Gasification is a process that converts carbonaceous materials (coal, biomass, organic waste) into carbon monoxide and hydrogen by reacting the raw material at high temperatures with a controlled amount of oxygen and/or steam. The resulting gas mixture: syngas, can be used in energy production process. Syngas may be burned directly in internal combustion engines, used to produce methanol and hydrogen, or converted via the Fischer-Tropsch process into synthetic fuel. In addition, the high-temperature combustion refines out corrosive ash elements (chloride, potassium) allowing clean gas production after flying ash removal. Therefore, the main issue to syngas use in internal combustion engine is the removal of tarry product, ash and corrosive gaseous compounds. This paper consists in a state of the art on the composition of gaz from gazeifier considering the gasification operating conditions and the gazeified waste composition. The literature survey considers processes available to remove tarry products and particles from syngas produced in small scale gazeifier and to purify gas from unwanted gazeous compouds.