Organization of the biogas sector

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India's "National Project on Biogas Development" (NPBD) for mass diffusion of digesters was launched at the end of 1981, using a "multi-agency, multi-model" approach. The programme is centrally administered by the Department of Non-Conventional Energy Sources (DNES), within the Ministry of Energy. DNES is responsible for the coordination of implementation and R & D of family-sized and community biogas digesters. It has to approve designs and to allocate budgets for training and subsidies. At State, District, Block and Village levels, staff is provided for the biogas scheme as shown in Table 13.4, though not in all cases is the scheme fully staffed.

At State level, the organization is called "Biogas Cell". 14 States, with a target of 10,000 digesters, are supposed to have a staff of 6, the remaining States a staff of 2. 25 central departments in as many States have been set up, and others in a selected 100 Districts. In other Districts, State Governments have either set up such cells under the State Plan sector, or involved staff of allied schemes, e.g. minor irrigation programs (Khandelwal and Mahdi 1986). The broad terms of reference of the Biogas Cell attached to the central department in each State Government includes:

(a) Overall planning of the execution of the programme in the State;
(b) State-level coordination of different departments/agencies;
(c) Institutional financing;
(d) Arrangements for raw materials;
(e) Appointment of executive agencies and demarcation of areas;
(f) Monitoring of programme and the submission of progress reports to the Government of India; (g) Maintenance of subsidy accounts and the submission of expenditure reports the Central Government.

Agencies vary at State level: they may be State Department of Agriculture, Agro-Industries Corporation, or State Department of Non-Conventional Energy, etc. They have varying levels of involvement in extending technology.

At District level, the executive agencies are governmental: Khadi and Village Industries Commission (KVIC) and Action for Food Production (AFPRO). This multi-agency approach is necessary if targets are to be met. The construction of 20,000 digesters annually is channelled through KVIC (1985-6 target). Since starting in 1974, they have constructed 161,000 floating drum digesters. KVIC has a technical staff of 300 (1 Director, 2 Assistant Directors, 40 Development Officers, 100 Assistant Development Officers and 160 Supervisors. In addition, many individual workshops have been recognized by KVIC.

AFPRO coordinates a network of NGOs at grassroots level, using the fixed dome digester (the Janata Model) exclusively (janata = people). AFPRO concerns itself with institution building, placing emphasis on the organization of many training courses in rural area, by competent NGOs. AFPRO has planned and initiated action to develop 80 - 100 Biogas Extension Centres (BEC), involving 60 - 100 NGOs. To date, 60 NGOs, with 90 such centres have been developed, and are involved in construction activity. Their total construction capacity is about 9,000 digesters per year. Most of these NGOs, like AFPRO, promote several rural technologies, biogas among them. Each BEC is capable of constructing 100 biogas plants per year, as well as providing regular after-construction services to plant owners. Each BEC would have a staff of one supervisor and a master builder. The former has the task of education and motivation of farmers, collection and processing of applications, levying cement and other materials, supervision and coordination. The latter acts as leader of the construction teams, professional rural builders hired by the farmers at daily rates. AFPRO has raised overseas funds (the Canadian Hunger Foundation) to support 80 - 100 BECs over a 3 - 5 year period. It is expected that, after this initial support each centre will be self-sufficient.

Table 13.4 : Organization Structure (India)

Sources: Mahdi, S.S. (1982). Khandelwal, K.C. and Mahdi, S.S. (1986).

Indonesia The biogas development programme in Indonesia is in the initial stages. Only a small number of plants exist, the reason being that firewood is plentifully available in most areas.

The Bandung Institute of Technology, its Bogor Biological Institute and other governmental institutions are engaged in research and development work. Efforts are being made to evolve an efficient model through suitable modification of existing Indonesian and Chinese designs.

Some demonstration units have been set up at places like Denpasar, Petung, Atuag, Bogor, Baruajak and Bah. The units are made of oil drums with floating gas holders. There is opposition to the use of pig dung as a feed stock by the Muslim population.

