Chapter 01 · Climate & transitionEnergy & Transition
Biogas
Definition
A mixture of methane (typically 45–75% by volume) and carbon dioxide, with trace gases, produced by the anaerobic digestion of organic matter in oxygen-free conditions. Feedstocks include animal manure, food waste, sewage sludge, crop residues and the organic fraction of municipal solid waste; production routes span engineered biodigesters, landfill gas recovery and wastewater treatment plants. Upgrading biogas by removing CO₂ yields biomethane ("renewable natural gas").
References
Definition and composition (45–75% CH₄); production pathways (biodigesters, landfill, wastewater); upgrading to biomethane; uses.
Anaerobic digestion process; feedstock co-digestion; biogas and digestate products.
Overview
What it means
Biogas converts a waste-management problem into energy: it captures methane that would otherwise escape (a potent greenhouse gas), displaces fossil fuels, and leaves digestate, a nutrient-rich fertiliser — a circular package. At household scale, biodigesters provide clean cooking fuel where biomass smoke is a major health burden; at industrial scale, gas can be injected into grids or used for combined heat and power.
How it is used
The IEA's Outlook for Biogas and Biomethane assesses feedstock potential and policy; deployment concentrates in Europe (grid injection), China and India (household and farm digesters) and landfill-gas capture worldwide. Sustainability issues include methane leakage from plants and competition between feedstock uses.
Why it matters
Biogas addresses three problems at once — waste, methane emissions and energy access — making it a staple of circular-economy and clean-cooking strategies, and a flexible complement to variable renewables.