Biogas Analysis: Measuring Methane, CO₂ and H₂S

A biogas analysis determines the composition of the gas from the digester and post-digester. According to the German Agency for Renewable Resources (FNR), raw biogas typically contains 50–75 vol.% methane and 25–45 vol.% carbon dioxide, plus water vapour, 20–20,000 ppm hydrogen sulphide and small shares of oxygen and hydrogen. The values change with substrate, temperature and feeding – which is why they are measured, not estimated.

Each gas answers its own question: the methane content shows how much energy the gas carries. Hydrogen sulphide attacks the gas engine, pipes and catalyst and shows whether desulphurisation works. Oxygen matters when air is added for biological desulphurisation, and hydrogen is an early sign of disturbed digestion.

For raw biogas, the BioBasic measures methane and H₂S, optionally CO₂, O₂ and H₂ – at up to five measuring points with one device, around 22 minutes 20 seconds per point. For biomethane after upgrading, the GA 220 Biomethan and the BioBasic Biomethane measure every second. Measurement is extractive: the device stands outside the Ex zone, and ATEX-certified flame arresters protect the plant.

Which measuring point in your plant needs which gas is shown on the page gas analysis for biogas plants – with an interactive plant map and configurator.