The Indonesian Board of Voluntary Services is promoting the biogas programme by putting on demonstrations at the village level to convince villagers and village leaders. The Bogor Biological Institute is also launching a biogas programme based on the use of agricultural wastes as a feedstock.

In 1981 the FAO/TCP biogas project was initiated in Indonesia with the objective of setting up a few demonstration units, providing training and preparing a comprehensive programme for incorporation of biogas technology in the integrated rural development programme. The Government is planning to formulate a national biogas development programme, with Bali as the focal development centre.

Iran The Centre for Endogenous Development Studies is engaged in propagating a biogas development programme in western Iran. Trials are being carried out at Niazabad with KVIC-design plants.

Israel The Israeli project on the utilization of agricultural wastes was based from the beginning on the integrated approach (Rousseau et al, 1979), employing economic evaluation studies, and tailored to differently structured farms. The biogas produced during the anaerobic digestion is only one of several products.

Several institutes and commercial companies are involved in developing anaerobic digestion of organic wastes in Israel. Only a few large scale commercial systems and demonstration systems of 200 m have been built in Israel and two other countries, based on the "Nefah" technique. Methanogenic Thermophilic Anaerobic Digestion was selected to treat manures and slaughterhouse wastes of high solid contents ( over 15% dry matter). Economic evaluation studies in Israeli Kibbutzim, with feedlots and over 300 milking cows per cowbarn, showed the benefits of the treatment of the high solid content material. The thermophilic temperature (55°C) changes the viscosity and allows treatment of the wastes. A higher digestion rates is achieved as well as eliminating Salmonellae and reducing other pathogenic bacteria populations. As evident from the experiments, done in Israel and other countries, there is a reduction of several orders of magnitude in coliform bacteria and in most cases total elimination of Salmonellae. An integrated commercial system has been developed that solves ecological problems in an economic way by Methanogenic Thermophilic Anaerobic Digestion (MTAD). The products of the system are Biogas and a peatmoss substitute for the greenhouse and mushroom industry. In addition, a liquid fraction is produced, used as a fertilizer. The process simultaneously reduced BOD and COD and is effective against pathogenic bacteria. The main saleable product of the process is a substitute for sphagnum peatmoss (called Cabutz or Peatrum), which was examined as a casing-soil substitute for growing Champignon mushrooms, and is also used commercially in Israel as growth medium for pot-plants. This material was produced from the digested slurry by separation on a vibrating screen and the fibrous peat-like material which was obtained by sieving and leaching was tested for its physical and chemical properties. It was found to maintain high hydraulic conductivity and air capacity, as well as adequate water and nutrients retention, like peat-moss, as was shown for digested slurry from cow manure (Marchaim, 1983).

This Israeli MTAD process works at the highest possible organic loading of the wastes collected, since economic evaluation showed that the higher solids content in the added material is important if a profit from the anaerobic digestion plant is to be achieved. MTAD was demonstrated not only as a process which converted part of this material into useful substances, but also as a decontamination process. The process is used to treat manures, rumen content from slaughterhouses and other agro-industrial wastes, e.g. instant coffee waste.

Japan In Japan, anaerobic fermentation research and development was viewed more as an anti-pollution measure, rather than as an energy alternative. Since 1973, nationwide efforts have been made to reduce pollution problems resulting from animal, human and industrial wastes. Several institutions like the National Institute of Animal Industry, Chiba, the Public Works Research Institutes, Fermentation Research Institute, Inage, Hitachi Plant Construction, the Ministry of Agriculture, and the Agency for Industrial Science and Technology have been working on anaerobic fermentation of organic wastes.

