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The electrical energy produced using renewable fuel created from agriculture and municipal waste products is termed biogas electricity. Biogas is produced in anaerobic digesters using microbes to convert organic wastes into methane gas. This gas is then used to generate electricity in power plants, both large and small, rather than using non-renewable fuels. An alternate method of production of biogas occurs in landfills. The organic matter in the landfill undergoes anaerobic decomposition deep within the landfill mass, and in specially designed landfills the resulting methane gas is trapped for later use as fuel.
Small-scale production of biogas electricity occurs primarily on farms where manure is converted to methane gas using an anaerobic digester. The chemical energy in the methane is converted to mechanical energy when the methane is burned to power a turbine. This, in turn, converts the mechanical energy to electrical energy that can be used as a power source for the farm. In small-scale energy production, a microturbine or engine is generally used to produce electricity. Excess heat may also be trapped and used to heat water or a small building.
Large-scale, centralized production of biogas electricity is less common than the agricultural conversion of manure to electricity, increasingly popular on farms around the world. Industrial production is costly and requires a high level of maintenance, but provides a beneficial alternative for sewage treatment and waste disposal. Biogas can be used alone or in conjunction with other fuels in power plants. With additional processing, it can also be used to heat homes as biomethane or compressed to burn in vehicle engines.
There are three main advantages of biogas electricity over the conventional production of electricity using coal or natural gas. Biogas is a renewable resource created from all kinds of organic waste matter. Manure, crop wastes and sewage are commonly used, and all are continually produced. Waste management is another benefit of biogas. The third benefit of biogas electricity is the reduction of greenhouse gasses released during outdoor decomposition of wastes.
A potential problem of biogas electricity is the emission of nitrous oxide during the production of biogas using anaerobic digesters. Methods of reducing the emissions are being devised. Manure left to decompose outdoors gives off significantly more nitrous oxide than the amount emitted during biogas conversion and burning. Nitrous oxide and methane, another gas produced by decomposing organic matter, are both considerably more potent greenhouse gasses than carbon dioxide. Using the manure or other organic matter to produce biogas for energy production, rather than allowing it to decompose outdoors, is believed to reduce the total amount of greenhouse gas emissions.