Q. With reference to biogas production via Bio-methanation method, consider the following statements:
1. Under this, organic material is microbiologically converted under anaerobic conditions to biogas.
2. The energy content of the biogas produced under the process is proportional to the Methane content.
3. The biogas has a lower calorific value than natural gas.
Which of the statements given above is/are correct?

[A] 1 and 2 only

[B] 2 and 3 only

[C] 1 and 3 only

[D] 1, 2 and 3

Answer: D
Notes:
  • Statement 1 is correctUnder Bio-methanation organic material is microbiologically converted under anaerobic conditions to biogas. 
  • Statement 2 is correct: The energy content of the biogas is proportional to the CH4 content. Usually, the AD biogas contains between 40–75% CH4 and 25–60% CO2, besides other components in minor quantities such as H2, N2, NH3, H2S, H2O and others trace organic and inorganic components. 
  • Statement 3 is correct: Because of the presence of CO2, the biogas has a lower calorific value than natural gas, and therefore cannot be directly injected into the natural gas grid.  

Source: Article