Big digesters to treat industrial wastes, particularly from alcohol distilleries have been set up. High temperature digestion in thermophilic range, especially for industrial wastes, is being adopted. There are no differences in the quantity of gas produced in thermophilic and mesophilic digestion procedures. However, thermophilic digestion has the advantage that it allows for the reduction of the retention period to five-seven days and makes possible higher loading rates (2.5 times), thus increasing the scope for reduction in digester size.

In 1974, the Sun Shine Project was initiated with the objective of developing new energy technology. Among other subjects the Project includes investigations into anaerobic digestion of animal, human and solid urban wastes. Interest in small digesters has again been renewed. Small digesters, using a steel tank with an agitator and a water coil for heating the slurry, have been developed. The digester has a double wall for insulation against low temperatures.

Republic of Korea The Institute of Agricultural Engineering and Utilization, the Rural Guidance Bureau of the Office of Rural Development (ORD) and the College of Agriculture undertake research, development and extension. The Rural Guidance Bureau provides technical assistance and financial loans to farmers. However, there is no regular loan system and a 33-50 per cent governmental grant system has been discontinued. Most of the biogas development programme is being undertaken by the farmers themselves.

Rapid urbanization and the shortage of animal wastes slowed down the construction of family units in rural areas. The emphasis has shifted to the establishment of village-size units, gas storage and purification, and power generation. Many of the plants are not operated during the cold months, i.e. December- March, when temperatures drop as low as 17°C. Various attempts to maintain the temperature of the gas-holders through the provision of protective covers of straw or vinyl did not meet with much success. Provision of heating for the smaller plants was not justified. Conditions are more amenable in the southern part of the country which remains comparatively warmer during winter months.

ORD had helped install more than 30,000 small plants in the country by 1975. Farmers are not totally dependent on biogas for their energy needs. It supplies only 3-6 per cent of home heating, and less than half of the cooking needs. Each farming family has a cooking fire in addition to an unmodified LPG burner for biogas. The change of emphasis to large village-sized plants is intended to provide for most of the heating, cooking and power needs. Cow and pig excreta are the main feedstocks. ORD is engaged in the development of village-scale digesters. A 40-family, 155 m digester is operated at the Livestock Experiment Station, Suweon, established under the Korea-UK Farm Machinery Project. The plant utilizes 2.4 tonnes of dung obtained from the poultry farm and 170 cattle and has a retention time of about 40 days. Part of the gas is used to heat the digester to maintain the optimum temperature. Many more such units are being set up. Experiments are continuing on the use of biogas in kerosene engine applications and home heating. The Institute of Agricultural Engineering and Utilization is experimenting with PVC and concrete fixed-dome digesters. The College of Agriculture, Suweon, is working on a two-stage digester of reinforced plastic insulated with paddy husk. Use of night soil in biogas plants is also receiving attention. A plant using night soil as a feed-stock is operating in Kyong Jushi.

Lao People's Democratic Republic A number of demonstration units have been set up with the assistance of FAO, most of them of the Chinese fixed-dome design. A training course on biogas technology has also been organized.

Malaysia Biogas technology is new to Malaysia. Even though there are ample supplies of oil and natural gas, the Government has been giving attention to reducing dependence on conventional energy sources, especially on the part of small land-holders. One of the main hindrances to the propagation of biogas is the religious tradition which prohibits the handling of animal wastes, especially of pigs. Many biogas plants have been installed for reasons of sanitation rather than energy production. Some oil palm plantations digest the waste materials as treatment before disposal. However, the gas produced is not collected.

Research developments in biogas technology are coordinated by the National Institute of Scientific and Industrial Research.

Nepal Nepal is a landlocked mountainous country with an area of about 147,180 km² , of which 23.5% is plain, 60.5% rugged hills and 16% mountains. In 1984 Nepal had a population of about 16 mill. increasing annually by 2.6%.

