Question

What is biogas? Write in brief about the production process.

Answer 1

Biogas is a mixture of methane CH₄ (50-60%), CO₂ (30-40%), H₂S (0-3%) and other gases (CO, N₂ , H₂ ) in traces.

Biogas production process: 

a. A typical biogas plant consists of digester (made up of concrete bricks and cement or steel and is partly buried in the soil) and gas holder (a cylindrical gas tank to collect gases). b. Raw materials like cow dung is mixed with water in equal proportion to make slurry which is fed into the digester’ through a side opening (charge pit). 

Anaerobic digestion involves following processes: 

i. Hydrolysis or solubilization: 

Anaerobic hydrolyzing bacteria like Clostridium and Pseudomonas hydrolyse carbohydrates into simple sugars, proteins into amino acids and lipids into fatty acids.

ii. Acidogenesis: 

Facultative and obligate anaerobic, acidogenic bacteria convert simple organic substances into acids like formic acid, acetic acid, H₂ and CO₂

iii. Methanogenesis: 

Anaerobic methanogenic bacteria like Methano bacterium, Methanococcus convert acetate, H₂ and CO₂ into Methane, CO₂ and H₂O and other products. 

12 mol CH₃ COOH → 12CH₄ + 12CO₂ 4mol H.COOH → CH₄ + 3CO₂ + 2H₂ O CO₂ + 4H₂ → CH₄ + 2H₂ O