A less mobut more sustainable method of waste disposal is anaerobic digestion. Ithis process waste deposes iaenclosed chamber, unlike ia landfill site. Digestiotakes place iaoxygen-freet environment. Bacteria thrive ithis environment by using the oxygethat is chemically bined withithe waste. They depose waste by breaking dowthe molecules to form gaseous by-products ( methane ) and small quantities of solid residue. Anaerobic sewage plants produce significant quantities of methane, which cabe burnt to generate electricity. Liquid and solid organic fertilisers are also formed, and cabe sold to cover operating costs. For several years, sewage sludge and agricultural waste has beetreated by anaerobic digestion, and the process is now being used for municipal solid waste. It requires the biodegradable sectioof the waste to be separated from other material and put into digestiochambers. Currently, the UK has only a small number of plants, and each cahandle only a few hundred tonnes of waste each year. However, the usage of anaerobic digestioas a sustainable waste disposal method is forecast to increase. Many other countries already utilise anaerobic digestioto dispose of large amounts of waste. Denmark for example, treats 1.1 milliotonnes of waste by anaerobic digestioevery year. As well as recycling waste, individuals caadopt more sustainable ways of disposing it. One way is to post any organic waste such as food and gardewaste. Organic waste breaks dowover a few weeks into a mulch which cabe used as a soil fertiliser. Individual households have practiced small-scale posting for many years, and the UK Government is now encouraging this oa wider scale. Large-scale posting schemes are also being developed, with the collectioof organic waste from parks and civic amenity sites. Gardeand food wastes are collected directly from households iseparate kerbside collections. Large central facilities cathepost the collected organic waste. These schemes are to help the UK meet its target of recycling and posting 33% of household waste by 2015. |