Some 94% of the population is engaged in agriculture, 60% in the hilly areas, 40% in the Terai plain. Total forest area in 1977 was 4 mill. ha, plus 2 mill. ha scrubland, giving an annual yield of firewood of just under 7 millions m , while the estimated demand was just under 10 millions m , creating an annual deficit which is expected to rise to 8.6 millions m³ /year by the end of the century (Krishna Yantra Bikash 1985). The livestock population is estimated to be about equal in numbers to the human population (H.M. Govt. 1985). It is estimated that the energy consumption in 1980/81 was 8,886 KT firewood, 210 XT agricultural wastes and 93 KT animal wastes (554 kg, 13 kg and 5.8 kg per capita/year, respectively. A rural household consumes about 55 l kerosene/year for lighting.

Organization of energy sector

Overall coordination is directed by the Water and Energy Commission (WEC), headed by its Secretary (WECS). This commission is responsible for planning in both energy and water. Biomass saving technologies, i.e. biogas plants and wood-saving stoves, have been give highest priorities. The Biogas and Agricultural Equipment Company (PV) Ltd. was established in 1977, with the joint investment of the Agricultural Development Bank (ADBN), the United Mission to Nepal and the Nepal Fuel corporation. ADBN is responsible for loans and subsidies to farmers, and acts as coordinator for activities.

Its annual budget is Rs. 11.258 (US' 536,100) with a break even point of 350 digesters constructed annually.

The potential for biogas plants fed by cattle manure (gobar), the only fuel at present available, is limited by the fact that only a very small percentage of farmers own 5 - 6 head of cattle, the minimum number required to operate the smallest digester. The Water and Energy Commission considers 375,000 family- sized units to be the upper limit for the market. Installations and Construction

Both fixed dome and floating drum plants are built, though the latter (at first the only model available) has been practically phased out in the last few years. Up to 1986, more than 2,060 digesters have been built, over 70% of them in the Terai. The figure of 200 - 300 constructed per year has remained fairly constant.

Between 1973 and 1979, plants of 7 and 13 m3 were built, while between 1979 - 1986 the dominant size was above 10 m (fixed dome). It was planned to raise the number of plants built per year to 1,120 by 1990. Characteristic of the Nepalese version of the fixed dome digester is that the dome is covered with earth to a depth of 60 cm, with the digestion chamber dug out underneath it in situ. Inlet and outlet chambers are built of brick. This digester is largely built of local materials. In the floating drum model, the taper design is preferred in the Terai, where the water table is high. The latter is the more productive model, with a specific yield of 0.42 and a retention time of 56.7 days (compared with 0.3 and 83 days for the fixed dome model) but this does not compensate for the higher specific cost of construction.

No solution has been found to the problem of low ambient temperatures: in winter, production decreases by up to 50% in the Terai, and ceases altogether in the hills.

Utilization of effluent

No detailed information is available on the use of the slurry: it is assumed that farmers spread it on their fields after drying.

Costs and benefits

Construction costs per m³ decrease with increasing size of the digester, and are lower per m³ for floating dome digesters. The Company is training masons, but its building capacity is still above demand. But for the subsidies, building and running the plants would not be economically feasible for the farmer. Only in the main towns, where firewood is expensive, and in the case of community digesters, whose yield replaces diesel oil to run machinery, does the cost:: benefit ratio balance. In the hills, the 25% subsidy compares with a 41% -subsidy that would be needed to bring the cost: benefit ratio to 1:1 or better. Clearly, the biogas digester is not, at this stage, an attractive proposition to small farmers.

Research and development

There is no overall coordination or planning in this field. The Biogas Company is conducting research on biomass digestion and biogas appliances (including the Red Mud Plastic cover), the Soil Science and Agricultural Chemistry Division at Trithuvan University in Katmandu conducts research on effluent utilization. United Mission to Nepal has tested a tunnel design, 20% cheaper that the fixed dome, but has not yet published results.

