Microbes in Energy Generation

Biogas is a renewable, non-conventional source of energy produced by the anaerobic microbial fermentation of organic waste such as cattle dung, plant residues, and sewage.

Key significance:

• Provides clean fuel for cooking and lighting, especially in rural India
• Converts waste into useful energy, reducing pollution
• Produces enriched slurry usable as organic manure

A typical biogas plant consists of:

1. Inlet tank: for mixing waste (dung/slurry) with water
2. Digester: underground airtight tank where anaerobic digestion occurs
3. Gas holder/dome: collects and stores the biogas produced
4. Outlet tank: for removal of spent slurry (used as manure)

Biogas plant

The process occurs in three sequential stages, each driven by a different microbial group.

Organic Waste (cellulose, proteins, fats)

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 STAGE I: Hydrolysis/Solubilisation – Hydrolytic bacteria  (breaks down complex polymers into soluble monomers) 

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STAGE II: Acidogenesis - Fermentative (acidogenic) bacteria  (converts monomers into organic acids, H₂, CO₂) 

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STAGE III: Methanogenesis - Methanogens (Methanobacterium, Methanosarcina) (converts acids + H₂ + CO₂ into methane) 

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BIOGAS (CH₄ + CO₂ + traces)

• Rural cooking fuel and lighting (reduces dependence on firewood/kerosene)
• Slurry used as nutrient-rich organic fertilizer
• Reduces environmental pollution from untreated organic waste
• Renewable and continuously replenishable energy source
• Reduces greenhouse gas emissions compared to fossil fuels

Limitations

• Requires consistent supply of organic waste/dung
• Efficiency drops in colder climates (methanogens are temperature-sensitive)
• Initial setup cost can be a barrier for small farmers

• Meaning: Biogas is a renewable energy source obtained through microbial fermentation. Key microbes: Archaebacteria and Bacillus.
• Composition: Mixture of CH₄, CO₂, H₂S, H₂, and N₂. Methane is the main combustible gas.
• Substrate & Plant: Cattle dung is the common raw material. Plant has a digester and gas holder. Developed by KVIC and IARI in India.
• Stage I – Solubilisation: Hydrolytic bacteria break down proteins, fats, and cellulose into simpler soluble compounds.
• Stage II – Acidogenesis: Fermentative bacteria convert monomers into organic acids (e.g., acetic acid), H₂ and CO₂.
• Stage III – Methanogenesis: Methanosarcina and Methanobacterium convert acetate + H₂ + CO₂ into methane (biogas).