Answer: Methane
Gobar Gas (a form of Bio gas) is a clean unpolluted and cheap source of energy which is produced from cattle dung in a bio gas plant commonly known as gobar gas plant through a process called digestion. It consists of 55-70% methane which is inflammable and used as cooking gas in rural area.
Source: http://gk.queryhome.com/2239/which-main-constituent-gobar-biogas-generated-composition
