Biogas is a mixture of methane, CO2 and small quantities of other gases produced by anaerobic digestion of organic matter in an oxygen-free environment. Its precise composition depends on the type of feedstock and the production pathway. The methane content of biogas typically ranges from 45% to 75% by volume. Biogas is usually produced using the following technologies: 

• Biodigesters: These are airtight systems (e.g. containers or tanks) in which organic material is broken down by naturally occurring micro-organisms. Contaminants and moisture are usually removed before use of the biogas. 
• Landfill gas recovery systems: The decomposition of municipal solid waste (MSW) under anaerobic conditions at landfill sites produces biogas (also known as “landfill gas”). This can be captured using pipes and extraction wells along with compressors to induce flow to a central collection point. 
• Wastewater treatment plants: These can be equipped with anaerobic digesters to stabilise and reduce the volume of sewage sludge. Wastewater facilities can also treat wastes from bio-based industries such as pulp and paper. 

Biomethane (sometimes also referred to as a “renewable natural gas”) is a near-pure source of methane, and so is extremely similar to natural gas. It is produced mainly through biogas upgrading by removing CO2, water and other contaminants, using methods such as water scrubbing, membrane separation or pressure swing adsorption. Biomethane can also be produced through gasification of solid biomass followed by methanation, although this is far less common. 

Consumption of biogases is increasing. However, biogases are still a relatively small part of the global energy mix – representing around 3% of total modern bioenergy production. Biomethane use has increased at a rate of 20% annually over the past 5 years, although from a low base (it is currently around 1% of natural gas demand).

Most markets rely on public incentives to provide support and certainty to biogas and biomethane producers. These include: production targets, supply- and demand-side incentives, and indirect support.