anaerobic digestion

Anaerobic digestion is a natural biological process whereby organic material is broken down in the absence of oxygen by special bacteria. The process is carried out in a sealed airtight container called a digester. The process produces a number of useful by-products. These are:

• Biogas - a mixture of methane and carbon dioxide that can be used as a fuel to produce heat or electricity
• Bio-liquid - can be used as an agricultural fertilizer
• Solid residue - similar to compost that can be used as a soil conditioner

Anaerobic digestion can used to treat a range of organic wastes. Examples include animal and agricultural waste, food processing waste, sewage and the organic fraction found in municipal solid waste.

Anaerobic digesters come in many sizes and designs. The choice of system has to be tailored according to a number of factors such as location, size, the type of feedstock you intend to use and how the by-products will be used.

For an on farm digester with an annual capacity of around 3,000 tonnes per year the capital cost will be between £100,000 – £200,000 with annual running costs of around £2,000. Larger systems with a capacity to handle 10,000 tonnes per year will cost £500,000 to install. Our site assessments will be sufficient to tell you whether a scheme is viable in your circumstances.