After reading this essay you will learn about:- 1. Sources of Biogas 2. Biogas Technology 3. Programmes in Developing Countries 3. Experience 4. Uses 5. Financial Assistance from Government.
Sources of Biogas:
Fuel can also be produced from organic waste products viz., sewage, garbage, manure or crop residues. These wastes decompose in the absence of air—methane gas released. This methane gas acts as a biogas.
This is an alternative source of energy, which has immense utility in waste disposal and energy generation in environmentally sound manner. Domestic or community bases biogas plants are now effectively operated in various countries over past couple of decades.
A biogas plant supplies energy and fertilizer. It improves hygiene and protects the environment. ‘Biogas’ is produced by putrefactive bacteria which break down organic material under airless conditions. The process is called “anerobic digestion“.
All feed materials consist of organic solids, inorganic solids and water. The waste of much feed materials can be used for biogas generation.
A biogas plant is simple so that it can be operated by housewife also. Biogas consists of about 60% methane and 40% carbon dioxide. It is somewhat lighter than air and has an ignition temperature of approximately 700°C (diesel oil 350°C; petrol and propane about 500°C). The temperature of the flame is 870°C.
Biogas digester can decompose a number of organic wastes. Usually, for better gas production the following percentage of organic wastes are mixed together.
Cattle manure (65%), Poultry manure (55%), Straw (59%), Grass (70%), Leaves (58%), Kitchen waste (50%), Algae (63%), Water hyacinth (52%). The first gas from a newly filled biogas plant contains too little methane. The gas formed in the first 3 to 5 days must, therefore, be discharged unused.
During the digestion process, gaseous nitrogen (N2) is converted to ammonia (NH3). In this waste soluble form the nitrogen is available to the plant as a nutrient.
Three types of biogas plants are known:
Balloon plant, Fixed-drum plant and Floating drum plant. Fixed-dome plants are considered to be less expensive and easily operable, though there is scope for gas leakage and fluctuation of gas pressure.
Biogas Programmes in Developing Countries:
Most countries became aware of biogas technology by the middle of the twentieth century.
However, real interest in biogas was aroused from 1973 onwards, with the onset of the energy crisis, which drew general attention to the depletion of fossil fuel, energy resources and the need to develop renewable sources of energy, such as biogas. The importance of biogas as an efficient, non-polluting energy source is now well- organised.
International organisation like ESCAP, FAO, UNBIDO, WHO, UNEP have done considerable work in disseminating and development of biogas technology in developing countries in particular Afghanistan, Bangladesh, Bhutan, Myanmar, China, India, Indonesia, Iran, Israel, Korea, Malaysia, Nepal, Sri Lanka, Thailand, Philippines, Cuba, Chile, Brazil, Costa Rica, Mexico, Africa, Panama etc.
India has a total population of about 1.2 billion (1210.2 crores) people of whom 80% live in rural areas in some 576,000 villages. About 70% of them are landless. There are about 237 million head cattle, under the ownership of approximately 52 million households: of these 57% own 1-3 head of cattle, 27% own 4-6 head, 8.7% own 7-9 head and 6% own above this number.
According to rough estimates, 50% of India’s total energy comes from non-commercial sources, upon which the majority of the rural population survives.
Firewood (§5%), Dungcakes (15%) and agricultural wastes (20%). On average, these items cover 84% of rural household energy requirements. Between 1/3 and 1/2 of all recoverable cattle dung is burned as fuel. The annual requirement for firewood has been estimated as 133 tonnes. Total annual production is 49 million tonnes, leaving an annual deficit of 84 million tonnes.
Latest estimates by the Advisory Board on Energy give a figure of 16 – 22 million small biogas units in the country, on the assumption that 75% of all manure is available.
Experience with Biogas in India:
Activities have gained momentum since NPBD was launched in 1981 and DNES in 1982. Today, it is generally accepted among richer farmers that a biogas plant is desirable. The earlier period was taken up with problems, such as convincing bankers to give loans and setting up the organisational structure, subsidy system etc.
Problems which arose can be classified as:
(a) Design faults;
(b) Construction faults (unskilled builders or poor materials);
(c) Difficulties of financing (obtaining bank loans and delays in subsidy payment);
(d) Operational problems due to incorrect feeding (often the result of over-sized digesters, a status symbol) or poor maintenance;
(e) Organisational problems arising from the difference of approach and lack of coordination at the three levels of agency.
