Bio gas

Biogas is a mixture of gases that are produced after plant and animal material are broken down by microorganisms in a process called anaerobic digestion.2 Anaerobic digestion — which occurs in a closed, oxygen-free space called a digester — takes substances like manure from factory farms, sewage sludge or food waste and “eats” the material, leaving mostly methane and carbon dioxide, among other gases. The material left over is called digestate. Biogas can be converted into biomethane through the removal of hydrogen sulfide, carbo monoxide and moisture. It cna be treated and made into compressed natural gas CNG, or liquefied natural gas (LNG), with the removal of siloxane sand hydrogen sulfide to be used to generate power or distributed through pipelines to homes and businesses.

Biogas is being marketed as a “renewable” energy solution, designed to help mitigate climate change. The process of anaerobic digestion converts organic material into biogas, which can be used to produce electricity on-site, for heating, or as vehicle fuel.

It's mostly methane. They're a co-product of factory farms.

Around 15% of poultry farms in the UK process poultry manure in anaerobic digestors. Soil association, 2024

AD plants work by being fed with manure and crops such as maize, which are broken down inside the plant by microorganisms producing methane which can be used to heat farm buildings or fed into the national grid. A solid digestate material is also produced and can be used as a fertiliser for crops which may then be fed back into the AD plant.

Another reference from Friends of the Earth on Bio-gas not being good: https://foe.org/wp-content/uploads/2024/02/Factory-Farm-Gas-Brief_final-v2.pdf

It can also increase the number of dairy cattle we have: Jevons paradox.