3.1. Geographic and climatic conditions

As already mentioned, the most important geographical parameter for a biogas dissemmation programme is temperature. Mean temperatures of between 20 and 250C throughout the year with low seasonal fluctuations are the most favourable for biogas plant locations. As gas production tends to follow the curve of the average daily temperatures, the course of the temperature for one year will show the months for which insufficient gas production can be assumed.

Another favourable geographic characteristic for optimum use of the biogas plant is a slightly hilly terrain. In this case, the spreading of the liquid slurry will be possible due to natural slopes. Very rocky underground or a high groundwater table would be unfavourable. In both of these cases more work is involved in building the plant which also increases the costs.

3.2. The biogas plant in the agricultural farm and household system

3.2.1. The target groups

When biogas dissemination began, the opinion was that biogas plants should be built wherever they were ecologically necessary and feasible (thus e.g. also in the Sahel). Today, after about 15 years of experience with biogas programmes, it is now known that biogas plants can only be disseminated where, as agricultural technology, they can become an integral element in the living and working world on the farm. This central condition for a biogas dissemination programme requires "biogas favourable" farm and household systems to have definite structural features. A typical and ideal location for a biogas plant could be described as a farm on which animals are permanently kept indoors and where, as far as possible, mixed farming is practised. The farmer is the owner of the farm and has the power of disposal over his land so that he is able to profit from the investment in a biogas plant over the long term. The cattle are kept indoors every day and are put to pasture for a few hours at the most. The amount of dung occurring on the farm amounts to over 30 kg fresh weight daily. The quantity of water necessary for filling the plant and corresponding approximately to the amount of dung, can be constantly obtained without any unreasonable amount of work, also by women and children; water is not in short supply. Stabling with a concrete floor from which excrement and urine can be directly pushed into the inlet tank of the biogas plant would be ideal. The floor of the stabling is high enough for the overflow of the compensation chamber to lie above the terrain so that the slurry can flow down a slope into the neighbouring fields where, as far as possible, fodder grass is grown. (The floor of the stabling has to be at least 35 cm higher than the overflow of the biogas plant). The toilet could also be connected to the biogas plant; there is no prejudice against a toilet being connected. The gas is used as regularly as possible and completely in the direct vicinity of the plant. Experience in the use of organic fertiliser would be of advantage for optimum utilisation of the slurry. It would be favourable for regular filling of the plant if the people using the gas and those operating the plant were identical. Although in recent years the technical concept has been more and more successfully modified to the needs of the users, e.g. increasing operator friendliness, the integration into the farm and household routines remains a central criterion for the selection of a location. Where and which compromises on the ideal "biogas farm" described above are possible depends on very many factors which have to be examined in each individual case. (Colleagues with experience in biogas dissemination programmes should always be consulted in cases of doubt.) For example, the requirement of a short distance to the point of gas consumption could be deviated from. Long pipelines are only a cost factor and the function of the plant is retained even at distances of over 100 m (too great a loss of pressure can be counteracted by larger diameter of pipes). Also the connection to stabling favoured within German development cooperation is e.g. in India and Nepal, not a standard. Also toilets should only be connected to the biogas plants according to the express wishes of the customer.

Family structures could also be stated here as central criteria in the success of a dissemination programme. Division of labour and allocation of tasks in the household and on the farm according to sex, i.e. particularly the position of the women have to be carefully observed. In polygamous households where each woman has her own kitchen, the integration of biogas plants is hardly possible in the living and working world of the woman.

It is far less of a problem when the women take it in turns to cook in one kitchen. In this case it would be particularly important to investigate how the operation of the plant would be organised, or if coordination between the women is probable. If the women take it in turns to gather fuel, then operation of the biogas plant in turn could be organised. Despite this, it would have to be investigated who would be in absolute charge and whether, e.g. the first wife had the priority to supervise operation of the plant.

