Carbonization;  Thermal decomposition

Pyrolysis (from Greek πuρ (pyr) = “fire” and λuσις (lysis) = “decomposition”) is a chemical process in which bonds of a compound are spontaneously broken by high temperatures (500–900 °C). Extreme pyrolysis of carbon-containing substances, which leaves mostly  carbon as the residue, is called carbonization. The production of charcoal from wood is an example of pyrolysis and carbonization.