Technology

Anaerobic Digestion (AD)

Anaerobic Digestion (AD) is a proven technology in which micro-biological activity is used to convert organic material, producing biomethane that can be used for the production of renewable heat and power and a compost like output. As a sustainable process, AD has been identified by the Government as a preferred technology for the production of green energy and is eligible to receive significant financial subsidies through the Feed-in Tariff and Renewable Heat Incentive Schemes.

There are various forms of AD ranging from low efficiency plug flow type solutions to high rate multi-stage processes. AD is not a new technology and has been in use for over 100 years for the treatment of wastewater and sewage. There are over 200 wastewater treatment facilities in the UK that incorporate AD.

The process of AD itself is identical no matter which type of AD is used. Organic matter is broken down in the absence of Oxygen to produce methane rich biogas. The biogas can be utilised as a renewable fuel to produce heat and power. It can also be upgraded to Natural Gas standard and fed directly into the gas grid to be used in our homes.

The AD process is shown simplified in the diagram below:

In recent years, AD has become popular for the treatment of source segregated organic waste and organic waste separated from the residual waste stream. This is especially the case in continental Europe where AD has flourished. The use of AD for the treatment of organic waste has not been the preferred solution in the UK, however with the introduction of the Renewables Obligation (RO), the Energy Act 2008 and the landfill tax accumulator, waste producers now have the required incentives to consider AD as a viable waste management and renewable energy option.