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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]
Aylsham (/ˈeɪlʃəm/ or /ˈeɪlsəm/) is a historic market town and civil parish on the River Bure in north Norfolk, England, nearly 9 mi (14 km) north of Norwich. The river rises near Melton Constable, 11 miles (18 km) upstream from Aylsham and continues to Great Yarmouth and the North Sea, although it was only made navigable after 1779, allowing grain, coal and timber to be brought up river.
The town is close to large estates and grand country houses at Blickling, Felbrigg, Mannington and Wolterton, which are important tourist attractions.
The civil parish has an area of 4,329 acres (17.52 km2) and in the 2001 census had a population of 5,504 increasing to a population of 6,016 at the 2011 census. For the purposes of local government, the parish falls within the district of Broadland.[2]