In Africa, the man is normally in charge of lighting in the household. In these cases, there could be a conflict of interests between the man and the woman concerning the use of gas for lighting and for the stove. The man who (normally) pays for the plant, naturally wants to save on his budget for lamp oil. The woman, who under some circumstances fills the plant and is in charge of firewood, wants primarily to use the gas for cooking. If there is no reconciliation of interests, the ruins of a biogas plant could appear on the farm in due course. It can be assumed that the woman who is responsible for cleaning the stabling, will neglect the plant if the husband insists on using "his" biogas plant for "his" light.

3.2.2. The demand for biogas plants

Although theoretically, all farms with the a.m. structural features may be considered for biogas, the actual dissemination is defined mainly by how willing the farmers are to invest in this technology. For the farmers, the biogas plant is a capital good binding a high amount of funds which will improve the energy, agricultural and hygienic situation of his farm and of his household. The attraction of a biogas plant for the farmers initially stems from the use of the gas. In view of this, dissemination concepts focussing on the utilisation of slurry have hardly been able to move the farmers to an investment unless some kind of simultaneous energy benefit, which was in a ratio to the amount of the investment, existed. Favourable regions for biogas dissemination have proved to be where farms have a bad supply of energy sources, but where a healthy economic substance exists. In these regions, the factor "comfort" plays a considerable role in the development of the demand - in particular on farms with a high to medium farm or family income. The biogas lamp as a source of light cannot compete with an electric light bulb. A connection to the electricity supply however does not have to be a reason for excluding a possible biogas programme. A low-cost biogas plant can turn out to be an interesting investment especially in regions where the fossil sources of energy are traded at high prices.

It is difficult to reach small farms with a low capital background with dissemination programmes although these farms, in comparison to the economically stronger ones, often suffer from a bad supply of energy. Their insufficient solvency and their weak capital background make the purchase of a biogas plant costing several hundred US dollars a hurdle which is often too high to take. The poorer classes of smaller farmers could only become members of the target group in India where subsidy programmes could be implemented on a long-term basis and in countries where the prices for plants are very low. To link the introduction of a new technology directly to the social question has proven to be a demand which could rarely be fulfilled in reality in past projects.

In the initial phase of a dissemination programme at least, orientation to economically more healthy farms seems advisable. They can be the forerunners which' when the technology has been established and no longer constitutes an investment risk, the weaker farms could possibly follow.

3.2.3. The potential

The development of demand is, on the whole, part of a long-term process during the course of which biogas technology grows into a generally accepted part of agricultural technology. Experience in India has shown how approx. seven years pass between the introduction of the technology to one region and the appearance of a dynamic demand. A dynamic demand develops where high potential exists. The potential increases with unfavourable energy supply conditions and with the number of farms (families) with sufficient livestock and a high and secure income from their farms. Important in estimating the potential is not only the expected number but also the possible density of biogas plants. If a high density of potential ''biogas customers" exists, the positive demonstration effects of the plants within the rural region influence the development of demand more rapidly. Apart from this, the potential density of plants and the potential number are important basic values when calculating the infrastructural demand of the dissemination programme. If the farms of potential biogas customers are scattered throughout the region, a greater demand can be expected on customer acquisition, advisory services and servicing. If ultimately only a few plants could be built the infrastructural expenditure for biogas dissemination would be in an unfavourable ratio with the macroeconomic benefit expected. Critical orientation values pro or contra a dissemination programme could be if less than 10% of all farms in the region were "biogas capable" or if less than 3 farms per km² could be considered for a biogas plant.

