We consider five metal production pathways. The first pathway we consider is traditional BF-BOF steelmaking with coal. In this process, a large (50-100m tall) blast furnace is filled with alternating layers of iron ore and metallurgical coke. Preheated blasts of air are pumped into the furnace through tuyeres, facilitating reduction of iron ore by coke to produce CO and CO2-rich blast furnace gas, which exits through the top of the furnace, and liquid iron and slag, which are tapped through holes near the bottom of the furnace. The resulting intermediate, pig iron, is decarburized in a basic oxygen furnace before secondary steelmaking (alloy addition, desulfurization, homogenization) and tertiary steelmaking (casting or working steel into sheets, rolls, and other forms). The second pathway we consider is DRI steelmaking using natural gas. In this process, lump or pelleted iron ore is loaded into a shaft furnace and is converted to metallic iron below the iron melting point, while a reducing gas atmosphere (H2/CO) is maintained in the shaft furnace through use of a gas reformer with a natural gas feed. DRI can be discharged hot or cold from the furnace, then converted to steel in an electric arc furnace with relatively low energy and material requirements. Unlike blast furnaces, which require metallurgical-grade coke, DRI shaft furnaces can handle a variety of diDerent reducing agents: most DRI shaft furnaces in operation today use natural gas, though some use gasified coal and the technical barriers to hydrogen firing are low. DRI/EAF steelmaking with hydrogen, which does not yet exist on an industrial scale, is the third pathway we consider. In this process, low-carbon electricity would be used to split water and produce hydrogen, which could then be fed into a shaft furnace to reduce iron ore to DRI. EAF steelmaking from DRI would proceed similarly for natural gas and H2powered options.