Experiences with biogas

The Biogas Company claims that 95% of the family-sized plants built are in operation, including most of the 709 floating dome models built in the earlier stages of the program, some of which are now 13 years old (1986) but this figure is unchecked and seems high. Of the 38 community digesters built, 80% are said to be in working order. Although the Government has given biogas technology the highest priority, it would be necessary to built a total of 375,000 digesters to achieve a saving of 12% in firewood. This would necessitate the training of more masons, while in the meantime demand is still below building capacity. A problem arises from the fact that farmers are not prepared to use effluent that has been produced with an admixture of night soil in the feedstock. The absence of comparative research on the production of different designs is a drawback.

Pakistan The Federal Ministry of Petroleum and Natural Resources, the Ministry of Natural Resources, and the Appropriate Technology Development Organization are engaged in biogas development. More than 100 plants of the floating gas-holder type had been set up by 1975. It was planned to set up 1,000 plants during 1981. The Government provides incentives to tile beneficiaries for the plants in the form of free appliances and gas-holders. The Ministry of Natural Resources has plans to create alternative energy sources in 50 selected villages mainly through the establishment of biogas plants. Some 35 biogas plants have been established by the Appropriate Technology Development Organization.

Attention is being given to the development and establishment of fixed-dome design plants because of their lower costs and the non-requirement for steel in their construction.

Papua New Guinea Work on integrated biogas systems, which include necessary provisions for the utilization of effluent for growing algae and aquatic plants, fish culture and fertilizer has been in progress since 1970. A bag-digester type of plant, much cheaper than the conventional design, is also being developed. The digester is made of 0.55 mm thick hypalon laminated with neoprene and reinforced with nylon sheet.

The Philippines Interest in biogas development grew with encouraging reports of the official mission of the Philippine Coconut Administration after its return from a European tour in 1965. In earlier days, the main interest in biogas stemmed from its pollution prevention and public health aspect" rather than from its fuel energy generation potential, as firewood was plentifully available. Now biogas is considered as the most feasible form of renewable energy resource for rural areas. A variety of feedstock consisting of domestic urban wastes, agricultural and animal wastes and food processing, distillery and industrial wastes are available for biogas generation.

Maya Farms has been the pioneer in the development of biogas technology since 1972. In order to obtain the necessary experience and to assess the suitability of different types of plants, demonstration models of Indian, Chinese and European types were set up. The models were later modified and used as pilot plants. A farm workers' dormitory night-soil biogas digester has also been designed. Biogas produced at the farm meets 40% of the total power requirement of the farm and is used for home applications, cooking vats in the canning plant, fueling of burners for heating and gasoline engines, running a feed mill, operating a 60-kVA electric generator and running farm vehicles. The organizations engaged in extension of biogas technology are the National Housing Authority, the Engineering Battalion of the Military, and the Department of Community Development. The Development Bank of the Philippines grants loans to farmers at low interest rates.

As a part of the development efforts, a "crash programme"" aimed at establishing plants in every region, province, town and locality, was initiated as early as 1976. More recently, the Bureau of Animal Industry (BAI) in cooperation with the Energy Development Board, launched the Biogas Barangay programme in 1980. Loans are made available to livestock owners through Financial institutions. Demonstration projects at the regional and provincial levels have been established by BAI. About 450 plants have been established under the programme. Fresh pig manure availability is estimated at 8.9 million metric tonnes per year, indicating a biogas production potential of 502 million m per year. The Indian design with a floating gas-holder is more popular. Recently, 10 digesters with a fixed-dome design have been established.

The National Institute of Science and Technology (NIST), University of Philippines, Central Luzon State University and Maya Farms are the institutions actively engaged in research. Various aspects, such as optimum requirements for biogas production, loading rates, feedstocks and their suitability, and microbiology are being investigated. Ten methanogenic isolates to be used as starter culture have been developed by NIST. Integrated biogas systems which involve cultivation of algae, fish and rice as components of the system are being developed at the University of Philippines.

