Biochar is made through a process called “pyrolysis”. All this means is that biochar is created in a low oxygen and low temperature environment (< 700°C). This is different from your backyard grill where there is an abundance of oxygen. Typically biochar is made in a customized container that can be sealed to limit the amount of oxygen present. Depending on the temperature of the pyrolysis technique you can produce biochar in a matter of minutes, hours, or even days. Lower temperatures produce more biochar whereas higher temperatures produce less, however, in these higher temperatures you also produce syngas and bio-oil.
Syngas is a mixture of various gases that is emitted in higher temperature biochar production techniques. This gas can be burned as fuel either in the pyrolysis process or in certain set-ups can be captured for use as a cooking, heating, and other uses.
Bio-oil is a sticky tar like substance that is also produced during high temperature pyrolysis techniques. This product also has the potential to be used as fuel either for heating or electricity production.