A Pilot Investigation Project P B Ghate This paper discusses the advantages of large size community biogas plants over smaller individual family plants. It describes a pilot project, still under implementation at the time of writing, designed to investigate these advantages, and discusses results observed so far on the basis of preliminary cost data. The question of scale economies is discussed in some detail It also discusses the economic or social viability of a biogas based decentralised energy system such as this one and the charges that might have to be levied to achieve financial viability. The last part of the paper attempts to assess the role of such a system is meeting rural energy needs, especially for irrigation pumping, when viewed in relation to the electricity and diesel alternatives; BIOGAS (gobargas) is the cumbustible gas produced by the anaerobic fermentation of cellulose containing organic materials such as cattle dung, crop residues and vegetable wastes, water hyacinth, etc. The biogas plants currently being extended in India consist of a well-shaped brick masonry digester into which a cowdung and water mixture is introduced through an inlet pipe. Gas collects in an inverted steel drum,. or gas holder, which floats on the slurry and from which the gas is led off through a pipe at the top. The spent slurry is displaced automatically through an outlet pipe and is as rich in nitrogen (N), phosphorous (P) and potassium (K) as farm yard manure. While about 50,000 small family size plants have been installed around the country (with daily gas production capacities ranging typically from 2 to 10 cubic matres) very few community plants have been installed so far largely because of the formidable organisational and managerial problems involved. 1 The advantages of large size community plants, however, are fairly well recognised.