3.3. Dissemination structure

Even if today the technical performance of biogas plants no longer constitutes a problem, and even if regions favourable for biogas can be relatively easily identified, the establishing of an efficient and sustainable dissemination structure continues to remain the key problem of numerous biogas projects. The success of a dissemination programme is not only calculated from the total number of well functioning demonstration plants plus farmers who are interested and are able to pay for plants plus trained masons. Biogas technology is in need of a professional dissemination structure to offer the product biogas plant, to supply it ready to function and to provide an adequate "after-sales" service. The biogas plant must be a quality product and requires the relevant measures. To be able to keep to the quality standard demanded, the interaction of various components (execution of building, planning, advisory service) is essential. The importance of this central point cannot be stressed enough. A newly introduced technique or technology is normally continuously optimised by manufacturers and users during the course of time and finally improved to attain the utmost maturity. With biogas plants however, it is imperative for the technology to be more or less perfect from the beginning, i.e. a plant must be gas-tight in every case, inlet and outlet must not become blocked and the gas pipes have to be laid so that no condensed water blockages occur. If these basic requirements are not met, the plant will not only operate more badly - it will not function at all. (The fact that plants can still be optimised by technical improvements is not contradictory here.) These process control necessities ultimately define the technical building standards which the dissemination structure must guarantee. In the initial phase, the executing organisation will have to carry out considerable tasks: technical modification, advice of potential customers, liaison with and qualification of the private sector, quality control, promotional measures towards developing a market etc. Although it should be made sure at the planning stage that the private sector is integrated as far as possible into biogas dissemination, independent artisanal tradesmen will only disseminate plants independently in exceptional cases. Dissemination of biogas plants by the private sector will need institutional support in the medium term. Only in programmes during which a market had been developed by institutional involvement was biogas technology interesting for the private sector. However, the profit margin for the simple household plants is so small that complete integration of the technology into the private sector will be very improbable in the long term without financial assistance from third parties in the form of topping-up funds. A cooperation between the private and the public sector will then be essential. The dissemination organisation is ultimately to contribute to creating an economic relationship to provide biogas plants with the quality standards described and in line with the potential demand. This also includes extension services and possibly backstopping for the craftsmen in the realms of organisation, calculation and technology.

3.3.1. Dissemination Institutions

As the potential customers all keep cattle and considering that biogas technology has the character of agricultural technology, it seems obvious to entrust those organisations with biogas which are normally in direct contact with the farmers. The proximity to potential user groups is an elementary criterion for the selection of the organisation or institution. Normally it is the agricultural development organisations or their extension services which are in constant contact with the farmers.

The organisations which also have a particularly favourable background are those who have experience in technical innovations and their demands on dissemination policy. These organisations normally have experience in integrating or the institutional authority to integrate credit programmes in the context of their business relationships with the agricultural development banks.

The demand for integration of biogas dissemination into agricultural development organisations can, of course, not be prescribed basically, as the extension services vary greatly in organisation and manpower from country to country. What is decisive when making the selection is that the institution entrusted with this not only has the organisational capacity, the proximity to the target group, the financial backing but also and primarily, the interest in the biogas dissemination planned which will make it a motor in the development and not a brake.

Especially where matters concern budgets, cooperation between organisations under various ministries is feasible and often also desirable. Distributing competences to varying executing organisations, e.g. to energy agencies and agricultural agencies simultaneously, is often anything but smooth. Any division of tasks has to be organisationally established by clearly allocating tasks and lines of competence and communication.

As the success of the project depends directly on the counterpart organisations identifying themselves with the technology, long-term interest should be a central criterion in selecting the dissemination institution. What is often overlooked where projects of technical cooperation are concerned, is the fact that the mandate of the counterpart organisation is not the dissemination of the technology per se but to solve problems identified on highest political levels in line with the situation. Biogas technology can be the solution to a problem here. However, it is e.g. not the task of a water conservation authority to build biogas plants, but to identify and execute measures geared to protecting water resources. Likewise, it is not the job of national energy authorities to build biogas plants but to find solutions to quantitatively and qualitatively improve the supply of energy in rural regions. In the past, counterpart organisations not infrequently lost interest after abstract dreams of wanting to build some thousand plants within a short period had vanished and reality, despite intensive work, resulted in only twenty plants per year. Particularly in planning within the organisations which think in terms of nationally and quantitatively impressive categories, the qualitative benefit of biogas plants to the individual farms is of little importance. In this respect, organisations working with the farmers on a daily basis, have a far better view of the situation.

3.3.2. Craftsmen's qualifications

The building of the plant itself should be placed in the hands of the private sector. Whether it can work independently of institutional support and supervision is a matter which is ultimately defined by qualifications, the profit margin and the interest of the craftsman in handing over a biogas plant to the customer which is able to function. Qualifications, mainly of the masons, is very significant where fixed-dome plants are concerned. Supervision of construction can only be dispensed with in cases where self-employed entrepreneurs are interested in the quality of the plant and this is linked to guarantee agreements. Normally, a separate building control capacity is indispensable if the gas-tightness of each plant is to be guaranteed.

