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.