NOVELTY - The method (10) involves comprising process (105) of cooling synthesis of gas to condense heavy organic impurities, and process (110) of adsorption of light organic impurities and inorganic impurities by adsorption bed at exit of cooling process. The adsorption bed is regenerated in process (120). The regeneration process is comprised with process (125) of desorption of adsorption bed and process of cooling adsorption bed. The regeneration process is comprised with process (135) of tar decantation collected during cooling process.    USE - Method of treating synthesis gas transmitted from gasification process of hydrocarbon fuel for producing biomethane.    ADVANTAGE - Since the adsorption process is directly carried out at the exit of the cooling process, the washing process of washing with the solvent and regeneration solvent is eliminated in the treating process. Hence the cost of installation of the device for treating the synthesis gas is reduced, and the environmental impact of the device and the energy consumption of the device are reduced.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for a device for treating synthesis gas transmitted from gasification unit, has adsorption beds and permutation unit that circulate synthesis gas in adsorption beds, when adsorption beds are in phase of desorption. The lavage fluid of gas is implemented by a cooler. The lavage fluid is water or oil.    DESCRIPTION OF DRAWING(S) - The drawing shows a flow chart illustrating the process of treating the synthesis gas transmitted from gasification process. (Drawing includes non-English language text)    Step for treating synthesis gas transmitted from gasification process (10)    Step for cooling synthesis of gas to condense heavy organic impurities (105)    Step for adsorption of light organic impurities and inorganic impurities by adsorption bed at exit of cooling process (110)    Step for regenerating adsorption bed (120)    Step for desorption of adsorption bed (125)    Step for tar decantation collected during cooling process (135)