Tar is a complex mixture of condensable hydrocarbons,which includes single ring to 5-ring aromatic compounds along with other oxygen-containing hydrocarbons and complex polyaromatic hydrocarbon (PAH) [82]. In the past three decades, interest has grown on the subject of catalysis for biomass gasification. The advances in this area have been driven by the need to produce a tar-free product gas from the gasification of the biomass, since the removal of tars and the reduction of methane content increase the economic viability of the biomass gasification process. The criteria for the catalyst are fundamentally the same and can be summarized as follows