NOVELTY - Method for producing methane involves generating hydrogen from water by electrolysis; and withdrawing a total product stream from the electrolysis, which contains hydrogen, oxygen and water. The total product stream is then supplied to a reactor in which the hydrogen is converted to methane with carbon dioxide in at least one methanation stage in heterogeneously catalyzed reaction.    USE - For producing methane from hydrogen with electrolysis device. The renewable methane can be used in the heat and traffic sector e.g. for providing high-temperature process heat, in passenger cars or in hybrid vehicles.    ADVANTAGE - The present method involving coupling between electrolysis of water and methanation is affected with a simplified purification of the hydrogen resulting from the electrolysis and simple process management. The removal of oxygen by catalytic oxidation of the oxygen with hydrogen to obtain water can take place inside the methanation reactor, has the advantage that expensive intermediate apparatuses for purification of the gas stream can be omitted completely. The energy released by catalytic oxidation can be utilized to further heat up the entire gas stream, so that the necessary activation energy for starting the methanation reaction can at least partly be provided inside the reactor, without this amount of energy having to be provided by an external source. For oxygen removal, palladium catalyst is used, which completely converts the oxygen during long downtimes. Preferably, the reaction for oxygen removal is carried out at a temperature (300-350 degrees C). At this temperature, damage of the catalyst is avoided and at the same time a complete conversion is ensured. For the methanation stage, nickel catalyst is used, since this catalyst is suitable for high conversions of the hydrogen with a high yield of methane at the same time.    DETAILED DESCRIPTION - An INDEPENDENT CLAIM is included for plant for producing methane with electrolysis device in which hydrogen is generated from water by electrolysis, reactor (33) in which the hydrogen is converted to methane in heterogeneously catalyzed reaction in at least one methanation stage (33b); and conduit (30), through which total product stream which contains hydrogen, oxygen and water, is guided from the electrolysis device into the reactor.    DESCRIPTION OF DRAWING(S) - The figure shows schematic representation of the method for production of methane.    Conduit (30)    Reactor for methanation (33, 40, 42)    Stage for removal of oxygen (33a)    Methanation stage (33b)    Heat exchanger (51)