Methanation process comprising the conversion of CO 2, which originates from a power station flue gas of a power station (2, 2a) fired with a carbonaceous fuel and having a connected water/steam circuit, to methane in a methanation plant, wherein the power station (2, 2a) is formed as an integral component of a connected industrial plant, in particular formed by a smelting plant or a chemical plant, and is integrated into at least part of the material and/or energy streams of the industrial plant, and at least part of at least one carbonaceous material or material stream occurring as a by-product or waste product during a production process in the industrial plant is fed to the combustion chamber of the steam generator of the power station (2, 2a) as carbonaceous fuel, wherein a coproduct gas is supplied to the combustion chamber of the steam generator of the power station (2,2a) as carbonaceous material stream and fuel, which contains one or more gaseous by-products or waste products of the industrial plant, and wherein hydrogen (19a, 19b) obtained from the coproduct gas and/or produced by means of electrolysis is supplied to the methanation plant, and wherein the power station (2, 2a), a CO 2 exhaust gas treatment and the methanation plant are integrated into the material and/or energy streams of the industrial plant, and wherein the heat energy arising as waste heat in the conversion of CO 2 to methane in the methanation plant is coupled out (33, 34) at least in part into at least one material and/or heat energy stream (13, 14, 37) and this material and/or heat energy stream (13, 14, 37) is supplied at least in part to at least one medium flowing into the combustion chamber of a steam generator of the power station (2, 2a) on the burner side and/or to the water/steam circuit of the power station (2, 2a) and/or to the CO 2 exhaust gas treatment which is connected upstream, in terms of process engineering, of the methanation plant, and/or to one or more operating stages of the attached industrial plant. wherein a coproduct gas is supplied to the combustion chamber of the steam generator of the power station (2,2a) as carbonaceous material stream and fuel, which contains one or more gaseous by-products or waste products of the industrial plant, and wherein hydrogen (19a, 19b) obtained from the coproduct gas and/or produced by means of electrolysis is supplied to the methanation plant, and wherein the power station (2, 2a), a CO 2 exhaust gas treatment and the methanation plant are integrated into the material and/or energy streams of the industrial plant, and wherein the heat energy arising as waste heat in the conversion of CO 2 to methane in the methanation plant is coupled out (33, 34) at least in part into at least one material and/or heat energy stream (13, 14, 37) and this material and/or heat energy stream (13, 14, 37) is supplied at least in part to at least one medium flowing into the combustion chamber of a steam generator of the power station (2, 2a) on the burner side and/or to the water/steam circuit of the power station (2, 2a) and/or to the CO 2 exhaust gas treatment which is connected upstream, in terms of process engineering, of the methanation plant, and/or to one or more operating stages of the attached industrial plant.