Work out biogas plant sizing instantly with clear inputs, formula shown and shareable results.
Digester volume is daily slurry feed times hydraulic retention time — 30-50 days for mesophilic dung digestion depending on temperature. Slurry volume is dung plus dilution water, and the gas holder is sized at roughly 60% of daily production to buffer between generation and cooking demand.
Digester volume
Slurry (m3/day) = dung x (1 + water ratio) / 1000; digester = slurry x retention time
Gas
Gas (m3/day) = dung x gas yield per kg; holder = 60% of daily gas
Biogas is flammable and asphyxiating, and digesters can accumulate hydrogen sulphide. Never enter a digester without confined-space procedures, and install the plant to the applicable national biogas standard.
A crossbred cow yields 10-15 kg of collectable dung a day, a buffalo 15-20 kg. Two to four cattle typically support a 2 m3 family plant.
One cubic metre of biogas roughly equals 0.4 kg of LPG or about 3.5 kWh of thermal energy — enough to cook for four to five people for a day.