Question

Explain the structure of the biogas plant.

Answer 1

Hint: Biogas is a mixture of gases containing predominantly methane produced by microbial activity which may be used as fuel.

Complete answer:
During growth and metabolic activities, the bacteria produce different types of gaseous end products. These gases produced by the activity of microbes are known as biogas. The major component of biogas is methane (50-70%) which is highly inflammable, other gases are carbon dioxide (30-40 %) and a mixture of other gases hydrogen and hydrogen sulfide, etc. (10%).
Certain bacteria that grow anaerobically on cellulosic material produce a large amount of methane along with CO₂ and H₂. These bacteria are called methanogens. The Indian Agricultural Research Institute (IARI) and the Khadi and Village Industries Commission (KVIC) introduced the technology of biogas production in India.
Biogas plant consists of:
Mixing tank: present above the ground level.
Inlet Chamber: The mixing tank opens underground into the digester.
A concrete tank: 10-15 feet deep, in which biogas and slurry are fed. It is known as a digester. The ceiling of a digester has an outlet with a valve for the supply of biogas.
A floating cover is placed over the slurry, which keeps on rising as gas is produced in the tank due to microbial activity. It has an outlet which is connected to a pipe to supply biogas to nearby houses.
The spent slurry is removed through another outlet and is used as fertilizer. So, biogas plants are more often built in rural areas. The gobar (cow dung) has a surplus amount of bacteria. Thus, dung can be used for the generation of biogas, commonly called gobar gas.

Note:
- The bacteria are commonly found in sludge during sewage treatment. These bacteria are also present in the rumen of the cattle.
- Biogas can be compressed after removal of CO₂ and can be used in motor vehicles.
- It is a renewable energy resource.
- The closed system is called an anaerobic digester, biodigester, or bioreactor.