Work out biogas from sludge instantly with clear inputs, formula shown and shareable results.
Digester gas yield is around 0.9-1.1 cubic metres per kilogram of volatile solids destroyed, with destruction of 45-55% at conventional mesophilic retention times. At 60-65% methane, biogas holds about 6 kWh of thermal energy per cubic metre, of which a gas engine converts around 38% to electricity.
Biogas yield
Gas = volatile solids fed x destruction % x yield per kg VS destroyed
Energy
Thermal kWh = methane volume x 9.94; electrical = thermal x engine efficiency
Digester gas is explosive in air and contains hydrogen sulphide. Gas systems must comply with the applicable gas safety standard with flame arrestors, relief and detection.
Yes — thermal hydrolysis, sludge pretreatment or co-digestion with food waste can raise volatile solids destruction to 60-65% and substantially increase gas. Co-digestion often doubles gas output.
Digester heating typically consumes 30-50% of the thermal energy in a temperate climate, more in winter. Only the surplus is available for export or additional electricity generation.