Understanding Biogas

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What is Biogas?

Biogas is a mixture of different gases produced by the breakdown of organic matter in the absence of oxygen called anaerobic digestion. It takes place through four successive stages: hydrolysis, acidogenesis, acetogenesis, and methanogenesis; the anaerobic digestion process is dependent on the interactions between the diverse microorganisms that are able to carry out the four aforementioned stages. Organic manure is generated as a byproduct in this process.

How biogas is produced?

Biogas is generated in four stages

1) Hydrolysis

The hydrolysis process serves the purpose of breaking down the organic macromolecules into smaller products, which in turn can be utilized by acidogenic bacteria.

2) Acidogenesis

By absorbing the products of hydrolysis through their cell membranes, acidogenic microorganisms are able to produce intermediate volatile fatty acids and other products. One important outcome of the amino acid breakdown is the production of ammonia, which, at sufficiently high concentrations, is an inhibitor of anaerobic digestion.

3) Acetogenesis

Acetogenesis is the process by which these higher volatile fatty acids and other intermediates are converted into acetate, with hydrogen released as a by-product.

4) Methanogenesis

Methanogenesis marks the final stage of anaerobic digestion, where intermediates are consumed by methanogenic microorganisms to produce methane.

Component of biogas

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1) Mixing Tank / Slurry Tank

To the inlet of the biogas plant is the mixing tank with or without a crusher. In this mixing tank, the biomass is mixed with the water in a ratio to form a slurry which then enters the digester.

2) Balloon(Digester)

The digester (air-tight) is a chamber in which slurry is entered, where anaerobic digestion takes place in absence of the oxygen and in the presence of different types of bacteria. These bacteria are capable of decomposing the substances in absence of oxygen. The biomass is decomposed, that is, broken down to basic substances like methane, hydrogen, carbon dioxide, hydrogen sulphide, and solid waste. This gas mixture is stored in the balloon and accessible through an outlet valve on the top.

3) Sludge Tank

The solid waste along with the gas produced in the digester is collected in a sludge tank which is rich in nitrogen and is applicable as manure and fertilizers.

4) Biogas Stove

The gas collected from the outlet valve is transferred through pipe either through a filtration system or directly to the biogas stove for cooking purposes. The biogas stove is different from a standard LPG stove due to different operating pressure.