A method of producing direct reduced iron, DRI, comprising: operating a hydrogen direct reduction, DR, plant, wherein iron ore is reduced in a shaft furnace in a hydrogen rich atmosphere, the shaft furnace being connected with a process gas loop arranged to receive top gas from the shaft furnace, treat the top gas before heating it in a heater device, and returning to the furnace a reducing gas comprising at least 85 vol.% hydrogen, wherein a hydrogen stream is added to said process gas loop upstream of said heater device; operating an industrial plant generating CO-bearing gas and/or waste heat and/or hot gases, wherein the industrial plant includes a natural gas DR plant operating on reformed natural gas to produce DRI from iron ore, said natural gas DR plant including a further shaft furnace and a further process gas loop, said further process gas loop including heater-reformer means to generate a syngas from natural gas, to be fed to the further shaft furnace as reducing gas; wherein at least part of said hydrogen stream is produced by at least one of: electrolysis means configured to produce hydrogen from steam recovered from one or more components of the industrial plant and/or from steam generated using waste heat and/or hot gases emitted by the one or more components; and gas shift reactor means configured to convert CO-bearing gas emitted by at least one component of the industrial plant into hydrogen and to remove CO 2 . operating a hydrogen direct reduction, DR, plant, wherein iron ore is reduced in a shaft furnace in a hydrogen rich atmosphere, the shaft furnace being connected with a process gas loop arranged to receive top gas from the shaft furnace, treat the top gas before heating it in a heater device, and returning to the furnace a reducing gas comprising at least 85 vol.% hydrogen, wherein a hydrogen stream is added to said process gas loop upstream of said heater device; operating an industrial plant generating CO-bearing gas and/or waste heat and/or hot gases, wherein the industrial plant includes a natural gas DR plant operating on reformed natural gas to produce DRI from iron ore, said natural gas DR plant including a further shaft furnace and a further process gas loop, said further process gas loop including heater-reformer means to generate a syngas from natural gas, to be fed to the further shaft furnace as reducing gas; wherein at least part of said hydrogen stream is produced by at least one of: electrolysis means configured to produce hydrogen from steam recovered from one or more components of the industrial plant and/or from steam generated using waste heat and/or hot gases emitted by the one or more components; and gas shift reactor means configured to convert CO-bearing gas emitted by at least one component of the industrial plant into hydrogen and to remove CO 2 . electrolysis means configured to produce hydrogen from steam recovered from one or more components of the industrial plant and/or from steam generated using waste heat and/or hot gases emitted by the one or more components; and gas shift reactor means configured to convert CO-bearing gas emitted by at least one component of the industrial plant into hydrogen and to remove CO 2 . <EOS>