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Anaerobic Digestion
Anaerobic digestion is a sequence of processes by which microorganisms break down biodegradable material in the absence of oxygen.[1] The process is used for industrial or domestic purposes to manage waste or to produce fuels. Much of the fermentation used industrially to produce food and drink products, as well as home fermentation, uses anaerobic digestion.
Anaerobic digestion occurs naturally in some soils and in lake and oceanic basin sediments, where it is usually referred to as "anaerobic activity".[2][3] This is the source of marsh gas methane as discovered by Alessandro Volta in 1776.[4][5]
The digestion process begins with bacterial hydrolysis of the input materials. Insoluble organic polymers, such as carbohydrates, are broken down to soluble derivatives that become available for other bacteria. Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. In acetogenesis, bacteria convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide amongst other compounds. Finally, methanogens convert these products to methane and carbon dioxide.[6] The methanogenic archaea populations play an indispensable role in anaerobic wastewater treatments.[7]
Anaerobic digestion is used as part of the process to treat biodegradable waste and sewage sludge. As part of an integrated waste management system, anaerobic digestion reduces the emission of landfill gas into the atmosphere. Anaerobic digesters can also be fed with purpose-grown energy crops, such as maize.[8]
Anaerobic digestion is widely used as a source of renewable energy. The process produces a biogas, consisting of methane, carbon dioxide, and traces of other 'contaminant' gases.[1] This biogas can be used directly as fuel, in combined heat and power gas engines[9] or upgraded to natural gas-quality biomethane. The nutrient-rich digestate also produced can be used as fertilizer.
With the re-use of waste as a resource and new technological approaches that have lowered capital costs, anaerobic digestion has in recent years received increased attention among governments in a number of countries, among these the United Kingdom (2011),[10] Germany,[citation needed] Denmark (2011),[11] and the United States.[12]
Fleet is a town and civil parish in the Hart District of Hampshire, England, centred 38.2 miles (61.5 km) WSW of London and 13 miles (21 km) east of Basingstoke. It is the major town of the Hart District, and has large technology business areas, fast rail links to London, and is well connected to the M3. The Fleet built-up area has a total population of 42,835,[2] and includes the contiguous parishes of Church Crookham, Crookham Village, Dogmersfield, and Elvetham Heath. The town has a prominent golf club, an annual half marathon, an athletics club, and four football clubs. The nearby service station on the motorway is named after the town.
Hart, of which Fleet is the main town, was voted the best place to live in the UK by the Halifax Quality of Life study in 2011, 2012,[3] 2013,[4] 2014, 2015, and again in 2017,[5] above areas such as Elmbridge in Surrey and Wokingham in Berkshire.[6] This is due to the highly affluent majority of the population, better weather and health conditions, high levels of access to leisure space, and the town's surrounding countryside which includes woodlands and the Basingstoke Canal.[5]
Local landmarks include Fleet Pond, the largest freshwater lake in Hampshire, and a High Street with many Victorian and Edwardian buildings. Fleet holds a weekly Saturday market in Gurkha Square.
