Which gas makes up most of the energy content in biogas?

Methane makes up most of the energy content in biogas.

Biogas is produced when microorganisms break down organic matter without oxygen, a process called anaerobic digestion. The resulting mixture contains methane and carbon dioxide, along with smaller amounts of water vapor, hydrogen sulfide, and other gases. Methane is the combustible component that provides most of the fuel value.

Biogas can be collected from digesters treating sewage, animal manure, food waste, or other biodegradable material. It may be burned directly for heat and electricity or cleaned into biomethane, which can be used similarly to natural gas.

Biogas is not the same as pure methane. Raw biogas also contains carbon dioxide and impurities, so upgrading is needed before it can meet many pipeline or vehicle-fuel standards. The renewable origin of its carbon distinguishes biomethane from fossil natural gas.