different fruits, seeds and nuts. Unlike industrial oils and fats, which are mostly produced from petroleum, they are generally non-toxic and biodegradable, without requiring any further treatment. However, they pollute the environment as they degrade due to their oxygen demand and their capacity to break down into water emulsions. An overview of the main types used is shown in Table 123).

23) Table 1 shows only the most common types. In many countries, a range of other varieties is used in part on a small industrial scale, e.g. rice bran, cashew nut, safflower, mahua, neem, mustard, tobacco, rubber plant, khakhan, dhupa, kokum, thumba seed and others besides.

Table 1 - Use of various fruits, seeds and nuts




Fruit and fruit flesh

For human consumption or medicinal purposes and animal feed

Cotton seed Sunflower seed Soya beans Palm kernels Cocoa beans Sesame seed Corn (germ) Rapeseed Linseed

Coconut Hazelnut Walnut Peanut

Palm fruit Olives

For technical applications and fuel

Castor oil plant Linseed Perilla seed Oiticica seed



*) The subdivision into use for human consumption and use for medicinal and technical applications is based on the principle application and may change. For example, rapeseed, palm kernels, soya beans, sunflower seeds and peanuts are potential raw materials for fuel production (Elsbett motor).

Production processes for vegetable oils and fats differ according to the required yield and raw material type. They can be categorised as follows:

- fruit processing
- processing of seeds and nuts by mechanical extraction (pressing)
- processing of seeds and nuts by solvent extraction.

Processing, in which the raw materials are separated into oils and oil-bearing solid residues, comprises the following operations after harvesting and any storage:

1. Preparation by raw material husking and cleaning, crushing and conditioning24).

24) Conditioning means treating the raw material so that it has certain chemical or physical and chemical conditions in order to obtain the highest possible oil yield from the subsequent pressing operation.

2. a) Boiling of the fruit or
b) Pressing or pressing and/or
c) Solvent extraction of oil-seeds/nuts.

3. a) Skimming of the liquid oil phase if boiling is carried out
b) Filtration of the pressed fat if pressing is applied
c) Separation of the crude oil while at the same time evaporating and recovering the solvent where solvent extraction is carried out.

4. Conditioning (drying) and reprocessing of residues.

5. Crude oil improvement by refining

a) Degumming
b) Neutralisation
c) Bleaching
d) Deodorisation.

6. Further processing of the refined crude oil.

2. Environmental impacts and protective measures

The intensification of land use in connection with projects for oil and fat production can have negative environmental implications (single-crop agriculture, erosion, water and soil contamination, loss of soil fertility, destruction of wildlife habitats). Farming methods and harvesting practices must be controlled and optimised from the outset.

2.1 Hazard potential of the different processing stages

The forms of environmental pollution shown in Table 2 below can arise during intermediate storage and the different stages of processing.

Table 2 - Hazard potential during storage and processing

Type of pollution


Cleaning Crushing Conditioning

Pressing Boiling


Refining Improvement










Pollutants (including smell)













Flue gas


Waste/special waste





*) From the burning of palm fruit stems, which have a residual oil content of 0.38%, in charcoal kilns.

2.2 Processing of fruits (palm fruit, olives)

Fruits are processed in the producer countries in the tropics (palm fruit) or around the Mediterranean (olives) by relatively small rural concerns and by medium-sized industrial companies. Figure 1 gives an overview of the various production processes, and in the following we examine in detail palm fruit processing.

Fig. 1 - Oil production from fruits

With palm fruit, some 2 to 3 tonnes of wastewater are produced per tonne of crude oil. Due to its organic residues, the wastewater has a particularly high biological and chemical oxygen demand for cleaning (water pollution). Moreover, dissolved solids (sludge particles), oil and fat residues, organic nitrogen and ash residues are the principle constituents of the wastewater.

The first operation in the treatment and reprocessing of wastewater is that of separating settleable solids. The residual oil content is collected in an oil trap. There are also combined sludge and oil traps which are oil traps with an integrated sludge chamber and are 92% effective. A 100% reduction in wastewater and pollutant discharge into surface water can be achieved by any of the following measures:

· discharge by spraying
· discharge by other irrigation systems
· drainage into settling tanks
· drainage into municipal and urban sewage treatment systems.

No soil conservation problems due to wastewater penetration have been reported to date.

Additional storage facilities and areas should be kept in reserve in case of leaks of solvents, lyes and acids in the event of accidents, and equipment to deal with such accidents should be to hand at all times.

Figure 2 shows a percentage analysis, based on 100% palm fruit bunches, which can be used to estimate the potential waste and wastewater volume.

Fig. 2 - Palm fruit processing with percentage analysis

Minimum requirements for wastewater drainage into watercourses in Germany are laid down by the 4. Abwasser-Verwaltungsverordnung (4.AbwVwV) [4th Wastewater Administrative Regulation] of February 1987, some details of which are shown in extract form in Table 3 below as a guide.

Table 3 - Minimum requirements (from 4.AbwVwV)

Quantity of wastewater in m3/t initial product

Settleable solids ml/l

Chemical oxygen demand (COD) mg/l

Extractable substances mg/l

Random sample

Mixed sample*)

Mixed sample*)

2 h

24 h

2 h

24 h

Seed dressing







Edible fat and oil refining

10 10-25

0.3 0.3

250 200

230 170

50 30

40 20

*) Within 2 to 24 hours

An alternative, more environmentally friendly method than draining wastewater into surface water consists of recycling the wastewater as process and boiler feed water (circuit system). The World Bank "Environmental Guidelines" (see item 6 in References) gives a technical description of biological wastewater treatment methods for palm oil extraction plants as practised in Malaysia.

Considerable quantities (per tonne of raw material, approx. 0.7 to 0.8 tonnes) of waste of vegetable origin (cellulose, husks, stems, pressing residues) arise during production, and the disposal of them must be taken into account when such facilities are planned. Due to their content of oil-bearing, organic components, the stripped bunches pose a major odour problem, as do pressing or extraction residues. Transport and dumping should be organised on this basis (e.g. dumping far from populated areas). The remaining solid residues are often incinerated to produce process steam, although this is not an ideal form of recycling as the waste contains silicates which vaporise when burnt and form a glassy coating in the furnace. It should be ensured that the incineration process is controlled and waste air is not used to separate the husks from the kernels (contamination with silicates) as is frequently observed. Heat exchangers with integrated self-cleaning systems are one possible solution. The incorporation of organic waste (mulch) in farmed arable soils raises a number of problems as the soil cover could, under certain circumstances, be destroyed (erosion risk) if waste were ploughed into it. On the other hand, prior mechanical comminution of the waste - which would facilitate its application to arable soils - could nullify its cost effectiveness, although under certain circumstances it would make a practical contribution to soil structure improvement.

2.3 Processing of oil-seeds and nuts

Three different processes may be used to extract the oil from oil-seeds and nuts:

- pressing
- solvent extraction
- a combination of pressing and solvent extraction.

Processing produces waste, dust and odorous substances as well as wastewater in a quantity of some 10 m3/tonne seed. Cylinder mills, fans and pneumatic conveyors are also sources of noise.

Figure 3 provides an overview of the processes used.

The environmental implications arising and the environmental protection measures which can be taken are described below in the sequence of the individual processing stages.

Fig. 3 - Oil production from oil-seeds and nuts

2.3.1 Storage

There are three methods of storage:

- bagged under cover
- loose in a warehouse
- loose in a silo.

Dust is produced during the filling operation in the latter two cases, in variable quantities depending on the equipment used. The dust is of organic origin and relatively harmless (direct contact is unpleasant and can cause skin irritation, visual and respiratory difficulties). If only because of dust explosion risk, aspiration (extraction) is essential for the mechanical processes described below (cleaning, crushing, conditioning). Thus instead of quantities of dust being released during the cleaning, screening or crushing operations, the dust-laden air is extracted, collected and cleared of solids via a central dust-removal installation, normally cyclones (maximum separation efficiency of 95%) or, better still, via filters (separation efficiency of up to 99%).

If mould should be found and if the presence of aflatoxins is suspected (in peanuts), there is no risk of contamination of the soil or groundwater under the stores, as the metabolism of the particular mould fungi limits the presence of aflatoxins to the food product only (peanut kernels). Preventive measures (air humidity control and monitoring) and the regular checking and sorting of stocks are essential here. Any possibility of the fungal spore dissemination must be eliminated (prevention of strong air currents, stores to be protected from the wind), otherwise peanuts not yet affected can be infested, causing health risks to employees as the spores can enter the lungs and, once established there, can multiply.

2.3.2 Cleaning and crushing

The mechanical cleaning and crushing of oil-seeds and nuts generate noise and dust, which can be controlled by aspiration and dust-extractor installations (collecting filters, electrostatic precipitators/cyclones) - thereby also preventing dust explosions.

2.3.3 Raw material conditioning

Raw materials are generally conditioned by the addition of steam (heating), an operation which enables the degree of wetting of the product to be controlled. The so-called vapours, the odorous substances, are released as condensate. Gaseous emissions and emissions of odorous substances can be limited by cleaning the

outside of machines and pipes with alkalis (caustic soda, caustic potash). The sulphur content can be determined by the analysis of the local raw material to be processed, and on the basis of this appropriate emission monitoring equipment can be developed.

2.3.4 Pressing process

No environmentally relevant substances other than the vapours are produced in the preliminary and final pressing of oil-seeds. However, during the washing (usually with steam jets) of the fat-sprayed machines, oily water is drained into the wastewater system. Here too oil traps are required. The heat from the vapours can be recovered in heat exchangers as an energy-saving measure and to reduce odours.

2.3.5 Solvent extraction

In the fluid extraction process, the oil in the unpressed or prepressed products is chemically dissolved with solvents and discharged in the form of miscella (oil-solvent mixture) (see figure 4).

The solvent most commonly used is hexane (C6H14)25) which is to be regarded as both a nerve and an environmental poison. Hexane-contaminated production residues must therefore be treated or disposed of. The following can be contaminated with hexane: the air, extracted product, miscella (residual oil-solvent mixture) and water.

25) Hexane is a hydrocarbon of the paraffin group. It constitutes a fire hazard and must be regarded as a nerve poison. At high concentrations, hexane is narcotic and states of intoxication may be observed, although these are overcome quickly and without any consequences for health where oxygen or fresh air is provided. In the case of prolonged exposure, paralysis together with cardiac and respiratory problems arise. Severe poisoning can result in death, in some cases weeks later. Constant exposure causes death by suffocation. Some cases of skin irritations through to necroses (tissue destruction) have been observed as a result of hexane and employees must therefore be given training in the handling of hexane. Surplus quantities, which cannot be released into the environment under the terms of discharge regulations (e.g. 4. AbwVwV in Germany) must be disposed of as special waste. In storage, the general regulations applicable to the handling of chemical products should be observed. Hexane can be stored in drums under stands fitted with extractor systems and collector sumps. Another solvent which is sometimes used is benzol, but it is not recommended in view of its high level of toxicity and other problems. Air polluted with hexane

· is formed due to leaks in the plant and the conveying pipes.

Hazards: Air-hexane mixture is explosive once the explosion threshold of 1 to 7% is reached.

Remedy: The concentration is measured with probes at suitable points (conductivity meters) and an alarm triggered if the threshold is exceeded. Particular care must be exercised when entering tanks and in all cases fumes must first be removed.

· is formed during the extraction process in the extractor and during the subsequent steam treatment of the extracted product in the toaster.

The waste air can be treated by absorption plants, in which the air is fed through a mineral oil bath and the hexane transfers from the air into the mineral oil. The hexane pollution in the waste air released into the atmosphere should not exceed 150 mg hexane per m3 air at a mass flow of 3 kg/h. The explosion safety threshold is 42 g/m3 air. Extracted product polluted with hexane and residual hexane-oil mixture (miscella)

The solid raw material residues and the miscella are largely stripped of hexane by steam distillation, in which meal (animal feed) and a water-hexane mixture are produced, or where hexane and crude oil are separated out from the miscella. The hexane can be collected and reused (hexane recycling).

The hexane content of the meal must not exceed 0.03% for transport safety reasons. As hexane is heavier than air, there is a risk with lengthy transport times that the hexane could sink and concentrate, thereby exceeding the explosion safety threshold (42 g/m3). As hexane vaporises relatively quickly, no consequences have yet been observed with regard to the health of cattle fed on the meal. Hexane-water mixture

If hexane-contaminated wastewater is to be disposed of, 50 parts per million (ppm) hexane, for a total wastewater quantity of 3 - 5 m3/t feedstock, should not be exceeded.

Hexane-water mixtures are separated by the density difference and the (theoretical) insolubility of the two media in each other, in order to condition (produce) disposable wastewater. They are separated by the drawing off of the two fractions in a settling tank at 40°C. Water, as the heavier fraction, is drawn off at the bottom, while the lighter hexane, which floats, is pumped off from the top. Cooling to 40°C is essential so that the separation operation is carried out well below the boiling point of hexane (68°C). The residual hexane content in the water is reduced by evaporation in a boiler (90°C, to stay below the boiling point of water). Wastewater polluted with hexane

The total quantity of water supplied in the form of steam which is added is 12%, related to the quantity of raw material used in the steam treatments (see 2.3.3). 50% of this remains in the meal, the other half being converted into the liquid state by condensation. Thus some 0.06 m3 wastewater per tonne of feedstock is contaminated with hexane. It is not possible to give more precise details about potential risks to the environment arising in tropical areas due to non-compliance with this limit (long-term consequences of possible damage to the ecotope) as research in this area is woefully inadequate.

2.3.6 Refining

The oils produced by extraction must - for reasons of durability, taste, appearance and consistency - be cleared of impurities such as free fatty acids, particles of dirt and seed, lecithin, carbohydrates, fats, gummy or mucilaginous substances, pigments, waxes and oxidation products. The purpose of refining is to remove undesirable by-products whilst retaining desirable ones, e.g. vitamins, antioxidants (tocopherols) or certain technical properties. Refining comprises basically the degumming, neutralisation, bleaching and deodorisation of the crude oil, and it is in these processes that most of the wastewater and unpleasant odours are produced. The lyes and acids used in the process bring with them a potential risk of injury to personnel (safety measures and training necessary). Figure 4 illustrates the refining process schematically.

Either a chemical or physical method can be used for oil neutralisation (removal of free fatty acids). The chemical process involves the neutralisation of acid using caustic soda, whilst the physical process neutralises by steam distillation. Physical neutralisation is the norm for palm, coconut and palm nut oil, whereas cottonseed and sunflower oil are generally also neutralised chemically as steam distillation is inadequate in view of the high lecithin content.

Since the treatment of the wastewaters formed is easier, and the quantity of wastewater lower during the physical process, efforts are being made the world over to develop processes which separate off the lecithin in the said oils so that they can be neutralised physically.

Fig. 4 - Schematic representation of refining Physical refining

During the physical process, the preliminary stage involves degumming the oil, normally with phosphoric acid, which coagulates and precipitates proteins which are then removed in separators. The separated solid matter is added to the meal, from which animal feed is made. To prevent phosphate discharge into the refinery wastewater, phosphoric acid is now being replaced by citric acid, which does not degrade into pollutants because of its organic origin, among other things.

The degummed crude oil is then bleached with active clay (clay with a high silicate content)26), since the natural pigments of the crude oil are adsorbed into the active clay and absorbed into the active clay bed. One of two possible processes is used to recover the residual oil which the spent active clay contains. In smaller plants, a steam treatment is used to recover at least some of the oil, but wastewater is also produced. In large-scale plants, all the oil is removed from the active clay in special extraction installations. The oil recovered in this way is of an inferior quality. The process itself produces wastewater and waste air which contain solvent residues, and must be clarified or purified (separators, filter installations).

26) In some countries, charcoal is used for bleaching, but should be avoided in view of the shortage of resources.

Extracted active (bleaching) clay can be dumped without harming the environment, and provision must be made for dumps at the planning stage. Non-extracted active clay can also be dumped without any direct environmental hazard, although there is the problem of odour as the oils contained degrade enzymatically thereby producing, amongst other things, sensorily active fatty acids which give off a rancid odour. The proportion of active clay used is around 3 - 5 percent by mass in relation to the crude oil used.

During the subsequent steaming process, odorous substances (aromatics) and flavourings and approx. 20 - 100 kg of fatty acids per tonne of oil are stripped (at 180 to 270°C under a light vacuum of 4 to 10 mbars) by steam distillation. The steaming vapour is first fed through separator devices, such as hydrocyclones (centrifugal separators) to remove the oil droplets entrained with it and the fatty acids, and then condensed by direct contact with cooling water and recirculated. Using this method, only small quantities of wastewater are produced and they can be treated biologically with a maximum fat quantity of 20 - 25 mg/l wastewater. The oil-contaminated fatty acids can in turn be processed further in soap factories for soap production or in the chemical industry to manufacture other products. Chemical refining

In the chemical process, the crude oil is first degummed and then immediately neutralised in one process stage. First, phosphoric acid (or more recently citric acid) is added to degum the crude oil by precipitating the protein. Then, in contrast to the physical separation, the acidic crude oil - acidic due to the free fatty acids it contains (2 - 10%, depending on the oil-seed and storage conditions) and the citric or phosphoric acid added - is neutralised by the addition of lyes, usually soda lye. This yields a mixture of neutralised oil, mucilages and soapstock.

After separation, the crude oil obtained is bleached and steamed as in physical refining. The same by-products are also produced, although the active clay consumption is considerably lower. Moreover, the steaming operation yields only about one tenth of the oil droplets and fatty acids obtained in physical refining. Processing of soaps and mucilage

Disposal problems are associated with the processing of soapstock and mucilage. The soap is first boiled and separated with sulphuric acid (to break up the emulsion). This produces fatty acids which can be separated from the acid solution in settling tanks. The acid solution is then neutralised and cooled with slaked lime. Organic substances should be separated by mechanical or biological processing, and the remaining wastewater must comply with the following conditions for drainage (standard German values as a guide):

- maximum temperature 35°C
- max. sulphate content due to addition of sulphuric acid 600 mg/l.

The quantity of wastewater from chemical wet neutralisation and the subsequent soapstock fractionation is around 0.5 m3/t of initial product under modern production conditions. This is only equivalent to about 5% of the total wastewater from a refinery, but because of the high organic content and consequently the much higher Chemical Oxygen Demand (COD), this alone amounts to 50 - 60 % of the admissible total COD load of a refinery in Germany. The discharge of wastewater must therefore be inspected to ensure compliance with the relevant limit values. Comparison of physical and chemical refining based on environmental factors

Wastewater quantities from neutralisation, particularly where there is a preliminary condensation vapour stage, can be considerably reduced by the use of the physical distillation process. However, this process, compared with the chemical refining process, consumes a far higher quantity of active (bleaching) clay. For reasons of economy therefore, chemical refining is popular although - as described above - it is characterised by the generation of large quantities of heavily contaminated wastewater which requires checking at the point of discharge into sewers and/or natural bodies of water to ensure that limit values are observed. Physical refining is preferable to chemical refining as active clay has a lower environmental impact.

3. Notes on the analysis and evaluation of environmental impacts

3.1 Air

Limit values for air pollution are laid down in Germany by the guidelines of the Technische Anleitung zur Reinhaltung der Luft (TA-Luft - Technical Instructions on Air Quality Control), and comply with the Bundes-Immissionsschutzgesetz [BImSchG - Federal Immission Control Act]. Further reference material is to be found in the Richtlinien des Vereins Deutscher Ingenieure [Guidelines of the Association of German Engineers VDI] for maximum immission concentrations [MIK] which are concerned with the establishment of limit values for certain air contaminants.

Under the terms of TA-Luft, the dust emission for organic substances in industrial plants may not exceed 50 mg/m3 air at a mass flow of 0.5 kg/h. The waste air from extraction today may not contain more than 150 mg hexane/m3.

3.2 Noise

Where noise levels are over 70 dB(A), noise-reducing measures such as hearing protection (ear muffs etc.) or silencing devices on machines must be provided. For comparison: leaves rustling in the wind produce a noise level of 25 - 35 dB(A) and normal conversation ranges from 40 - 60 dB(A). Years of exposure to around 85 dB(A) or more during most of a person's time in work is deemed damaging to the hearing at the workplace. It is, in fact, just as harmful to be exposed constantly to a uniformly low noise level as to a correspondingly higher one for a short time.

In Germany, the Technische Anleitung zur Lbekfung [TA-L - Technical Instructions on Noise Abatement] establishes principles for noise protection and approximate emission values. The following approximate atmospheric immission values27) apply to:

27) Immissions are the effect of air-borne contaminants, vibrations, radiation and noise on humans, animals, plants and property (e.g. buildings).

- areas containing mainly commercial premises: daytime 65 dB(A), night 50 dB(A),
- areas containing mainly residential accommodation: daytime 55 dB(A), night 40 dB(A).

It should be borne in mind that noise immissions inside buildings can have more damaging consequences because of building materials and methods used, in which case the values should be assumed to be correspondingly lower.

3.3 Wastewater

In crude oil refining, a wastewater quantity of 10 to 25 m3/t initial product must be assumed (see Table 3, details from Germany's 4. AbwVwV). The following are the principal constituents of the wastewater:

- sodium sulphate or sodium chloride
- calcium phosphate
- fatty acids (in part as calcium soap)
- mono-, di- and triglycerides
- glycerin
- protein
- lecithin
- aldehyde
- ketones
- lactones
- sterines.

A refinery's wastewater output can be reduced by up to 90% if the vapour cooling water is managed in a circuit - a system however, which results in higher COD concentrations in the circuit water. The minimum requirements for the final discharge of refinery wastewater must take account of this circumstance. However, despite the higher COD concentration where the cooling water is managed in a circuit, there is an overall general reduction in pollutant load. Biological wastewater treatment cannot yet be described as the most modern state-of-the-art process in view of the land required, the higher energy consumption and the problem of sludge disposal.

In Germany, the 4. Allgemeine Verwaltungsvorschrift [4. AbwVwV - 4th General Administrative Regulation] establishing minimum requirements for the discharge of wastewater from oil-seed processing and fat and edible oil refining applies with regard to wastewater control.

Table 4 indicates the minimum requirements imposed on the wastewater. In works with biological wastewater treatment, a 5-day biological oxygen demand (BOD5) of 25 mg/l and a chemical oxygen demand (COD) of 100 mg/l is prescribed28).

28) BOD5 stands for the biological oxygen demand which is required by microorganisms in a five day period for the processing of organic substances in industrial water. In the case of COD, the quantity of oxygen produced by an oxidant to oxidize organic substances in wastewater is calculated.

Table 4 - Minimum requirements of the 4.AbwVwV


Quantity of contaminated water

Settleable solids


Extractable substances


m3/t (1)




Type of sample

random sample


24 h

2 h

24 h

Oil-seed processing







Crude oil refining for edible oil production







10 - 25






Analysis process

DEV H 2.2 (2)

Appendix to 2. AbwVwV of 10.01.80 (3)

DEV H 17/18-1

Analysis of measured values

Single value or mean value (4)

Single value or mean value

*) Within 2 or 24 hours

(1) Initial product

In crude oil refining for the production of edible oil and edible fat, the following initial products are used:

- crude oil, produced in the oil extraction process
- reject and reprocess batches passing through the refining process once again.

(2) German standard process for water testing.

(3) If the value specified for settleable solids are exceeded in a single sample, 0.3 ml/l can be used to obtain the arithmetical mean if the dry mass of the filterable substances (DEV H 2.1) does not exceed 30 mg/l.

(4) Analysis of the precipitated sample.

The values given in Table 5 should apply for the discharge of acid solutions from soap fractionation.

Table 5 - Limit values for the discharge of acid solutions from soap fractionation


0.3 m3/t oil

Maximum temperature


pH value

6.0 - 9.0

Settleable solids which can precipitate in 30 mins.

10 mg/l


250 mg/l


600 mg/l

Generally speaking, oil processing is linked to a laboratory in which checks are constantly carried out using a standardised measuring procedure. COD, BOD, special waste requiring disposal, dissolved solids and the oils and fats should be constantly tested for content. Regular temperature checks should also be carried out in situ.

In addition, the World Bank gives the following information relating to the wastewater in question here:

- In principle cooling water should not be discharged; if it cannot be recycled in the circuit, it should only be discharged if the temperature of the water into which it is released does not rise by more than 3°C,
- The pH of the wastewater and liquid waste should be kept constant between 6.0 and 9.0,
- The BOD value of the wastewater should be less than 100 mg/l,
- The COD value of the wastewater should be less than 1000 mg/l,
- The dissolved solid content of the water should be less than 500 mg/l,
- Additional preservation and storage facilities and areas should be kept available in case of accidents resulting in leaks of solvents, lyes and acids. Equipment should also be kept to hand to deal with any such accident situations.

