NOVELTY - Generating biomethane from biogas or digester gas and hydrogen, comprises (a1) supplying biogas from a biogas plant or a digestion tower, which is stoichiometrically or superstoichiometrically mixed with hydrogen without its previous purification, to a biomethanation reactor, (b) charging the biomethanation reactor with bacterial suspension or fermentation residue (3), (c) conducting the suspension phase to the gas phase in countercurrent or in co-current, and (d) reacting carbon dioxide with hydrogen by methane bacteria of the suspension to obtain methane and water.    USE - The method is useful for generating biomethane (claimed).    ADVANTAGE - The biomethane can be supplied to a natural gas system without carbon dioxide separation.    DETAILED DESCRIPTION - Generating biomethane from biogas or digester gas and hydrogen produced by electrolysis using regenerative energy or from algae or cyanobacteria using sunlight, comprises (a1) supplying biogas from a biogas plant or a digestion tower, which is stoichiometrically or superstoichiometrically mixed with hydrogen without its previous purification, to a biomethanation reactor, or (a2) supplying carbon dioxide-rich gas partial stream which is produced in a biogas plant using biogas treatment by physical- or chemical methods, and is stoichiometrically or superstoichiometrically mixed with hydrogen, to a biomethanation reactor, (b) charging the biomethanation reactor with bacterial suspension from a main fermenter (1) or a secondary fermenter (2) or with fermentation residue (3) of a biogas plant or from the digestion tower of a wastewater treatment plant, (c) conducting the suspension phase to the gas phase in countercurrent or in co-current, and (d) reacting carbon dioxide with hydrogen by methane bacteria of the suspension to obtain methane and water.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic representation of the biogas plant.    Main fermenter (1)    Secondary fermenter (2)    Fermentation residue (3)    Electrolyzer (4)    Separator (8)