Biomass is produced by the anaerobic degradation of animal wastes like cow-dung (or plant waste) in the presence of water. This degradation is carried out by anaerobic micro-organisms called anaerobic bacteria in the presence of water but in the absence of oxygen.Slurry of cow-dung and water is made in the mixing tank. This slurry flows into the digester having no oxygen. Anaerobic micro-organisms decompose or breakdown complex compounds of the cow-dung slurry. It takes a few days for the decomposition process to be completed and generated bio-gas. The biogas is stored in the gas tank above the digester from which they are drawn through pipes for use.