3.4 Waste

Types of waste defined in § 2 of the German Abfallgesetz [Waste Avoidance and Waste Management Act] are determined for oil- and fat- producing facilities in the ordinance on the determination of waste and residues Verordnung zur Bestimmung von Abfen und Reststoffen. Waste types are further qualified by waste codes in accordance with the information bulletin entitled "Abfallarten der Landesarbeitsgemeinschaft Abfall" [LAGA - Waste types of the state working group on waste]. Waste groups 52 (acids, lyes, concentrates) and 55 (organic solvents, dyes, varnishes, adhesives, fillers and resins) are relevant.

3.5 Soil

Soil contamination problems in the production of vegetable oils and fats only occur in connection with improper disposal of waste and wastewater (see also sections 3.3 and 3.4).

3.6 Choice of site

The following is to be borne in mind when choosing a site:

- The plant or plant complex should not be sited near ecologically sensitive habitats (marshlands, protected areas, national parks etc.).
- Local resource protection agencies or authorities should be involved at an early stage in the selection of the site or alternatives.
- Because of the odour nuisance, the plant should not be sited in the immediate vicinity of residential areas. Generally speaking, plants should be sited on high ground above the local topography; the sites should not constitute areas through which air passes and the prevailing wind currents must not affect populated areas. Local climatic and meteorological studies can be used to obtain useful information.
- The plant or plant complex should be built close to surface water (preferably flowing water), and this water must have the maximum dissolving and absorption capacity for wastewater.
- At the site it should be possible to recycle wastewater - following minimal treatment - for agricultural and industrial purposes.
- The plant should only be built in a municipality if the production wastewater can be treated in the municipal sewage system.

Processing facilities for fruit are sited in the actual growing areas as the crop has to be processed immediately after harvesting. Economic processing capacities in industrial countries start at 15 to 20 t feedstock per day.

Oil-seeds and nuts are transported in some cases over long distances to the processing industries. Processing capacities for pressing plants start at around 200 t/day, and those of solvent extraction plants at around 100 t/day. In highly industrialised countries, however, capacities of 1000 to 2000 t/day are commonplace. Refineries can operate economically from 50 t/day but plants in industrialised countries have processing capacities of 100 to 300 t/day. The question to be answered when deciding on the capacities to be installed is whether it would be preferable (for reasons of environmental protection and employment) to have small, decentralised plants rather than one large plant. Wastewater and waste air treatment systems and likewise waste disposal can also be organised decentrally as can the operation of a test laboratory.

3.7 Transport

Decentralised processing can obviate the need - as sometimes happens in view of the amount of traffic to and from large plants - to rethink local transport routes and traffic plans, and can avoid the associated noise, air pollution and traffic jams, as well as the risks to pedestrians from heavy goods traffic transporting raw materials or products to or from the plant. A transport sector and traffic study should be produced for route selection and for the analysis of problems and possible remedies.

4. Interaction with other sectors

Oil-cake or meal are by-products of crude oil production and are frequently processed further in the same plant to make animal feed (see environmental brief Livestock Farming).

As soap and fatty acids are produced in the refining process, a soap factory can be built alongside the plant. This eliminates problems with the sale of fatty acids or the fractionation of the soapstock (acid solutions). Likewise, the production of edible oil or edible fat in the refinery can be linked to the production of baking or cooking fat, shortenings or margarine.

Filling installations are often linked to refineries as edible oil and edible fat are now sold almost exclusively in a packaged form. The linking of filling installations to refineries is advantageous as the oils and fats are packed immediately and so have no chance of becoming rancid, and plant wastewater produced during the filling process can be treated and disposed of with the wastewater from the refinery (see environmental brief Wastewater Disposal).

Steam is required to produce and refine vegetable oils in small and large plants, thus oil mills or refineries often operate their own steam production plant. National provisions for large furnace installations must be observed in this regard (in Germany: the TA-Luft).

5. Summary assessment of environmental relevance

5.1 Crude oil extraction

In the extraction of vegetable oils from fruit and seeds, the cleaning, crushing and conditioning operations generate dust which it must be possible to remove with centrifugal cyclones. Dust is also produced when meal and press cake are made and it must be possible to remove it in the same way.

As this dust is of vegetable origin, it can be biologically degraded without the need to take any technical environmental protection measures (small plants), or it can be used as fertiliser (castor-oil seed meal). Production plants should not, however, be sited close to populated areas. The same is true of the larger quantities produced by large-scale plants in which the dust, after extraction, must be collected and dumped in a well-organised manner.

When oil-bearing fruits are extracted and boiled, large quantities of waste-water are produced which can be degraded biologically, albeit at the expense of a high oxygen consumption. For this reason, mechanical pre-cleaning is necessary - an operation in which sediments are precipitated and removed from time to time.

All oil mill wastewater should be fed through oil separators as larger quantities of wastewater containing vegetable oil cause the formation of a thin film of oil on bodies of water which interferes with the oxygen supply. Wastewater with an excessively high oil content must also pass through a biological treatment plant in which organic substances can be degraded by constant aeration (oxygen supply).

Extraction processes produce wastewater which can contain solvents. Measures must therefore be taken to ensure that the maximum solvent discharge into the environment is not exceeded.

5.2 Crude oil refining

Large quantities of falling water are produced in the refining of crude vegetable oils and fats and these are passed through oil separators for disposal. The water is fed back into the refinery after passing through a recooler. Excess falling water can be discharged into the surrounding water once it has passed through a biological treatment plant in which organic substances are degraded.

When soapstock is separated into fatty acids, acid solutions are produced which can no longer be used in the circuit. Before their discharge into treatment plants or water, they must be specially treated (neutralised) as they are acidic and contain - in addition to fat and mucilaginous substances - sulphate ions, which must not exceed certain values as they lead to salination of the wastewater and can destroy concrete drainage pipes.

A 100% reduction in wastewater and pollutant discharges into surface water is considered to be feasible if one of the following measures is taken:

· discharge by spraying
· discharge by other irrigation systems
· drainage into settling tanks
· drainage into municipal and urban sewage treatment systems.

In oil and fat production, the environmental pollutants formed and released in waste air or wastewater depend largely on compliance with technical tests and countermeasures for environmental safety purposes. Constant supervision of normal plant operation is essential to ensure that limit values are observed in terms of pollutant removal. Personnel is to be appropriately instructed in the framework of continuous training and upgrading. Training and preparation campaigns aimed at women are recommended for environmental protection jobs.

In view of the potentially serious negative implications for the environment and health in large plants in particular, the appointment of safety, environmental protection and works officers should also be demanded and the women concerned should be involved in the selection process.

6. References

Abwassertechnische Vereinigung (ATV) (Ed.): Lehr- und Handbuch der Abwassertechnik, Bd. I - VI, Ernst Verlag, Berlin, various years.

Abwassertechnische Vereinigung (ATV) (Ed.): Arbeitsblatt A 115, Hinweise f Einleiten von Abwasser in eine ntliche Abwasseranlage, draft of 22.03.1990.

Adam, W.A.: Waschmittel und Gewerschutz, FSA 77, 1975.

40. Anhang zur Allgemeinen Rahmen-Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer, GMBI. (joint ministerial circular) 1989, Nr.25, page 517 ff.

Baily's Industrial Oil and Fat Products, Vol.2, 1982.

Brammer, H.: Industrielle Verarbeiter von Speisefetten im Lichte von Umweltfragen, FSA 75, 1973.

Brauch, V.: Einsatz von physikalisch-chemischen Reinigungsmitteln in der Fettindustrie, FSA 84, 1982.

Brunner K.H.: Kontinuierliche Alkaliraffination und on-line Verlustanzeige, FSA 88, 1986.

Conze, E.: Abwasserschle in der Speisefettraffination und ihre Entstehung, Mchkeiten zur umweltfreundlichen Beseitigung, FSA 84, 1982.

Deutsches Einheitsverfahren zur Wasseruntersuchung: Verlagsgesellschaft Deutscher Chemiker, Weinheim a.d. Bergstra, loose-leaf collection, last issue on 26.03.92.

Dieckelmann, A., Hirsch A. et al.: Abluftverbrennung und Abluftnutzung aus hemischer Produktion, FSA 85, 1983.

Jennewein, H.: er Wasserreinigung in m FSA 75, 1973.

Jongenelen C. H. and Veldhoen: Fermentation von Abwern in einem Senfermentator, FSA 82, 1982.

Kaufmann H.P. et al.: Technologie der Fette, Verlag Aschendorff, M, 1968.

Krause, A.: Abluftprobleme in der Fettindustrie und in verwandten Gebieten, FSA 80, 1978.

Krause, A.: Pflanzliche und tierische Fette und ihre Wirkung auf Mikroorganismen in biologischen Klnlagen, FSA 85, 1982.

Lehr- und Handbuch der Abwassertechnik, 3. Auflage (Ernst u. Sohn), Bd. 5, 1985.

Liebe, H.G., ME.W.: Neues Verfahren zur Reduzierung geruchsintensiver Emissionen, FSA 88, 1986.

Air Quality Guidelines for Europe, WHO regional publications European series: No.23/1987).

Mahatta, T.L.: Technology and Refining of Oils and Fats (Production and Processing of Oils and Fats). Delhi: Small Business Publ. without year of publication, 360 pages (SBP Chemical Engineering Series. 49).

Morger, M.: Abwasseraufbereitung in Betrieben der Speisen-, Fett- und Molkereiprodukteindustrie in werkseigenen Klnlagen, FSA 88, 1986.

Niemitz, W.: Abwasser und Abfall. Schwerpunkte der Umweltprobleme industrieller Produktionen, FSA 75, 1973.

Nr, H.G.: Umweltschutz zwischen Wunsch und Wirklichkeit, FSA 86, 1984.

Organisch verschmutzte Industrieabwer in Nahrungsmittel-, Genuittel und Getreindustrie, 1984.

Pardun, H.: 50 Jahre Technologie pflanzlicher e und Fette, FSA 85, 1983.

Schmidt-Holthausen, H.J.: Verfahren zur Abwasser-Aufbereitung in der Speisefett- und Fettverarbeitenden Industrie, FSA 81, 1979.

Segers, J.C.: Mchkeiten und Beschrungen bei Verringerung der Umweltbelastung infolge der Raffination von en und Fetten, FSA 87, 1985.

Segers, J.C.: Superdegamming. A new degamming process and its effect on the effluent problems of edible oil refining, FSA 84, 1982.

TA-Luft, Technische Anleitung zur Reinhaltung der Luft of 27.02.1986, GMBI. (joint ministerial circular) p.95, rep. p.202.

TA-L, Technische Anleitung zum Schutz gegen L of 16.07.1968, appendix to volume no.137 of 26.07.1968.

Umweltbundesamt - German Federal Environmental Agency (Ed.): Handbuch Abscheidung gasfger Luftverunreinigungen, Erich Schmidt Verlag, Berlin 1981.

VDI (Verein Deutscher Ingenieure): VDI-Handbuch Reinhaltung der Luft, Beuth Verlag, Berlin and Cologne, Feb. 1992.

VDI (Verein Deutscher Ingenieure): VDI-Richtlinien zur Gerchmessung, Schallschutz, Schwingungstechnik: 2560, 2564, 2567, 2570, 2571, 2711, 2714, 2720, 3727, 3749, 3731, 3742.

Verordnung ie Herkunftsbereiche von Abwasser of 03.07.1987, BGBl. (Federal Law Gazette) I, p.1529.

World Bank: Environmental Assessment Sourcebook, Volume II Sectoral Guidelines, Environment Department, Technical Paper Number 140, Washington D.C., 1991.

World Bank: Environmental Guidelines, Environmental Department, Washington D.C., August 1988.

Zockoll, C.: Sicherheitstechnische Fragen beim Silobetrieb, FSA 81, 1979.

1. Scope

Sugar is the only food extracted from two different plants - the sugar beet (beta vulgaris) and the sugar cane (saccharum officinarum) - which grow in different regions. Competition between these two international cash crops only arises in small border areas where both are considerably below their physiological optimum, usually latitude 25 to 38 degrees north. The main sugar beet growing areas are located in the temperate climate of Europe and North America in regions with average mid-summer temperatures of 16° to 25°C and an annual rainfall of at least 600 mm, but sugar beet is also grown in the sub-tropics in the winter months. Irrigation is essential where the rainfall is less than 500 mm. Beet thrives best on deep loamy soils with a neutral to weakly alkaline reaction, and in intensive farming requires adequate mineral compound fertilisation. Since beet can only be grown in the same field every fourth year to ensure a healthy crop (avoiding, for example, beet nematode, the main cause of the disease known as beet sickness), the catchment area of a sugar beet factory is very large. The vegetation period is generally five to six months, with yields in a temperate climate ranging from 40 to 60 t/ha, and in the sub-tropics averaging 30 to 40 t/ha. The sugar content ranges from 16% to 18%. Sugar cane grows in tropical lowland climates, and is farmed almost exclusively between latitude 30° south and 30° north, and particularly between the north and south 20°C isotherms. Besides intensive sunlight, a rainfall of at least 1,650 mm or irrigation is essential. Heavy, nutrient-rich soils with a high water capacity are preferred; pH values in the weakly acidic to neutral range are best. Nutrient requirements are high due to the huge mass production. Pest and disease attack have been reduced by resistance breeding and plant development, with biological pest control playing an increasingly important role. Sugar cane is suitable for monoculture and is indeed mainly grown as such. Plant cane is generally harvested after 14 to 18 months, and the new growth (ratoon) after 12 to 14 months. Yields are from 60 to 120 t/ha; the sugar content is on average 12.5%. Harvest quantity and sugar content decline as stocks age, with the result that the total useful life does not normally exceed 4 to 5 harvests.

Sugar factories are agro-industrial centres which contract out the cultivation of their raw material or, alternatively, grow it themselves, have their own energy and water supplies and large, varied workshop complexes. The plant installed is designed to handle a single natural raw material. Where used for direct processing of the harvest, the seasonal processing period coincides with the period of use of the sugar production plant. New plants process between 5,000 and 20,000 t daily (24 hr), although in order to handle 10,000 t/day, sugar production plants must have an appropriate infrastructure. The production plant should be situated wherever possible in the centre of the cane or beet growing area, it should be close to water and should be connected to the public railway and road networks. The by-products arising during sugar manufacture - molasses, sliced beet and cane bagasse - are either used or processed further in the plant, or alternatively form the raw materials for other industries.

· Harvesting, storage and cleaning of the raw material

Sugar beet is harvested almost exclusively mechanically while sugar cane in contrast is harvested largely manually (cutting of stalks). The raw material is then transported to the factory by rail or road. Exceptionally, sugar cane is transported by water. Sugar beet can be stored for one to three days, depending on the temperature and method of storage, whereas sugar cane cannot be stored and must be processed immediately after harvesting or in any case no more than 12 hours later; sugar losses of up to 2%/24 hr are possible. Sugar beet is always washed before processing, but sugar cane is usually only washed if it has been harvested by machine.

· Cutting, crushing and extract purification

Sugar beet is chopped in slicing machines, and sugar is extracted from the slices in the countercurrent with water at 60 - 70°C in an extraction plant; the water is then removed mechanically and before drying the extracted beet is usually mixed with up to 30% molasses, normally made into pellets and used as animal feed. Because of their residual sugar content (approx. 0.8%), the slices - after drying - can be used as silage (preserved by fermentation) and as an agricultural feedstuff.

Sugar cane is prepared by revolving knives, crushers and/or shredders and then the juice is extracted in four to seven rollers in line or is extracted like sugar beet in a diffuser. A fibrous residue (bagasse) with a low sucrose content is produced at a rate of 25 to 30 kg/100 kg cane. The fibre content is approx. 50%/bagasse.

· Extract purification

Beet and cane are processed in a very similar way after the raw juice has been extracted. The raw juice is purified mechanically and chemically. First fibre and cell particles are removed mechanically, then the juice is purified chemically by precipitation of some of the nonsucrose substances dissolved or dispersed in the juice, and the precipitate is then filtered off. In the beet sugar industry, repeated precipitation with calcium carbonate has proved successful, an operation in juice purification where lime and carbon dioxide are introduced into the juice at the same time. Synthetic flocculants, in particular polyelectrolytes, improve particle agglomeration and reduce sedimentation times in the decanter from the normal 40 - 60 minutes to 15 - 20 minutes. In the cane sugar industry, simple liming (defecation) is usually employed as the extract purification process, lime/sulphur dioxide treatment (sulpho-defecation) being less common and lime/carbon dioxide treatment rare. The decantate is then finely filtered for a second time and goes directly to the evaporation station. The sediment or sludge concentrate (approx. 25 to 30 kg/100 kg raw material) is usually separated in rotary vacuum filters into filtrate and filter sludge/cake (approx. 3 to 6 kg/100 kg raw material), the filtrate returned to the process and the filter sludge separated.

· Evaporation and crystallisation

The clear juice (from 12 to 15% dry matter/dry sugar content) is continuously concentrated by multiple stage evaporation until it has a dry content of 60 to 70%, each stage of this process being heated with the steam (steam-saturated air released when the clear juice is concentrated) from the previous stage. In the boiling process, more water is removed from the concentrated juice (syrup) in boilers operating at an approx. 80% vacuum. The juice is boiled at a lower temperature than normal because of the low pressure in the equipment, thus preventing any discoloration due to caramelisation. When a certain ratio of sugar to water (supersaturation) is reached, crystals form. By adding more syrup and evaporating more water, crystallisation continues under controlled conditions until the required crystal size and quantity are obtained. The boiling process is then complete and the resulting boiled mass, now called massecuite, is drained from the vacuum pans into crystallisers. As the massecuite is constantly cooled, the supersaturation changes, causing the sugar crystals to grow once again. The massecuite is then transferred from the crystallisers into centrifuges, in which the crystallisate is separated from the syrup, leaving behind the yellowy brown raw sugar. The centrifuged syrup is boiled to form a massecuite once again and the crystallisate obtained from it is centrifuged. The syrup produced from the centrifuging is called molasses. If, when the massecuite is centrifuged, the crystallisate is cleaned of the residual syrup still attached to it by a water and/or steam jet (affination), white sugar is extracted in just one process from beet or cane. In refining (recrystallisation), a plant-intensive technology, raw sugar and poor quality white sugar are dissolved, and then decoloured and filtered by the addition of activated carbon or bone char, or ion exchange resins. Refined sugar, which meets the most exacting requirements in the sugar processing industry, is extracted from the subsequent crystallisation process. The quantity of molasses produced ranges from 3 to 6% of the raw material fed in, depending on the technological quality of the raw material and the end product. The sugar content of the blackstrap molasses is around 50%.

· Storage

The sugar extracted is cooled and dried before storage or packaging. It can be stored loose, packed (1 kg) or bagged (50 or 100 kg). The essential factor for proper storage is a relative humidity of around 65% in the store. This is approximately the point of equilibrium between the absorption and the release of moisture from the sugar crystals.

2. Environmental impacts and protective measures

Typical environmental impacts caused by sugar manufacture are due to:

- wastewater from beet and cane washing, the boiler house (boiler blow-down water) and extract purification in the evaporation and boiling station (excess condensate and purification water), refining (regeneration water from the ion exchange resins), the manufacture of alcohol, yeast, paper or chipboard (where molasses and bagasse are further processed in the plant), site cleaning and rainfall;
- emissions into the air from the boiler plant (flue gases from processes in which solid, liquid and gaseous combustibles are burnt), airborne substances (soot and flue ash), raw material processing, extraction, juice purification and juice concentration (ammonia) and from biochemical reactions of organic wastewater components in lagoons (ammonia and hydrogen sulphide);
- solid waste from raw material treatment (earth, plant remains), the steam generator (ash) and extract purification (filter sludge).

2.1 Cultivation, harvesting, storage and cleaning of the raw material

Because of the demands placed on it, the soil is heavily polluted due, in particular, to many years of single-crop agriculture (sugar cane), the main pollutants being:

- the fertilizer and pesticide feed,
- adverse effects on the natural cycle due to soil compaction and salination, dehydration and microorganism decimation.

Precautions in agriculture:

- growing not to be allowed in marginal soils
- examination of soils for chemical and physical properties, water-retention capacity, drainage properties and workability (important where crops need to be irrigated),
- fertilisation to be in line with crop requirements in terms of time and quantity,
- checking of pesticides for suitability for targeted pest control and establishing of a precise dosing concentration and quantity,
- observation springs to be made for the constant monitoring of groundwater and any changes to it.

The environmental effects caused by the harvesting and transport of the raw material are basically air pollution from the burning of sugar cane fields (flue ash) and contaminated access routes. Clarification agents containing lead (lead acetate solution) should no longer be used for the polarimetric sugar analysis of beet and cane extracts; instead the environmentally friendly reagents aluminium chloride or sulphate alone should be used.

Odours are rarely a nuisance in beet storage, occurring more frequently with sugar cane especially where it is stored for more than one day. Sugar beet is normally supplied with 10 to 20% moist dirt attached. In dry seasons, this percentage can be under 5% but can be over 60% in times of frequent and prolonged rainfall. Accordingly, the quantity of suspended solids in a flotation and washing operation, where some 750% water on one beet can be assumed, can range from around 7 to 80 kg per m3 water. The water pollution, after one operation, stands at around 200 to 300 mg BOD5/l, although this value can rise to over 1,000 mg/l if larger quantities of sugar and other beet components should transfer into the flotation water. Washing and flotation water are today kept in a closed circuit, continuously purified in basins with mechanical sludge removal and cleared of plant fragments using narrow-mesh sieves. The recycling of the flotation and washing water reduces the wastewater quantity to around 30 to 50% in the case of beet. This reduction in quantity means that wastewater treatment is at last a feasible option. The earthy sludge concentrate produced is deposited, wherever possible, in dips, boggy soils and lowlands which can then be put to agricultural use. The water is kept at a pH of about 11 using waste lime from lime kilns so as to prevent any odour nuisance due to microbial activity in the flotation water.

The burning of sugar cane before harvesting is still common practice, its only advantage being that it facilitates manual harvesting, as all the dry parts of the plants are removed by burning and the harvest volume is thereby considerably reduced. Cutting speed and thus earnings per worker are higher as the piece work pay is not based on harvested weight but unit of length/row. The drawbacks are the adverse effect on cane quality due to damage to the cell tissue and thus increased risk of infections at points of damage, destruction of organic matter, damage to the soil structure due to increased drying, increased soil erosion particularly on hilly sites, and finally air pollution in the form of fumes and flue ash emissions. Sugar cane field burning would therefore seem to be contraindicated for biological and ecological reasons.

The level of contamination of the harvested crop depends directly on the harvesting technique and soil and weather conditions during harvesting. Hand-cut cane can contain between 7 and 20% foreign matter, while the percentage weight when mechanically harvested is 3 to 5%.

If the cane is washed, one can estimate 3 m3 to 10 m3 washing water/t (fresh water, excess condensate, hot well water and recycled washing water).

If cooled excess condensate and hot well water is not fed into the circuit, it can all be used for washing instead of fresh water.

In this way, both the factory's water consumption and the pollutant freight of its wastewater can be reduced. Depending on the washing system, the BOD5 value can be anything from 200 to 900 mg/l. Foreign matter could be removed by pneumatic dry separation to obviate the need for cane washing. The sludge concentrate is treated and the odour nuisance prevented in the same way as in the beet sugar industry.

2.2 Raw material cutting, crushing and extraction

Noise nuisance is produced by the high-speed slicing equipment for sugar beet and in the whole area of mill extraction (sugar cane). Individual ear muffs are required. Dust is generated with particular intensity in the area of sugar cane intake and transfer to the mill tandem. No direct hazard to personnel is caused where these operations are automated.

The intermediate products of the sugar industry are ideal nutrient media for a large number of microorganisms. The whole range of activities, ranging from the preparation of the raw material through to crystallisation, also provides a promising culture medium. The risk of microbial contamination is particularly high in extraction, where not even the most stringent technical hygiene measures and optimum process management can obviate the need to use disinfectants. Repeated high-pressure steam disinfection at the points in the mill tandem most at risk (links in the chain and connecting elements) is only about 60% as effective as biocides. A chemical treatment can also be used during mill operation, while steam treatment can be effectively applied when the mill is not working. Major disinfection operations can lead to heavy sugar losses and are therefore not economically viable. The substance most frequently used to disinfect extraction plants is still formalin (approx. 35% aqueous solution of formaldehyde). It is added in batches at a concentration of around 0.02 to 0.04% in relation to the quantity of raw material processed. The formaldehyde concentration in the juice decreases constantly throughout the subsequent process stages. In the clear juice, levels are less than 1 mg/kg while only traces can be found in the syrup and concentrations of around 0.10 mg/kg in white sugar. It is nonetheless clear that, however it is used, formaldehyde is removed from the sugar to the extent that the technically unavoidable residues are rendered harmless. Traces of formaldehyde are also found in the condensates which are produced from evaporation and which are returned to the factory's water circuit. Formalin is controversial in the light of the carcinogenic effect attributed to it, but is still the preferred disinfectant in extraction. Alternative substances, e.g. thiocarbamate, quaternary ammonia compounds, cresol derivatives, hydrogen peroxide and the like, have all been tested over recent years. Their effectiveness as disinfectants when used in extraction plants is comparable to that of formalin. Thiocarbamate, cresol and hydrogen peroxide - like formalin - are also removed by the extraction water during the process, thus only traces can be found in the extracted slices. Quaternary ammonia compounds, by contrast, are irreversibly adsorbed or precipitated along with other organic substances during extract purification.

