Biogas is one of the most widely available biofuels in the world. This gas is produced anaerobically, primarily using biological waste material like sewage sludge, manure, solid waste from municipal dumpsites, agricultural wastes, etc. Energy crops and various types of wood can also be used to generate biogas.
The main components of biogas produced from waste matter are methane (75%) and carbon dioxide (25%). In the case of biogas produced in a wood gasifier, the major constituents include hydrogen, nitrogen, and carbon monoxide, along with trace amounts of methane.
How is biogas produced?
Biogas production involves the use of a special apparatus set-up, comprising of a fermentation tank or digester, and a container to collect the biogas generated. Raw material is introduced into the digester, in slurry (liquid) form. Here, anaerobic microorganisms decompose it. During the decomposition process, biogas is released. The gas collects in the gas holder, where it is stored and then transported to industries or homes to be used.
The digester is a cylindrical, waterproof tank with an inlet on one side to receive the slurry. On the opposite side is an outlet, where the spent slurry is removed into an overflow tank. Biogas rises to the top of the cylinder and flows through an attached pipe, into the gas holder.
Uses of biogas:
Biogas has a variety of applications. In residential sections, biogas may be used for cooking, lighting, water, and space heating. It can be used to generate electricity as well as to substitute compressed natural gas as a vehicle fuel. For commercial purposes, biogas must be cleaned up to give it the same quality as natural gas. This involves removing water and hydrogen sulfide particles, and some amount of carbon dioxide. The resultant gas is called biomethane or renewable natural gas.
Advantages of biogas:
Biogas production offers two-fold benefits. It generates a cheaper and cleaner fuel than traditional combustible fuel sources like fossil fuels. At the same time, its production eliminates a large proportion of waste products, thereby destroying disease-causing pathogens that reside in waste.
When biogas burns, emits less carbon dioxide and the methane in it undergoes better combustion than burning the same amount of coal. Methane itself is a greenhouse gas so not allowing it to remain in the atmosphere goes a long way towards minimizing greenhouse gas emissions.