Lack of monitoring and surveys may lead to problems in the future. Alternative fuels to cattle dung must be found. The tendency to buy oversized digesters as a status symbol reduces the gain to the user. It is clear that benefits derived from the effluent are 2-3 times higher than the direct benefits of biogas, though this and other points are assumptions that are not backed by proper research.
Up to 1986, a total of 642,900 digesters had been built: in 1985/6 alone, the total was 185,800. In view of the huge potential, targets have been gradually increased. Construction capacity almost doubles each year. At the current capacity, it would still take 50 years to saturate the market.
However, this biogas programme, together with others (e.g., wood-saving stoves), has to compete with the pace of deforestation and other environmental hazards. Community and Institutional Biogas Plants (IBP) are being constructed in India. Poor farmers and dalits are supposed to be involved and to participate in operation of community biogas plants (CBP).
Use of Biogas:
The gas is commonly used for cooking and lighting. There are number of enterprises in each state that produce stoves and lamps. At some CPBs and IBPs, biogas operates engines or agricultural equipment. A number of enterprises in India manufacture or adapt diesel engines.
i. Utilisation of Effluent:
The effluent is usually dried in the sun, either separately or in combination with agricultural wastes. Partial composing is performed, after which it is applied to the fields in a solid state. There is no information on how widespread the use of effluent is, how it is applied or in what quantities.
A study was made comparing its use with that of fresh dung, for various purposes as of October 1985. It was found that the sale value of digested spent slurry, scientifically composted, is 8 times higher than that of fresh manure sold to the owner of a digester.
ii. Cost of Installation:
Cost of installation varies according to the type and size of the plant, increasing by about 65% between 1981 and 1986 or about 13% per year. There are also variations from state to state and district to district. There is an effect of economy of scale in both digester types.
A comparison of cost may be made on the basis of cost per m3 of digester volume. For the same hydraulic retention time (HRT), the Janata plants are cheaper by 33% or more than KVIC digesters.
iii. Annual Costs and Savings:
Annual costs through depreciation, interest on loans, maintenance, repairs, overheads, and labour costs have been calculated comparatively for digesters of 2 m3 gas/day for KVIC and Janata models. In the first 5 years, annual costs amount to Rs. 2,480 for a KVIC model at 40 days HRT, and Rs. 1,770 for a Janata plant at the same HRT, the latter model costing Rs. 1,920 for the 55 days HRT type.
On the other hand, annual savings through replacement of kerosene by biogas and fertiliser by composted effluent yield a marginal annual gain in the first 5 years.
Thereafter income and profit are dubious: first, calculations are made on the assumption that kerosene is used as fuel, when wood is more common, and secondly, there is a tendency to buy digesters larger than necessary. Furthermore, figures on income and profit are based on the subsidy given to the farmers.
Financial Assistance from Government:
In 2000, DNES provides financial assistance to:
(a) Purchaser’s subsidy;
(b) Service charge to State Governments and the KVIC;
(c) Turnkey construction fee;
(d) Incentives to promoters;
(e) Training programmes;
(f) Repair of plants with structural problems.
i. Organisation of the Biogas Sector:
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 24.25, though not in all cases is the scheme fully staffed.
ii. Potential for Biogas Generation and Digester Construction:
The only fuel available for family-sized digesters is cattle dung. This facilitates the assessment of potential, but, on the other hand, it restricts the use of biogas to cattle-owners.
On the assumption that 4 head of cattle are required to generate 2m3 gas (the cooking needs of a rural family of 8), there is a potential for 22 million digesters, though when cost to the family is taken into consideration, the maximum potential is 10 million plants, representing 19% of cattle-owning families.
Given an average capacity of 4 m3 gas per day, 40 million m3 could be generated daily. This would involve about 71 million head of cattle (10 kg dung per day, 20% or 0.28 m3 gas per kg total solids, about 30% of India’s total cattle population).
Up to at state level, the organisation 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 programmes.
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) Monitoring of programme and the submission of progress reports to the Government of India;
(f) Maintenance of subsidy accounts and the submission of expenditure reports to 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 (1985-1986 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 recognised 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 organisation 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.
Up to 1985, 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.