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What is Bio-gas Generator or Biogas Plant
The bio-gas generator or biogas plant is the small where bio-gas is produced from the biomass waster materials like cow dung. The figure below shows a typical bio-gas generator or biogas plant which uses cow dung for production of biogas. Cow dung is produced in huge quantities especially in the countries that are major producers of milk like India, Australia, US, China and others. The cow waste which would have created the environmental pollution can be effectively used for producing biogas, which is an excellent sources of renewable energy. This biogas can be used for cooking and heating.
The bio-gas generator or the biogas plant shown in the figure uses process of digestion for production of biogas. Digestion is the biological process that occurs in the absence of oxygen, but in the presence of anaerobic organisms at atmospheric pressure and temperature of about 35-70 degree Celsius. The main part of this biogas plant is the digester where digestion process occurs.
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Parts of Bio-gas Generator or Biogas Plant
Let us see the various parts of this biogas plant or bio-gas generator:
1) Foundation: The biogas plant shown here has been built within the surface of the earth underground and it is on the foundation that the whole biogas plant is based. The foundation forms the base of the digester where the most important processes of biogas plant occur. The foundation base of the digester is made up of cement concrete and brick ballast. The construction should be built in such a manner that it should be able to provide stable foundation for the digester walls and be able to sustain the full load of slurry filled in it. The foundation should be waterproof so that there is no percolation and leakage of water.
2) Digester: The digester is the most important part of the cow dung biogas plant where all the important chemical processes or fermentation of cow dung and production of bio-gas takes place. The digester is sometimes also called as fermentation tank. In this cow dung biogas plant digester is built underground over the foundation. It forms cylindrical shape made up of bricks, sand and cement. Almost at the middle of the height of digester, two openings are provided on the opposite sides for inflow of fresh cow dung and outflow of used cow dung.
3) Dome: The hemispherical top portion of the digester is called as dome. Dome has fixed height, where all the gas generated within the digester is collected. The gas collected in the dome exerts pressure on the slurry in the digester.
4) Inlet chamber: The cow dung is supplied to the digester of the biogas plant via inlet chamber, which is made at the ground level so that the cow dung can be poured easily. It has bell mouth sort of shape and is made up of bricks, cement and sand. The outlet wall of the inlet chamber is made inclined so that the cow dung easily flows to the digester.
5) Outlet Chamber: Through the outlet chamber the digested slurry from which the biogas has been generated is removed from the biogas plant. A few steps are usually provided in the outlet chamber so that some person can go into the pit and clean it. The opening of the outlet chamber is also at the ground level. The slurry from the outlet chamber flows to the pit made especially for this purpose.
6) Mixer: It is the first part of the bio-gas generator, where the water and cow dung are mixed together in the ratio of 1:1 to form the slurry which is fed into the inlet chamber.
7) Gas outlet pipe and valve: The gas outlet pipe is located at the top of the dome where the biogas produced in the digester is collected. The flow of the gas through from the dome via gas pipe can be controlled by valve. The gas taken from the pipe can be transferred to the point of use.