Question

A biogas plant works to its maximum capacity when
A) Conditions are aerobic and sewage is supplied
B) Conditions are anaerobic and temperature 40 degree Celsius.
C) Conditions are aerobic and temperature 40 degree Celsius.
D) Conditions are anaerobic and sewage is supplied

Answer 1

Biogas is the mixture of gases like carbon dioxide, methane which is produced by the digestion of organic wastes/materials under specific conditions of temperature and oxygen availability. A biogas plant is a unit where biogas is produced by fermenting organic waste in the absence of oxygen.

Complete answer:
To answer this question, we must know the principle of working in a biogas plant. Biogas is a mixture of gases that is produced by the anaerobic digestion of the household organic waste in a closed system. This closed system is known as a bioreactor or biodigester. The microorganisms which bring out the fermentation are called the methanogens.

The substrate used in the biogas plant is sewage which is rich in organic matter. It normally contains municipal waste like food, vegetables, plants etc. This substrate on digestion with methanogens produce biogas which is a mixture of carbon dioxide, methane, hydrogen sulphide etc.

Conditions required for digestion:
- Methanogens are anaerobic organisms that ferment the substrate in the absence of oxygen.
- The ambient temperature of 40-50 degree Celsius. These mesophiles are highly efficient and bring about fermentation at a faster pace.
- The absence of oxygen is the limiting factor for digestion to take place. So, option A, C is the incorrect presence of sewage is not the limiting factor for digestion so option D, A is incorrect.

As the conditions optimum for the digestion of the waste is temperature and absence of oxygen, the correct answer is option ‘B’.

Note: The advantages of biogas are-
- It is a renewable source of energy.
- It is highly efficient and does not cause pollution.
- The biogas is used in running vehicles, as household cooking gas.