2.3 Extract purification

The filter sludge produced in sugar factories has a dry content of 50 to 60%, up to three quarters of which is in the form of calcium carbonate, depending on the juice purification process, the rest consisting for the most part of organic substances. In beet sugar factories, it is usually pressed to a dry content of at least 70%. Because of its phosphate and nitrogen content, it is used mainly as fertilizer and instead of lime for soil neutralisation. In cane sugar factories, the sludge is either passed on to farmers or spread directly on to the factory's own fields. The high protein content in the dry cane filter sludge (14 to 18%) means that it can be used as supplementary fodder in cattle farming. The solid content is separated in almost all cases by continuous filtration through rotary filters and secondary filtration using precoated filters. The quantity of wash water produced is so low that it can be disposed of with the filtrate.

The auxiliary substance most frequently used in extract purification is lime (CaO). Depending on the purification process used, consumption ranges from around 0.75 kg CaO (defecation) to 20 kg per tonne of raw material (two-stage calcium carbonate precipitation). Lime and carbon dioxide is obtained from limestone in the coke-fired shaft furnaces of beet sugar factories. It is not economical for cane sugar factories to produce their own burnt lime because they need such small quantities of it. The CO2-rich gas produced in lime burning consists of around 35 to 40% CO2, the rest being N2. If the oxygen supply is inadequate, carbon monoxide (CO) may be produced. Since the combustion temperature is below 1,200°C, no nitrogen oxides (NOx) are formed. The washing water (8 to 10 kg/kg limestone) produced during gas purification is not organically loaded. The crushing of burnt lime is associated with the generation of large quantities of dust, necessitating the use of dust separators. Breathing apparatus must also be worn by personnel working in the immediate vicinity of the lime kiln, particularly personnel involved in cleaning work.

2.4 Evaporation, crystallisation and sugar drying

Some 4 - 6 m3 cooling water/t raw material - depending on whether single or central condensation is used - is required to condense the steam from the last vessel of the evaporation plant and the evaporation crystallisers. In the cooling water circuit, the mixed condensate (hot well water) produced from the condensers (steam condensation) at 40 to 50°C must be recooled to 20°C maximum in cooling towers, grading houses or evaporation lagoons (mist formation) so that it can be reused. The level of pollution of the condensate produced is determined by the technical conditions in the evaporation and boiling station and the condensation plant. Organic pollution and sugar losses in the mixed condensate can be kept very low where correctly designed juice separators are fitted, with values of around 30 to 150 mg/l BOD5 in raw sugar factories (cane processing) and 5 to 15 mg/l in the beet sugar industry of today. Incrustations are removed from evaporator pipes and other hot surfaces by cleaning with an approx. 5% soda solution followed by a 2 to 5% hydrochloric acid solution. The acids and lyes used for cleaning can be neutralised and fed into the water circuit.

Sugar dust from sugar driers or defective dust-extraction systems can give rise to severe air pollution. This is not only a health hazard but, at a grain size of < 0.03 mm, also highly explosive if the dust/air mixture concentration is within the explosion limit (approx. 20 to 300 g/m3). A low dust level is 2 g/kg sugar. Dust is separated in dry electro-filters or in wet dust-extractors (scrubbers). If no dust separators are installed (e.g. older white sugar factories), breathing masks must be provided. The concentration must be kept low by means of adequate ventilation and precautions must be taken to prevent ignition of the explosive atmosphere (smoking ban, no repair work which produces frictional heat or sparks, installation of explosion-proof electrical systems) in order to minimise the risk of explosion.

2.5 By-product manufacture

Dry slices: the water obtained from the mechanical drying of the extracted beet slices is recycled in the extraction process. The slices are mostly dried in drum type driers (700 to 900°C) to a dry content of 25 to 90%. The mixture of combustion gas from natural gas or oil plus flue gas from steam production is used as the drying gas. A waste gas quantity of 1.5 to 4.5 m3/kg extracted slices - depending on the drying system used - must be expected. The dust content of waste gases from the drier depends, inter alia, on the quantity of molasses added and process management (temperature, holding time). The dust concentration in the untreated gas ranges from 2 to 4 g/m3. Similar dust concentrations may also arise after the cooling drum, the pelleting station, the bagging plant and the pneumatic conveyors. The total carbon concentration ranges from 300 to 1,200 mg/m3, depending on process management. The SO2 concentration after the slice drying plant depends, inter alia, on the fuel used, the drying process and slice composition. SO2 concentrations of up to 1,000 mg/m3 in the waste gas have been encountered.

Sugar extraction from molasses: more sugar can be extracted from the molasses if additional expenditure is allowed for operating costs and equipment. The regeneration- and wash water then produced is heavily contaminated and must be handled separately if the chloride concentration in the total wastewater exceeds 2,000 mg/l.

Biotechnical processing of molasses: the biotechnical recycling of beet molasses almost always takes place in different plants; in contrast, it often forms part of a sugar factory and also gives rise to high wastewater loads. Yeast, ethanol, citric acid and much more can be produced from molasses by fermentation. The waste load remaining from baker's yeast manufacture is around 156 kg COD/t molasses or 187 kg/t baker's yeast. The distillation residue (vinasse) which remains is highly diluted (aqueous) (up to 96% water) and can be used as cattle feed (approx. 50 l/day and animal). As these difficultly biodegradable substances cannot be removed by economically feasible treatment processes, the process wastewater from yeast manufacture has to be thoroughly biologically treated, and then recycled for agricultural use where possible. However, even after biological treatment, the process wastewater must not be discharged directly into the drains. Since the climatic conditions of sugar-cane-growing countries favour eutrophication processes, stringent requirements must be laid down with regard to wastewater purification.

2.6 Energy supply

Some 300 to 400 kg steam and 35 to 40 kWh electrical energy is required to process 1 t beet to white sugar. Every factory must be equipped with steam and electrical energy generation plants (heat/power linkage). Oil, gas and coal are used as primary energy sources and waste gas purification is essential where emission limits are exceeded.

The steam and electrical energy requirement for sugar cane processing (to drive the roller mill with steam turbines) stands at around 550 kg steam/t cane (raw sugar production) or 615 kg steam/t cane (white sugar production) and 35 to 40 kWh electrical energy/t cane. The mean calorific value of bagasse (approx. 50% moisture) is around 8,400 kJ/kg (mean calorific value of oil around 42,000 kJ/kg). The bagasse produced is sufficient to cover the factory's energy requirements. Incomplete burning of bagasse (water content > 50%) increases the emission of flue ash and carbon particles.

To start up the factory (start of campaign), other energy sources have to be used. If a refinery is also operated, it may also be necessary to back up the bagasse with other fuels. Maintenance firing is also essential where the plant is shut down for a prolonged period. A complete conversion to other energy carriers is essential where bagasse is used as a raw material for paper or chipboard manufacture.

2.7 Water management

There is no stage in sugar production where water in some quantity is not required. The technical water requirement of the sugar extraction process in a beet factory is around 20 m3/t beet. The amount of process water introduced can be reduced to 0.5 m3/t by the introduction of water circuits. For practical reasons, highly contaminated (transport, purification, regeneration, hot well water) and slightly contaminated (turbine cooling, pump cooling, seal and gas scrubbing water, condensate excess) water circuits should be kept separate, as water with a low level of pollution (in Germany < 60 mg/l COD or 30 mg/l BOD5) can be drained into receiving streams. In a well-managed factory, the quantity of highly contaminated wastewater produced can be reduced to 0.2 m3/t beet; it should not exceed 0.5 m3/t, beyond which the cost of wastewater treatment would then become uneconomic. Pollution rises in the course of the campaign, reaching COD values of 6,500 mg/l or BOD5 values of 4,000 mg/l and more. In sugar cane processing, large quantities of cane washing water (up to 10 m3/t) and mixed condensate are produced during steam condensation and raw sugar refining, which must be managed in a circuit system (large land areas required for evaporation lagoons, high investment costs for cooling towers). Cane washing water (260 to 700 mg/l BOD5), filter residue (2,500 to 10,000 mg/l BOD5) and washing water from decolorising carbon and ion exchange resins in refineries (750 to 1,200 mg/l BOD5) are all heavily contaminated. The purification water also includes wastewater required for cleaning the production areas and plant during and after the campaign, and for cleaning sugar transport vehicles. There are also juice and water overflows at plant breakdowns (clear juice, for example, has a BOD5 of about 80,000 mg/l) so that values of up to 18,000 mg BOD5/l can occur. Negligence is the main cause of excessive wastewater contamination. If a plant is carefully managed, this wastewater does not exceed values of 5,000 mg BOD5/l. Low organic pollution and sugar losses in the mixed condensate (30 to 150 mg/l) can only be achieved by the installation of separators in the steam pipes.

The aim of establishing water management in a sugar factory must be to eject or treat as low a quantity of polluted water as possible. Water recycling heads the list of measures to be taken inside the factory. Water management must be such that, once closed circuits are established, unpolluted or only slightly polluted water requiring no further treatment is discharged into the drains.

The treatment processes for wastewater which can be carried out in sugar factories are largely determined by local factors. The management of the wastewater and circuit conditions inside the plant have a major effect on plant size and the level of degradation which can be achieved.

Wastewater treatment begins with the mechanical removal of suspended particles followed by aerobic treatment. The simplest and by far the most desirable treatment method for the processing of organically polluted, concentrated sugar factory wastewater is its collection in a series of lagoons using an overflow system. The wastewater then purifies itself. The time required for adequate degradation of the wastewater in the lagoons is determined by the following factors:

- height of water level in the lagoon
- lagoon area
- subsoil below the lagoon/adequate sealing against the subsoil
- weather conditions
- external flows of water.

The lower the water level and the warmer the weather during the degradation processes, the faster the water in the lagoon is treated. Lagoon depth should not exceed 1.20 m in temperate climates, while 1.50 m is acceptable for subtropical/tropical zones (sugar cane growing). If there is a high level of evaporation, the content of the wastewater is concentrated; if there are external flows of water and rainfall is high, the lagoon wastewater is diluted. The treatment of wastewater with a concentration of 5,000 mg BOD5/1, as is usual in the domestic sugar industry, requires a constant degradation efficiency of 99% or more to reach a BOD5 value of 30 mg/l. At a lagoon depth of 1 m and a degradation period of 6 to 8 months, values of 100 mg BOD5/l can be achieved, which is equivalent to partially biologically treated water. In sugar cane growing areas, complete biological purification - a BOD5 of less than 30 mg/l - can be achieved within five or six months with good lagoon management. This long-term process of degradation in lagoons could solve the wastewater problem for the sugar industry if sufficient lagoon area were available. The sugar cane processing industry, in fact, generally has sufficient land area available and so uses the lagoon process almost without exception.

Organic substances are degraded by both aerobic and anaerobic processes. In the anaerobic stages, fermentation and putrefaction occur, thus the possibility of odour nuisances, primarily due to the formation of hydrogen sulphide and butyric acid, cannot be ruled out. This drawback can be overcome, however, by selecting suitable locations and by adequate additional aeration. During the activated sludge process, oxygen is introduced into the water in the form of air via an aeration system.

Small-scale continuous systems operate with a substantially higher microorganism density and a higher oxygen supply, and achieve a degradation level of around 90%. Atmospheric pollution is clearly higher at 2 to 7 kg COD/(m3/day) and the energy required for the air supply stands at around 3.5 kWh/(m3/day).

Anaerobic wastewater purification plants consist of large tanks (around 3,000 to 7,000 m3) in which anaerobic bacteria degrade the organic pollutants to form biogas (approx. 75 to 85% methane). This is particularly effective where wastewater is heavily contaminated. The organic content is 80 - 85% decomposed, with the remaining degradation taking place aerobically in the aeration system. The benefits of this process are that the methane gas can be used directly as an energy source to heat the tanks and that the problems of odour can be overcome; an additional factor is that less space is required than in the case of lagoon systems.

Compared to the large quantities of sludge produced in the flotation and washing water circuit, and in some cases occurring in the form of lime sludge from juice purification, the quantities produced in wastewater conditioning are very low. Recycling is as for filter sludge (see 2.3). The form of "large-scale wastewater processing" most frequently used is overhead irrigation or, rarely, basin irrigation. The preconditions for this are level undrained areas, deep soils with no tendency to silting and a low water table (> 1.30 m). During the passage through the soil, the following processes take place:

- mechanical filtration on the surface
- absorption of the dissolved substances by bacteria in the soil
- biological oxidation of filtered and adsorbed material by bacteria in the soil in the intervals between the individual doses of wastewater.

Basin-irrigation is carried out mostly on small parcels of land surrounded by earth walls (so-called retaining filters). Mechanisation is severely restricted by parcel size and the earth walls. Only crops which grow vertically and which are not sensitive to overdamming are suitable, e.g. tree crops and meadow areas.

Sprinkler irrigation is the most expensive biological treatment process. All settleable solids must be removed to minimise malfunctions in the sprinkler irrigation installations. The load should be intermittent and the quantity rained onto each area must remain small (< 500 mm/vegetation period - individual doses not exceeding 80 mm). If the wastewater is first treated in lagoons to at least 180 mg BOD5/l, drained areas can also be irrigated if the water table is suitably low. In addition to wastewater treatment in the soil, the wastewater recycled for irrigation also acts as a fertilizer.

3. Notes on the analysis and evaluation of environmental impacts

3.1 Emission-limiting requirements

Two types of requirement are imposed on sugar factories: general and special. The provisions regarding general regulations to limit emissions contain:

- emission values, which current technology can keep to admissible levels,
- emission-limiting requirements conforming to the state of the art,
- other requirements to protect against harmful environmental impacts by air pollution and
- processes for determining the emissions.

The following general requirements are imposed:

- reduction in the quantity of waste gas by enclosing plant components,
- registration of waste gas flows,
- circulating air management and process optimisation through more efficient use of waste heat,
- waste gases must be released so that they are freely discharged without obstruction in the general airstream,
- chimneys should be at least 10 m above the ground and project 3 m above the roof ridge, but should be no more than twice the height of the building,
- in the field of wastewater treatment, including lagoons, anaerobic degradation shall be eliminated by technical or structural measures as far as possible.

The special requirements (e.g. in Germany in accordance with the TA-Luft [Technical Instructions on Air Quality Control]):

- the drum inlet temperature in sugar beet slice drying plants must not exceed 750°C or equivalent measures to reduce odours must be applied,
- dust emissions in the damp waste gas must not exceed 75 mg/m3(f),
- where solid or liquid fuels are used, the sulphur content by weight must not exceed 1 % in the case of solid fuels related to a net calorific value of 29.3 MJ/kg, or equivalent waste gas purification must be carried out.

A crucial factor in all emission considerations is the emission load resulting from the quantity of waste gas discharged from the chimney, multiplied by the pollutant concentration. This concerns primarily the load from sulphur, nitrogen oxide, carbon monoxide and dust.

The following emission limits apply to furnace installations with a furnace heat output of < 50 MW:




liquid fuels


dust CO Nox SO2

mg/m3 mg/m3 mg/m3 mg/m3

50 250 400 2000

80 175 300 1700

5 100 200 35

Source: TA-Luft [Technical Instructions on Air Quality Control]

The emission values relate to an oxygen content by volume in the waste gas of 3% for liquid and gaseous fuels. In the case of solid fuel, 7% applies where coal is used and 11% applies where wood is used.

Flue ash and soot are the main air pollutants where bagasse is used as fuel, but flue gases from bagasse do not contain any toxic substances. Where fuel oil is used in the cane sugar industry, a sulphur content of 0.5 to 1.0 % by weight in the fuel oil is permissible.

The main parameter of any biological treatment and in any watercourse is the biochemical oxygen demand (BOD). This is the quantity of oxygen in mg/l which is consumed by microorganisms at 20°C within a degradation time of five days. The chemical oxygen demand (COD), on the other hand, is the standard for the content of oxidisable substances found in water, i.e. the method covers not only biologically active substances but also inert organic compounds. It is essential to use the COD method (evidence provided using potassium permanganate or potassium bichromate) as a fast method of determining the level of water pollution.

In its guidelines for the cane sugar industry, the World Bank takes the view that three parameters are of fundamental importance when it comes to assessing sugar factory wastewater pollution with biodegradable substances and their impact on the environment:

· BOD5 for determining the oxygen-consuming organic material;

· TSS (total suspended solids mg/l) for establishing the total quantity of suspended matter (primarily inorganic substances from cane and beet washing water);

· pH as extreme pH changes are harmful to water fauna.

The minimum requirements regarding the pollution levels in wastewater to be released into bodies of water are based on the treatment processes normally applied in the various industries and must conform to the state of the art.

For sugar production and associated industries (including alcohol and yeast production from molasses) the following minimum requirements are specified in Germany (source: (1)):

A cm3/l random sample

COD mg/l mixed sample

BOD5 mg/l mixed sample

(TF) random sample

Seal and cond. Water







Other water







A = volume of suspended solids

TF = toxicity to fish, expressed as the minimum dilution factor of the wastewater at which all test fish survive under standardised conditions within 48 hours.

These values apply to random samples in the case of lagoons.

Due to local circumstances it may be necessary to limit other parameters for discharging into watercourses, e.g. temperature, pH, ammonia, chloride.

In the USA, the Environmental Protection Agency (EPA) has imposed limit values for cane sugar factories (raw sugar factories and refineries).

General limit values regarded as "best available technology economically achievable" (BATEA or BAT) are:



Raw sugar factory

(kg/t cane)

max.daily value




pH 6.0-6.9




White sugar factory

(only mixed condensate)

(kg/t raw syrup)

max.daily value




pH 6.0-6.9




Liquid sugar factory

(only mixed condensate)

(kg/t raw syrup)

max.daily value




pH 6.0 - 6.9




With regard to sugar factories, the noise immission guide values are (in Germany) 60 dB(A) in the daytime and 45 dB(A) at night. Cane sugar factories are generally located in the centre of the growing area, very rarely in the vicinity of sizeable residential areas. The design of factories is light and open (due to the climate); cane is received and conveyed to the mill in the open air (large quantities of dust generated).

Noise emissions can be restricted by structural and acoustic measures, with housings provided around sources of noise and soundproofing.

Where the noise from certain tasks or areas of the factory cannot be restricted or insulated, personnel shall be issued with appropriate individual protective gear.

These include, in particular, tipping and bagging plants, cane handling and roller extraction, washing plants for the raw material and the centrifuge station. In the workshop area, they include mainly work at rotary machines with a diameter > 500 mm, sheet metal processing machines and drilling and punching machines. The acoustic power level in these areas ranges from between 80 and 130 dB(A). At values of > 85 dB(A), individual protective gear (ear plugs, ear muffs) must be worn. With acoustic pressure levels of > 115 dB(A), the combined use of both items is recommended.

3.2 Technology for the reduction of emissions and emission monitoring

Measures to prevent damage due to atmospheric sulphur dioxide immissions in flue gases comprise the retention of SO2 in desulphurisation plants (e.g. absorption in lime milk) and the use of low-sulphur fuels. The installation of a scrubber before the chimney inlet has proved successful in reducing the emission load in waste gases. As well as its action on dust, this scrubbing operation achieves an SO2 separation of some 30%. If sludge from calcium carbonate precipitation is used as the washing liquid, pure gas dust concentrations of less than 75 mg/m3(f) are obtained. At the same time the SO2 emission is reduced by 60 to 70 %. "Calcium carbonate precipitation scrubbing" is therefore a particularly good dust and SO2 separation method as it does not pose any additional wastewater or residue problems.

Dust emissions occurring inside the sugar factory are reduced with scrubbers or fabric filters and the pure gas concentration is less than 20 mg/m3. Dust levels are kept low in the same way during further processing stages.

In the cane sugar industry, the generally high proportion of flue ash necessitates flue gas purification measures. Older furnace plants can be easily fitted with wet or dry separators (cyclones: approx. 96% effective, more investment- and maintenance-intensive than wet separators). The water requirement figures for wet separation are approx. 0.025 m3 water/25 m3 gas.

Emissions and the temperature in the waste gas from steam generation and slice drying are measured and monitored by integrated, continuously operating measuring instruments. In the cane sugar industry, portable, manually operated equipment (e.g. Orsat apparatus) is used mainly to determine, for example, oxygen, carbon dioxide and monoxide. If state-of-the-art waste gas purification systems are installed in new plants, and if dust emissions are below 75 mg/m3, daily measurements with a portable unit are adequate.

Any odour nuisance due to ammonia emissions is largely suppressed in advance by closed-circuit systems.

In principle lagoons should be fitted with additional aeration equipment, and aeration rollers have proved extremely successful here. They should not be located in the immediate vicinity of a factory or residential area (upwind).

A number of processes can be used to measure rate of discharge, e.g. measurement of flow rate with an impeller device and integration via the discharge cross section, or direct determination with a measuring weir.

The mixed samples taken for wastewater assessment are analysed for BOD5 according to DEV (source: (5)) and for sludge deposits, COD and toxicity to fish according to DIN. The EPA has specified the analysis methods for the cane sugar industry in "Methods of Chemical Analysis of Water and Wastes". In the case of lagoons, random samples are adequate in view of the low fluctuations over time of wastewater composition and the long retention times.

Control services and control mechanisms should be put in place to check that environmental provisions are observed, e.g. environmental protection consultants. Their task would also involve checking that environmental protection installations are in good working order and are regularly maintained, and they would also be responsible for personnel training and making personnel aware of environmental issues. Medical care should be provided inside the works and for the local population.

3.3 Limit values issued to protect health

Substances for which maximum workplace concentrations (MAK values) or technical approximate concentrations (TRK) apply in Germany: mg/m3 Application/source

Ammonia 35 - Raw material treatment, extraction, juice purification, juice concentration, lagoons;

Asbestos dust 0.025 - Heat insulation, filter aids (diatomaceous earth);

Lead 0.1 - Laboratory: lead acetate solution for the clarification of juice samples for polarisation analysis;

Calcium oxide 5 - Milk of lime manufacture: juice purification, juice neutralisation, wastewater treatment; lime burning;

Hydrogen chloride 7 - Evaporator station: cleaning with dilute hydrochloric acid to remove incrustations (calcium carbonate);

Formaldehyde 1.2 - Disinfectants: at places in the production area at risk from microorganisms, mainly extraction;

Hydrazine 0.13 - Anticorrosives for boiler feed water (chemical oxygen bonding with hydrazine hydrate);

Carbon dioxide 9000 - Juice purification (calcium carbonate precipitation); lime burning;

Sulphur dioxide 5 - Made from sulphur in sulphur furnaces, juice purification (calcium sulphite precipitation), acidification of the extraction water, waste gases where fossil fuels are used;

Hydrogen sulphide 15 - Raw material treatment, lagoons;

Dust (generally) 6 - Cane receipt and crushing, slice and sugar drying, sugar bagging; storage of excess bagasse.

Synthetic flocculants do not create dust or irritate the skin when handled, and do not constitute any toxicological hazard. Carcinogenic substances and substances which are suspected of having carcinogenic potential are: asbestos dust, alkali chromates and lead chromate (laboratory reagents), formaldehyde, hydrazine, fumes from VA welding.

The lethal dose (LD50) of a 39% formaldehyde solution is 800 mg/kg body weight (oral: rat); according to the working materials ordinance Arbeitsstoff-Verordnung classified as "low toxicity" and labelled with the hazard symbol R22 ("harmful if swallowed!) (necroses of the mouth, oesophagus, stomach).

Measures: in principle toxic chemicals must always to be kept sealed; the wearing of rubber gloves is recommended for analysis work; vessels and instruments must be thoroughly cleaned; installation of effective extraction and ventilation systems.

4. Interaction with other sectors

Sugar is produced jointly by agriculture (crop growing) and industry (processing technology), and there are close links in the ecological and technical fields. The use of modern agricultural knowledge and methods in the growing of the raw material, particularly with regard to fertilizer and pesticide application, largely determines the technological value of beet and cane (all physical, mechanical, chemical and biological properties of the raw material). High-quality raw material facilitates the tasks of extraction and juice purification and this in turn is reflected in improved technological - and hence in the final analysis economic - performance of the factory (higher sugar yields).

