Question

Biogas generation is mainly based on the principle of-
a. Fermentation
b. Degradation
c. Purification
d. Both (a) and (b)

Answer 1

Hint: Biogas is a naturally occurring gas. Biogas is produced by anaerobic digestion with methanogen or anaerobic bacteria, which ferment material inside a closed system of biodegradable materials.

Complete answer:
Biogas is a naturally occurring gas that is generated by breakdown of organic matter by anaerobic bacteria. It is a renewable energy produced biologically rather than the fossil fuels which are produced by geological processes.

Biogas is primarily composed of methane gas, carbon dioxide and traces of nitrogen, hydrogen and carbon monoxide. It occurs naturally in compost heaps, as swamp gas, and as a result of enteric (intestinal) fermentation in cattle and other ruminants. It can also be produced in anaerobic digesters from plant or animal waste that is collected from landfills. It is then burned to generate heat or used in combustion engines to produce electricity.

On the other hand, purification is the process of removing contaminants from a substance. Since, there is no concern of purification of organic matter for production of biogas. Therefore, biogas production does not involve the process of purification in any aspect.
So, the correct answer is option D

Additional information:
Biogas can be compressed after removal of Carbon dioxide, the same way as natural gas is compressed to CNG, and used to power motor vehicles. Biogas can be cleaned and upgraded to natural gas standards, when it becomes bio-methane. Biogas is considered to be a renewable resource because its production-and-use cycle is continuous. Also, it generates no net carbon dioxide.

Note: As the organic material grows, it is converted and used. It then regrows in a continually repeating cycle. From a carbon perspective, as much carbon dioxide is absorbed from the atmosphere in the growth of the primary bio-resource as is released, when the material is ultimately converted to energy.