Singapore There is not much scope for small-scale biogas plants in Singapore. Biogas produced at the sewage treatment works is used for operation of dual-fuel engines to generate electricity.

Sri Lanka Of the total energy consumed, 60% derived from firewood. Some 80% of the firewood is used in the rural areas. The forest reserves are being depleted and the availability of firewood is declining. Interest in various non-conventional energy sources, e.g. wind, biogas and waste materials, is developing. A demonstration plant was established by the Industrial Development Board as early as 1974. Further research work is being carried out at the Peradeniya and Katubedda Universities. Biogas digesters are being established in a rural village under the Asian Rural Energy Project with the assistance of UNDP. An integrated farming system with biogas as a component is being developed at the In-service Training Institute at Gannoruwa.

Thailand Thailand has a total population of some 50 million, growing at an annual rate of 2%, of which about 83% lives in rural areas. The country is divided into 5 regions: South, Central Plain, North, North-east and East, totalling 513,000 sq.km. About 75% of the population is engaged in agriculture, including pigs and cattle.

Four fifths of these farm families own less than 5 pigs or less than 4 cows. All but 10% of rural fuel is in the form of biomass (wood, charcoal, residues): in 1983 requirements were estimated at 41 million m . The total sustainable firewood supply was estimated at 28.5 million m in that year, according to one authority (Atal et al. 1984), but only 11 million m according to TSTR (1986). The rate of deforestation during 1976-80 was 333,000 ha per year, leading to a decline of 41% in the last 25 years.

Installations

The Central, North-east and South Regions have between them 94% of the plants built to date (1986). Central Region has 1,000 plants, almost equally divided into Type 1 floating drum models (in which the dome floats on the slurry) and fixed dome model=. Northeast Region has a total of 689, and South Region 689 plants, in both cases some 75% being fixed dome models (Source: Thailand Institute of Scientific and Technological Research).

The planned target of installations by 1986 was 10,000, but by the end of 1984, 5,000 had been built, at the most. 70% of these were built on cattle farms, 30% on pig farms.

The climate favours biogas production, except in the north, ambient temperatures enabling a potential specific yield of 0.3 to be attained, with a 20-30% decrease in winter. Use is almost exclusively for cooking, with a few adapted gasoline engines run on biogas. NEA is conducting research and disseminating small digesters to be used for lighting. More than half the families owning biogas plants use it in combination with other fuels.

Effluent utilization

Effluent is dried and spread on fields in a solid state, partially composted.

Costs and benefits

There is no subsidy on biogas digesters: the payback period on investment is in the region of 5 years or more, when biogas is used to replace charcoal. Consequently, the use of plants is confined to families with relatively high incomes. The Government does subsidize demonstration plants, paying 100% of their costs, and giving a subsidy of 50% for special promotion schemes: about 500 digesters have been built on this basis. In addition, training courses and technical advice are free.

Experiences with biogas

Not more than 61% of the plants installed are operating properly. Of those abandoned, more than half worked for less than a year. Generally the reason is poor construction.

It is worthy of note that, unlike in India, Nepal, etc., farmers in Thailand are not familiar with the uses of dung, either as manure or as a fuel. In this respect, at least, the biogas program has proved a success, since nearly all plant owners use the effluent as fertilizer.

Organization of the biogas sector

The National Energy Administration (NEA) is the Government Agency responsible for the biogas program in all its administrative aspects, and chairs a national committee on biogas that includes representatives from all interested Ministries, Research Institutes and Extension Agencies. The NEA allocates subsidies for demonstration plants to various Extension Agencies, irrespective of design, cost or after-service. All Government Departments use their existing infrastructure for the dissemination of biogas plants; the most active is the Sanitation Department of the Ministry of Public Health, which provides construction and training through 7 regional centres. Its organizational structure for Regional Centre 4 is shown below, in Figure 13.6. The Department of Agriculture Extension maintains a network of provincial station, in which biogas is a minor activity, conducting courses and aiding farmers to build plants. The NEA has 7 regional energy development centres, dealing with biogas, but higher priority is given to tree planting and wood- savina stoves

Fig. 13.4: Organizational structure of Regional Centre 4, Sanitation Division

Viet Nam Tuhem Agricultural Station and the Institute for Electrical and New Energies, Hanoi, are involved in biogas research. Aspects like use of local construction materials, design of clay burners, and the use of different feedstocks and their mixtures are being investigated, A few demonstration units in different regions have been established. A national biogas development programme is being considered by the Government.

