Biogas is a mixture gas, main composition is methane (CH4) and carbon dioxide. Methane covers 40% ~ 70%, carbon dioxide covers 30% ~ 40% and also a bit of other gas like hydrogen, carbon monoxide, hydrothion sulfide oxygen, nitrogen,etc. Because there are abundant of methane, the biogas can be used to generate electritity power. Biogas is a kind of product that organics is resolved by bacterium under the anaerobic condition. Garbage in the city, sludge in the sewage treatment plants, livestock excreta from farm and straws all can be used to produce biogas.