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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]
Newmarket is a market town in the English county of Suffolk, approximately 65 miles (105 kilometres) north of London. It is generally considered the birthplace and global centre of thoroughbred horse racing[2] and a potential World Heritage Site.[3] It is a major local business cluster, with annual investment rivalling that of the Cambridge Science Park, the other major cluster in the region.[4] It is the largest racehorse training centre in Britain,[5] the largest racehorse breeding centre in the country, home to most major British horseracing institutions, and a key global centre for horse health. Two Classic races, and an additional three British Champions Series races are held at Newmarket every year. The town has had close royal connections since the time of James I, who built a palace there, and was also a base for Charles I, Charles II, and most monarchs since. The current monarch, Queen Elizabeth II, visits the town often to see her horses in training.
Newmarket has over fifty horse training stables, two large racetracks, the Rowley Mile and the July Course, and one of the most extensive and prestigious horse training grounds in the world.[6] The town is home to over 3,500 racehorses, and it is estimated that one in every three local jobs is related to horse racing. Palace House, the National Heritage Centre for Horseracing and Sporting Art, the National Horseracing Museum, Tattersalls racehorse auctioneers, and two of the world's foremost equine hospitals for horse health, are in the town, which is surrounded by over sixty horse breeding studs. On account of its leading position in the multibillion-pound horse racing and breeding industry, it is also a major export centre.
