Anaerobic Digestion

Slideshow of images for Wales Energy Crops Information Centre

Whilst energy crops such as Short Rotation Coppice (SRC) and Miscanthus tend to be grown for dry combustion, other crops such as rye grass are being trailed as “wet” biomass feedstocks for anaerobic digestion. In addition, anaerobic digestion can utilise other biomass sources such as garden waste e.g. grass clippings and kitchen wastes, silage, livestock slurries/manures and catering wastes. In order to work effectively there needs to be good balance between fatty material and plant materials, as carbon to nitrogen ratio’s are important and should be between 20 –30 for optimum performance. Energy crops such as Miscanthus and other grasses low in nitrogen can help meet this balance.

Anaerobic digesters rely on bacteria to break down organic materials in the absence of oxygen. A biogas is produced which can then be utilised as a heating fuel, or following further treatment as a transport fuel.

Anaerobic digestion is a valuable integrated waste management technology that is becoming increasing economically viable. In addition to helping compliance with legislation on the safe handling of waste, it also provides opportunities for developing renewable energy enterprises. A download sheet on Anaerobic Digestion can be downloaded from the CALU website.

The Sustainable Environment Research Centre (SERC) – in Wales has substantial expertise in this field and further information can be accessed via their website. The company Greenfinch can also provide commercial guidance and supply AD systems.