Biogas is an important solution of present day energy crisis. The gas produced by action of bacteria on biomass is called biogas. It consist of CH4 , CO2 , H2 S , & NH4 these gas produced during anaerobic digestion of organic wastes from plant & animal. Special category of bacteria called methanogen that are commonly used for production of biogas. Most common methanogens are Methanococcus & Methanobacterium.

  • Biogas can burn in gas stove to provide heat. Biogas can be used for cooking, street-light & driving engine. Biogas burn without smoke & produce large amount of heat so help in controlling the water pollution.
  • Biogas is the ultimate waste product of the bacteria feeding off the input biodegradable feedstock (the methanogenesis stage of anaerobic digestion is performed by archaea – a micro-organism on a distinctly different branch of the phylogenetic tree of life to bacteria), and is mostly methane and carbon dioxide, with a small amount hydrogen and trace hydrogen sulphide. (As-produced, biogas also contains water vapour, with the fractional water vapour volume a function of biogas temperature). Most of the biogas is produced during the middle of the digestion, after the bacterial population has grown, and tapers off as the putrescible material is exhausted. The gas is normally stored on top of the digester in an inflatable gas bubble or extracted and stored next to the facility in a gas holder.
  • The methane in biogas can be burned to produce both heat and electricity, usually with a reciprocating engine or microturbine often in a cogeneration arrangement where the electricity and waste heat generated are used to warm the digesters or to heat buildings. Excess electricity can be sold to suppliers or put into the local grid. Electricity produced by anaerobic digesters is considered to be renewable energy and may attract subsidies. Biogas does not contribute to increasing atmospheric carbon dioxide concentrations because the gas is not released directly into the atmosphere and the carbon dioxide comes from an organic source with a short carbon cycle.
  • Biogas may require treatment or ‘scrubbing’ to refine it for use as a fuel. Hydrogen sulphide, a toxic product formed from sulphates in the feedstock, is released as a trace component of the biogas. National environmental enforcement agencies, such as the U.S. Environmental Protection Agency‎ or the English and Welsh Environment Agency, put strict limits on the levels of gases containing hydrogen sulphide, and, if the levels of hydrogen sulphide in the gas are high, gas scrubbing and cleaning equipment (such as amine gas treating) will be needed to process the biogas to within regionally accepted levels. Alternatively, the addition of ferrous chloride FeCl2 to the digestion tanks inhibits hydrogen sulphide production.