Methane production
Methane is produced during anaerobic decomposition of sewage and other organic wastes by bacteria. The methane thus produced is collected and used as fuel in many countries. The methogenic bacteria are able to utilize acetate, methanol, formate, and H₂ + CO₂ of the organic wastes for the production of methane gas. The starting materials in the wastes are, however, complex organic molecules such as cellulose, starch, fats and proteins. These are first broken down by other micro-organisms into simpler substrates such as acetate and H₂ + CO₂. The methogenic bacteria then act on these to produce methane, as shown in diagram.

In anaerobic sludge digestion process, upto 600 litres of methane is produced per kg dry organic matter. The biogas generated in such a process contains 60-70% methane, 25-30% CO₂ and the rest is H₂ + N₂. In our own country, small and inexpensive installations have been set up in the villages to convert cow-dung into biogas. About 200 to 1000 litres of methane per kg dry cow-dung is produced at 55˚C, in such installations. In most systems, the amount of biogas generated increases with the increase in temperature. The time for the generation of gas is also reduced at high temperatures.

Production of Methane