Anaerobic digestion

Anaerobic digestion (AD) is a process in which biodegradable waste is decomposed in the absence of oxygen in a sealed environment over a period of 25-30 days (rather than 20+ years if in landfill). This prevents methane (24 times more polluting than CO2) from escaping into the atmosphere. AD produces:

  • Biogas (mainly methane plus CO2);
  • A digestate which can be liquid or solid. This can be used as a nutrient-rich soil conditioner.



There are many benefits to biogas and biomethane production including:

  • Reduction of organic waste entering landfill
  • Reduction in greenhouse gas emissions of 75-200% compared to fossil fuels
  • Prevention of methane emissions
  • Reduction of waste transportation, when the AD plant is located near the site of waste production
  • Stops effluent (e.g. from intensive rearing units) from entering water courses - helping to meet the Water Framework Directive.