How Do Biogas Plants Work?
What is anaerobic digestion?
Anaerobic digestion is a natural biological process where micro-organisms break down biodegradable material in the absence of oxygen. Inside a sealed digester, bacteria feed on food waste, animal dung, and agricultural residue, releasing methane-rich biogas as a by-product.
What are the 4 stages of biogas production?
- Hydrolysis: Complex molecules (carbohydrates, fats, proteins) break into simple sugars and amino acids.
- Acidogenesis: Bacteria convert these into volatile fatty acids.
- Acetogenesis: Acids are converted into acetic acid, hydrogen, and CO₂.
- Methanogenesis: Methanogen bacteria produce methane (CH₄) — the energy-rich component of biogas.
What goes into a biogas plant?
Common feedstock includes kitchen and food waste, vegetable market waste, cattle dung, poultry litter, and crop residue. A balanced carbon-to-nitrogen ratio (around 25:1 to 30:1) keeps the bacteria healthy and gas output stable.
| Feedstock | Typical biogas yield (m³/kg) |
|---|---|
| Food / kitchen waste | 0.4 – 0.6 |
| Cattle dung | 0.2 – 0.3 |
| Poultry litter | 0.3 – 0.5 |
| Vegetable waste | 0.3 – 0.5 |
What can biogas be used for?
Biogas can replace LPG for cooking, generate electricity through gas engines, or be upgraded into Bio-CNG for vehicles. The leftover slurry is an excellent organic fertiliser, closing the loop on waste.
Planning a waste-to-energy project?
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Request a Free QuoteFrequently Asked Questions
Do biogas plants smell bad?
No. A properly sealed and balanced biogas digester is odour-free because the process is fully enclosed. Smell usually indicates a leak or overloading.
How long does it take to produce biogas?
After commissioning, a digester typically begins steady gas production within 15–30 days as the bacterial culture establishes itself.
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