Latin America. and the Caribbean Very little information on biogas development is available for this region. The available information for various countries of the region is summarized below. The Organizacion Latinamericano de Energia encourages, coordinates and supervises biogas technology. It maintains close contact with member countries and keeps detailed records of research, development, construction and utilization. Altogether 8,712 plants have been built in the region, of which 72% are working adequately. Roughly one third are of the continuous type and one third semi-continuous. By and large, finance has come from outside donations or private sources. Consequently, little experience has been obtained at family level.

Argentina Although biogas technology has been in use for several decades, its use has been limited to decontamination of sewage, and until recently no use was made of the biogas. In addition, there are some plants being used for research. Therei. no central authority in charge of the topic. Since 1988, there are the beginnings of efforts to disseminate the technology to rural areas and train workers. At that date, there were only 50 units in the country.

Barbados FAO funded the building of 4 units in the '80s, which were used for the treatment of sewage. Both biogas and effluent are being utilized.

Bolivia With the encouragement of OLADE (Organizacion Latinamericana de Energia) a small number of digesters have been built in the last 10 year, half of the in the rural sector. The predominant model is the OLADE-Guatemala (discontinuous) model (qv). Only some 30% of all the digesters are at present in operation (1988). Costs have been high. There is a technical problem concerning operation of biodigesters in the cold highland.

Brazil Development of biogas technology reached the pilot plant stage in 1979: widespread dissemination began the following year, under the aegis of the Ministries of Agriculture and Energy. A total of 7389 units, mostly of the Chinese type, had been built by 1988, of which 75% were working adequately at that date.

Auxiliary equipment has been successfully manufactured by private companies. The program has been well accepted in the rural sector, as well as in municipal sanitation, but the absence of subsidies and limited number of extension workers have limited dissemination. Although biogas is widely used for heating, lighting, cooking and the generation of electricity, the success of the program lies in the use of the effluent as fertilizer: it is in this field that return on investment" is found.

Colombia The few digesters that have been built have been installed by wealthy farmers. The dominant model (70%) is the Indian Floating Dome,

Costa Rica A small number of biogas digesters have been built by private investors and by the Institute of Technology. Although half-bag and full-bag models are preferred, building costs have been high. Consequently, rural development is very low. A National Biogas Commission operates under the Ministry of Energy and Mines.

Cuba The National Energy Commission and Ministry of Agriculture co-ordinate a National Biogas Group, under which some 550 digesters have been built since 1983, almost all of the small Indian type (6 m capacity). Financing has been done by Government. Most of the digesters serve remote rural dairies, where the gas generates their electricity. The percentage of digesters operating adequately is high.

Chile The few digesters that have been built are at the level of demonstration plants.

Dominican Republic The first demonstration plants were constructed by OLADE in cooperation with the National Energy Policy Commission in 1980.

Few plants have teen built (half of them the Chinese model) and of these, less than half are operating today.

Ecuador Biogas technology was introduced into the country by the Peace Corps and OLADE in 1974. The National Institute of Energy (INK) began a program for training and dissemination in 1980, and has been responsible for the building of half the 65 plants that existed in 1988. Most of these are of the Indian type. However, only 35% are operating adequately. The Government has subsidized the cost of a number of plants, in addition, others were built from donations by OLADE, the Peace Corps and FAO. Changes in methods of cattle management were necessary during the early stages, but in general, the technology has been well accepted in rural areas, though it is beyond the resources of small farmers.

