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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]
Northampton /nɔːrˈθæmptən/ (About this soundlisten) is a large market town and the county town of Northamptonshire in the East Midlands of England. It lies on the River Nene, 60 miles (97 km) north-west of London and 50 miles (80 km) south-east of Birmingham.[2][3] One of the largest towns (as opposed to cities) in England,[4] it had a population of 212,100 at the 2011 census (223,000 est. 2019).
Archaeological evidence of settlement in the area dates to the Bronze Age, Romans and Anglo-Saxons. In the Middle Ages, the town rose to national significance with the establishment of Northampton Castle, an occasional royal residence which regularly hosted the Parliament of England. Medieval Northampton had many churches, monasteries and the University of Northampton, all enclosed by the town walls. It was granted a town charter by Richard I in 1189 and a mayor was appointed by King John in 1215. The town was also the site of two medieval battles, in 1264 and 1460.
Northampton supported the Parliamentary Roundheads in the English Civil War, and Charles II ordered the destruction of the town walls and most of the castle. The Great Fire of Northampton in 1675 destroyed much of the town. It was soon rebuilt and grew rapidly with the industrial development of the 18th century. Northampton continued to grow with the arrival of the Grand Union Canal and the railways in the 19th century, becoming a centre for footwear and leather manufacture.
Northampton's growth was limited until it was designated as a New Town in 1968, accelerating development in the town. It unsuccessfully applied for city status in 2000.[5]
