Biogas or gobar gas is a combustible gas.It is produced through the anaerobic breakdown of waste biomass.The biogas plant consists of the following parts:- 1) Inlet or charge pit:- for passage of slurry into the digester.The raw material used is cattle dung, farm refuse, organic waste.2) Digester:- cylindrical tank which is airtight, above which is present a floating gas holder of metal with an outlet of gas and pit for removal of sludge.Here the organic wastes get solubilized into simpler substances called monomers (solubilisation).Monomers change to organic acid by fermenting microbes (acidogenesis).Organic acid mostly formed is acetic acid.Methanogens become active and act on components of microbial digestion and form methane gas (methanogenesis).3) Outlet:- consists of sludge which is used as manure.The methane gas formed in this process is used for cooking and lighting.