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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]
Downham Market, sometimes simply referred to as Downham, is a market town and civil parish in Norfolk, England. It lies on the edge of the Fens, on the River Great Ouse, approximately 11 miles south of King's Lynn, 39 miles west of Norwich and 30 miles north of Cambridge.[2]
The civil parish has an area of 5.2 km² and in the 2011 census had a population of 9,994 in 4,637 households.[3]
Fire Station in 2006, now a heritage centre
It was an agricultural centre, developing as a market for the produce of the Fens with a bridge across the Ouse. During the Middle Ages, it was famed for its butter market and also hosted a notable horse fair. The market is now held Fridays and Saturdays.
Notable buildings in the town include its mediaeval parish church, dedicated to St Edmund, and the Victorian clock tower, constructed in 1878. The town is also known as the place where Charles I hid after the Battle of Naseby. In 2004 the town completed a regeneration project on the Market Place, moving the market to the town hall car park. The decorative town sign depicts the crown and arrows of St Edmund with horses to show the importance of the horse fairs in the town's history.
A heritage centre, Discover Downham, opened in a former fire station in 2016.[4] The town is twinned with Civray, Vienne, France.[5]
