Biogas predominantly containing methane gas is produced by the action of microbes. Certain bacteria growing anaerobically produce methane gas in large quantities along with the release of ${\mathrm{C}\mathrm{O}}_2$ and ${\mathrm{H}}_2$ and hence such bacteria are also known as methanogens. Excreta of cattle contain methanogens in large amounts and hence cattle dung is used in making biogas. Biogas is made in the biogas plant where cattle dung is added to the biowaste. Biogas is supplied to the nearby houses through the pipes while the remaining waste is used as manure. Manure is rich in fertilizer and hence used in agriculture.