Biogas Stove Calculator

This calculator turns raw biogas digester output into practical cooking capacity by chaining together energy content, burner losses, and burner power draw. It starts from pure methane's energy content of 36 MJ per cubic meter and scales it down by your biogas's actual methane fraction (usually 55-65% for cattle-dung digesters, since biogas is a methane-CO2 mixture, not pure methane) to get energy content per cubic meter of your specific gas. Multiplying that by daily biogas production gives total daily energy available, and multiplying again by burner efficiency (the fraction of gas energy that actually reaches the pot rather than being lost as unburned fuel or escaping heat) gives useful cooking energy. Dividing useful energy by the burner's rated power (converting megajoules to kilojoules and dividing by kilowatts, which are kilojoules per second, then converting seconds to hours) gives total cooking hours available per day at full burner output.

Meals per day is a rough conversion assuming about 4 MJ of useful energy per family meal — a coarse average that will run high or low depending on what's actually being cooked. The calculator also estimates two supply-side numbers useful for the digester side of the system: LPG-equivalent savings (1 cubic meter of biogas replacing roughly 0.45 kg of LPG) and daily dung feedstock needed, using a rule-of-thumb yield of about 25 kg of cattle dung per cubic meter of biogas produced — a figure that varies with digester temperature, retention time, and dung freshness. Because burner efficiency and feedstock yield are both broad averages rather than measurements of your specific setup, use these numbers to size a system in the right ballpark, then refine with real measurements from your own digester and burner once running.