Excess bagasse can be used for the additional generation of electricity for the national grid (power stations sector) or for briquette production (domestic fuel supply). Bagasse is also a raw material for the manufacture of hardboard, cardboard or paper (wood and paper sector). Molasses, as well as extracts from cane and beet, are used as the raw material for fermentation processes (fermentation technology and biotechnology sector). Sugar is processed in numerous branches of the food industry. Refined sugar can be used in drug manufacture (pharmaceuticals sector).

All sugar beet and some sugar cane processing factories are equipped with lime kilns for the production of calcium oxide and carbon dioxide, and there are thus parallels with the cement/lime sector.

There are also links with the water supply, wastewater treatment and solid waste disposal sectors generally.

5. Summary assessment of environmental relevance

The impact on the environment from the sugar extraction process and the processing of the by-products from it are manifold, but can be kept to a reasonable, and in part legally prescribed, minimum level by means of established methods and processes. In new beet sugar factories the proportion of costs required for installations to protect the environment stands at some 15 to 20 % of total investment costs, while the figure for cane sugar factories is 10 to 15 %.

The wastewater produced can be minimised by optimum design of internal water circuits and the use of established purification processes (lagoon degradation/biological treatment plants). The rational control of the process must prevent any sugar solutions entering water circuits. This not only reduces pollution but increases profitability. Dumps for filter residues and earth can be used for soil conditioning once the load has been degraded. The production of fuel in the form of biogas should be taken into account when planning new factories.

Emissions from power stations and drying plants can be contained with the treatment technologies which have now been developed. A large quantity of soot and ash must be expected in the waste gas, particularly where bagasse is used as fuel, and consequently installations to optimise the combustion process and waste gas purification must be provided.

The open design of factories in warmer climates appears to obstruct possible noise prevention measures, thus noise nuisance would seem to be avoidable only by siting factories at an appropriate distance from residential areas.

In principle the environmental impact caused by sugar factories can be minimised by current technology. In the preparatory phase, it must be ensured that the plant installed will continue to be both fully operational and fully used for many years. This calls for the training of specialists at a technical level who realise the need for regular maintenance work. Training projects for sugar technicians and workmen can be appropriately integrated in sugar factories.

Sugar factories contribute to the general economic development of a country, including the intensification of agriculture, infrastructural improvement, start of the general industrialisation of rural areas and job creation in agriculture and manufacture, all of which attracts the potential workforce in the surrounding area. This generally leads to the uncontrolled growth of local communities and overburdening of the infrastructure and public services. Settlements in the immediate vicinity of the site must therefore be prevented from the outset. To minimise detrimental effects at the earliest possible stage, close cooperation must be sought at planning stage with the relevant authorities on the regional development plan. Likewise, the affected population groups - and this includes women - should be involved in the decision-making process at all planning phases so as to resolve environmental problems which may arise, e.g. land-use conflicts.

6. References

(1) Achtzehnte Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer (Zuckerherstellung), January 1982.

(2) Autorenkollektiv, Die Zuckerherstellung, Fachbuchverlag Leipzig, 1984.

(3) Bronn W.K.: Untersuchung der technologischen und wirtschaftlichen Mchkeiten einer Abfallminderung in Hefefabriken durch Einsatz von anderen Rohstoffen anstelle von Melasse, Forschungsbericht, 1985.

(4) Davids, P. und Lange, M.: Die TA-Luft, Technischer Kommentar, Herstellung oder Raffination von Zucker, 672 - 678, Verlag des Vereins Deutscher Ingenieure, 1986.

(5) Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlammuntersuchung, Fachgruppe Wasserchemie, 1979.

(6) Groeueranlagen-Verordnung, Dreizehnte Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes, 1983.

(7) Hugot: Handbook of Cane Sugar Engineering, Elsevier Scientific Publishing Company, 1972.

(8) International Commission for Uniform Methods of Sugar Analysis, Report on the Proceedings of the 20th Session, 1990.

(9) Korn, K.: Harmonisierung von Umweltschutz und Kostenbelastung an Beispielen der deutschen Zuckerindustrie, Zuckerindustrie 12, 1987.

(10) Meade, G. P., Chen J. C. P.: Cane Sugar Handbook, John Wiley Sons, N.Y. 1985.

(11) National Institute of Occupational Safety and Health, Registry of Toxic Effects of Chemical Substances, 1984.

(12) Persche Mitteilungen des Instituts fdwirtschaftliche Technologie und Zuckerindustrie zu Fragen lternative Chemikalien zur Desinfektion und Reinigung von Sen in der Zuckerindustrie, 1991.

(13) Reichel, H. U.: Auswirkungen der TA-Luft und der Groeueranlagen-Verordnung auf die Zuckerindustrie, 1985.

(14) TA-Luft: Erste Allgemeine Verwaltungsvorschrift zum Bundes-Immissionsschutzgesetz, 1986.

(15) Technische Regeln fliche Arbeitsstoffe, Bundesarbeitsblatt, 1985.

(16) UNEP - Industry & Environment Overview Series, Environmental Aspects of the Sugar Industry, 1982.

(17) Untersuchungen esinfektionsmittel fen Einsatz in Extraktionsanlagen, Nickisch/Hartfiel/Maud, Zuckerindustrie 108, 1983.

(18) Zucker-Berufsgenossenschaft, Lbereiche in der Zuckerindustrie, 1978.


Appendix 1: Flow chart - raw sugar manufacture from sugar cane

Appendix 2: Flow chart - white sugar manufacture from beet

Appendix 3: Flow chart - refining raw cane sugar

Appendix 4: Water management in a beet sugar factory

Appendix 5: Wastewater control in a cane sugar factory

Flow chart - raw sugar manufacture from sugar cane

Flow chart - white sugar manufacture from sugar beet

Flow chart - refining raw sugar cane

Water management in a beet sugar factory

Wastewater control in a cane sugar factory

1. Scope

Wood is man's oldest material and energy source; it is particularly important as it is a renewable resource. Despite the availability of metal, synthetic (plastic/ chemical) and mineral materials it is still important as a raw material. Because of their technological properties, tropical woods have been accepted - particularly in the last thirty years - as valuable functional and decorative materials. In most tropical and subtropical countries, wood still plays a vital role as an energy source.

The major timber sub-sectors are as follows:

- production (timber industry, incl. reforestation), felling and transport
- mechanical woodworking (sawing, shaping, milling, sanding)
- manufacture of wood board materials (plywood, chipboard and fibreboard)
- transformation into other products with extensive chemical modification of timber
- combustion.

This article focuses mainly on the primary, i.e. mechanical processing of wood, the manufacture of wood products and charcoal production, with only a brief look at combustion.

The manufacture of paper and pulps from wood is regarded as a separate, secondary processing sector and is not covered by this brief but by the environmental brief Pulp and Paper.

The environmental impacts of woodworking and wood processing operations, in the form of dust, noise and odours, can be countered to a large extent by appropriate siting, namely downwind from residential areas (see also the environmental brief Planning of Locations for Trade and Industry). The problem of wastewater, on the other hand, calls for closer attention. Direct effects on personnel can be at least reduced by the wearing of suitable hearing protection and breathing equipment.

In terms of the scale of environmental impacts it should be borne in mind that advancing slash and burn (shifting cultivation) can be the most dangerous environmental impact of timber felling, and is frequently the most significant factor in forest destruction.

The major effect on employment to be considered is that the workforce in the timber industry is almost exclusively male.

2. Environmental impacts and protective measures

2.1 Mechanical woodworking

Wood is a raw material which regrows and is obtained mainly from natural woodland, with plantations still playing only a minor role in many countries.

The dual system of national forestry authorities and private timber concessionaries often results in a clash of business management and forestry policy interests - being founded largely on conflicting principles.

Woodworking per se begins in the sawmill with debarking, unless this has already been done in the forest, followed by the cutting into lengths and cutting to size of timber supplied from the forest. The cut timber is either used directly as building lumber or is upgraded by shaping, milling, sanding and painting or impregnation.

Sawmills are workshops in which round wood is processed into sawn lumber (primary processing). Mechanical woodworking goes hand in hand with noise and dust, and is often carried out in the same mills which carry out surface treatments with paint, stains etc., processes which result in the formation of gaseous and substances with strong odours.

· Noise

The mechanically driven transport, cutting, milling, shaping and dust extractor installations in the timber industry generate noise, a problem which is exacerbated where sawmills are built to an open design in warmer climates.

However, because most sites are selected because they are close to raw material sources, they tend to be far from residential areas. Thus it is only mill personnel who are mainly affected. For this reason, the wearing of hearing protection should be compulsory and, where new plant or new equipment is to be installed, emphasis should be placed on providing tooling which is enclosed and designed to reduce noise.

Further negative effects on machine operators exist in the form of vibrations. The reduction of vibrations is an important factor when laying the foundations and erecting operating and control stations.

· Dust emissions

Alongside noise, dust is emitted from mechanical woodworking processes. In sawmills, wood cutting produces wood shavings, but because the wood is in most cases supplied fresh from the forest or is fibre-saturated, dust emissions do not present a major problem in relative terms, and fabric filters or wet extractors are not generally required. However, where wood shavings are stored in the open air, measures must be taken to protect against airborne dust.

Far more significant is the dust generated by mechanical woodworking in joinery works, cabinet-making and similar businesses, where both dust quantity and qualitative dust composition differ from that in a sawmill. The crucial factor is the fineness of the dust, expressed by its grain size and grain size distribution. Fine dust is naturally more difficult to remove than coarse dust and constitutes a greater health hazard to man, particularly where the particles are small enough to reach the lungs. The fine dust content is particularly high in sanding operations, and not so high in operations which produce shavings.

The inhalation of wood dust, particularly hardwood dust, can result in the absorption of harmful substances found in wood, which in turn can lead to serious illnesses. Thus, before any wood processing is undertaken, the health risks arising from working with wood must be thoroughly investigated and adequate precautions taken.

To reduce the quantity of dust generated at workplaces machines must be fitted with extractor systems, a measure which is justified as both a health precaution for employees and a fire and explosion prevention measure. Machines must be enclosed whenever possible and the extraction and transportation installations must be designed to handle the quantities of dust produced. If the extractor unit is likely to generate a high partial vacuum in the workroom, a pressure compensation system must be provided, but this must not cause any draughts in the workplace. Even where the industrial building is of an open design, every effort should be made to prevent draughts.

If harmful substances are released during the woodworking operations, the exhaust air cannot be returned to the work areas. Furthermore, where exhaust air is returned, the dust load at the workplace must not exceed permitted levels. The extracted dust must be discharged through non-flammable, fracture and wear-resistant extraction pipes, which must be designed and their rate of extraction dimensioned so that no undesirable deposits are able to form in the system.

Before the exhaust air is discharged into the environment the dust it contains must be separated off, for which purpose centrifugal separators or fabric filters are used. More costly and more effective fabric filters are required where extracted air contains sanding dust. Due to the risks of fire and explosion the extractor installations must be fitted with preventive safety devices, such as pressure relief valves, bursting discs, spark detection installations, smouldering fire alarms and fire extinguishing equipment.

· Gaseous emissions

When wood is dried, volatile constituents of wood in the exhaust air generate odours, and this exhaust air must therefore be released so as to avoid any odour nuisance.

Since wood processing mills are often sited in isolated locations, as already mentioned, the employees are those most subject to gaseous emissions.

This problem can be minimised by an appropriate choice of site (in terms of distance, allowance for the prevailing wind direction).

Otherwise, gaseous emissions are only of minor significance in sawmills.

· Analysis and evaluation of environmental impacts

In Germany timber mills are governed by the Technische Anleitung zur Reinhaltung der Luft TA-Luft [Technical Instructions on Air Quality Control] and the Technische Anleitung zum Schutz gegen L TA-L [Technical Instructions on Noise Abatement]. Accordingly the TA-Luft of 1986 restricts the mass concentration of wood dust in inhalable form to 20 mg/m3 at a mass flow of 0.5 kg/h. Lower limit values apply correspondingly to various dusts from woods treated with certain wood preservatives.

For most of the organic substances involved in wood processing, the upper limit is 150 mg/m3 at 3 kg/h. For airborne dust, which is a health hazard, concentration values of 0.45 mg/m3 and 0.30 mg/m3 are specified.

The acoustic pressure level is taken as the basic unit to describe the noise situation. Where measured and assessed values are indicated, three fundamentally different frequency weighting curves are used: single measured value, effective level and evaluation level (German DIN standards, guidelines of the Association of German Engineers VDI). In Germany the permissible limit values are 35 and 70 dB(A), depending on the preconditions for assessment.

In the case of wood preservatives their composition must be carefully examined (preservatives containing PCB's are banned in Germany). They must be kept sealed and accident-proof during storage. No wood preservatives dripping from treated timber are allowed to seep away in an uncontrolled fashion. Appropriate fire and accident prevention measures must be taken and waste must be disposed of correctly.

Where sawmills or mechanical woodworking mills are to be built or re-equipped, these statutory provisions must be applied as guidelines where there are no national regulations.

· Interaction with other sectors

The sawmill industry generally obtains its raw products from nearby forests. It must be ensured that the timber comes only from a properly managed forest (management strategy, coordination of individual usage plans, yield regulation, forestry and wood crop techniques) operating on the principle of sustainability.

Sawmills supply their products primarily to the wood-processing trade and industry (building, furniture and packaging sectors) and also for export. On the other hand the waste material produced contributes to supplying the derived wood product industry, particularly the chipboard industry, with raw materials.

The burning of waste wood concerns all aspects of timber usage and is therefore considered in a separate section.

Mechanical woodworking is primarily associated with the generation of noise and dust, with gaseous emissions and odours occurring only to a limited extent during artificial drying or treatment, and merely constituting a nuisance. Generally speaking, the sawmill industry does not damage or endanger the environment, except where wood preservatives are used, but even this problem can be avoided by careful siting of mills relative to residential areas.

2.2 Derived wood product manufacture

The term "derived wood products" covers chipboard, fibreboard and plywood. In addition to wood, these products - with the exception of a few types of fibreboard - contain an organic or inorganic bonding agent and in some cases additives.

The bonding agents used are mainly amino and phenolic resins, condensation products from an amino compound (urea, melamine) or a phenolic substance (phenol, resorcin, cresol or formaldehyde). Chipboard bonding agents on a diisocyanate adhesive base are a relatively new development. Polyvinyl acetate adhesives are used for wood core plywood.

· Chipboard manufacture

Practically all varieties of wood, wood waste and in some cases fibrous plant substances, bark and biomasses can be used as the feedstock for board. The first stage in the process is the machining of the raw material. Long cut or round wood is either cut into chips with drum chopping machines or processed directly into shavings with cutters. The next stage in shaving processing is drying, following by sizing, intermediate storage, bonding and hot pressing of the cut material. The initial production stages take place in enclosed installations without any significant emissions, these occurring only at the stage of hot bonding in the chipboard press at temperatures of 160 to 220°C. The final production stages comprise trimming, sanding and formatting of the board.

The main bonding agents used are amino and phenolic resins, condensation products from an amino compound (urea, melamine) or a phenolic substance (phenol, resorcin, cresol or formaldehyde). Chipboard bonding agents on a diisocyanate adhesive base are a relatively new development. Polyvinyl acetate adhesives are used for wood core plywood.

· Plywood manufacture

The term "plywood" covers veneer plywood and wood core plywood, the latter containing a central layer of rods, while veneer plywood is made by bonding together a number of individual sheets of veneer.

Suitable untreated wood is cut into veneer by sawing, cutting or scraping, dried and then bonded and pressed. The final production stage comprises trimming, sanding and formatting.

· Fibreboard production

A distinction is made between soft fibreboard, medium-density fibreboard (MDF) and hardboard.

Soft fibreboard contains no bonding agents. Hardboard likewise contains no adhesive, or at the most very small quantities of a phenol-formaldehyde bonding resin. MDF, like chipboard, contains 7 to 9% bonding agent.

The first stage of fibreboard production involves the production of fibres from wood, a process carried out by heat or chemical treatment.

It is then pressed by a number of different processes.

· Manufacture of mineral-bonded derived wood products

These products are made from wood chips, wood shavings or wood fibres and a mineral bonding agent such as cement, gypsum or magnesite. Wood is the main component, accounting for at least 85% of the dry weight. Manufacture is similar to that for chipboard, except that drying and hot pressing are not required.

3. Notes on the analysis and evaluation of environmental impacts

Noise emissions are produced in wood transport, cutting and preparation in all four manufacturing processes. Dust emissions may arise in stores. As in sawmills the resultant nuisance can be reduced by a sensible choice of site and by providing suitable precautions for employees (enclosed workstations, personal hearing protection).

Extremely fine dust is produced in the final stages of chipboard, plywood and fibreboard manufacture and this must be removed by means of centrifugal separators or fabric filters, as it is a health hazard to employees.

Gaseous emissions are produced only in the drying of wood shavings and the pressing of shavings and veneers.

In chipboard and plywood pressing, where amino bonding resins are used, formaldehyde is the main substance yielded in terms of the mol ratio of the bonding resin. Where phenol-formaldehyde bonding resins are used, only traces of phenol are found, and smaller quantities of formaldehyde are produced than is the case with amino bonding resins. Phenol and formaldehyde are both potential health hazards. In Germany formaldehyde emissions at the workplace must not exceed 0.6 mg/m3 and the finished board formaldehyde content must not exceed 10mg/100g board weight, according to EC Directives. After fitting the boards formaldehyde concentration must not exceed 0.1 ppm in the ambient room atmosphere.

The Gefahrstoffverordnung [Ordinance on Hazardous Substances] of 1986 specifies the formaldehyde emission values for all derived wood products in Germany. These gaseous immissions do not occur during the manufacture of mineral- bonded derived wood products.

Wastewater problems occur during the cleaning of the bonding machines and presses. In fibreboard manufacture, wastewater is produced during the wet process and contains wood particles, wood substances, bonding agents and other treatment agents which can be cleaned using physical processes (sedimentation, flotation or filtration) and/or biological processes. Semi-dry and dry processes do not produce any wastewater.

Residues in the form of wood particles can be returned to the production process in chipboard manufacture, but are otherwise burnt.

In addition to the specific statements in the text, the information relating to mechanical woodworking is also applicable to the analysis and evaluation of environmental impacts.

4. Interaction with other sectors

The wood product industry is reliant upon the forest as its raw material supplier, except where wood waste can be used, as is the case in the chipboard and fibreboard industry. The basic tenet here is that of the principle of sustained yield. The environmental brief Forestry contains detailed information on this subject.

Round wood can be fully utilised by linking sawmills wherever possible to fibreboard and chipboard manufacture.

Derived wood product factories are major power consumers which today generate their power with wood very rarely nowadays. The environmental briefs Overall Energy Planning, Thermal Power Stations and Renewable Sources of Energy should be consulted in this regard.

Wastewater management issues are also addressed in a separate environmental brief.

· Charcoal production

Charcoal is produced by the thermal decomposition of wood carried out without air (wood pyrolysis). This process also yields gaseous and liquid reaction products such as wood gas, wood vinegar, wood spirit and wood tar.

Charcoal is produced at temperatures of between 400 and 600°C, and is used as a fuel, a reducing agent in metallurgy and as a raw material for the chemical and pharmaceutical industries. Wood tar and the other liquid organic substances can be processed or alternatively burnt as an energy source.

Charcoal production is the only process still used today on an industrial scale in which wood is chemically modified to a substantial degree. Charcoal production is not therefore classified as part of the timber industry, but constitutes a separate sector of the chemical industry.

In many countries charcoal is an important source of energy for cooking and heating. The favourable ratio of weight to calorific value means that it can also be transported considerable distances from the place of production to its market. This fuel is in particular demand in cities because it produces heat without a great deal of smoke.

Charcoal is often produced in small businesses (with the exception of the East Amazon, Caracas), which either fell the raw material themselves or have charcoal production plants for wood waste in the immediate vicinity of sawmills. The latter arrangement is particularly useful where there is no derived wood product plant downline from the sawmill.

Gaseous emissions from charcoal production, in the form of smoke and strong odours do not merely constitute a nuisance: where the process is inefficiently managed pyrolysis derivatives, such as benzpyrene may constitute a health hazard to employees, and at high concentrations also to the general population (cancer risk). The comments made on the siting of sawmills apply here too.

The charcoal production process yields considerable quantities of pyrolysis water - up to 15% of the feedstock; this wastewater contains, inter alia, pyrolysis tar and water-soluble organic substances. Whereas liquid pyrolysis products must be conditioned according to the regulations for chemical industry installations in charcoal production on an industrial scale, no such solution yet exists for the small business.

If large-scale charcoal production from wood waste is sited close to wood processing mills appropriate measures must be taken to prevent pollutants from penetrating the water or soil.

· Burning of wood waste

The quantity of residual material (sawdust, splinters, bark, pieces) varies from process to process and product to product; tropical hardwood cutting produces extremely large quantities of waste (up to 60%). Waste disposal may take the form of combustion for energy production, as it is not possible to market the wood waste elsewhere because of the siting of the mill close to the saw of supply of the raw material. The presence of a downstream pulp or paper mill is a rare exception.

Complete incineration produces carbon monoxide, organic hydrocarbons, tar and soot. It is almost impossible to influence the nitric oxide emissions from wood furnaces.

5. Summary assessment of environmental relevance

While plywood mills process high-quality round timber, chipboard and fibreboard are the result of the value-adding utilisation of different wood varieties, some of which are low grade.

Gaseous emissions represent further harmful environmental impacts of chipboard and fibreboard plants, the main principal hazardous substance being formaldehyde. By contract, bonding with phenolic resins and diisocyanates help reduce emission values. One exception, in terms of emissions, is the manufacture of adhesive-free fibreboard.

Gaseous emissions from wood shaving driers have few environmentally harmful properties, especially in the case of hardwood, although the intensity of the odours produced constitutes a nuisance. The same siting criteria apply as for sawmills.

6. References

Anonymous 1976: Planung von Absaug- und Entstaubungsanlagen; Internationaler Holzmarkt 67, Heft 24, p.1...6.

ASP; without year of publication: Arbeitzsmedizin - Sozialmedizin - Prntivmedizin; ASP-Hefte 4, 7, 10; Gentner Verlag Stuttgart.

Baldwin, S.; Geller, H.; Dutt, G.; Ravindranath; N.H.; 1985: Improved Woodburning cookstoves: signs of success; Ambio; 14; 4/5; 280-287; 1985, 47 ref.

Baller, Gerd; 1987: Lschutz im Tischlerhandwerk; dds; No. 5; p.115; No. 6, p.67.

Baller, Gerd; 1987: Staub- und Spabsaugung im Tischlerhandwerk; No. 8, p.47; No. 9, p.65.

Baums, M.; Brann, U.; 1986: Die Gefahrstoffverordnung ist in Kraft getreten; Kommentar und Hinweise f holz- und kunstoffverarbeitende Industrie; Holz-Zentralblatt 112 (1986), p.1833...1841.

Bernert, J.; 1976: Emissionen von Holzspanplattenwerken, Wasser, Luft, Betrieb 20, p.27...34.

Birjukov, V.; Oskov, N.; Zamaraev, M.; Sokolov, V.: Vervollkommnung der Verfahren zur Beseitigung schicher Emissionen holzverarbeitender Betriebe; Holztechnologie 18, p.235...238.

Blanchet, G.; 1984: Beehive charcoal kiln in Zaire; Bioenergy 84 Proceedings of conference 15-21 June 1984, Gothenburg, Sweden, Volume III, Biomass conversion (edited by Egneus, H; Ellegard, A) 160-162; 1984.

Bringezu, St.; 1988: Zur Prund Bewertung der Umweltvertrichkeit von Holzschutzmitteln. Holzschutz und Umweltschutz haben gemeinsame Ziele; als Roh- und Werkstoff, 1989; p.421 ff.

Brocksiepe, G.; 1971: Holzverkohlung; in Chemische Technologie Band 3; p.417...492; Carl Hanser Verlag, Munich.

Brocksiepe, G.; 1976: Holzverkohlung; in Ullmanns Enzyklope der Technischen Chemie Band 12, p.703...708; Verlag Chemie Weinheim.

Bundesgesundheitsamt [German Federal Health Office], without year of publication: Vom Umgang mit Holzschutzmitteln; eine Informationsschrift vom BGA; own publication Berlin.

Busch, B.; Energiegewinnung aus Rinde; Holz-Zentralblatt 107, p.351...352.

Buslei, Wilfried; 1989: Holzstaub, Verdacht auf Krebs; dds; No. 9, p.44; No. 10 p.70; No. 11 p.54; No. 12 p.96.

