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.