Anaerobic digestion and its usefulness
November 23rd, 2009
Dating back to the seventeenth century, there has been interest in manufacturing gas by means of a natural decomposition of organic materials. Scientists Stephen Hale and Robert Boyle first reported on the process. They noticed that a flammable gas happened to be released when sediment on the bottom of lakes and streams was disturbed. Sir Humphrey Davy noted that cattle manure produced gases, including methane gas in 1808.
Lepers built the first anaerobic digester back in 1859 at their colony in Bombay, India.
Technology developed gas lighting from the use of a septic tank which produced gas lighting (for a sewer gas destructor lamp) as a byproduct of its decomposition process in England in 1895. The Imhoff tank, an early design of digester was patented in Germany in 1907.
The process of anaerobic digestion
The process known as anaerobic digestion is actually a break down of microorganisms into material that is biodegradable without oxygen. This is a process used widely in the treatment of waste water. Anaerobic digestion will reduce landfill gas emissions into the atmosphere and is in widespread use as a renewable source of energy due to the fact it produces a biogas which is rich in methane as well as carbon dioxide. These gases help in the replacement of fossil fuels, a non renewable source of energy
How anaerobic digestion works
Also known as methane recovery, this digestive process starts out when materials break down due to bacterial hydrolysis (breakdown by enzymes). Carbohydrates, as well as other organic polymers, are accessible by other bacterial forms and converted into amino acids and sugars and are then further broken down, finally, into acetic acid which when combined with ammonia, hydrogen, and some carbon dioxide will produce methanogens which convert to carbon dioxide and methane. The process of anaerobic digestion makes excellent use of such biodegradable materials as manure, sewage, biomass, municipal waste, and other green or energy waste crops.
Where it’s headed
Originally the process was relatively expensive, requiring significant technical expertise, plus the fact not much was produced during the process, there was little demand for its use except for industrial types of application. More recently however, the process has been perfected and costs have been lowered considerably enabling it to be seen as a viable source of alternative renewable energy.
The process was recognized academically during the 1930’s and research found the anaerobic bacteria or microorganisms vastly sped up the process also known as fermentation. Long known as sources of energy, methane and similar naturally formed gases needed to be contained and controlled.
Usefulness of anaerobic digestion
As the process of anaerobic digestion has proven to be most effective with organic wet material, it has been useful in treating sewage and effluent. Most anything organic can be processed through anaerobic digestion. Biodegradables such as grass clippings, waste paper, animal waste, sewage, and left over food will break down into gases as a result of the anaerobic digestion process.
Europe and Germany use the process in operations they call biogas plants. It has found to be useful in developing countries as low cost energy used for lighting and cooking. Countries such as China and India are working on use of small biogas plants that could be applied for local use as cooking and lighting sources.