CRIR; 1985: Forest Product Research International - Achievements and the Future; Carbon from Biomass - Woodgas in Practice; Proceedings Volume Five; own publication Pretoria/RSA.

Deppe, H.-J., Ernst, K.; 1990: Taschenbuch der Spanplattentechnik, 3. Auflage edition, 1990; DRW-Verlag Stuttgart.

DRW 1970: Maschinen und Maschinenstran in der Holzindustrie; DRW-Verlag Stuttgart.

Ernst, K.; 1987: Umweltfreundliche Holzwerkstoffe; Holz als Roh- und Werkstoff, 1987; p.411.

Ernst, K.; Schwab, E. Wilke, K-D.: Holzwerkstoffe im Bauwesen Teil 1: Materialkunde; EGH Entwicklungsgemeinschaft Holzbau; own publication, Munich.

Ferreira, F.A.; Alfenas, A.C.; 1985: Injurias em folhas de Eucalyptus spp. causados por condensados pirolenhosos originiarios de fornos de carvoejamento; Foliar injury in Eucalyptus spp. caused by condensed pyrolignins from charcoal kilns; Revista arvore; 9; 2; 186-190; 1985; 7 ref.

Graf, E. 1989: ologische Aspekte zur chemischen Holzbekfung; Holz als Roh- und Werkstoff, 1989; p.383 ff.

Hartmann, E.; Havla, R., 1984: Technologie und Technik der energetischen Nutzung von Holzresten unter besonderer Berhtigung der Wegewinnung durch Verbrennung; VEB Wissenschaftlich-Technisches Zentrum der holzverarbeitenden Industrie; own publication: Dresden.

HII, G.S.C.; Tay S.S.; 1980: An assessment of sawmill pollution in Sarawak; Malaysian Forester; 43; 2; 238-243; 1980; 5 ref.

Kauppinen, T.; Lindroos, L.; Mnen, R., 1984: Holzstaub in der Luft von Swerken und Sperrholzfabriken; Staub-Reinhaltung der Luft 44, p.322...324.

Knigge, W.; Schulz, H., 1966: Grundriss der Forstbenutzung; Entstehung der Eigenschaften, Verwertung und Verwendung des Holzes und anderer Forstprodukte; Verlag Paul Parey: Hamburg/Berlin.

Koch, D.; Funke, T.; Grosse Wiesmann, G.; Wiemer, H-J.; Weber, H-J.; 1985: Werkstoffe und Gefdungen im Tischlerhandwerk; Schriftenreihe der Bundesanstalt feitsschutz; Forschungsbericht Nr. 441; Wirtschaftsverlag NW: Bremerhaven.

K, E.; 1972: Holz-Lexikon, Bd. 1 und Bd. 2; DRW-Verlag Stuttgart.

Kollmann F. 1951: Technologie des Holzes und der Holzwerkstoffe Bd. 1 und Bd. 2; Springer-Verlag.

Lemann, M.; 1981: Abgasreinigung mit Werinnung; Holz-Zentralblatt 107, p.41...42.

Lingelbach, K.; 1982: Maahmen zur Senkung von staub- und gasfgen Luftverunreinigungen an einem Spanplattenwerk; Bericht 50 441-3/8 des T Kassel; Umweltbundesamt [German Federal Environmental Agency]: Berlin.

Lorenz, W.; 1982: Heizen mit Holz; Technik am Bau 2/82, p.117...121.

Maier, G.; 1988: Spabsaugung an Maschinen. erlegungen zu Strgstechnik und Konstruktion; Holz als Roh- und Werkstoff 1988; p.311.

Mamit, J.D.; Wee, H.B.; Lai, C.J.; 1985: The survey of the disposal of woodwaste by sawmills in Sarawak; Technical Report (Timber Research and Technical Training Centre); Sarawak; No. TR/4; 15pp.; 1985; 3 ref.

Marutzky, R. 1977: Untersuchungen zum Terpengehalt der Trocknungsgase von Holzspantrocknern; Holz als Roh- und Werkstoff 36, p.407...411.

Marutzky, R.; Mehlhorn, L.; May, H.-A.; 1980: Formaldehydemissionen beim Herstellungsprozevon Holzspanplatten; Holz als Roh- und Werkstoff 38, p.329...335.

Marutzky, R.; 1981: Emissionstechnische Erfassung von luftverunreinigenden Stoffen aus Anlagen zur Herstellung von Holzspan- und Holzfaserplatten; Gesundheitsingenieur - Haustechnik - Bauphysik - Umwelttechnik - 102, p.300-335.

Marutzky, R.; 1981: Mchkeiten zur Verkohlung und Vergasung von Holz und anderen pflanzlichen Reststoffen; Holz-Zentralblatt 107, p.315...317.

Marutzky, R.; 1984: Holzreststoffverbrennung - Techniken, Umweltschutzmaahmen, Wirtschaftlichkeit; Holz-Zentralblatt 110, p.1693...1694 and 1713...1714.

Marutzky, R.; 1987: Grenzen der Emissionsminderung bei Holzsptrocknern unter Berhtigung der neuen TA-Luft; Holz als Roh- und Werkstoff 1987; p.421.

Marutzky, R.; Flentge, A.; Mehlhorn, L; 1987: Zur Messung der Formaldehydabgabe von Holzwerkstoffen, Baustoffen und Mn mittels der 1m3 Methode-Kammer Methode; Holz als Roh- und Werkstoff, 1987; p.339.

May, H.-A.; Mehlhorn, L.; Marutzky, R.; 1981: Gefahrlose Sptrocknung bei der Spanplattenfertigung; Schriftenreihe "Humanisierung des Arbeitslebens" Bd.21; VDI Verlag Dorf.

Mayrhofer; W; Pimminger, M; Gritzner, G; 1987: Untersuchungen zur Abgasreinigung von Sptrocknern; Holz als Roh- und Werkstoff, 1987; p.379 ff.

Nantke, H-J.; 1986: TA-Luft - Was ist bei der Spanplattenherstellung zu beachten? Holz-Zentralblatt 112, p.2183.

Nimz, H.H.; 1988: Probleme, Kentnisse und Hoffnungen zum Thema "Holzstaub"; Holz als Roh- und Werkstoff 1988; p.117 ff.

Patao, D.N.; 1987: Sample Survey of charcoal and fuelwood consumption in Region 1; FPRDI, Vol. 16, No. 1, Jan-June 1987; p.58 ff.

Peters, F.; 1983: Energieerzeugung aus Holzreststoffen; Industriefeuerung 25, p.49...58.

Philipp, W.; 1980: Verbrennung von Rinde und deren Abwenutzung; Holz-Zentralblatt 106, p.1457...1458.

Robertson, D. (Ed); 1983: The Sixth International FPRS Industrial Wood Energy Forum 82, Volume II: Power and Heat Plants; Forest Products Research Society: Madison, WI/USA.

Robertson, D. (Ed.); 1983: The Sixth International FPRS Industrial Wood Energy Forum 82, Volume II: Gas and Charcoal Production from Wood/Biomass Fuels; Forest Products Research Society: Madison, WI/USA.

Rong, M; 1981: Herstellung von Holzspan- und Holzfaserplatten -Verfahrenstechnik und Emissionen luftfremder Stoffe; Gesundheits-Ingenieur - Haustechnik - Bauphysik - Umwelttechnik 102, p.287...295.

Saeman, J. (Ed.); 1976: Wood Residue as an Energy Source; Forest Products Research Society: Madison, WI/USA.

Salje, E. (Ed.); 1975: Umweltschutz bei der Holzbearbeitung; Tagesbericht; Deutsche Messe- und Ausstellungs-AG: Hannover.

Salje, E.; Geerken, J. 1988: Verringerung der Staubemissionen beim Frn; Holz als Roh- und Werkstoff, 1988; p.340 ff.

Schlotterhausen, R; 1986: Holzwerkstoffe - Merkmale und Verarbeitung; Wedra Verlagsgesellschaft: Stuttgart.

Wolf, Dr. J; without year of publication: Sicherheitswissenschaftliche Monographien Gesellschaft fherheitswissenschaft; Bergische UniversitWuppertal, Wirtschaftsverlag NW GmbH.

Soine, H.; 1982: Energiegewinnung aus Holzabfen; Holz als Roh- und Werkstoff 40, p.217...222, 263...268 and 281...286.

Smith, K.R.; 1986: Biomass combustion and indoor air pollution: the bright and dark sides of small is beautiful; Environmental Management; 10; 1; 61 to 74; 1986; 52 ref. BLL.

Strehler, A.: Wegewinnung aus Hackschnitzeln und Scheitholz; Holz-Zentralblatt 110, p.292...294.

Tsai, C.M.; 1983: Study on the quality improvement of urea-formaldehyde resin bonded plywood; Memoirs of the College of Agriculture, National Taiwan University; 23; 2; 80-82; 1983.

Tsai, C.M.; 1984: Effect of adding urea or melamine to urea-formaldehyde resin on the elimination of formaldehyde release from plywood; Technical Bulletin, Experimental Forest, National Taiwan University; No. 155; 14pp.; 1984; 65 ref.

VDMA 1986: Holzfeuerungsanlagen - Emissionsvorschriften, Holzbrennstoffgruppen; Einheitsblatt 24178 Teil 1; Verband Deutscher Maschinen- und Anlagen- bau e.V./Frankfurt.

VKE 1985: PVC - Ursache fxin-Bildung? Informationsschrift des Verbands Kunstofferzeugende Industrie/Frankfurt.

United Nations Industrial Development Organisation; 1983: wood processing industry; Sectoral Studies Series, Division for Industrial Studies, United Nations Industrial Development Organisation; No. 4; 83 pp.; 1983; 59 ref. UNIDO/IS. 394, Limited distribution.

Vorreiter, L. 1958: Holztechnologisches Handbuch, Bd. I und II.; Verlag Georg Fromme: Vienna/Munich.

1. Scope

1.1 Introduction/general information/terminology

· Pulp

- Pulp (in the context of this brief) is the common name for vegetable cellulose in the form of fibres or bundles of fibres, more or less free of residual plant parts.

Cellulose is the principal supporting component of all plants and thus in theory, pulp can be obtained from any type of plant. However, as the various fibre properties and also the fibre content can differ widely, in practice only relatively few types of plant are used for pulp production.

- Wood is the chief raw material used in pulp production. Generally speaking, softwood has longer fibres and hardwood shorter ones.
- In addition to wood, annual plants are used for pulp production, mainly in countries with scarce wood resources (China, India etc.).
- Pulp is produced for mechanical processing into board, paper etc. and for chemical processing to films, synthetic fibres etc.
- Pulp is produced from the stated raw materials by means of chemical, chemical-mechanical or mechanical processes.
- Pulp can also be obtained from waste paper (recycling) although in this case it can only be used for paper and board production.
- The auxiliary materials used are water, steam, mechanical and electric energy and chemicals.
- By-products and waste are produced which can cause direct or indirect atmospheric and water pollution, but which can be reduced by measures within the production plant (internal means) and by installations downstream from them (external means).

· Paper and board

- In the context of this brief, paper is a thin fibrous mat made principally from pulp, with or without surface treatment, manufactured from the above-mentioned types of cellulose.
- Board is thick (stiff) paper.
- Cardboard is strong board (thickness), made by a special process.
- Depending on the type of pulp or waste paper and how they are pretreated, the properties of the paper, board or cardboard can be adapted for their intended uses, thus the range of different paper and board types is manifold.
- The wastewater produced during paper and board manufacture contains pollutants which can be removed by appropriate cleaning processes.

1.2 Pulp production

Table 1.2 summarises the basic data on pulp, such as yield, specific energy consumption, relative consumption of chemicals, relative pollutant quantities and relative environmental pollution. Some basic terms are also defined below:

1.2.1 Raw materials

· Wood

a) Softwood: Mainly pine, fir and spruce varieties, for pulp with long fibres (high strength).

b) Hardwood: Mainly beech, birch, eucalyptus, poplar, other types and mixtures (medium strength) too, depending on the location.

· Annual plants

a) Agricultural by-products: Various types of straw (wheat, rice etc.), bagasse, i.e. sugar cane following extraction (low strength). For special papers: linters, i.e. by-product from the cotton oil industry (high purity and strength).

b) Others: Reed, bamboo, jute, kenaf etc. (less commonly used).

· Waste paper

Different grades, sorted into unprinted clippings from paper-processing (e.g. printing) through to mixes from domestic collections.

1.2.2 Products and processes

Apart from the hygiene sector (e.g. for nappies) pulp is not an end product but an intermediate product for paper manufacture, and as chemical conversion pulp, is the raw material for the chemical industry (fibres, films, plastics).

Pulp is available in a number of different forms, the most important of which are:

· Groundwood (Mechanical wood pulp)

Groundwood fibers produced mainly from softwood with a grinding stone and containing practically the same constituents as the original wood, except for some extractives. It provides the highest yield and generally is not bleached or only to a low to medium brightness.

Applications: For mass-produced papers at the lower end of the quality scale. Typically: newsprint, writing and printing paper containing wood, duplex board.

Characteristics: Products are of low strength, they yellow in daylight and are not very resistant to ageing.

The chemicals most frequently used (for bleaching): sodium didithionite, peroxides - peroxide being the least polluting bleach.

Plant sizes: 50 - 600 t/day.

· TMP - thermomechanical pulp

Comparable with groundwood, but defiberation between rotating discs. Slightly lower yield but better strength properties. Is bleached like groundwood.

Applications: as for groundwood.
Characteristics: as for groundwood.
Plant sizes: 300 - 600 t/day.

· CTMP - chemi-thermomechanical pulp (includes APMP)

In contrast to TMP, pulping is facilitated by a chemical pretreatment. The yield is slightly lower, but despite this the mechanical properties of the fibres are improved. Is usually bleached to medium or high brightness.

Applications: As absorbent in the field of hygiene products (nappies etc.), for mass produced printing and writing paper midway along the quality scale.

Characteristics: Depending on the raw material, products are medium to low strength; they yellow quite readily and are not particularly age-resistant.

· SC (or NSSC) - semichemical pulp

Still contains considerable quantities of non-cellulose substances. Wood chips or other fibrous raw materials are pretreated with chemicals in pressure vessels and with steam under pressure. Pulping is then carried out in refiners with a relatively low power consumption. Is not usually bleached.

Applications: Packaging papers, particularly corrugated medium in corrugated board.

Characteristics: Produces fairly stiff paper and board, depending on the raw material used.

Chemicals most often used: sodium sulphite, sodium hydroxide and/or sodium carbonate. Recycling or disposal within the mill is necessary.

Plant sizes: 50 - 500 t/day.

· Chemically produced pulp

Contains only low to very low quantities of non-cellulosic substances, low yields due to the removal non-cellulosic materials. Wood chips or other fibrous raw materials are pulped with chemicals and steam under pressure. This is usually followed by bleaching and then either drying and pressing into bales as commercial pulp or, in an integrated plant, further processing into paper products.


- Unbleached: mostly as packaging paper, also added to lower strength pulps (reinforcing).
- Bleached: mostly for writing and printing papers, also as an additive to lower strength pulps, cellulose for chemical feedstock (dissolving pulp), mostly produced from hardwood.

Characteristics: High strength in the case of softwood products. Bleached substances yellow only slightly and are highly age resistant. High purity for chemical raw materials.

Pulping chemicals: Sodium hydroxide, Na2S (alkaline processes: "soda", "sulphate") and Ca, Mg, Na and NH4 bisulphite (acid processes: "sulphite"). Recovery and regeneration of chemicals is a precondition for economic and non-polluting operation. Some of the spent liquor from the sulphite process can be processed by fermentation to form yeast and alcohol or, in its dried form, can be sold as a binding agent.

Bleaching chemicals: Chlorine (the use of which is on the decline), sodium hypochlorite, chlorine dioxide, oxygen, sodium and hydrogen peroxide.

Plant sizes: softwood as raw material: 500 - 1300 t/day; annual plants as raw material: 50 - 250 nnt/day.

· Waste paper pulp

Waste paper contains a mixture of pulps from various sources, depending on the composition and sorting of waste paper, and is a substitute for fresh pulp (cheaper, energy-saving). It is pulped mechanically. May be de-inked and bleached following removal of non-paper fibres and other impurities.

Applications: In principle, for all paper and board types, with or without the addition of fresh pulp.

Characteristics: Quality slightly or moderately inferior to fresh pulp, depending on the quality, sorting, cleanliness etc. Chemicals for de-inking and bleaching are detergents, fatty acids, dispersants, dithionite, peroxide.

Plant sizes: 50 - 400 t/day.

1.3 Paper and board production

1.3.1 Basic fibrous material, pulp (raw materials for paper and card production)

All the products listed under 1.2.2 are basic materials for the paper industry. In most cases a mixture of two or more of them are used to give the paper the required characteristics or for reasons of economy.

1.3.2 Products and processes

Paper and board types are usually classified into the following main groups on the basis of intended use:

- printing and writing (graphic) papers
- industrial papers
- special papers.

Practically all papers and boards are produced on continuously (or in the case of boards sometimes semi-continuously) operating machines, the principle of which is the dewatering of the aqueous fiber suspension on a wire to form a fibrous mat which is then pressed and dried. The sheet of paper thus produced is packed in the form of rolls or packs of sheets. The pulp fibres are pretreated in "beating" machines (refiners) to give them the properties required for the individual type of paper, and additives are used to give properties such as ink absorbance, water-resistance, stiffness, colour. Fillers such as kaolin (alumina), and more recently calcium carbonate and sulphate improve the paper surface for certain printing processes.

The product groups are characterised as follows:

· Printing and writing (graphic) papers

These writing and printing papers are basically subdivided into those containing wood1 (coated and uncoated)2 and those not containing wood pulp (likewise coated and uncoated), the former mainly as mass-produced papers, the latter for high quality and special applications. Today, both kinds contain increasing quantities (in some cases up to 100%) of waste paper.

1 "wood containing": containing not only pure, chemically produced pulp but also groundwood, CMP etc.
"wood free": containing only chemically produced material.
2 coated: surface treated with dominatingly inorganic pastes.

· Industrial papers

These include mainly packaging papers and boards, comprising many brands of grey common wrapping papers (made from recycled paper) through to high-quality packaging materials for food and luxury goods, in some cases surface treated, multi-layer or coated for costly print processes. Corrugated board, made from fresh unbleached pulp or recycled corrugated board (a rising trend) depending on quality, accounts for a portion of industrial papers in quantity terms.

· Special papers

These cover a wide range of paper types which cannot be specifically allocated to the two product groups described above, e.g.:

- papers for hygiene applications (tissues, kitchen rolls, toilet paper)
- filter papers for use in industry, the home, the laboratory etc.
- transparent papers for drawing
- photographic papers
- base paper for parchment, vulcanized fibre
- cigarette paper
- capacitor paper etc.

1.4 Secondary and auxiliary installations

· Energy supply

Energy is required in the form of mechanical energy (electricity) and heat (steam). Where no hydraulic power is available, electrical energy is obtained either from the national grid or generated by a power plant inside the mill (steam or gas turbines). Fossil fuels (heating oil, natural gas, coal), and also wood and wood waste (bark) or other waste substances are used for steam production.

The spent liquor from chemical pulp production is an important "waste" product in terms of energy. It is burnt in special boilers ("recovery boilers")to produce steam to cover process energy needs.

· Water

The availability of fresh water is a basic requirement for pulp and paper production. The water demand may exceed 150 m3/t of product, but in very modern mills it may be no more than 2 m3/t, although this also depends on the quality of the process management.

· Wastewater treatment

Mechanical, biological and/or chemical wastewater treatment are now standard in any pulp and/or paper mill.

2. Environmental impacts and protective measures

2.1 Area: Raw and auxiliary materials

2.1.1 Fibrous raw material

· Wood

The afforestation and reforestation of suitable areas for the raw materials supply of paper and pulp mills are advantages in terms of climate, water resources and the labour market.

The use of timber must be planned with a view to maintaining a balance between the cutting and growth rates.

Vegetable fiber resources are renewable - in the case of wood by reforestation. Special measures are essential for such single-crop agriculture; in-depth studies of cultivation measures as well as socio-economic aspects (e.g. competition for land usage) are essential.

· Annual plants

Agricultural products used as raw materials should not automatically be regarded as environmentally advantageous. For example, if straw is not ploughed back into the soil, increased fertiliser use is necessary, whilst the humus content in the soil will drop. The widespread burning of straw is also undesirable and the collection of straw is relatively energy intensive (pressing in bales for transport, yet still bulky, truck capacities by no means fully utilised). Furthermore, the large stocks which have to be held because of the relatively short harvest period create a fire risk.

In the case of bagasse (waste from cane sugar production) used as a fibrous raw material for paper, conditions are more favourable in that it does not have to be collected separately, but nonetheless large stocks need to be held to cover periods when the sugar factory is closed. The competition between raw material for paper and fuel in the sugar factory is described in the environmental brief Sugar.

In short, the use of annual plants is only environmentally positive under certain conditions. It is generally insignificant and only relevant in special cases.

· Waste paper

This raw material enables significant savings to be made on energy compared to fresh pulp, with the exception of fully chemical pulp as modern pulp mills are energy selfsufficent. However, paper cannot be recirculated ad infinitum. For every circuit there is a sacrifice in quality due to fibre damage. However, the use of waste paper must be regarded positively from the environmental viewpoint, in most of today's cases of application.

2.1.2 Water

Production water (river and well water) is required in relatively large quantities (see 1.4 above) and must meet certain minimum purity criteria. It must be processed, but can be recycled in internal circuits a number of times. In less favourable instances the use of wells can result in a long-term change in the groundwater table. As far as water requirements are concerned detailed analyses with a view to meeting the needs of competing usages are essential at the paper mill design stage.

2.1.3 Energy

The environmental impacts of electricity generation and the use of fossil fuels, also used in pulp and paper mills, are known and can be found in the environmental briefs on Thermal Power Stations and Power Transmission and Distribution.

Sector-specific fuels arising in mills during pulp production or in the wood-processing industry are

- spent liquor from the cooking and impregnation process
- bark, sawdust, splinters.

Concentrated spent liquors are burned in recovery boilers specially designed for this purpose, thereby releasing the pulping chemicals in the form of molten ash for regeneration. Spent liquors replaces some, and in modern chemical pulp mills all, of the fossil fuels.

Wood waste is likewise burned in special boilers and thereby replaces fossil fuels. (For relevance of emissions, see 2.2). Typical specific energy consumptions are listed in table 1.2.

2.1.4 Chemicals, auxiliary materials

Although some of the chemicals to be added, particularly bleaching agents, such as chlorine, sodium chlorate, caustic soda and peroxides, are bought in by pulp and paper mills, their production requires considerable quantities of energy. A reduction in bleach consumption requires a generally greater acceptance of less bright paper on the part of the consumer, but would be a major environmental protection measure.

The production of other auxiliary materials, such as dyes, starch, clay and resin, is likewise heavy on energy, but is less significant because of the relatively small quantities used.

2.2 Emissions from pulp and paper mills

2.2.1 Aqueous emissions

Table 2.2.1A gives a detailed survey of sources, substances emitted, impacts, and reduction measures and the degree of reduction of aqueous emissions, while table 2.2.1B provides information on typical emission limits in terms of quantity.

Considered first are:

- emissions
- their impacts and
- reducing and protection measures

before the downstream treatment plant (wastewater treatment plant). This is followed by the effect of these reducing and protection measures.

A: Quantity

The quantity of wastewater is approximately the same as the quantity of fresh water used. Thus a reduction in fresh water consumption by creating internal circuits results in a reduction in wastewater quantities, which is also a major cost factor when designing wastewater treatment plants.

B: Quality

Quality factors in aqueous emissions are

- content of undissolved substances (settleable/filterable)
- content of dissolved substances, comprising

· reaction products from pulping and chemical recovery
· reaction products from pulp bleaching
· concentrated condensates from chemical recovery
· chemical residues and soluble content of waste paper cleaning
· dissolved substances from paper manufacture and coating
· dissolved substances from secondary installation wastewater.

In terms of impact they are all capable of:

changing pH, consuming O2, causing discoloration or turbidity, they may be toxic, either individually or in combination.

Primary reduction measures are internal recirculation before the remaining wastewater and pollutants are transferred to the

C: Wastewater treatment plant

(secondary treatment, downstream plant) where they are purified to such a degree that they can be discharged into public sewage systems.

2.2.2 Emissions into the air

There is an wide variety of major sources in pulp mills and they are affected in some cases by highly complex technical factors. They range from dust produced in raw material crushing, through vapours and gases escaping from reaction vessels and liquor tanks to flue gases from recovery, bark, sludge and oil/coal boilers, the waste gases from lime burning and degassing systems of bleach tanks and bleaching towers.

