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close this bookCERES No. 058 (FAO Ceres, 1977, 50 p.)
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Biogas plants

It is estimated that about 1 350 million tons of cow and buffalo dung are burned every year as cooking fuel in India. This represents a serious problem; as much of this cattle dung could ,be used as fertilizer to increase agricultural production.

To try to avoid this wastage, the Indian Agricultural Research Institute in New Delhi began; as far back as in 1939; research on a process that would permit the use of cattle dung as fuel as well as fertilizer. This had led to the development of the gobar biogas plant, which produces combustible gas to be used as fuel, and se slurry residue used as fertilizer. Fermentation of a mixture of dung and water takes place in an underground chamber or well, and this produces gas, collected under a floating cap and piped, without further processing, to a stove or a lamp. By now, more than 10 000 gobar gas plants are used in India.

Experience has shown that the dung from four or five cows can produce enough gas to meet the lighting and cooking requirements of a family of five. Although the investment required to build a plant is relatively high (a few hundred dollars-depending, of course, on the size of the plant), it is recovered within a few years in the form of fuel, fertilizer and better crop yields. There are practically no maintenance or operating costs; some biogas plants in India have been operating continuously for more than 20 years.

Research and case studies have been carried out in India to determine the optimal designs, construction methods and materials, sizes and different uses of gobar gas plants (for instance, improving school or factory sanitation facilities by fermenting human excrements, and recovering the gas to reduce fuel expenditures).

Potential users in other countries can obtain detailed information from various sources:

Mohan Parikh, Yantra Vidyalaya, Suruchi Campis, Bordali, Gujarat, India 394601; Indian Council of Agricultural Research, New Delhi, India; FAO, Rome (Agricultural Development Paper No. 75, "Processing and utilization of animal by-products"); Nigel Florida, cuso, 151 Slater Street, Ottawa, Canada; a book in French, "Gaz de furnier," published by La diffusion nouvelle du livre, Soissons, France.