In areas where loam mortar is used for building training is absolutely essential in the field of craftsmanship. It can be assumed that masons who are used to working with cement or lime-sand mortar are in possession of the necessary skills. A dome construction which appears complicated is far easier to build than a straight or cylindrical. On the other hand, it cannot be assumed that skills exist for particular skills for particular details of construction. The masons are in need of clear instructions on mixing ratios, the quality of bricks and, mainly, on plastering methods for the gas-tight dome. If the masons are able to read and write (as e.g. in Java), and are accustomed to working from drawings their training becomes far more simple. Intensive explanations of the drawings combined with a visit to a biogas building site could be sufficient here. If it cannot be assumed that this knowledge exists, the masons will have to be trained intensively not only in the field of quality but will also have to be made familiar with construction dimensions. In this case a biogas programme has to rely on a permanent team of trained and constantly upgraded masons who do not always have to be specialised in the construction of biogas plants.

3.3.3. The availability of building materials and gas appliances

An important factor of sustainable biogas dissemination is the local availability of suitable building materials. Basically, good bricks, clean sand, Portland cement and cement agents for waterproofness (which also guarantees gas-tightness) are needed. An advantage also, but materials which can be substituted, are gravel and stones from the fields, bricks can be replaced by cement blocks. If these materials are not among locally available ones they can normally then not be obtained at affordable prices. In this event, a plant modified within the scope of an R&D project may have to be developed. Only subsequent to successful development which has to be oriented to the economic capabilities of the country, can the question of a dissemination programme be considered again.

Where water pipes exist, the acquisition of gas pipes provides no problem. As biogas is stored and transported only under low pressure, practically all water pipes are suitable for use as gas pipes if the pipe connections can be made gas-tight. Most favourable in this respect are PVC pipes bonded with couplers as these are inexpensive and easy to handle. In contrast, good-quality ball valves for use as main gas cocks are rarer - because they are expensive - on local markets. As each plant only requires one or two such cocks, these could be easily obtained centrally. What is important here is that these are ball valves and not stop valves. The best ones are here only just good enough even if their price sometimes amounts to 2 or 3% of the total cost of building. If the material is available generally, this will have a decisive influences on continuation of building after the project has finished. If gas taps and especially gas appliances are difficult to obtain after the end of the project, e.g. when no convertible currency is available, this can lead to serious problems. Direct imports of gas appliances from India, Brazil or China should only be allowed during the demonstration phase of a project as an interim solution; or if large quantities are needed constantly where a private dealer could set up a worthwhile sales system. Before thinking of imports however, investigations must be made into which locally available market products can be converted for use with biogas (e.g. pressure lamps, gas stoves).

If larger quantities of gas are available (over 15 m³/day), the gas can be used in motors, incubators, heaters or generators. Such devices for using gas are normally not available on the local market. Kerosine and bottled-gas appliances can be converted for biogas with relatively few problems in simple workshops. When planning a project it must be remembered that every material which is not available on the local markets places extra demands on the structure of dissemination. The following questions should be answered here:

- can materials and appliances be obtained on neighbouring markets? - can local dealers be commissioned to obtain material at affordable prices? - can common market appliances be converted? - or are imports necessary which cannot be carried out by local dealers? 3.3.4. Standardising biogas plants

Standardising biogas plants in the dissemiantion region is a focal element for a successful dissemination programme. Every biogas dissemination programme for household plants can and should restrict itself to standard sizes regarding digester and gasholder volumes (e.g. VD = 6, 9, 12, 18 m³). Standardisation provides clear instructions for building and thus reduces the spectrum of individual improvisation. Individual planning for each plant is then unnecessary.

Standardisation is also possible for larger plants if the range of applications is limited. Where the amount of substrate available, the geographic location and the structure of potential farms greatly vary, individual solutions become essential. In this case, a technical planning office has to be set up within the dissemination programme to react to various demands with specialist knowledge.

