Anaerobic bacteria are among the oldest ...

Biodigesters recovery of methane from manure through a process called anaerobic digestion. Here's how it works. Methane is a gas that contains molecules of methane with one atom of carbon

and four hydrogen atoms (CH4). This is the main component of "natural" gas used in many homes for cooking and heating. It is odorless, colorless, and gives about 1,000 British thermal units (Btu) [252 kilocalories (kcal)] of heat energy per cubic foot (0. 028 cubic meters) when burned. Natural gas is a fossil fuel that was created eons ago by the anaerobic decomposition of organic materials. It is often found together with oil and coal. The same types of anaerobic bacteria that produce methane gas produced as today. Anaerobic bacteria are among the oldest forms of life on Earth. They have evolved to photosynthesis green plants released large amount of oxygen in the atmosphere. Anaerobic bacteria break down or "digest" organic matter in the absence of oxygen and produce "biogas" as a byproduct. (Aerobic decomposition, or composting, requires large quantities of oxygen and produces heat).

Anaerobic decomposition occurs naturally in swamps, marshy soils and rice fields, deep water, and in the digestive system of termites and large animals. Anaerobic processes can be controlled in "reactor" (sealed container) or a covered lagoon (pond used to store manure) for waste. The main advantages of anaerobic digestion are nutrient recycling, waste and odor. Except for very large systems, biogas production is a strattera 25mg highly useful but secondary benefit. Biogas produced in anaerobic digesters consists of methane (50% to 80%), carbon dioxide (20% to 50%) and traces of other gases such as hydrogen sulfide carbon monoxide, nitrogen, oxygen and hydrogen. The relative proportion of these gases in biogas depends on the material and process control. When burning cubic feet (0. 028 cubic meters) of biogas makes it about 10 Btu (2. 52 kcal) of heat energy as a percentage of methane composition. For example, biogas composed of 65% methane gives 650 Btu per cubic foot (5,857 kcal / cubic meter). Anaerobic decomposition is a complex process. It occurs in three main stages, as a result of various microorganisms. First group of microorganisms converts organic material to form the second group of organisms used to form organic acids. Methane producing (methanogenic) anaerobic bacteria utilize these acids and complete the process of decomposition. A number of factors affect the rate of digestion and biogas production. The most important is temperature. Anaerobic bacteria communities can endure temperatures ranging from below freezing to above 135 Fahrenheit (F) (57. 2 Celsius [C]), but they thrive best at temperatures around 98F (36. 7S) (mesophilic) and 130F (54 . 4C) (thermophilic). Bacteria activity, and thus biogas production, falls significantly between about 103 and 125F (39. 4 and 51. 7C) and gradually from 95 to 32F (35 0C). In the thermophilic range, decomposition and biogas production is faster than in the mesophilic range. However, this process is very sensitive to interference, such as changes in raw materials or temperature. While all anaerobic digesters reduce the viability of weed seeds and disease-causing (pathogenic) bacteria, the higher the temperature of thermophilic digestion result of more complete destruction. Although the reactors operating in the mesophilic range must be large (to accommodate a longer period of decomposition within the tank [residence]), the process is less sensitive to upset or change in operating mode. To optimize the digestion process, biodigester should be kept at constant temperature, a rapid change in bacterial activity breaks. In most parts of the United States Court of digestion requires a certain level of isolation and / or heating. Some installations circulate the coolant from biogas in engines or around the reactor to keep warm, while others burn part of the biogas for heating the reactor. In properly designed heating system generally leads to an increase in biogas production during cold periods. Trade-offs in maintaining optimum temperature reactor, the maximum gas, minimizing costs a bit more complicated. Research reactors in north-central parts of the country indicate that maximum net biogas production can occur in autoclaves operated at temperatures as low as 72F (22. 2C). Other factors affecting the rate and amount of biogas production. These include the pH of the water / solid ratio of carbon / nitrogen ratio of mixing the digestion of the material, particle size of material to digest, and confinement time. Preliminary sizing and mixing of the source material for even consistency allows the bacteria to work faster. PH self-regulating in most cases. Soda may be added to maintain pH corresponds, for example, when too many "green" or material high in nitrogen is added. It may be necessary to add water to the original material if it is too dry or if the nitrogen content is very high. Carbon / nitrogen ratio of 20/1 30/1, the better. Sometimes blending or mixing digesting material can help the process of digestion. Antibiotics in livestock feed have been known to kill the anaerobic bacteria in the reactors. Complete assimilation and retention time depends on all the above factors. Materials taken from anaerobic digesters is called sludge or waste water. It is rich in nutrients (ammonia, phosphorus, potassium, and more than a dozen trace elements) and is an excellent soil conditioner. It can also be used as a livestock feed additive when dried. Any toxic compounds (pesticides, etc.), raw material in the reactor can be focused in wastewater. It is therefore important to check the waste water before using it on a large scale. .