TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The hydrogen used in the step (e) is obtained from hydrogen storage and/or purchased from third parties. The oxygen used in the step (a) is obtained from oxygen storage and/or purchased from third parties.    TECHNOLOGY FOCUS - INSTRUMENTATION AND TESTING - Preferred Method: In the step (d) at least 80 vol.%, preferably 90 vol.% carbon dioxide-containing gas is removed. The method further comprises producing hydrogen and oxygen from water by electrolysis in an electrolysis plant operated with electrical current obtained from mains power source and/or a factory on-site power generation plant, and storing hydrogen in hydrogen storage and oxygen in oxygen storage, where water is obtained from public water network. The water accumulating in the methanation reactor or methanolation reactor is supplied to the electrolysis plant. The electrical current excess for the electrolysis, is used from renewable energies. The method further comprises combusting methane or methanol obtained from natural gas network, in addition to the fossil fuel. The method additionally makes use of industrial oxygen purchased from third parties, for combustion of the fuel, in addition to oxygen obtained from the electrolysis. The factory on-site power generation plant which comprises at least one power generation unit, is operated with methane or methanol obtained from the methane- or methanol storage. Preferred Components: The shaft furnace plant further comprises a hydrogen storage associated with the electrolysis plant, comprising at least one hydrogen supply pipe to the methanation- or methanolation reactor; at least one oxygen storage associated with the electrolysis plant, comprising at least one oxygen supply pipe to the combustion zone and/or outlet zone of the shaft furnace; at least one methane- or methanol supply from the methane- or methanol storage to the combustion zone of the shaft furnace; an electric power generation plant for providing electrical current to the electrolysis plant; and a gas- or liquid pipe for conducting methane or methanol from the methane- or methanol storage into a natural gas network. The power generation plant is designed and arranged such that it is operable with methane or methanol obtained from the methane- or methanol storage. The water electrolysis plant comprises at least one power supply pipe from public network and at least one power supply pipe from the power generation plant.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Components: The fuel comprises methane and/or methanol which is obtained from methane- or methanol storage, and is supplied as a fuel to the combustion zone of the shaft furnace. The fuel used in the step (a) comprises fossil fuel. The substitute fuel used in the step (a) comprises waste oil or animal meal. EXAMPLE - No suitable example given.