Question

The calorific value of biogas is
A. 10 - 20 mj/$m^3$
B. 23 - 28 mj/$m^3$
C. 35 - 40 mj/$m^3$
D. 5 - 10 mj/$m^3$

Answer 1

Biogas has a high amount of methane and the calorific value of biogas is defined by the amount of methane present. The more the amount of methane, the more is the calorific value.

Complete answer: Biogas is the mixture of gases that are produced by the anaerobic breakdown of organic compounds. It primarily consists of methane and carbon dioxide. It can be produced from raw substances such as agricultural wastes, plant material, municipal waste substances, manure, sewage, green, or food waste substances. The organic material is broken down by bacteria in an oxygen-free environment and the process is known as anaerobic digestion. This process recycles organic materials and converts them into biogas that contains gases and valuable soil products. It can help with heat and electricity production. Biogas contains about 50 - 70% methane and 30 - 50% carbon dioxide. The calorific value of biogas is determined by the amount of methane gas because other factors do not contribute to the energy release. In biogas, the methane content is very high that provides a high calorific value, because of this, it can be used in many applications such as power generation. It has a mean calorific value of about 25 mj/$m^3$ i.e., 1/$m^3$ of biogas is equivalent to about 1.25KG of natural coal.
Hence, the correct option is B.

Note: The calorific value of biogas depends upon the efficiency of burners and the value for biogas is specified by its methane value. It contains traces of gases such as hydrogen, nitrogen, carbon monoxide, oxygen, and hydrogen sulphide.