Energy
Pyrolysis
Pyrolysis is heating biomass with very little oxygen so that it cannot fully burn. Volatile compounds leave as gas and oil, and a porous carbon rich solid remains. That solid is biochar, and the gas can be captured and used as process heat.
Temperature and duration decide how stable the resulting char is, which is why conditions are recorded for each batch.
Running the process on its own gas is what makes it efficient, because the heat needed comes from the material itself.