| Experiments Home |
|
| Renewable Energy |
|
|
| Anaerobic Digestion |
|
|
|
|
  |
 The Solar Car Book A complete kit for making a cool solar racecar. Everything is included: wheels, axles, motors, wires and a genuine one-volt solar cell. |
Anaerobic Digestion
Anaerobic digestion is a process in which microorganisms break down biodegradable material in the absence of oxygen. The process is widely used to treat wastewater sludges and organic wastes because it provides volume and mass reduction of the input material.[1] As part of an integrated waste management system, anaerobic digestion reduces the emission of landfill gas into the atmosphere. Anaerobic digestion is a renewable energy source because the process produces a methane and carbon dioxide rich biogas suitable for energy production helping replace fossil fuels. Also, the nutrient-rich solids left after digestion can be used as fertiliser. The digestion process begins with bacterial hydrolysis of the input materials in order to break down insoluble organic polymers such as carbohydrates and make them available for other bacteria. Acidogenic bacteria then convert the sugars and amino acids into carbon dioxide, hydrogen, ammonia, and organic acids. Acetogenic bacteria then convert these resulting organic acids into acetic acid, along with additional ammonia, hydrogen, and carbon dioxide. Methanogenic bacteria finally are able to convert these products to methane and carbon dioxide.[2] The technical expertise required to maintain anaerobic digesters coupled with high capital costs and lower process efficiencies have so far limited the level of its industrial application as a waste treatment technology.[3] Anaerobic digestion facilities have, however, been recognised by the United Nations Development Programme as one of the most useful decentralised sources of energy supply, as they are less capital intensive than large powerplants.[4] Utilising anaerobic digestion technologies can help to reduce the emission of greenhouse gases in a number of key ways:
History
Scientific interest in the gases produced by the natural decomposition of organic matter, was first reported in the sixteenth century by Robert Boyle and Stephen Hale, who noted that inflammable gas was released by disturbing the sediment of streams and lakes.[5] In 1808, Sir Humphry Davy determined that methane was present in the gases produced by cattle manure.[6][7] The first anaerobic digester was built by a leper colony in Bombay, India in 1859. In 1895 the technology was developed in Exeter, England, where a septic tank was used to generate gas for street lighting. Also in England, in 1904, the first dual purpose tank for both sedimentation and sludge treatment was installed in Hampton. In 1907, in Germany, a patent was issued for the Imhoff tank, an early form of digester. Through scientific research anaerobic digestion gained academic recognition in the 1930s. This research led to the discovery of anaerobic bacteria, the microorganisms that facilitate the process. Further research was carried out to investigate the conditions under which methanogenic bacteria were able to grow and reproduce.[8] This work was developed during World War II where in both Germany and France there was an increase in the application of anaerobic digestion for the treatment of manure. For more information see the following links:
References
External links
This article is licensed under the GNU Free Documentation License. It uses material from Wikipedia Encyclopedia article "Anaerobic Digestion" |
