Anaerobic digesters are used to create anaerobic, meaning without oxygen, conditions so that anaerobic bacteria can efficiently digest biomass, sewage or other organic matter. This breaks down the waste into simpler substances like methane, carbon dioxide, water and nitrates. The methane that the bacteria create can be captured and used for fuel. Wastewater treatment plants sometimes use cogeneration plants fueled by the methane produced. The waste heat produced by the generator, usually a reciprocating engine but sometimes a microturbine, to heat the water to the optimum temperature for bacterial growth. Less frequently, dairies and pig farrms use anaerobic digesters or anaerobic lagoons to treat animal waste. Anaerobic is a technical word which literally means without air. ... An anaerobic organism or anaerobe is any organism that does not require oxygen. ... The simplest hydrocarbon, methane, is a gas with a chemical formula of CH4. ... Cogeneration (also combined heat and power or CHP) is the use of a power station to simultaneously generate both heat and electricity. ... Components of a typical, four stroke cycle, DOHC piston engine. ... This machine has a single-stage radial compressor and turbine, a recuperator, and foil bearings. ...
External Links
Methane (Biogas) from Anaerobic Digesters (http://www.eere.energy.gov/consumerinfo/factsheets/ab5.html)
Anaerobicdigestion is the breakdown of organic matter by bacteria in the absence of oxygen.
Anaerobicdigesters have been around for a long time, and they are commonly used for sewage treatment and for managing animal waste.
If the digested materials include low levels of toxic heavy metals or synthetic organic materials such as pesticides or PCBs, the effect of digestion is to significantly concentrate such materials in the digester liquor in order to dispose of this liquid properly.
The key by-products of anaerobicdigestion include digested solids (useful as a soil amendment) and methane, the primary component of "bio-gas," which can be used to fuel a variety of cooking, heating, cooling, and lighting applications, as well as to generate electricity.
Thermophilicdigestion yields higher levels of gas and kills more pathogenic bacteria, but it has certain disadvantages as well, the greatest of which is the added cost of maintaining higher temperatures and keeping the digester stirred to maximize contact between the bacteria and the organic matter.
Anaerobicdigesters are installed for various reasons-as a means of resolving environmental problems, as a means of economically re-using an otherwise wasted resource, as a source of additional revenue.
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