Community Biogas Plant at Pura for Water Pumping & Illumination

It is reported that only about 10% of Karnataka's Electrical Energy flows to rural areas, and that, even when villages are electrified, less than 10% of their households obtain domestic connections. These connections are solely for the purpose of lighting, and the requirements of cooking are almost are never considered in conventional planning, though this accounts for almost 90% of the energy consumption in villages. Rural folk, therefore, have to use the so-called 'non-commercial' fuels, viz., the main fire wood, dung cakes and vegetables wastes. Where firewood is the main source of cooking fuel, its gathering becomes a major activity this crucial household chore. But, fuel wood is becoming scarce with the increasing felling of trees resulting in the chore becoming more and more difficult. In this context, the provision of cooking energy needs becomes a very important development task.

One approach to this problem is to step up centralised energy production, and to set up transmission lines to villages even if they are remote from the grid. This approach involves heavy investments, long gestation times; and quite often, it does not yield adequate returns.

Another approach is to make maximum use of locally available renewable energy sources. One such explorable resource is the large amount of cattle-dung produced in a village. This dung can be anaerobically fermented in biogas plants (gobar gas plants) to yield a combustible biogas fuel in addition to a sludge which serves as an excellent fertilizer. Though such an idea is superficially attractive, it is important to examine the feasibility of the biogas approach to decentralized rural energy supplies.

In order to obtain an understanding of energy consumption patterns in rural areas, a detailed survey was carried out in six villages in Kunigal Taluk, Tumkur District. The survey was designed to provide information on (1) the population of village; (2) The number of households; (3) the number of cattle excluding goats and sheep; (4) the amount of dung collected in the houses; (5) the consumption of Kerosene for illumination, of water for drinking and other household uses, and of firewood for cooking fuel; (6) the efficiency of village stoves (5%); (7) the species of wood used in the villages as firewood etc.,

Simultaneously, an experimental biogas plant was set up in the Indian Institute of Science and operated since the end of 1976 to obtain reliable information of gas yields, gas composition, Nitrogen content of sludge etc., over 18 months of operation. This experimental plant showed the following performance : (1) 34 cm3 of biogas per g. of wet dung, (2) Biogas composition : 80% methane and 40% carbon dioxide, (3) 2.16% Nitrogen in biogas sludge.

The village of Pura was then chosen for feasibility study . Pura with a population of about 340 and 60 households, and a cattle population of about 146 has a wet dung availability of about 1,350 kgs. per day corresponding to an estimated biogas yield of about 45 cubic meters per day. Preliminary estimates indicate that this gas production is sufficient to meet all the cooking energy needs of the village which currently requires 570 kgs. of firewood per day, and leave enough gas to run a Kirloskar 5 HP biogas engine for several hours for compressing gas for pipeline distribution, for lifting water for house-hold water requirements, for electricity generation, etc.,