In paper mills, the situation is less complex, with fewer factors involved, the main source being waste air from dryers.

Table 2.2.2A gives a detailed overview of source, substances emitted, impacts, reduction and protection measures which can be taken inside the mill and the degree of reduction in the most important departments, while table 2.2.2B provides quantity data relating to typical emissions in the sector, values currently achievable and limit values.

External plants are avoided wherever possible in the case of waste air cleaning plants; they are incorporated in the various process stages so that the media extracted can be recirculated.

The main emission components are carbon dioxide and monoxide, dust (wood and mineral), steam, sulphur dioxide, reduced sulphur compounds (mercaptans and the like), nitric oxides and hydrocarbon compounds.

Their most significant impacts are:

- they range from being hazardous to health to toxic, they present a fire risk, they give rise to odours and smog, they may be a contributory factor to acid rain and they reinforce the greenhouse effect.

Reduction or protection measures range from internal collection, recirculation, combustion or other chemical conversion processes to downstream (external) gas scrubbers, filters and absorbers.

2.2.3 Solid waste

Table 2.2.3 describes the sources, materials, impacts and possible countermeasures specific to solid waste.

The main sources are as varied as for gaseous emissions. They comprise for the most part wood waste such as sawdust, bark, fiber bundles, and also mineral waste such as lime sludge, sand and spent auxiliary materials such as screens, felts, plastic film, wire etc. The main impact is the dumping space requirement.

Reduction and protection measures involve essentially a reduction in volume by incineration and the return of recyclable materials to the manufacturer (metal parts, for example).

2.2.4 Noise

The principle sources of noise are:

raw material preparation, such as wood debarking and chopping, transport equipment, refiners, vacuum pumps, finishing machines, steam blow-off in the boiler house, drive units.

The impacts may range from nuisance and disturbance to nearby residential areas at night to physical health problems and hearing impairment.

Possible reduction measures are:

wood debarking and chopping and heavy goods transport in daytime only, since intermittent operation is possible. Also enclosure of machines, and if applicable sound-proofing materials, steam blow-off with silencers only, new plant sited a suitable distance from residential areas. (With few exceptions, machines are already being designed with noise reduction in mind). internal measures: prescription of hearing protection to be in the relevant departments.

3. Notes on the analysis and evaluation of environmental impacts

3.1 Aqueous emissions

The monitoring of these emissions demands continuous or semi-continuous sampling and appropriate equipment, both for the individual wastewater flows and for the combination of them.

Routine analyses can be confined to temperature, pH, settleable or filterable solids, biochemical oxygen demand (BOD5), chemical oxygen demand (COD, measured as potassium chromate consumption), fish toxicity, adsorbable organic halogen compounds (AOX) in relevant cases (i.e. where chlorine or bleaching agents containing chlorine are used).

Special analyses include, inter alia, the determination of turbidity, colour, odour, conductivity, colloids, oils and fats.

Analysis methods for routine and special tests are listed in table 3.1.1.

Minimum requirements for the discharge of wastewater into public sewage systems have been established and have come into effect in a number of countries in order to assess the environmental impact of aqueous emissions.

For the German pulp and paper industry, the Wasserhaushaltsgesetz [WHG - Federal Water Act], the Abwasserabgabengesetz [AbwAG - Wastewater Charges Act] and the Bundesimmissionsschutzgesetz [BImSchG - Federal Immission Control Act] are of particular relevance. These laws and their enforcement ordinances lay down minimum requirements which must be observed following application of emission-reducing purification or cleaning processes (see in this regard tables 3.1.2A and 3.1.2B).

In Switzerland, assessment criteria are established in the ordinance on water discharge "Verordnung bwassereinleitung", in Austria the standards orm cover this area, and in the USA, the "Effluent Limitations Guidelines and New Source Performance Standard for the Bleached Kraft, Groundwood, Sulfite, Soda, Deink and Non-integrated Paper Mills Segment of the Pulp, Paper and Paperboard Mills" in the EPA (Environmental Protection Agency) programme apply.

In some other countries, although similar values exist, they are all too frequently in the form of guidelines, and compliance with them is seldom monitored.

Likewise, pollutant concentration data is often given as an assessment criterion, though it would be more correct to restrict the absolute quantity of the emission. The concentration assessment may well lead to a dilution of emissions to the limit values if adequate fresh water is available, but "dilution is no solution to pollution".

To obtain a reliable assessment of the expected emission situation for an extension or new-build project, consideration must be given not only to emission quantity and quality but also to the drainage situation. The essential determining factors here are:

- flow rates with seasonal minima and maxima
- initial loading of watercourses/rivers
- use of water downstream from the discharge point (drinking water, irrigation, fishing, industry).

3.2 Emissions into the air

As the major part of emissions into the air and the main emission components (dust, CO2, CO, NOx) stem from the combustion plants for steam generation, the relevant environmental brief Thermal Power Stations should be consulted.

Typical sectoral emissions (particularly pulp mills) are:

sulphur dioxide (SO2), reduced organic sulphur compounds (TRS), chlorine/chlorine dioxide gas (Cl2, ClO2), certain hydrocarbons (HC).

The routine monitoring of these emissions is in some cases carried out by continuous display and recording equipment, which must be inspected and calibrated by supervisory bodies at prescribed intervals.

Non-continuous inspections (special inspections) are carried out on intermittently collected samples by laboratory staff. The measuring methods for this are prescribed in Germany by the TA-Luft [Technical Instructions on Air Quality Control]. As with wastewater (see above), other countries have their own specific measuring methods which are defined in the relevant clean air regulations.

The substance-specific emission limits currently applicable in Germany, in accordance with the TA-Luft, are listed in table 2.2.2B. It should be noted in this regard that the TA-Luft does not contain a limit value for TRS compounds which are responsible for the odour nuisance generated by sulphate factories. For this reason, the limit values currently contained in the USE-EPA - which are largely in line with the state-of-the-art - are recommended as guidelines.

The limit values given in table 2.2.2B can be used as guidelines for extension and new-build projects in countries where provisions in this area are inadequate or do not yet exist yet.

3.3 Solid waste

There are only a limited number of analysis methods for the environmental impacts of solid waste; for example, there are none for bark, sawdust-type wood waste, bale wire, plastic bags and felt. Other solid waste (constituents of waste sludge, lime sludge, waste gas dust etc.) is routinely examined.

As solid waste cannot be described as altogether typical of the sector, the analysis methods described in the relevant environmental briefs (Solid Waste Disposal, Timber) should be consulted.

Limit values to assess the environmental impacts of the aforesaid substances in the form of ordinances are rarely prescribed. In Germany they exist in respect of the suitability of substances for disposal (see in this regard the environmental briefs Solid Waste Disposal and the Disposal of Hazardous Waste). The Compendium of Environmental Standards also contains information about substances which can be critical in waste sludge (heavy metals from printing inks, toxic compounds etc.).

3.4 Noise

Noise is measured and assessed as noise immission. The unit of measure used in Germany is the dB(A) to DIN standard 45 633.

Immission limits vary according to the type of area, ranging from 70 dB(A) for purely industrial zones to 35 dB(A) for health resort and residential areas as a night limit.

No special measures are required to comply with a noise immission level of around 50 dB(A) in the immediate surroundings of modern pulp and paper mills, provided that the mills are housed inside buildings and are fitted with state-of-the-art sound-proofing.

In Germany, for example, this means that a pulp and paper mill can only be built in industrial or principally industrial areas.

If the relatively large amount of land required to build a paper mill is available, the noise restrictions do not in many countries represent a major barrier to such projects. In fact, the noise immission values may be conformed to even outdoor design of mills, as is frequently the case in tropical countries, as long as it is at an adequate distance from neighbouring areas used for residential or other purposes requiring protection.

4. Interaction with other sectors

4.1 Areas typical of the sector

4.1.1 Raw materials

Pulp and paper mills are extremely capital intensive and have a very long service life (some are over 100 years old). For this reason, the long-term reliability of raw material supplies is of fundamental importance.

· Wood

Planned and organised cooperation with the forestry sector is essential. This collaboration can be structured in a number of ways: it ranges from the simple purchase of trunk timber, thinning timber or wood chips and sawmill waste through to the management of a mill's own forests. In view of the large time span between the planting and the felling of trees, long-term planning is required for new-build projects. Proper afforestation work is essential, along with the appropriate capital investment and the necessary organisation.

One important aspect of interaction with other sectors is that of competition in the standing timber and sawmill waste market (sawmills, plywood manufacture, the wood processing and wood product sector).

Interaction with the agricultural technology sector exists in the context of so-called "agro-forestry", in which trees are used to provide shade and as windbreaks. This could be interesting if the correct types of tree for paper production were chosen, and it could also be an additional source of income for farmers.

Other competition with pulp wood derives from use of wood as fuel (see the environmental brief Renewable Sources of Energies) or wood for charcoal or building.

· Annual plants

With few exceptions, the annual plants which can be used for pulp and paper production constitute waste or by-products from agriculturally based industries (e.g. sugar production).

In global terms this group is not significant as far as paper manufacture is concerned, but may be important locally if no wood is available. The raw material potential for pulp and paper production therefore depends on the market for the products of these other industries. Relatively short-term changes in farming programmes can greatly reduce raw material supplies or lead to arable land being withdrawn from production for reasons of pricing policy.

· Examples of annual plants


Large quantities produced worldwide, but with low potential for use due to the costs incurred in its collection, transport and storage; significant emission problems in its processing to pulp. Change of crop programme, e.g. due to introduction of short-stemmed cereal varieties, could jeopardise projects. Competitive situations could arise with a demand for straw as bedding for cattle or as fuel for heating and cooking.


The sugar cane residues following sugar extraction are traditionally used in the sugar factory itself as a fuel (energy self-sufficiency). It is therefore in competition with fossil fuels if it is to be used for paper manufacture, hence the interaction with the agro-industry.

Of minor importance in terms of quantity, but interesting in terms of fibre properties are raw materials such as:


In the form of jute sticks, the waste from the ailing jute (textile) industry. Competition with fuel. Jute cuttings: competition with the textile industry.


Flax straw as waste from the linseed oil industry. Transport and cleaning very costly. Competition with textile manufacture.


Since sisal is little used now for ship hawsers, efforts are being made to cultivate its use as a raw material for special papers. Very high transport and preliminary cleaning costs. Competition with sack and bag production.


Plays a (minor) role in special paper production (Philippines) alongside (minimal) use for textile purposes.


Waste product from cottonseed oil factories. Is a raw material for special, chemically pure cellulose for the chemical and pharmaceutical industries, also for special papers and filter material. Advantage: produced centrally - at the oil mill. Competition on the product side from wood dissolving pulp.


Important building material in all countries where it grows (in practice only a natural crop, cultivation difficult), therefore only limited quantities available for pulp and paper. Competition exists for use as a vegetable (bamboo shoots).

Esparto or alfa grass:

Like bamboo, it is not cultivated and is collected only for insignificant quantities of paper production (special papers) (North Africa and Spain). Competition exists with use as a braiding material.

· Waste paper

The potential for waste paper supply is directly dependent on paper consumption in the region or catchment area and on market price (determined by the economic climate). In countries with large stocks, lower qualities are most vulnerable to the economic climate.

Waste paper can be an important raw material in countries where a paper industry is to be established for a relatively low initial investment.

There are links here with the paper-processing industry.

In many countries, "competition" exists in the form of the recycling of paper which in the end is too dirty for reprocessing (e.g. newsprint which is used first as wrapping matter and finally as toilet paper).

4.1.2 Auxiliary materials and additives

· Water:

Since the pulp and paper industry requires large quantities of water, there is competition with other sectors, e.g.:

- water for domestic and industrial use,
- agriculture (irrigation),
- other industries which consume water.

This can have a direct effect (surface water) or an indirect and delayed effect (well water). The competitive situation vis-a-vis agricultural and other businesses can be mitigated by appropriate wastewater treatment so that the water can be reused to a greater or lesser extent. However, all aspects of the possible salination of the soil must be taken into account here.

The availability of water is one of the most important factors in selecting a suitable site for a new mill.

The environmental impacts of other auxiliary materials and additives are not typical of the sector (chemicals, energy).

4.2 Areas not typical of the sector

Areas which are not typical of the sector but which are essential for the operation of a pulp and paper mill and concern mainly the infrastructure are simply listed here as an addition to the information given in the various texts (although this list is not exhaustive):

- water supply
- chemical industry, for alkaline chemicals (caustic soda, soda, aluminium sulphate, sulphuric acid, chlorine, sodium and hydrogen peroxide, sulphurous acids etc.) (in this connection refer to the Compendium of Environmental Standards)
- mineral oil industry, for fuel oils, lubricating oils, natural gas, LPG
- mining, for coal and possibly clay, limestone
- power stations, electricity transmission
- transport, roads, railway connections, waterways


- workshops for repair work and maintenance of mechanical and electrical machines and instruments
- general and technical colleges for the basic education of personnel
- hospitals, clinics, for medical care
- social areas.

There is therefore an interaction with many wider areas such as regional development, planning of locations, general energy planning, schools, health services, water supply and distribution planning, transport and traffic planning etc.

5. Summary assessment of environmental relevance

Given the state-of-the-art in the pulp and paper industry, and the technology developed or adapted for it in the field of recirculation, reduction or prevention of emissions which pollute the environment with proper operation monitoring, the following points can be made:

- With regard to wood as a renewable raw material, this industry is environmentally sustaining as long as the quantity of wood used is less, or possibly equal to the quantity growing to replace it. A further environmental protection feature arises with the processing of wood residues and waste (sawmill and brushwood) in pulp mills.
- In the case of annual plants the environmental impact is considerably less positive - the alternative use (fuel in the case of bagasse) involves replacement in the form of fossil fuels and therefore has negative impacts for the global CO2 balance, among other things.
- The still increasing use of waste paper as a raw material has generally positive environmental impacts: the processing of waste paper consumes less primary energy than fresh pulp and, overall, reduces the wood consumption per tonne of paper.
- Chemically produced pulp merits particular mention: in terms of both raw materials and energy, a modern production plant uses renewable feedstock (wood) only and therefore has no impact on the global CO2 balance.
- Aqueous emissions from pulp production are minimal in the case of unbleached pulp (as long as the mill is equipped with a recovery system), and the increasingly common replacement of chlorine and chlorine compounds as bleaching agents with chlorine-free media (oxygen and peroxide) already enables a large number of bleaching installations to comply with the relevant limit values.
- Aqueous emissions from paper manufacture can also be kept below the relevant limit values without difficulty by the use of water recirculation measures and highly efficient water treatment plants.
- Gaseous emissions from power station and recovery installations can be kept below limit values with the cleaning/scrubbing techniques developed. Odour emissions (mercaptans) are still a problem, particularly in the case of sulphate pulp factories. However, systematic collection and control measures in modern European plants are also achieving acceptable reductions below the (EPA) limit values in densely populated areas.
- Only a small quantity of solid waste is produced, and a large proportion of it can be used for energy (bark, wood waste). In the area of waste sludge disposal (incineration, dumping), attention must be paid to the problems of heavy metals from printing inks where mills use waste paper.
- The outdoor design of mills, normally applied in warmer climates, makes noise prevention measures more costly than in enclosed plants, thus noise nuisance can only be prevented by siting such mills further from residential areas.

In temperate and/or cold climates, the question of noise can easily be resolved by building design, insulation and process management (avoiding operating noise-emitting departments at night).

The early involvement of the population groups affected, particularly women, in the planning and decision-making process, means that their interests can be taken into account and helps reduce environmental problems (e.g. competition for the use of water, wood and land).

The implementation and monitoring of emission limit values and a generally environmentally oriented operation are only possible if the necessary control bodies are institutionalised and operate effectively. One option is to appoint industrial environmental protection officers, who should also be responsible for the training and further education of personnel and increasing the awareness of personnel for environmental matters.

6. References

W Brecht and H. L. Dalpke: "Wasser, Abwasser, Abwasserreinigung in der Papierindustrie".

Deutsches Wasserhaushaltsgesetz (WHG), Abwasserabgabengesetz (AbwAG) and the Bundesimmissionsschutzgesetz (BImSchG).

EPA (Environmental Protection Agency) "Effluent Limitations Guidelines and New Source Performance Standards for the Bleached Kraft, Groundwood, Sulfite, Soda, De-ink and Non-integrated Paper Mills Segment of the Pulp, Paper and Paperboard Mills".

NCASI, USA (National Council of the Paper Industry for Air and Stream Improvement), Bulletins (div.).

orm M 94 64.

Allan M. Springer: "Industrial Environmental Control, Pulp and Paper Industry".

SSVL Sweden (Sriftelsen Skogsindustriernas Vatten och Luftvardsforskning), The SSVL Environmental Care Project.

Appendix A: Tables

Table 1. 2. Basic Data Relating to Pulp



Yield as a % of raw material

Spec. energy consumption (kWh/t pulp)

Rel. chemical use in relation to raw material

Rel. pollutant output after process untreated,

Rel. environmental impact after treatment (a)


Annual plants


Annual plants


Annual plants


Annual plants


Annual plants


"mechanical" stock (wood pulp)





very low







Thermo-mech. pulp





very low







Chem. thermo- mech. pulp










Chem. mech. pulp



min. 930

min. 600








Semi- chemical pulp










low/very high (c)


Chemical pulp



very high


very high

very high

low/medium (b)

low/very high (c)


Waste paper stock






(a): state-of-the-art emission treatment
(b): noxiousness dependent on the type of bleaching chemicals: with or without chlorine
(c): dependent on the technical or economic feasibility of recovery or destruction of spent pulping chemicals

Table 2.2.1A Aqueous Emissions Pulp and Paper Mills Page 1

Sources/causes typical in sector

Substances emitted


Reduction measures (state- of-the-art) in mill

Degree of reduction (%)

Open water circuits

Large quantity of wastewater

Large treatment plant, high energy and chemical consumption

Closing of internal circuits

To approx. 80%

Undissolved substances from various sources/ careless process control

Organic fibre components and inorganic components (dirt), filler remains

Turbidity, color, oxygen consumption, smell

Division of process water flows, closing of circuits in mill, improved filtration

Varies depending on production type

Dissolved substances from pulp production and recovery

Ligno-sulphonates, other lignin decomposition products, crude tall oil etc., organic sulphur compounds, Na salts

Marked brown coloration, oxygen consumption (in part difficultly degradable), odour nuisance

Optimisation of process stages, leak prevention, recycling of leaked liquid

Up to 90%

Pulp bleaching

Decomposition products of lignin and hemicellulose, chlorinated organic compounds, Na and Cl salts

Oxygen consumption (in part difficultly degradable), discoloration, toxicity

Recycling of filtrates in plant, leak prevention, conversion to chlorine-free/ low-chlorine bleaching

Chlorinated compounds up to 100%, others only slightly


Organic compounds (methanol, ethanol, uncondensed gases)

High oxygen consumption, color, odour nuisance

Liquor stripping in/before condensation, combustion or separate processing of stripper gases

Up to over 90%

Table 2.2.1A Aqueous Emissions Pulp and Paper Mills Page 2

Sources/causes typical in sector

Substances emitted


Reduction measures (state- of-the-art) in mill

Degree of reduction (%)

Chemicals from waste paper pro-cessing

Printing ink components (in part containing heavy metals), dyes, processing chemicals, complex salts

Turbidity, oxygen consumption, toxicity (with heavy metals)

Closed circuit management (restricted), toxicity can be reduced indirectly by using printing inks without heavy metal components

Oxygen consumption low, toxicity high

Paper manufacture

Remains of chemical additives (dyes, brighteners, anti-foaming agents, retention and cleaning agents, fillers)

Turbidity, oxygen consumption (toxicity, if additive toxic)

As for waste paper

As for waste paper

Coating plant

Coating materials (latex, clay, emulsifiers, starch etc.)

Turbidity, oxygen consumption

Careful process management to prevent losses


Wastewater from secondary installations

Chemicals from water softening/ demineralisation, clarification salts etc.

Salt content



Table 2.2.1A Aqueous Emissions Pulp and Paper Mills Page 3

Sources/causes typical in sector

Substances emitted


Reduction measures (state- of-the-art) in mill

Degree of reduction (%)

Wastewater treatment plant

A) In the wastewater: oxygen-consuming substances (lignin and cellulose decomposition), dyes B) In treated sludge: organic and inorganic solids (incl. toxic components), products of bio-degradation

Turbidity, discoloration, oxygen consumption --

Mechanical (sedimentation, filtration, flotation), biological (aerobic, anaerobic) and possibly chemical (precipitation, adsorption with active carbon etc.) wastewater treatment Sludge incineration (possibly with flue gas scrubbing)

Colour: 95%, oxygen: up to around 60%, (pulp) and up to 95% (paper), colouring: up to 100% Over 90%

Table 2.2.1 B Examples of Quantitative Emission Values Aqueous emissions, pulp production, untreated

Table 2.2.1 B Examples of Quantitative Emission Values

Aqueous emissions, pulp production, untreated

Wastewater quantity m³/t

BOD kg/t

COD kg/t

ss kg/t

AOx kg/t


Wood pulp TMP CTMP SC C sulphate C sulphite

1) 2) 20 8 50 50 225 450

1) 2) 10-30 15-28 315) 10-20 40-605) 250-500* 60-200* *

1) 2) 3xBOD 3xBOD

1) 2)

3) 4) 1-2 5 0-0.2 5

Aqueous emissions, paper production, untreated

Graphic papers Newsprint MF writing and printing papers Industrial papers Common wrapping papers

25 80 70 180 0 50

1-2 0 3

0 - 3

10 40 30 80 0 10-30



*: no chemical recovery
* *: with chemical recovery
1) with water circuits largely closed in the mill
2) with water circuits largely open
3) with chlorinated bleaches largely avoided
4) with chlorinated bleach
5) value range SSVL (Sweden)
6) printing inks containing heavy metals can yield toxic sludges
TEF Toxicity Emission Factor

Table 2.2.2 A Emissions into the Air Pulp and Paper Mills

Table 2.2.2 A Emissions into the Air Pulp and Paper Mills Page 1

Sources/causes typical in the sector

Substances emitted


Reduction measures (state-of-the-art) in the mill

Degree of reduction (%)

Raw material crushing and cleaning (chopping of wood, straw etc.)

