The pyrolysis is degradation of biomass by heat in the absence of oxygen, which results in the production of charcoal, liquid, and gaseous products. The pyrolysis process can be divided into three subclasses: conventional pyrolysis, fast pyrolysis, and flash pyrolysis. The hemicelluloses break down first at temperatures of 470 to 530 K, cellulose follows in the temperature range 510 to 620 K, and lignin is the last component to pyrolyze at temperatures of 550 to 770 K. If the purpose is to maximize the yield of liquid products resulting from biomass pyrolysis, a low temperature, high heating rate, short gas residence time process would be required. For a high char production, a low temperature, low heating rate process would be chosen. If the purpose was to maximize the yield of fuel gas resulting from pyrolysis, a high temperature, low heating rate, long gas residence time process would be preferred.