P.P.Shelke

A silent energy crisis is developing in India due to fast developing oil crisis.  At this juncture, it is needless to say about our Endeavour to tap all possible resources of energy in order to effectively deal with this situation.  We have realized that the importance of biogas plants on a large scale in the country goes to the Khadi and village Industries Commission since 1962.  The commission granted subsidies and loans for construction of these plants.  The growing popularity of gobar gas plants is evident from the rapid increase in the number of plants from 1621 in 1968-69 to 29285 at the end of March 1976.  Beginning almost scratch in 1962, the commission had constructed 59919 gas plants till March, 31, 1978 and it is targeted to install half a million gas plants by 1983.  The Government had decided to continue the subsidy for the construction of new plants under tapering subsidy basis.

These plants operate on the principle of anaerobic fermentation leading to the production of combustible gas called Methane.  The gobar (Cow Dung) gas plant can digest almost all the farm waste as well as semi solid house wastes.  The biogas plant has two main parts.  One is digester called fermentation tank with an inlet to feed the fermentable mixture in the slurry form.  The other is the gas holder with a gas outlet.  The gobar gas manure contains good quality humus.  This manure easily mixes with soil and prevents breeding of flies and mosquitoes and is free from odors.  A serious limitation of biogas is that only a small minority of rural families owns the minimum number of cattle required to supply the dung to sustain a plant of even the smallest size.  Installation of one large plant for one village is an alternative to this problem.

On an average a cattle produces about 4 Kg of dung a day, cow dung can produce sixty liters of gas.  An average of 5 Kg dung is sufficient to produce enough gas to cook persons meals.  The heat value of one cubic meter of bio gas is equivalent to 1.1 litre of alcohol or 0.8 litre of gasoline or 0.6 litre of crude oil or 1.5 cubic meter of L.P.Gas or 1.4 Kg of charcoal or 2.2 KWH of electricity.  The biogas manure contains 2% nitrogen as against 0.5% in the FYM.  To operate one H.P. engine for an hour about 425 liters of gas is required.  To set up even the smallest size plant at least 30 Kgs. Of dung per day is required.( from 6-8 cattle).  The smallest size of Gobar gas plant is 70 Cft.

The gas production from the gas plants already installed in the country works out to 130.22 million cubic meters, which is equivalent to 81.36 million liters of kerosene, value Rs. 82.15 million.  It has been estimated that the fermentation of 75% of the dung collected from the country’s 226 million cattle production (1961 census) would yield about 196 million MWH (million megawatt hours) of energy per year.  This is equivalent to about 24 million liters of kerosene and at the same time, 236 million tones of manure will be available.  The nitrogen content of this manure will be around 3.5 million tones, which is more than the fertilizer capacity established in the country. 

It is possible to establish 4 to 5 million gas plants in 575 thousand villages of India.  This would provide energy to substitute commercial fuel equivalent to 5431 million liters of kerosene value of Rs. 5484 million and it will also be helpful in conserving organic manure to the extent of 89.3 MT valued Rs. 4464 million which is otherwise burnt as  dung cake.

Only the beginning has been made in the direction.  The task is so colossal that all possible resource will have to be pooled to fulfill the target.   

ECONOMIC VIABILITY OF BIOGAS PLANT

The economic viability of 3 cubic meters per day capacity bio gas as per the estimates of Khadi and Village Industries Commission.

•A.  Cost of Installation (INR)

1.  Gas container and frame                                    701.00

2.  Piping and stores                                                260.00

3.  Fermentation tank construction (digester)       1114.00

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                                                                               2075

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•B.   Recurring expenditure per year

1.  Interest on investment @11%                                               228.25

2.  Depreciation @ 10% on the gas container and frame             70.00

3.  Depreciation @ 5% on piping and stores                                13.00

4. Depreciation @ 3% on Fermentation tank (Digester)               33.42

TOTAL                                                           344.77

C. Against the annual expenditure the income will be 1. Cost of gas generated ( 3 cubic meter gas is generated every day and its cost for one year @ Rs. 10 per 21 cubic meter comes to) 337.58 2. Cost of manure produced ( approximate value of 16 tones of manure @ Rs. 30 per tonne) 480.00

Total annual income                          857.00

D. Excess of income over expenditure

Profit  (INR)                                                 512.81

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