Answer 1

Process of biogas production:

Anaerobic digestion involves three processes:

a. Hydrolysis or solubilization:

1. In the initial stage, the raw material (cattle dung) is mixed with water in equal proportion to make a slurry which is then fed into the digester.

2. Here anaerobic hydrolytic bacteria (e.g. Clostridium, Pseudomonas) hydrolyse carbohydrates into simple sugars, proteins into amino acids, and lipids into fatty acids.

b. Acidogenesis: In this stage, facultatively anaerobic, acidogenic bacteria and obligate anaerobic organisms, convert simple organic material into acids like formic acid, acetic acid, H₂, and CO₂.

c. Methanogenesis: This is the last stage in which anaerobic Methanogenic bacteria like Methanobacterium, Methanococcus convert acetate, H₂, and CO₂ into Methane, CO₂ and H₂O, and other products.

1. \[\ce{\underset{\text{(Acetic acid)}}{12mol CH3COOH} -> \underset{\text{Methane}}{12CH4} + 12CO2}\]

2. \[\ce{\underset{\text(Formic acid)}{4mol H{.}COOH} -> CH4 + 3CO2 + 2H2O}\]

3. \[\ce{CO2 + 4H2 -> CH4 + 2H2O}\]