Process of Biogas Production- The process of biogas production is explained using' gobar gas' as an example. 'Gobar gas' plants are based on excreta of cattle and other farm animals, which contains about 20% inorganic dust particles. The level of dust particles is reduced to about 10% by mixing the dung with water in 1:1 ratio. The feeding rate of a typical dung based biogas plant is at the rate of 3,500 kg dung/day.

Therefore, biogas production during winters and in colder regions requires thermal insulation and/or heating of the digesters. The pH of slurry should be around 7, which is not a problem when cowdung is used as substrate. Under favourable conditions, the biogas yield may be upto 60 l/kg of dung.

The digesters in various biogas production schemes may be operated either under mesophilic (20-25°C to 40-45°C) or thermophilic (50-55°C to 60-65°C) conditions, each involving different bacterial species. Mesophilic operation is safer and more stable but, thermophilic operation is more likely to inactivate pathogens and animal parasites.