In February 2008 the UK government announced plans to invest in a number of anaerobic digestion plants. This country currently lags behind many European counterparts in this source of renewable energy, including Belgium and Germany. So what are anaerobic digestion plants, and how are they of environmental benefit?
Anaerobic digestion is the process whereby organic matter is broken down in the presence of little or no oxygen. This produces a biogas which is made up of 60% methane and 40% carbon dioxide. Anaerobic digestion plants can take virtually any organic matter including grass clippings, food waste, sewage and animal waste, thus reducing the amount of this waste which goes into landfill sites. Anaerobic digestion plants are also considered to be more environmentally friendly than composting in terms of the amount of CO2 savings to be made.
In addition to biogas, anaerobic digestion plants also produce a solid and liquid residue called digestate, which can be used as a soil conditioner to fertilise land. The biogas itself is then used to produce heat or electricity or as a vehicle fuel. More on use as a fuel can be found on our Biogas page.
A relatively small amount of municipal waste is already sent to anaerobic digestion plants, but the government’s current focus appears to be on the use of agricultural waste in this way, as the farming industry has relatively high carbon dioxide emissions
There are basically three advantages of sending organic waste to anaerobic digestion plants – the reduction of waste going to landfill, lower carbon dioxide emissions than other forms of waste disposal, and the production of a renewable energy.
