Pyrolysis is a thermo chemical decomposition of organic material at elevated temperatures in the absence of oxygen (or any halogen). Pyrolysis is the heating of an organic material, such as biomass, in the absence of oxygen.  Because no oxygen is present the material does not combust but the chemical compounds (i.e. cellulose, hemicelluloses and lignin) that make up that material thermally decompose into combustible gases and charcoal.  Most of these combustible gases can be condensed into combustible liquid, called pyrolysis oil (bio-oil). Also there are some permanent gases (CO₂, CO, H₂, and light hydrocarbons).As ususl the final products of pyrolysis: one liquid pyrolysis oil, one solid bio-char and the syngas. The proportion of these products depends on several factors including the composition of the feedstock and process parameters. The pyrolysis usually occurs in the burning of many solid organic fuels like wood,cloth,and paper and also some kinds of waste plastic.