6th Framework Programme
1. What is biogas?

1. What is biogas?

Biogas is the gas that is the product of the digestion of organic materials under anaerobic conditions. Substrates such as manure, sewage sludge, municipal solid waste, biodegradable wastes or feedstock are transformed into methane and carbon dioxide.

Typical composition of biogas

  • 50-75 % Methane, CH4
  • 25-50 % Carbon dioxide, CO2
  • 0-10* % Nitrogen, N2
  • 0-1 % Hydrogen, H2
  • 0-3 % Hydrogen sulphide, H2S
  • 0-2* % Oxygen, O2

*often 5 % of air is introduced for microbiological desulphurisation

The process of anaerobic digestion is done by methane bacteria. Necessary milieu conditions are:

  • Anaerobic milieu
  • Temperatures between 15°C and 55°C
  • PH-values between 6.5 and 8.0
  • A variety of feedstock which is not that big
  • Avoiding retardants, such as heavy metal salts, antibiotics, disinfectants
  • Existence of trace minerals such as nickel and molybdenum