El Salvador Technology has not advanced beyond research and a certain amount of training. Three quarters of the plants built are no longer working. The University, the Agricultural College and the Peace Corps are among the bodies involved in the introduction of biogas into the country.

Grenada A small number of units have been built since 1979, half of them by the Agricultural School, but no national program exists for training or dissemination. Plants are too costly for individual farmers, but the use of the effluent for fertilizer has been well accepted.

Guatemala Activities were initiated in the 50s by OPINA, a private firm. By 1977, 13 units had been built, all on the southern coast. Dissemination to rural areas began in 1980, and work was consolidated by the establishment of a National Biogas Group. 400 units had been built by 1988, a good percentage of which were in adequate operation at that date. The most widespread model is an adaptation of the semi-underground Sichuan model, built largely of local materials, developed by CEMAT, a non-government R & D centre.

Especially interesting is the success of dissemination to small farmers in highland areas. A number of private institutions are involved in construction, with training and overall coordination of programs for training and dissemination organized by the Government, which also endorses loans and credit, through the Institute of Agricultural Science and Technology.

Guyana OLADE and the National Energy Authority introduced the biodigester into the country in 1980. By 1988, 20 units had been built, mostly of the Chinese type, the most successful, others of the OLADE/Guatemala model. Little information is available on dissemination and training.

Haiti Only a very few demonstration plants had been built by 1988.

Honduras Over 100 plants have been built since OLADE and the Government introduced them into the country in 1980, the best accepted being the Chinese model, which represents 77% of the total. Funding was from external sources: OLADE, ACAITI and FAO.

Operation of plants that were totally subsidized has not proved successful, due to poor location, in some cases, or loss of interest in others. The cost of biogas units is outside the reach of poor farmers.

Jamaica With OLADE support, the Government, through the Ministry of Energy and the Scientific Research Council, began the dissemination of the technology in rural areas. FAO has also instituted training and promotion schemes. 41 units had been built by the end of 1988, 71% of them being the Chinese model. There is a loan system for their construction, and returns have been good, especially in the use of effluent as fertilizer.

Mexico A few demonstration models have been built, but the level of operation is low. Since energy sources are cheap in Mexico, interest in biogas is correspondingly low.

Nicaragua Few units have been built; and many of these were of the piston-flow horizontal type, with which experience has not been good.

Panama The technology program began in 1979, but only demonstration models have been built, mostly the horizontal type with piston flow. A community digester project was unsuccessful.

Peru 61 digesters have been built since 1979, 77% of the Chinese model. Three quarters were working adequately up to 1988. Costs have been notably lower than in neighbouring countries.

Trinidad and Tobago The Government of Trinidad and the University of West Indies (Chemical Engineering Department) are conducting biogas research. Efforts are being made to develop a suitable anaerobic digester for sugarcane bagasse.

Uruguay Six out of 9 demonstration plants built in the 80s are of the Indian type. Efforts are now being made to introduce the Chinese model into small dairy cooperatives.

Venezuela Given the availability of oil, few plants have been built, and those for demonstration purposes. They are used for sewage treatment and the generation of electricity. Initiative came from The Ministry of Energy and Mines and the School of Agronomy of the University. No national program exists; but the use of firewood as fuel in rural areas constitutes a problem.

Africa

Burundi Biogas technology was introduced in 1981, since which time 140 plants have been built, mostly family units of the Chinese or BORDA type.

Kenya In the 70s, a national program, the Special Energy Program, began the dissemination of biogas plants, aiming at medium-sized farms. In the first decade, a wide diversity of types were built, most of which proved either unsuited to local conditions or defective in construction. Learning from this experience, by 188 some 250 plants had been built, backed by a training program, supervision of construction quality, and concentrating on a single type (BORDA floating cover). There is no subsidy available to users.

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