Biogas Energy
Introduction
We are familiar with the use of wood as
fuel, but we know that wood contains a very less amount of carbon. And a major
amount of impurities such as sulphur, chlorine, silicon and water decrease its
efficiency as a fuel. This results in the production of a large amount of smoke
and ash. When this wood is converted to charcoal by removing volatile
impurities and water, we get an excellent fuel with higher efficiency and low
production of smoke.
Similar observations can be noted for
biomass. When cow dung cakes are used as fuel, a large amount of smoke and ash
is generated. Can we modify these cow dung cakes to increase their efficiency?
Let’s learn about biogas, which is generated from biomass by the process of
anaerobic decomposition of organic matter.
What is Biomass?
Biomass is organic matter obtained from
living or recently living organisms, such as crop residue, animal waste, forest
debris, municipal solid waste etc. Biomass contains 75% of carbon along with
other molecules such as hydrogen, oxygen, nitrogen. And also a small number of
alkali metals, alkaline earth metals, and heavy metals.
What is Biogas?
Biogas refers to a mixture of gases
produced by the anaerobic decomposition of organic matter such as agricultural
waste, municipal waste, plant residue, food waste etc. Biogas consists of
methane, carbon dioxide along with the small amount of hydrogen sulphide, and
moisture.
What is a Biogas Plant?
The biogas plant consists of a
dome-like structure. Organic material such as discarded food residue, fats,
sludge, cow dung etc. are mixed with water and fed to the digester through the
inlet as shown in the figure.
The digester is a sealed chamber where
anaerobic decomposition of organic matter takes place. After a few days, the
organic matter completely decomposes to generate gases like methane, carbon
dioxide, hydrogen and hydrogen sulphide. These gases are then drawn through
pipes from the storage tank above the digester and distributed through
decentralization channels to nearby centres for use.
Advantages of Biogas
Non-polluting:
Biogas burns without smoke; hence no
harmful gas such as CO2, CO, NO2, and SO2 are evolved.
Reduces Landfills:
The slurry produced after the
production of biogas is used as manure in fields. The method of disposal is
safe and efficient and hence no space is wasted in the form of landfills.
Cheaper technology:
Biogas plants require very little
installation cost and become self-sufficient in a span of 3-4 months.
Generates employment:
Work opportunity for thousands of
people is created, especially in rural areas.
Renewable source of energy:
It is considered as a renewable source of
energy because
the production is dependent on the generation of waste which is an endless
process.
Disadvantages of Biogas
Not efficient enough on a large scale:
Since it is difficult to enhance the
efficiency of biogas, it is not economically viable to use biogas on a large
scale.
Contains impurities:
It contains many impurities which are
difficult to be controlled even after rounds of purification. Biogas when
compressed, to be used as fuel, proves to be highly corrosive to the container
Unstable and hazardous:
When methane comes in contact with
oxygen it reacts violently to produce carbon dioxide. The highly inflammable
nature of methane makes it prone to explosions.
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