3.3.5. Government consultation

Government consultation is a central and significant element in establishing a biogas programme. The government has to provide the material and financial basis for a biogas project by issuing directives and by providing a budget and has to place a mandate with other relevant state institutions as well as with executing institutions. Without such political will equipped with a budget, even the greatest interest of farmers in biogas technology, the most intensive involvement on the part of project staff and the best qualified craftsmen could hardly ever be converted into significant and sustainable dissemination. It is very improbable that, e.g. an agricultural development organisation would or could re-allocate its budget in favour of biogas technology without this kind of political and financial support.

On a state level, the complexity of biogas dissemination is normally underestimated. It is often referred to as "simple technology" and the essential personnel, organisational and financial investments are overlooked. Added to this, there is the problem that the benefit of the technology when the project is handed over is modest, in view of a few dozen plants which had been built contrasting with the targets globally formulated at planning workshops like "reduction of logging", "improvement in rural energy supply" or "substitution of fossil sources of energy". Especially where the supply of energy is concerned, biogas projects and biogas technology are often greatly overestimated. In hardly any country in the world does biogas technology provide more than 5% of the total rural energy demand, more probable is a share of 1 - 2%, and this only provided that an efficient biogas dissemination programme can be set up. The benefit of biogas technology is primarily derived for individual farms from the provision of infrastructure with diverse positive factors (energy, hygiene, less work, modernisation of the household, improvement in agricultural production etc). The availability of this ecological waste recycling concept increases the level of self-sufficiency and the availability of resources for the farm and the household, and by achieving this, ultimately improves the efficiency of regional agriculture. In this respect, the broad qualitative aspects of biogas technology can, over the long term, constitute a quantitative benefit for the overall economy.

In view of this, government consulting has the task of making the benefits of this technology and the efforts necessary for its dissemination transparent. Glossing things over proves to be counterproductive in the long run, too high expectations later turn into disappointment and lack of interest. Solely the number of plants built and actually in use will show the macroeconomic benefit. It must be emphasised that the construction of biogas plants during the consolidation of the dissemination structure and the formation of a market is only hesitant. This relatively low rate of growth compared to the infrastructure expenditure however, becomes overproportional when a demand has formed and the supply level has proved to be efficient. The establishing of a dissemination structure should be seen and communicated as an initial investment which will only begin to amortise after a certain duration. If, e.g. a Biogas Office with established posts for one engineer and two technicians, is formed in one region, the construction of only ten plants per year can be expected. With the consolidation of biogas technology in rural regions and the increasing efficiency of the dissemination structure, the construction of several dozen per year will be the next step and, when extended to other regions, a production of some hundred plants per year will follow. What is important, is to compile a dissemination concept with the state to conform to the rural productive powers. In this respect the following questions are important:

- which tasks should be taken over by state agencies permanently and which temporarily?
- what role can the private sector actually play? - or is it more favourable to support dissemination by non-governmental organisations?

It should be remembered that with such a dissemination concept the financial aid from the state (subsidies, tax relief etc.) increases individual profitability, accelerates demand and thus improves the infrastructural expenditure through a lower advertising expenditure, and finally allows a better ratio of plants built to the investment of resources. Financial aid is very often the cheapest way of promoting biogas. The scope for decision the governments have regarding such topping-up payments for individual plants, is nowadays often defined by structural adaptation measures and sector priorities defined over the long term in addition to the actual state household position.

3.4. Larger plants

So far, the household plants mainly focussed on have ranged from 6 to 20 m³ VD. What has been said so far also applies to plants for larger farms. For an analysis of potential, the larger plants have to be seen in relationship to their higher costs of construction. For these plants, greater involvement of the private sector is possible due to the higher volume of the order and the relevant profit margin. For plants of this size, environmental aspects are frequently very significant, consequently the macroeconomic benefits have to be evaluated differently. For the clarifying of wastewater, there is no alternative "yes or no", but only different, competing technical processes. Anaerobic processes, i.e. biogas plants, are here only one of many options. However, they do have the advantage of needing only a small amount of space and do not consume energy in warm countries, but provide it.