Organic dust

Fire risk constituting health hazard

Extracting of air and cleaning in cyclones (and/or filtering, recycling, burning or dumping of dust)

up to 100%

Waste gases from digesters, steaming out of equipment and vessels

Steam, turpentine, other HC compounds, SO2

Fire risk, odour nuisance, health hazard, acid rain

Condense steam and turpentine, recycle turpentine, burn residue, recycle SO2 in the process, scrub residual gases

99 +


Odour nuisance

Collect and burn TRS (cannot be condensed)

99 +

Fumes of spent liquor condensation plant

Steam, terpenses, methanol, TRS

Odour nuisance

Collect and burn gases

95 +






Acid rain

Absorption in alkaline gas scrubbers, recycling in process

99 +


Ozone formation

In development: noncatalytic conversion



Odour nuisance process

State-of-the-art process

99 +

Recovery boiler (waste gases)


Health hazard

Minimise by process



Greenhouse effect

Unavoidable, does not pollute global balance



Health hazard

Electro-filters, recycling in process

99 +

Table 2.2.2 A Emissions into the Air Pulp and Paper Mills Page 2

Sources/causes typical in the sector

Substances emitted


Reduction measures (state-of-the-art) in mill

Degree of reduction (%)






Acid rain

Use of S-free fuel oil or natural gas; in development: wood and bark gas

95 +


Health hazard

Minimise by process management


Lime kiln (waste gases)


Ozone formation

Reduction not yet state-of-the-art (cf. cement sector)



Odour nuisance

Minimisation possible by good process management

99 +


Health hazard

Electric filters and recycling in process

99 +





Steam boiler fired by bark or waste wood

CO2 and CO

Greenhouse effect, health hazard

Unavoidable, but does not affect the global balance, minimisation by process management

(waste gases)


Greenhouse effect, health hazard

Minimisation by process management

as above


Ozone formation

In development: conversion from non-catalytic to catalytic




Furnaces to destroy sludges and residues


Greenhouse effect, health hazard

As above, minimisation by process management

as above


Ozone formation

Currently not state-of-the-art


Health hazard

Scrubbers, cyclones, dump

Table 2.2.2A Emissions into the Air Pulp and Paper Mills Page 3

Sources/causes typical in sector

Substances emitted


Reduction measures (state- of-the-art) in mill

Degree of reduction (%)

Fumes of bleaching towers, bleach preparation, chlorine transport

Chlorine Chlorine dioxide SO2

Health hazard " "

Extract fumes and wash in scrubbers, return to process

Up to 100

Waste air from transport equipment for raw materials and products

Motor exhaust NOx, CO, HC, CO2

Health hazard, atmospheric effects

Catalysts, diesel operation with soot filters, use of electric vehicles where possible

Up to 90

Paper dryer, paper machine (ditto coating and laminating machines)





Organic solvents

Health hazard

Gas scrubbing, carbon filters with recovery, also use of water-soluble auxiliaries

Up to 95

Processing of additives, waste air from vacuum pumps





Waste air from transport equipment for raw materials and products

Motor exhaust, NOx, CO, HC, CO2

Health hazard

Catalysts, diesel with soot filters, use of electric vehicles where possible

Up to 90

Table 2.2.2B Emissions into the Air Typical for the Sector, State-of-the-Art, Limit Values

Table 2.2.2B Emissions into the Air Typical for the Sector, State-of-the-Art, Limit Values



State-of-the-art mg/Nm3

Typical limit values mg/Nm3


- Power boiler - Absorption plant, Mg, Ca bisulphite and magnefite process - Lime-burning kiln - Smelt-dissolving tank

less than 50 less than 50 less than 50 less than 50

50 (orm) 50 (orm) 50 (orm)


- Power boiler - Absorption plant, Mg, Ca bisulphite process - Ditto magnefite process - Lime-burning kiln with TRS burning

less than 50 less than 250 less than 250 less than 400

400 (orm) 700 (orm) 300 (orm) 400 (orm)


- Power boiler - Lime kiln

less than 100 less than 250

cf. TA-Luft generally: oil-fired: 170 solid fuel: 250

Organic C

- Lime kiln

less than 50

150 mg/m3 (TA-Luft)


- Power boiler - Lime burning kiln

less than 200 less than 900

400 mg/m3 HMW (LRV-K, 1989) (1,500 TA-Luft, rotary kiln for lime)


- Power boiler - Lime-burning kiln - Smelt-dissolving tank

less than 5 ppm V less than 8 ppm V 8.4 g/t BLS

5 ppm V (EPA) 8 ppm V (EPA) 8.4 g/t BLS (EPA)

Inorganic Chlorine/ Chlorides

- Bleaching plant - Chemical processing

Cl2 and CL: less than 10 mg/m3

Cl2: 5 mg/m3 (TA-Luft Cl: 30 mg/m3 as HCl (TA-Luft)

HMW: Mean hourly value LRV: Luftreinhalteverordnung (ordinance on clean air)

Table 2.2.3 Solid Waste Pulp and Paper Mills

Table 2.2.3 Solid Waste Pulp and Paper Mills Page 1

Sources/causes typical in sector

Substances emitted


Reduction measures (state- of-the-art) in mill

Degree of reduction (%)

Raw material transport and preparation: Wood

Bark Wood shavings

Space required

Burning for energy generation

> 95


Binding wire


Collection, compacting, scrap trade


Pulp cleaning

Knots, bundles of fibre, sand

" "

Incineration for energy generation, dumping

> 95 0

Quality Control

Rejected product


Return to process

> 85

Chemical recovery, removal of foreign ions

Lime sludge* or lime Sulphate soap**

Ground water pollution Process problems

Recycling in lime- processing industries, dumping Recycling as raw material for chemical works

0 - 80 Up to 100

Waste paper treatment

Iron wire, plastic film, string

Space required



Waste paper de-inking

Printing ink sludge (may contain heavy metals)

Ground water contamination

Incineration or special dump

Up to 85

* in sulphate and soda pulp mills ** ditto for softwood

Table 2.2.3 Solid Waste Pulp and Paper Mills Page 2

Sources/causes typical in sector

Substances emitted


Reduction measures (state- of-the-art) in mill

Degree of reduction (%)

Water and wastewater treatment

Fibre sludge, inorganic sludge, biological sludge

Space required

Recycle or burn fibre sludge

Up to 85

Dump inorganic and biological sludge, under certain conditions also use for soil improvement


Wear of consumables

Metal, plastic screens, synthetic textiles (felts), lubricants, cleaning agents

Space required

Return to manufacturer for recycling, dump, burn


Mill maintenance

Defective machine parts Packaging material

Return to manufacturer for recycling, (scrap), burn or dump


Table 3.1.1 Methods of Wastewater Analysis and Possibilities for Reducing Environmental Impact

Table 3.1.1 Methods of Wastewater Analysis and Possibilities for Reducing Environmental Impact Page 1

Pollutant/ properties


Analysis method

Methods for elimination or reduction


Undissolved substances


DEV H2, SM 148, 224

Mechanical treatment, flocculation, biol. treatment


Substances which can be precipitated


DEV H2, SM 224, z x/1/76

Mechanical clarification, flocculation, biol. treatment


Suspended matter


Difference from 1 and 2

Flocculation (filtration), biol. treatment



cm visibility

DIN standard 38 404-C2, SM 163, 232

Flocculation (filtration), biol. treatment



DIN standard 38 404-C1, SM 118, 206

Flocculation, coagulation, flotation




DIN standard 38 404-C4, SM 162

Cooling (towers, lagoons, trickling filters)



DEV B1/2, SM 136, 217



DEV C5/S5, SM 144, 221





DEV C8, SM 154, 226

Table 3.1.1 Methods of Wastewater Analysis, and Possibilities for Reducing Environmental Impact Page 2

Pollutant/ properties


Analysis method

Methods for elimination or reduction


Total, evaporation, and incineration residue


DEV H1/S3, SM 148, 224



mgO2/ l

DEV H5, SM 141, 219 DIN 38409-H91

Biodegradation, aerobic, anaerobic



mgO2/ l

SM 142, 220 Z x/2/76 DIN 38409-H41 and -A30 ARAVwV1) no.303

Biodegradation, aerobic, anaerobic


Total organic carbon, TOC


SM 138



mgO2/ l

DEV G2/J8, SM 140, 218


Total nitrogen, organic


DEV H11, H12

Biodegradation, aerobic, anaerobic






Oils, fats


DEV H17, H18 SM 137, 209



Lignin, tannin


SM 160






Organic poisons


SM 139


Table 3.1.1 Methods of Waste Water Analysis, and Possibilities for Reducing Environmental Impact Page 3

Pollutant/ properties


Analysis method

Methods for elimination or reduction




ARAVwV no.108




ARAVwV no.106/107, 202




DIN standard 38409-H14, ARAVwV no.302


Chloride etc.


DEV D5-7, D15, J7, SM 156 - 158, 228

Ion exchange, ultra-filtration, rev. osmosis


Nitrate, nitrite


DEV D9-10, E5 SM 131-135, 212-216

Biological decomposition


Heavy metals


SM 211, ARAVwV no.207 (Ca) no.209 (chromium)/214 (Ni)/206 (Pb)/213 (Cu)/215 (Hg)



Na+ etc.


DEV H13-15, SM 126, 147, 153

Ion exchange, ultra-filtration, rev. osmosis


Toxicity and biodegradability

DEV L2-3


Population equivalent



Toxicity to fish

TF**, %, TEF*

DEV L15, SM231 DIN standard 3842-L20, ARAVwV 401


Biological/ ecological water inspection (water quality classes)

DEV M1-7, SM 601-606

DEV: Deutsches Einheitsverfahren [German standardisation procedure]

SM: Standard methods (APHA)

Z: Zellcheming code of practice

1) ARAVwV: Appendix to the Rahmen-Abwasser-Verwaltungsvorschrift of 08.09.1989 [General Administrative Framework Regulation]

* TEF: toxicity emission factor ** TF: toxity to fish

Table 3.1.2A (Minimum) Wastewater Requirements (specific) As at January 1990 in Germany

Type of pulp or paper

COD kg/t max. 2)

BOD kg/t max.

BOD mg /l

AOX kg/t max.

Toxicity to fish TF max.

Substances which can be precipitated ml/l max.

Pulp (generally)





Paper: writing and printing papers, depending on type

5 - 7

0.7 -6



0.5 0.5

Based on waste paper









2) Tonne, air dry = 0.9 t absolutely dry

**) Not applicable to dissolving pulp until 31.12.1992

Table 3.1.2b Pollutant Units for the Measurement of Wastewater Discharges in Germany


Pollutants and pollutant groups assessed

The following units of measurement are equivalent to one pollution unit in each case

Threshold values by concentration and annual quantity


Oxidizable substances in chemical oxygen demand (COD)

50 kilograms oxygen

20 milligrams per litre and 250 kilograms annual quantity



3 kilograms

0.1 milligrams per litre and 15 kilograms annual quantity



25 kilograms

5 milligrams per litre and 125 kilograms annual quantity


Organic halogen compounds as adsorbable organically bound halogens (AOX)

2 kilograms halogen, calculated as organically bound chlorine

100 micrograms per litre and 10 kilograms annual quantity


Metals and their compounds:


5.1 5.2 5.3 5.4 5.5 5.6

Mercury Cadmium Chromium Nickel Lead Copper

20 grams 100 grams 500 grams 500 grams 500 grams 1,000 grams of metal

1 microgram 5 micrograms 50 micrograms 50 micrograms 50 micrograms 100 micrograms per litre

100 grams 500 grams 2.5 kilograms 2.5 kilograms 2.5 kilograms 5 kilograms annual quantity


Toxicity to fish

3,000 cubic metres of wastewater divided by TF

TF = 2

TF is the dilution factor at which the wastewater is no longer toxic in the fish test.

Appendix B: Glossary

Absolutely dry also called "oven dry" (= b.d. bone dry)

AP Waste paper

APHA American Public Health Association

APMP Alkaline peroxide mechanical pulp (special form of CTMP).

BLS Black liquor solids.

Brightness Measure of the "whiteness" of the paper, expressed as a percentage of "absolutely" white = 100% light reflection under blue light of a certain wavelength. Very bright papers have a brightness of 85 - 90%, newsprint around 60 - 65%.

Corrugating medium Relatively strong paper for the corrugated central layer of corrugated board.

De-inking Removal of printing inks from printed waste paper.

Dissolving pulp High quality chemical pulp for further chemical processing (films, fibers, etc.)

EPA The Environmental Protection Agency, USA.

"Fresh" pulp "Virgin" pulp obtained from the various raw (wood, etc.) fibre materials (as opposed to waste paper pulp).

Lime burning kiln Installation for chemical recovery in sulphate and soda pulp mills for the regeneration of burnt lime for the reprocessing of dissolving chemicals.

Mg and Ca bisulphite Chemical pulping process.

magnefite process

Refiner Grinding machine for the pulping and fibrillation of fibrous raw materials. Mostly disc refiners with toothed or grooved counter-revolving discs at low adjustable distances.

Rigidity Resistance to bending and folding of paper and board. Important for pressure loads where used for packaging purposes.

Shelf life Generic term for paper and board which concerns resistance to light, moisture and resistance to heat.

Smelt-dissolving tank Dissolving tank for ash from black liquor burning (sulfate process).

Strength For paper and board, a non-scientific generic term for tensile strength (breaking length), bursting strength, folding coefficient, edge tearing resistance.

TRS Total reduced sulphur, generic term for H2S and organic compounds with bivalent sulphur, e.g. mercaptans. Usually have an unpleasant odour at the tiniest concentrations.

Yield Ratio of quantity of product (absolutely dry) to quantity of raw material (absolutely dry) expressed as a percentage. Because in the trade, pulp is calculated at 90% dry matter content (10% moisture, called "air dry"), the yield can also be given on this basis. Vegetable raw materials contain from around 30% (for straw) to around 50% (for wood) pulp; yields are limited by this.

1. Scope

1.1 Terminology

A "textile mill" is generally defined as an industrial production plant which processes materials which can be spun, such as fibres, threads, yarns, twines, fabrics, knitted fabrics, fleeces, felts, synthetic skins and such like.

The "clothing" industry further processes the majority of products from the textile industry, but this environmental brief only considers the "textile industry".

1.2 Raw material

The textile industry originally processed exclusively natural, and for the most part indigenous raw materials obtained from both plants and animals (plants: cotton, flax, sisal, ramie, jute; animals: wool, silk, hair). However, the proportion of synthetic fibres (regenerated cellulose fibres such as synthetic silk, viscose staple fibre from wood and cotton waste, and later fully synthetic fibres such as polyamide, polyacrylic and polyester fibres, the raw material for which is petroleum) of the total fibre demand is on the increase throughout the world. In 1990, the chemical fibre industry covered some 45% of the worldwide demand for textile fibres, standing at 42.9 million tonnes.

Chemical fibre manufacture and its attendant environmental problems are not the subject of this environmental brief as it is in fact part of the chemical industry.

1.3 Production stages

1.3.1 Fibre conditioning

All natural fibres are polluted with extraneous matter and substances, and first have to be rendered "spinnable" by conditioning processes, some of which are expensive. By far the majority of natural fibres are produced in tropical or subtropical countries, not the industrialised world. This is where primary conditioning is also carried out, involving, for example:

- cotton ginning
- degumming of sisal, hemp and flax
- unreeling and degumming of silk and
- washing of wool.

Natural fibres are now being produced on a large scale, i.e. in "agrarian factories", characterised by single-crop agriculture. The problems which inevitably ensue (uprooting of new farmland, terracing, prevention of reforestation by overgrazing etc., social problems) must be taken into account when siting and planning such facilities.

1.3.2 Spinning and yarn production

Yarns/threads/twines are manufactured in specialised spinning mills according to the raw material and intended future use: cotton or 3-cylinder spinning mills, worsted, woollen and bast fibre spinning mills etc., the first of these being the most commonly used type. Indeed, over the last two decades, it has become firmly entrenched alongside the traditional OE rotor spinning process (OE = open end) as it produces considerably more cheaply, especially in the case of coarser yarns.

All spinning mills operate more or less on the basis of the same process: the fibrous material is (where necessary) further cleaned, aligned and, while being stretched and rotated about its axis, spun to a thread. Some of the yarn produced in this way is then twisted, i.e. two or more threads are combined by rotation to form a "twisted" yarn.

The finished yarns are today supplied to the subsequent processing stages in the form of so-called cheeses, i.e. bobbins weighing between 0.8 and 3.5 kg.

1.3.3 Weaving and knitting mills

Of these textile production techniques, weaving is by far the most important. It involves the production of a fabric from a set of threads aligned in one direction, called the "warp", by interlacing "weft" threads at right angles to it. Considerable technical improvements have been made to the looms used for this purpose in the last twenty years, resulting in a marked increase in productivity.

One particular feature of the production of woven fabrics is sizing. For certain articles one of the two thread systems, the warp, must be protected by a kind of glue coating, which involves "sizing" the warp threads with a protective coating - e.g. modified starch or a synthetic polymer - by immersion.

Unlike woven goods, knitted products have only one thread system, i.e. the threads which are made into a mesh run diagonally or longitudinally. The items are produced on linear or circular knitting or hosiery machines or warp knitting machines.

1.3.4 Textile finishing

The term textile finishing covers the bleaching, dyeing, printing and stiffening of textile products in the various processing stages (fibre, yarn, fabric, knits, finished items). The purpose of finishing is in every instance the improvement of the serviceability and adaptation of the products to meet the ever-changing demands of fashion and function.

Finishing processes can be categorised into purely mechanical and wet processes. The liquid phase for the latter type is primarily water, and - to a lesser extent - solvents and liquefied ammonia gas. Another important medium is steam. To achieve the desired effects, a range of chemicals, dyes and chemical auxiliaries are used.

Compared with textile production, textile finishing mills are generally smaller, offer a more diverse range of services and are less automated.

1.4 Mill sizes

1.4.1 Spinning mills

Spinning mill capacities are expressed in terms of "spindles" or "rotors", i.e. the number of these units installed. For purposes of comparison, one rotor equals approximately 3 - 4 spindles.

In the Federal Republic of Germany, cotton spinning mills have an average of 13,000 spindles and 1,100 rotors with 150 employees, while the figures for worsted/woollen mills are some 9,500 spindles and 120 employees.

In raw-material-producer countries mill sizes generally far exceed the average values stated above (up to 120,000 spindles/mill).

1.4.2 Weaving and knitting mills

Weaving mill capacities are normally expressed in terms of the number of looms.

In the Federal Republic of Germany the average mill size is 46 looms and 106 employees. Weaving mill projects in raw material producer countries are mainly for far larger units with up to 2,000 looms/mill.

In knitting mills, the number of installed production units gives no direct clue to production capacity because, in addition to piece goods sold by the metre, a wide range of finished goods (outer wear and underwear, hosiery etc.) is manufactured.

Capacities are therefore expressed in a number of ways according to product type: in tonnes (yard ware), 1,000 units (outer wear and underwear), 1,000 pairs (hosiery) or 1,000 m² (curtains). In 1991, the average mill size in the Federal Republic of Germany was 91 employees.

1.4.3 Textile finishing

Depending on the type of products finished, finishing capacities are expressed in t/year (fibre, yarn, knitted goods), million m²/year (fabric) or 1,000 items/year (ready to wear articles).

In the Federal Republic of Germany, the average production output for the total of 320 mills in the sector was calculated to be 2,500 t finished goods/mill and year in 1990 with an average of 116 employees per workshop.

Large mills in the USA and in Asia can have capacities of up to 50,000 t/year.

1.5 Site issues

In textile industry projects particular attention must be paid in all cases to the large quantities of water required for the finishing operations, which is why appropriate disposal facilities must naturally be provided for the process water.

With increased automation the space required by textile mills has declined. New mills have a more compact structure for shortening transport distances, among other things. The land requirement for a medium-sized vertical mill, including yard and access route areas and infrastructure systems with expansion options, is some 60,000 m².

2. Environmental impacts and protective measures

2.1 Fibre conditioning

Before they are processed, all natural fibres must be conditioned. This involves the removal of all manner of extraneous matter.

The by-products of conditioning (cottonseed and linseed, wool fat, silk gum) are in some cases commercially viable substances, and dry waste can in theory be returned in the soil as fertiliser, although another method of treating it is to compost it. A large proportion of the "waste" produced when native fibres are cleaned may therefore be regarded as commercial commodities, although all this requires additional treatment.

With regard to emissions, only cotton ginning and raw wool washing are of special significance.

Only about one third of the weight of a cotton boll is in the form of spinnable fibres. When the cotton is ginned (cleaned) - an operation normally carried out in situ - cotton seeds are obtained as a by-product, from which cotton seed oil and meal are produced. Another by-product is known as linters, which are used amongst other things in the manufacture of synthetic silk and viscose (spun rayon). The actual husks and waste constitute some 15% of the weight of the cotton boll and can be ploughed back into the soil.

Ginning is a dry, mechanical process which generates considerable noise and quantities of dust. While the latter of these two problems can be greatly relieved in modern mills by the use of extractor and filter systems, the wearing of ear protection is absolutely essential to combat the former.

Emissions from raw wool washing are far more problematic. In contrast to cotton ginning, raw wool is washed centrally in large industrial facilities remote from the place where the wool is obtained. The operation yields between 300 and 600 g attendant material per kg of washed wool. In addition to the wool fat which is a saleable commodity per se, being used for technical and cosmetic purposes, biocides and the like from sheep’s wool are present in the washing water. Raw wool washing may therefore be regarded as one of the major wastewater pollution problems in the textile industry.

Today, wool fat is generally extracted before the wastewater is discharged.

A further factor to be considered is that complex purification plants are used to condition the still highly polluted wastewater (COD around 15,000) so that it can be discharged into the drains (on the subject of wastewater purification, see also the environmental brief Mechanical Engineering, Workshops, Shipyards and Wastewater Disposal).

2.2 Spinning and yarn production

Because of the high spindle speeds reached on new machines (ring spindles up to 20,000 rpm, rotor up to 110,000 rpm), spinning mills can generally be assumed to generate a great deal of noise.

Noise levels of 70 to 100 dB(A) are commonly recorded in work rooms.

As the spinning process calls for a specific room climate, i.e. temperature and relative humidity, which must be as constant as possible and not affected by time of day or night, or season, practically all spinning mills today are fitted with powerful air-conditioning systems. To limit the cost of air-conditioning, the production plant must be well insulated against external temperature changes. In the sixties and seventies this led to a windowless architecture for textile mills with extremely good values for insulation against temperature variations and against noise.

Since the eighties, windowless designs have been frowned upon by the building authorities in the light of the physiological and psychological problems caused to employees. To improve workplace design fields of vision of around 2 to 5% of the floor area of the workrooms must be provided, and special glazing is needed for this.

The high mechanical stress on fibres during the spinning process results in the production of considerable quantities of dust, which must be carefully extracted for industrial safety reasons and in order to keep the product clean. Emissions can be prevented and dust extracted by means of special machine enclosures and extraction systems and via the air-conditioning system which keeps the air in the rooms circulating. Air is not reintroduced until it has been passed through automatic filter installations. The filter dust is not dangerous and its disposal is therefore not a problem.

2.3 Weaving and knitting

Although considerable progress has been made in the weaving sector over the last twenty years, the whole area of noise nuisance and, closely associated with it, vibrations coming from looms, cause major problems.

Noise levels of 85 to 107 dB(A) must be expected in weaving rooms, according to the design, type, fitting, erection and number of looms used, fabric structure, building type and size etc. The vibrations transmitted from the running looms to the building can, under certain circumstances, cause a nuisance to the local population and damage to nearby buildings, and to avoid this special vibration absorbers are now provided. Generally speaking, the comments made about noise and dust emissions with regard to spinning mills apply here too.

The sizing of warp threads in weaving mills gives rise to emission problems.

Natural substances such as starch and cellulose products and synthetic products such as polyvinyl alcohol, acrylates, PVC, oils and fats are used as sizing material.

The evaporation fumes produced during the drying stage consist mainly of steam. The small amounts of sizing agents contained are not regarded as environmental pollutants.

On the other hand the sizing liquor may no longer be discharged into wastewater in Germany as it is a "concentrate" according to Anhang 38 [Appendix 38] to the Rahmen-Abwasserverwaltungsvorschrift [General Administrative Framework Regulation on Wastewater].

However, the sizing coating itself has much more serious repercussions in the subsequent textile finishing stage where the size first has to be completely removed. In finishing works which handle primarily woven goods, up to half the wastewater pollution may derive from dissolved sizes during washing.

There is currently a trend in the USA towards the use of sizing agents which can be recycled; this aids the work of the finisher in terms of disposal, and also saves up to 90% of sizing agent due to recycling. In Europe, where the textile industry, in contrast to the USA, is largely horizontally structured, this trend has yet become established. From the point of view of recycling, which is attracting increasing economic interest, this could provide a certain environmental benefit in the woven products sector.

Emissions in the knitting industry are substantially lower than in the weaving sector, with noise levels of around 77 to 90 dB(A), and dust and vibration emissions are a rarity. More problematic are the slip agents applied to the yarn which, as in the case of the warp sizes, only appear at the textile finishing stage, where they pollute either the wastewater (from washing) or the waste air (in thermofixing).

2.4 Textile finishing

In contrast to textile production, noise plays only a very minor role in textile finishing. On the other hand odour emissions are generated from drying and thermofixing processes, and particularly wastewater pollutants, which transfer into the water during cleaning and the various textile finishing processes. The textile finishing industry both consumes relatively large quantities of water and generates large quantities of wastewater.

Only general comments can be made about water consumption in the finishing stage (see table 1), as this is determined not only by the type of fibres processed, but also by the article, type and extent of finishing, as well as the technology applied (continuous/discontinuous process) and batch size structure. For the textile finishing industry in the Federal Republic of Germany the latest figures of the TVI-Verband for 1988 set the specific water consumption at 120 l/kg goods (3).

Table 1 - Water consumption in the textile industry (amended per (1))

Fibre type/make-up

Mean water consumption in l/kg material


by fibre type


50 - 120


75 - 250

synthetic fibres

10 - 100


by make-up


100 - 200


80 - 120


0 - 400

2.4.1 Wastewater contamination

If textile finishing mills are sited in the catchment area of efficient municipal sewage works, textile wastewater should preferably undergo mechanical biological treatment before being fed to these works and discharged into the drains (indirect discharge). If this option is not provided, and the wastewater therefore has to be discharged directly into the drains, it must first be treated in the mill’s own treatment plant to meet legal requirements (direct discharge). (For more detailed information on the requirements applicable in Germany, see 3.3).

Although most of the substances in the wastewater are biodegradable, discharges into open drains can in some circumstances, during the biological decomposition stage, reduce the oxygen content of the drain water to below the level required for a healthy water quality and lead to fouling of the water.

The textile finishing industry also uses a range of compounds which are not biodegradable per se.

