Bio energy is a store house of solar energy which can play significant role in providing solution to rural energy crisis. It is a clean and cheap source of energy which improves sanitation and hygiene, removes the drudgery of women folk and produces enriched organic manure for use in agriculture. Bio energy may be obtained through bio-degradable material like animal dung, human night-soil, kitchen wastes, water hyacinth, agricultural residues and city wastes etc.
In India about 1,000 million tones of organic wastes in the form of crop residues and about 300 to 400 million tones of animal excreta are available annually. It is estimated that if all these materials are utilised, about 70,000 million cubic meters of methane gas equivalent to about 160 million tons of fuel wood could be produced.
This will meet nearly 50 per cent of the rural domestic fuel requirements of the country. This total biomass will yield approximately 6 million tones of nitrogen, 2.5 million tones of phosphate, 4.5 million tons of notassium and 50 million tones of compost fertiliser (Sixth Five Year Plan, p. 104).
In 1981-82 the total number of biogas plants installed in the country was 2.5 lakhs which increased to 17.5 lakhs in 1991-92 and 27.13 lakhs in 1997-98 exhibiting an increase of 985 per cent during the last 16 years. It generates fuel gas equivalent to the saving of about 86 lakh tones of fuel wood per year, valued conservatively at approximately Rs. 415 crore per annum. Besides these plants are generating about 41 million tones of enriched organic manure per annum for supplementing chemical fertilizers and improving soil fertility.
Under the production programme of biomass efforts are being made to develop new species of plants which could grow faster and mature in a shorter period of time so that fuel wood could be made available at the earliest possible time. Under the biomass utilisation programme, the two main components are biomass briquetting and biomass gasification.
The briquetting programme utilises agricultural and forest residues for making briquettes. It is estimated that about 145 million tones of surplus agricultural residues are available annually in the country which could be converted into briquettes to generate about 14,000 MW of power equivalent. Under the gasification programme, 12 designs of biomass gasifiers have been developed for generating thermal energy for industrial applications, for water pumping and also for power generation. These gasifies make use of wood chips, coconut shells and similar other biomass.
The gasifies of power generation capacity ranging from a 3 KW to 500 KW capacities have been developed. A 500 KW capacity biomass gasified system for power generation has recently been installed in Gausaba, Sundarbans Island, and West Bengal. Similarly one biomass gasified for captive power generation, at M/s Guru Tea Factory, Koonoor, Tamil Nadu, for drying tea leaves, and one 20 KW gasified system for electrification of a village in Tumkur district, Karnataka, have been installed. In order to promote biomass gasification and briquetting programmes, the Government of India is providing financial assistance in the form of subsidy and also a low interest rate loan from the Indian Renewable Energy Development Agency Ltd (IREDA).
The biogas programme is subjected to a number of problems like availability of adequate amount of cattle dung (8 buffaloes are needed to produce 2 cu.m. of biogas for a family of 6 members), water (1 litre of water per kg. of dung), labour (to prepare dung solutions) and space; non-operation of the plant at low temperature (the gas producing bacteria are active at a temperature of 35°C but become dormant below 20°C); unfavourable cost-benefit ratio; lack of financial support; and difficulty in post installation maintenance.
So much so that only afoul 45 per cent and 49 per cent of total bio-gas plants I Rajasthan and Uttar Pradesh respectively are in working condition (cf. national average of 77 per cent). Still biogas is a cheap and dependable sort of energy and play significant role in providing solution to rural energy crisis. The R&D efforts art on for improving the technology and reducing the cost of biogas plants. The technology for use in tins cold climatic regions of the country is also being I developed.