Direct reduced iron (DRI), also called sponge iron, is produced from the direct reduction of iron ore (in the form of lumps, pellets, or fines) into iron by a reducing gas which either contains elemental carbon (produced from natural gas or coal) or hydrogen.  When hydrogen is used as the reducing gas there are no greenhouse gases produced. Many ores are suitable for direct reduction.
Direct reduction refers to solid-state processes which reduce iron oxides to metallic iron at temperatures below the melting point of iron. Reduced iron derives its name from these processes, one example being  heating iron ore in a furnace at a high temperature of  in the presence of the reducing gas syngas, a mixture of hydrogen and carbon monoxide, or pure hydrogen.