Biogas Production, Mixture Different Gases, Varied Composition, Anaerbic Microorganisms, Domestic and Agriculture, Contains Methane in Bulk, Gobar Gas Plants

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Environment and Energy
Environment and Energy Introduction
Fossil Fuels Non-Renewable Sources of Energy
Non-Conventional Sources of Energy
Renewable Sources of Energy
Biomass Production and its Utilization for Energy

Biogas Production.
Biogas is a term used to r
epresent a mixture of different gases (in varied composition) produced as a result of action of anaerobic microorganisms on domesitc and agricultural wastes.

It contains methane in bulk (50-86%) and other gases in relatively low proportions viz., CO2 (25-35%), H2 (1-5%), N2 (2-7%) and O2 (0-01%). It is believed that in China there are five million simple installations of biogas in rural areas

Similarly, in India a large number of Gobar Gas Plants are being used by villagers not only as cheap source of energy, but also as a measure for pollution control, and for improvement of health and sanitation conditions.

Biogas plants also provide highly enriched organic fertilizer. In 1961, a Gobar Gas Research Station was also established at Ajitmal (district Etawah in U.P.), which has designed a variety of ‘gas plants’ suited to Indian conditions for supply of electricity at a cheap rate.

The digesters in ‘gas plants’ are al most entirely burried underground, with a fixed dome that serves as a gas holder.

Design of a Gobar Gas Plant Developed a Indian Agricultural

1. Cow dung Mixing Tank	9. Iron Rod
2. Earth Platform	10. Counter Poise Weight
3. Gas holder Slurry Level	11. Slurry Outlet Channel
4. Fermenter	12. Gas Cock
5. Cowdung Inlet Pipe	13. Gas outlet Pipe
6. Ledge	14. Drying Bed
7. Platform	15. Brick wall
8. Pulley	16. Gas mOisture Exit Trap

Biogas is produced by anaerobic digestion of animal waste, as discussed above. It involves three steps;

(i) hydrolysis, which converts organic polymers into monomers (with the help of hydrolytic bacteria);

(ii) acid formation, which involves conversion of monomers into simple compounds such as CO2, NH3 and H2 using a group of acid forming bacteria (acetogenic bacteria) and

(iii) methane formation involving conversion of simple compounds into methane (CH4) and CO2 utilizing anaerobic bacteria (methanogenic archaebacteria).

For commerical biogas production in India, cattle waste (dung) is the prime source. Following are the major operation for biogas

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Design of a gobar gas plant developed at Indian Agricultural Research Institute (IARI), New Delhi production :

(i) dung and water are mixed in 1:1 ratio, so that inorganic particles (or rajkans) are maintained at 10% level (dung usually has 20% rajkans);

(ii) dung feeding rate is maintained at 3,500 kg/day, although it may vary with the size of the digester.

In addition to dung, the input may include the following :

(i) recycling of 20% sharer of fresh slurry, (ii) use of night soil (3% of fresh slurry), (iii) use of wastes from kitchens and (iv) use of calcium amm nitrate (1% of fresh slurry).

It has been shown that the production of biogas can be increased by increasing the input from 38.6 litres/kg (where only dung is used) to 59.6 litres/kg (when dung is combined with other inputs).

These other inputs prove useful in growth and multiplication of bacteria, which help in anaerobic digestion. The optimum temperature for biogas production ranges from 35°C to 38°C, which is achieved sometimes through the use of solar panels. The pH or slurry is maintained at 7 (neutral medium).

Conservation of Energy