Anaerobic Digestion (AD) is the process where plant and animal material (feedstock) is converted into useful products by micro-organisms in the absence of air. Biomass is put inside sealed tanks and naturally occurring micro-organisms digest it, releasing a gas (biogas) rich in methane that can be used to provide clean renewable energy. This means AD can help reduce fossil fuel use and reduce greenhouse gas emissions. The material left over at the end of the process is rich in nutrients so it can be used as fertiliser.
AD is not a new technology - it has actually been used in the UK since the 1800s - and there are a growing number of AD plants in the UK processing our waste and producing energy.
Almost any biomass can be processed in AD; including food waste, energy crops, crop residues, and of course animal slurries and manure. AD can accept waste from our homes, supermarkets, industry and farms, meaning less waste goes to landfill. However, woody biomass cannot be used in AD because the micro-organisms can't breakdown the lignin, the compound that gives wood its strength.
A simple anaerobic digester producing biogas for domestic cooking in India.