Question

Bio gas production from waste biomass with the help of methanogenic bacteria is a

• A. Four step process.
• B. One step process.
• C. Two step process.
• D. Three step process.

Answer 1

The correct option is A Four step process.

The process of biogas production can be divided into four steps: hydrolysis, acetation, acidification, and methane formation.

1. Hydrolysis: In the first step (hydrolysis), the organic matter is enzymolyzed externally by extracellular enzymes (cellulase, amylase, protease and lipase) of microorganisms. Bacteria decompose the long chains of the complex carbohydrates, proteins and lipids into shorter parts.

2. Acetation and 3. acidification: Acid-producing bacteria, involved in the second step, convert the intermediates of fermenting bacteria into acetic acid (CH${}_3$COOH), hydrogen (H${}_2$) and carbon dioxide (CO${}_2$). These bacteria are facultatively anaerobic and can grow under acid conditions. To produce acetic acid, they need oxygen and carbon. They use the oxygen solved in the solution or bounded-oxygen. The acid-producing bacteria create an anaerobic condition which is essential for the methane producing microorganisms.

4. Methanogenesis: Methane-producing bacteria, involved in the third step, decompose compounds with a low molecular weight. They utilize hydrogen, carbon dioxide and acetic acid to form methane and carbon dioxide.

Thus, the correct answer is option A.