What Factors Influence Charcoal Quality?
Tom Miles, Biomass Cooking Stoves June 18, 2006

Temperature

100C -> Wood drying 19 MJ/kg

220C -> Wood becomes brown
250-270C-> Torrefaction 28% fixed carbon, 72% volatile 23.9 MJ/kg
280C -> Wood becomes deep brown-black

300C -> 68% char 32% volatile 40% yield soft, brown, friable