Below, we look briefly at the following types of wastewater pollution:

For dyes and many surfactants which do not degrade readily (but which are increasingly being replaced by more easily biodegradable ones), the said mechanical biological treatment is inadequate if there is insufficient biomass to absorb the dyes (the bonding of excess sludge to bacterial protein is the principle method by which water-soluble dyes are eliminated, see also 3.3). Past experience has shown that a combination of physico-chemical and biological wastewater treatment is required in most cases to achieve a satisfactory treatment level, with a facility for treating heavily polluted partial flows (e.g. dye liquor) separately.

· Settleable solids

The values normally found in the wastewater relating to settleable solids are subject to enormous fluctuations; they are dependent on a number of factors such as finishing process, fibre type, fibre make-up and whether batch or continuous treatments are used. Sometimes the undissolved substances remain in suspension and cannot simply be filtered off. Most values should be below 50 ml/l.

· Heavy metals

The pollution of textile wastewater with heavy metals is limited by the current state-of-the-art. Cadmium is hardly ever present and mercury is present only insofar as it is introduced via soda lye and hydrochloric acid (manufactured with mercury electrodes). Chromium, cobalt and copper may penetrate the wastewater from a number of dyeing processes, and zinc from more sophisticated finishing processes (wash and wear cotton articles) (zinc in the lower milligram range, the others mostly under 1 mg/l).

· Hydrocarbons

Hydrocarbons are more serious pollutants. They derive mainly from yarns which are coated with oil to give them the right slip properties, and to a lesser extent from the residues of sizing agents (impregnation).

· Organic halogen compounds

Other serious pollutants are chloro-organic compounds. The AOX total parameter (adsorbable organic halogen compounds) introduced for wastewater covers a spectrum of substances which are hardly comparable in terms of their ecological and toxicological properties (highly volatile chlorinated hydrocarbons, PVC, non-toxic green pigments, toxic chlorophenols etc.).

Sources for the AOX total parameter are primarily chlorinated bleaches, anti-felting finishing of wool, dye accelerators (carriers) used to dye synthetic fibres, chlorinated reactive dyes and solvent soaps with solvents from the chlorinated hydrocarbon range (per), which are incidentally also used as the sole "dry cleaning" agent for degreasing polyester articles.

The number of compounds used which are regarded as particularly environmentally pollutant has already fallen considerably. Whereas up to 5% carrier (colour accelerators for polyester fibres), based on product weight, was previously used, dyeing is now carried out mainly in high-pressure installations where only around 0.5% carrier is needed, basically as a precautionary measure, and even then only aromatic ester-based substances are used.

Pentachlorophenol (PCP), formerly used occasionally as a preservative for heavy fabrics, has been banned since 1986. However, products of a similar composition are used with native fibres, frequently from the range of pesticides manufactured; examples of such products are chlorinated phenoxyacetic acids, hexachlorocyclohexane, DDT and allied substances.

· Surfactants/detergents

An equally serious pollution problem is posed by surface-active agents, called surfactants or detergents, which are used as washing, emulsification and wetting agents, as adjustment agents for dyeing processes, as auxiliaries to improve smoothness and softness and for a range of other purposes, and to a far larger extent as dyes, and which in some cases are not fully biodegradable either. However, in the Federal Republic of Germany and other central European countries, a minimum 80% degradability under the conditions prevailing in treatment plants is required for products used specifically as washing agents. Since this ban has been imposed there has been a definite improvement in water quality.

Surfactant water pollution is due not only to its organic load, but also its surface-active action, which on the one hand hampers the self-purifying capacity of rivers and on the other causes problems for the micro flora and fauna, and fish.

· Colour

Water-soluble dyes are a further environmental pollutant specific to the textile finishing industry. If heavily coloured - something which cannot generally be determined in textile effluent after biological treatment - the light reaching plants is reduced. If wastewater from dyeing plants constitutes 20% or less of the municipal wastewater to which it is added, a mechanical biological treatment plant is generally able to bind this dye content to the excess sludge (by a sort of dyeing process) and then degrade it in the digestion tower.

Where this is not the case, substantial quantities of dye may pass through the treatment plant into the outlet and cause a perceptible coloration of the drain water.

Now that certain limit values for the density of colour of textile wastewater have been specified in Anhang 38 (appendix 38) of the Rahmen-Abwasser-VwV [General Administrative Framework Regulation on Wastewater], this wastewater now requires additional decolouring in some cases.

A partially anaerobic treatment stage, comprising the addition of ferrous (II) salts in conjunction with lime, active carbon biology and, more recently, processes using membrane technology (ultra-filtration, reverse osmosis) have proved to be effective processes. In special cases, partial dye recovery and process water recycling are possible in conjunction with membrane technology.

· Water temperature

Wastewater temperature is another major form of pollution. In dyeing processes, so much hot water is discharged that, in the absence of any counter-measures, total wastewater temperatures may exceed 40°C, even though 35°C is the maximum permissible temperature. In many cases this heat can be recovered in heat exchangers, then returned to the process.

· pH

A pH of between 6 and 9 is prescribed for wastewater discharged from treatment plants in the Federal Republic of Germany, as in most other European countries.

Because partially acidic and partially alkaline wastewater is produced in the mill, according to the treatment stage and process, a balancing tank to hold around 50% of the daily wastewater quantity is normally required by the approving authorities. Following a partial mutual neutralisation of the various flows, the wastewater is routed from here to the wastewater plant at a fairly balanced pH and at a constant quantity.

While wastewater from wool processing plants generally has excess acidity, which requires to be buffered with alkali, the pH of wastewater from cotton processing plants is usually in the alkaline range. In this case the simplest, and at the same time, most environmentally friendly method of neutralising the wastewater involves the use of flue gas.

· Major incidents

In principle major incidents may only be expected as a result of negligence, and a useful preventive measure is to appoint an "industrial water pollution control officer".

In some of the German Federal states, Abwasser-Eigenchungsverordnungen [AbwEV - wastewater self-monitoring ordinances] have been issued which oblige businesses in the textile finishing industry to fit control and measuring installations to keep an internal record of certain wastewater parameters and to report major incidents (27).

2.4.2 Gas and steam emissions

Gas and steam emissions are generated by textile finishing processes when fumes penetrate the exhaust air during the dyeing and drying operations, although these more general operations do not present any real environmental pollution hazard. Table 2 provides an overview of the main sources of exhaust air emissions in textile mills.

Exhaust air from the thermofixing of synthetic fibre articles is not only more unpleasant but also more noxious, for it entrains oligomers of fibres and fragments of smoothing agents (including ethylene oxide) which may constitute up to 0.2% of the weight of the goods. Heat recovery installations - which are a must in all cases for energy reasons - arrest a considerable proportion in the form of a fatty condensate, but these substances nonetheless penetrate the wastewater during the cleaning operation (high-pressure cleaners).

Formaldehyde, which makes the eyes water and irritates the skin, may be produced in connection with the high-grade finishing of cotton articles, but formaldehyde pollution has been dramatically reduced with the introduction of modern, low-formaldehyde, etherified products, which were also required due to the effects on pregnant women.

In Europe, an increasing number of plants are resorting to thermal and/or catalytic afterburning to treat exhaust air from tenters, and all organic substances are therefore combusted to form CO2, CO and NOx.

A further source of gas and fume emissions are coating installations, which yield solvents. There is a simple remedy - provided that chlorohydrocarbons are not used - that of elimination via the combustion air in the boiler plant.

In Germany, the requirements of the 2. BImSchV [Second Ordinance on the Implementation of the Federal Immission Control Act] apply to all the above-mentioned emissions. The plants concerned must be monitored on the basis of emission measurements.

2.4.3 Noise emissions

No significant noise is emitted in the textile finishing industry other than from the ventilation units commonly found elsewhere.

2.5 General impacts on the environment

In addition to textile-specific emissions which are the real object of this brief, forms of environmental pollution which are also found in many other branches of industry can occur.

· Furnace installations

Thermal energy consumption is relatively high, particularly in the finishing stage (~ 13 kWh/kg goods). The firing power from the boiler plant required for process heat (steam, hot water) and for space heating usually lies within the range of 6 - 10 MW (9 - 15 t steam/h). Moreover, because of the high energy efficiency in plants which need power and heat energy simultaneously, power/heat couplings are used. The environmental brief Thermal Power Stations contains further environmental information about these installations.

· Water treatment plants

A certain quality of process water (i.e. it must not contain iron or manganese, it must be not very hard but must be clear) is required for textile finishing (washing and dyeing processes) - a quality which is not often attained in surface, spring or tap water. The rinsing wastewater deriving from regeneration in treatment plants generally has a high salt content and must be fed to partial or complete treatment plants with the process wastewater.

· Traffic

Goods traffic: The large material turnover results in a constant stream of goods traffic for supplying raw materials, taking away finished goods and for transport within the plants from one processing stage to another.

Passenger traffic: Textile factories often operate a two to three shift system, and times of shift changes can result in traffic jams and other problems.

Reference is made to the environmental briefs Planning of Locations for Trade and Industry, and Transport and Traffic Planning, for information on environmental impacts and environmental protection measures.

· Socio-economic and socio-cultural factors

These days, plants for cloth manufacture, i.e. the textile production stages of spinning, weaving, knitting and finishing, are capital intensive operations. (In contrast to subsequent processing in the garment industry, where the wage bill accounts for a high proportion of costs.)

The high capital input means that the machines must run, especially in the spinning and weaving sector, in 3-shift and sometimes even 4-shift operation around the clock, and in many areas at the weekend too. In an average vertical operation, i.e. with a spinning mill, weaving mill and finishing section, and with a production of about 6 million running m/year, about 300 people are now employed in three shifts in industrialised countries.

The proportion of women employed has declined sharply, but traditional family structures are nonetheless greatly affected by multiple shift operation. Furthermore, the personnel structure has been moving in the direction of trained industrial workers, and constant further training is necessary even for supervisory personnel.

The legislative framework and options for the enforcement of provisions in individual countries have a substantial influence on the impacts a textile mill has on the environment.

On the one hand there are statutory regulations and their enforcement for clean water, air and soil and for the rational use of energy, and on the other there are regulations to meet the requirements of the employees in terms of working conditions. Due mention should also be made of environmental and industrial safety provisions which are inadequate or simply do not exist, excessive working hours, low pay levels and child labour. These factors all have an influence on the quality of life of those directly affected, and the economic situation of the textile industry generally.

3. Notes on the analysis and evaluation of environmental impacts

3.1 Air pollution control

Over a long period the fine dust in cotton mills can trigger damage to the respiratory tract and the lungs, resulting in a disease called byssinosis. For this reason industrial countries prescribe maximum dust concentrations, but these vary from country to country and are also measured and assessed by different methods (maximum occupational limits - MAK values) in the FRG and the OSHA rules in the USA), e.g.:

- Germany, Switzerland: 1.5 mg per m3 total dust content
- USA, Australia: 0.5 mg per m3 fine dust

Netherlands: 15 µm in the preliminary works 0.2 mg per m3 fine dust in the spinning mill

- Great Britain: 0.5 mg per m3 total dust
- Sweden: without fibres.

In Germany, the TA-Luft [Technical Instructions on Air Quality Control] (2) applies to the operation of furnace plants, and more recently also to drying plants (tenters), i.e. there is an approval obligation. Similar regulations apply in some other European countries too.

For other mostly gaseous substances which constitute a health hazard, the occupational limits of the Deutsche Forschungsgemeinschaft (German Research Foundation) are applicable.

Table 2 - Main sources of waste air emissions in textile finishing operations

Process/make-up Substrate

Substances emitted


Drying and thermofixing of textured synthetic products in their washed state

Mineral oil components from vaporising flushing oils

For washed goods, approx. 0.3% of the weight of the goods, due to the residual fat content of the products. Discharge purification for high loads from: cooling and aerosol separation, air scrubbing or thermal afterburning.

Disperse dyeing at atmospheric pressure

Carriers (aromatic halogen compounds)

Move to closed HT plant and thermosol process (without carrier) usually possible. Can be removed by powerful scrubbers or thermal afterburning.

Drying and fixing after printing

Heavy benzene components from emulsion concentrations of the pigment print process

Largely forced out by benzene-free swelling agents. Removal by activated carbon filters or thermal afterburning.

Drying and fixing after dyeing and after a water-repellent finish

Fumes and smells (cationic softeners, some dyes etc.), paraffins

Particularly where high temperatures are used (thermosol process), organic substances may evaporate or sublimate. Can be partially removed by air cleaning with chemical additives which have an absorptive action.

Drying after a synthetic resin finish (melamine, amino-formaldehyde preliminary condensates)


Physiologically harmful, but hardly a problem these days thanks to low-formaldehyde wetting agents. Only used for a few articles.

Drying after solvent treatment

Solvents included

In pre-cleaning, secondary cleaning and print post-treatment processes. To be removed by condensation and activated carbon filters.

3.2 Noise protection

Noise is a serious problem in spinning and weaving mills. As mentioned earlier in section 2.2, sound levels of 70 to 110 dB(A) are commonplace.

In Germany, guideline no. 2572 of the German Association of Engineers VDI (Gerche von Textilmaschinen), must generally be complied with (25).

Today, to prevent any adverse effects on health, individual hearing protection (ear plugs, ear muffs) must be provided from 85 dB(A) and are essential from 90 dB(A), according to the ordinance on workplaces Arbeitssten-Richtlinien and VDI guideline 2058, sheet 2.

Because of building insulation, which is standard and indeed compulsory (VDI 2571) today, external sound propagation is relatively low. Where other facilities are close by, DIN standard 18005 applies in Germany (23). The minimum distance of textile manufacturing plants from residential accommodation is established in North Rhine Westphalia in the so-called Abstandserla/I> [distance decree] of the Minister for Employment, Health and Social Affairs (Minister feit, Gesundheit und Soziales - 26).

3.3 Water pollution control

· Wastewater pollution parameters

The substances found in wastewater are classified by the proportions which can be precipitated and those which can be oxidised biologically or chemically. Chloro-organic compounds and toxic substances are also taken into account to a certain degree, e.g. some heavy metals used in textile finishing.

Anhang 38 [Appendix 38] of the Allgemeinen Rahmen-Abwasser-VwV [General Administrative Framework Regulation on Wastewater] for textile production and finishing (5) applies to the textile processing industry in the German Federal Republic. It contains a range of wastewater requirements throughout the treatment plant which may not be achieved by dilution or mixing.

The main contamination parameters are described briefly below.

For indirect discharges, state-of-the-art requirements apply, and for direct discharges the requirements of the generally accepted codes of practice also apply.

The draft of the said Anhang 38 of the Allgemeinen Rahmen-Abwasser-VwV specifies, for example, (6) the following requirements for wastewater discharged from textile mills (with the exception of water from raw wool washing, cooling systems, stencil plate production and chemical cleaning (dry cleaning) which are covered by special provisions).

- requirements according to the generally accepted codes of practice (additional for direct discharges)

COD 160 mg/l ammonium nitrogen 10 mg/l
BOD5 25 mg/l aluminium 3 mg/l
iron 3 mg/l total phosphorus 2 mg/l

- requirements per the state-of-the-art (for direct and indirect discharges)

Cu 0.5 mg/l AOX 0.5 mg/l
Cr VI 0.5 mg/l HHHC 0.1 mg/1
Ni 0.5 mg/l free chlorine 0.3 mg/l
Pb 0.5 mg/l HC 15.0 mg/l
Zn 2.0 mg/l sulphide 1.0 mg/l
Sn 2.0 mg/l sulphite 1.0 mg/1
TF dilution factor of 2
Colour: yellow 436 nm 7m - 1
red 525 nm 5m - 1
blue 620 nm 3m - 1

- General requirements

temperature max. 35°C at the point of discharge
pH 6 - 9 at the point of discharge
settleable solids 1.0 ml/l after 0.5 h settling time
odour no unpleasant odours
colour no visible discoloration of the wastewater


- COD chemical oxygen demand
- BOD5 biochemical oxygen demand in 5 days
- TF toxicity to fish
- AOX adsorbable organically bound halogen
- HHHC highly volatile halogenated hydrocarbons
- HC hydrocarbons
- EDTA ethylenediaminetetraacetic acid
- NTA nitrilotriacetic acid
- PVP polyvinylpyrrolidon

The following substances, mixtures etc. may never be discharged as wastewater or with wastewater:

- chromium VI compounds from the oxidation of sulphide dyestuffs
- chloro-organic carriers
- halogen-organic solvents
- arsenic and mercury and their compounds from use as preservatives
- pollutant concentrates, such as residual sizes, residual high-grade finishing agents, print pastes, dye preparations, residues of chemicals used, textile auxiliaries and dyes from drums
- surfactants which do not meet the requirements of the WRMG [law relating to the environmental compatibility of washing and cleaning agents] (22).

All these substances must be collected, recycled where technically feasible or disposed of correctly.

For partial wastewater flows, particularly from the following departments: desizing, bleaching, printing, dyeing, finishing, coating and backing, together with central barrel and drum cleaning, threshold values apply above which treatment is required. If various processes are carried out consecutively in a single mechanical unit, the wastewater from each must be dealt with as a partial flow.

Threshold values for partial wastewater flows beyond which treatment is required:

AOX 3.0 mg/l Cr 2.0 mg/l
HHHC 1.0 mg/l Cr VI 0.5 mg/l
HC 50.0 mg/l Zn 10.0 mg/l
Cu 2.0 mg/l Sn 10.0 mg/l
Ni 2.0 mg/l

The AOX threshold value for bleaching with chlorine to obtain a particular shade of white and the non-felting finishing of wool is 8 mg/l (up to 31.12.1996 max.).

All analyses and measuring procedures required to determine the said pollutants have now been standardised in Germany to DIN.

Table 3 - Measuring procedures for wastewater parameters in the wastewater treatment plant



- Filterable substances - Settleable substances - Chemical oxygen demand - COD - of the precipitated sample - Biochemical oxygen demand - BOD5 -of the precipitated sample - Toxicity to fish as TF dilution factor of the unprecipitated sample - Zinc, copper, chromium - Nitrogen from ammonium compounds from the unprecipitated homogenised sample - Effective chlorine from the filtered sample - Sulphide, total, from the unprecipitated sample - Sulphite, total, from the unprecipitated sample - Hydrocarbons from the unprecipitated homogenised sample

DIN1 38409-H2-2/3(July 80 edition) DIN 38409-H9-2(July 80 edition) DIN 38409-H41(December 80 edition) DEV2 H5A2 (4th issue 1966) with additional restriction on nitrification at 0.5 mg/l DIN 38412-L20(December 80 edition) DIN 38406-E21(September 80 edition) DEV E5.2(7th issue 75) DEV G4 1.b (7th issue 75, glassfibre filters) DEV D 7b(7th issue 75) DEV D 6.2(1st issue 60) DIN 38409-H18(February 81 edition)

1 DIN = German Standard
2 DEV = Deutsches Einheitsverfahren (German standardisation procedure)<<TOC4>> 4. Interaction with other sectors

While, on the raw materials side, the textile industry has close connections with plant production (natural fibres), the fibre industry (synthetic fibres) and the chemical industry (chemical, dyes, auxiliaries), its activity on the sales side is characterised by its interaction with the clothing industry downline.

Further references to relevant project areas are given in the text.<<TOC4>> 5. Summary assessment of environmental relevance

In investment projects in the textile industry sector a range of environmentally relevant criteria must be taken into account at the location planning stage. In raw material producer countries in particular special consideration must be given to the effects of material production. The early and full involvement of the population groups affected, particularly women in some cases, can help resolve any problems which may arise.

Special attention must also be paid to the environmental impacts of raw wool washing and textile finishing plants. While in the former the problem is posed by the considerable degree of wastewater contamination, in textile finishing mill projects due account must be taken of the high water and energy consumption, the wide use of chemicals, the process-specific pollution of wastewater and exhaust air and the disposal of waste. In this regard, special industrial environmental protection officers must be appointed.

The current state-of-the-art in the processes, process installations and supply and disposal plants, together with relevant laws and their enforcement, combine to ensure that thoroughly environmentally sound textile production is possible at all stages of manufacture.

With regard to the socio-economic environmental impacts of textile projects mention should be made of the much more stringent requirements relating to personnel qualification. The capital-intensive nature of modern, extensively automated spinning, weaving and knitting mills is leading to the maximisation of machine operating times, thus multi-shift operation, usually 7 days per week, is the norm.

The whole area of socio-economic and socio-cultural aspects of this type of operation and its legislative framework must be looked at carefully.

6. References

1. D G.: VDI-Berichte, Nr.310, 1978.

2. Technische Anleitung zur Reinhaltung der Luft - TA-Luft of 27.02.86; Gemeinsames Ministerialblatt GMBI 1986.

3. Year books for 1988 and 1990 of the Gesamtverband der deutschen Textilveredelungsindustrie, TVI-Verband EV.

4. 83. Allgemeine Verwaltungsvorschrift indestanforderungen an das Einleiten von Abwasser in Gewer (Textilherstellung) - 38. AbwasserVwV - of 5 September 1984, GMBI (joint ministerial circular) 1984.

5. Anhang 38 to the Allgemeinen Rahmenabwasserverwaltungsvorschrift f Textilherstellung - Draft of 20 December 1990.

6. Dr. Heimann, S.: Textilhilfsmittel und Umweltschutz; Melliand Textilberichte, 7/1991.

7. Natke, H.G., Thiede, R., Elmer, K.: Curt-Risch-Institut famik, Schall- und Meechnik, UniversitHannover: Untersuchungen der von Webereien ausgehenden Schwingungsemissionen und Hinweise zur Websaal-Bauplanung. Verband der Nord-Westdeutschen Textilindustrie M; Zeitschriftenreihe, Heft 66, 1985.

8. Trauter. R.: Rinnung und Wiedereinsatz von Webschichten mittels dynamisch geformter Membranen; Chemiefasern/Textilindustrie 37/89, 1987.

9. DIN 38409-H14-H14: Deutsche Einheitsverfahren zur Wasser-, Abwasser- und Schlamm-Untersuchung: Bestimmung der adsorbierbaren organisch gebundenen Halogene (AOX).

10. 2. Verordnung zur Durchf des Bundes-Immissionsschutzgesetzes (Verordnung zur Emissionsbegrenzung von leichtflen Halogenkohlenwasserstoffen - 2 BImSchV of 21 April 1986); BGBI (Federal Law Gazette) 1986, Part 1.

11. Kolb, M., Funke, B.: Die Entfung von textilem Abwasser mit Fe(II) + Ca(OH)2; Vom Wasser, Bd. 65, 1985.

12. Wysocki, G.; H B.: Chemie-Technik, 1974.

13. Oehme, Ch.: Trrbiologien in der Abwassertechnik; Chem.-Ing.-Tech. 56, 1984.

14. Croissant, B.: Efferenn K.; Frahne, D.: Reaktivfarbstoffe im Abwasser - sind sie durch ein bakterielles Symbiosesystem abbaubar? Melliand Textilberichte, 1983.

15. Erlaichtlinien f Anforderungen an Abwasser bei Einleiten in ntliche Abwasseranlagen of 28 June 1978.

16. Wiesner, J.; Jochen, E.: Energieverbrauch und Mchkeiten rationeller Energienutzung in der Verarbeitenden Industrie in Baden-Wberg: Textilindustrie, Informationen zur Energiepolitik, Heft 11c, Wirtschaftsministerium von Bad.-W Stuttgart, 1978.

17. Reetz, H.: Europche Abwasserregelungen im Vergleich; Melliand Textilberichte, 11/1991.

18. Christ, M.: Werinnung und Abluftreinigung bei der Textilveredlung; Textilpraxis International, 46/1991.

19. derung der 4. BImSchV Nr. 5.3 - Genehmigungspflicht fagen der Textilveredlung und von Feuerungsanlagen.

20. "Wastewater purification" working party J. Janitza, S. Koscielski, M. Schnabel of the ITV (Institut ftil- und Verfahrenstechnik Denkendorf) Behandlung von Textilabwern im Betrieb; Textilpraxis International, November 1991.

21. Gesetz zur Ordnung des Wasserhaushaltes (Wasserhaushaltsgesetz - WHG) of 23.09.1986.

22. Gesetz ie Umweltvertrichkeit von Wasch- und Reinigungsmitteln of March 05, 1987.

23. DIN 18 005; Schallschutz im Stebau, Planungsrichtlinien.

24. VDI 2058; Beurteilung von Arbeitsl am Arbeitsplatz hinsichtlich Gehhn.

25. VDI 2571 + 2572; Schallabstrahlung von Industriebauten.

26. Abstandserla(RdErl. d. Ministers feit, Gesundheit und Soziales NW of March 09, 1982).

27. Verordnung zur Eigenchung von Abwasser, Bayern (AbwEV) of December 09, 1990.

28. ITMF; International Textile Manufacturers Federation - International Textile Shipment Statistics, Vol. 14/1991.

29. World Bank; Environment Guidelines; Washington 1988, p.451 ff.