4.1 What is Biogas?

Biogas originates from bacteria in the process of biodegradation of organic material under anaerobic conditions. It consists of a varying proportion of CH₄ (methane) and CO₂ (carbon dioxide) and traces of H₂S, N, CO, O, etc. The content of CH₄ and CO₂ is a function of the matter digested and the process conditions like temperature, C/N ratio, etc. Methane is the most valuable component under the aspect of using biogas as a fuel; the other components do not contribute to the calorific ("heating") value and are often "washed out" in purification plants in order to obtain a gas with almost 100% CH₄. For further details of biogas production the use of the respective literature is recommended [3, 4, 5, 6].