The major requirements for steel and aluminum include electricity, natural gas, bauxite, carbon anode materials, coking coal, iron ore, and hydrogen. Non-materials inputs include capital costs (capex), fixed operations and maintenance (O&M), and labor. These material and non-material requirements are shown in Supplementary Table , along with their data sources. Minor inputs include limestone, oxygen, sodium hydroxide, and others. Energy and fuel inputs, including coal, natural gas, electricity, and hydrogen, are shown to scale in Figure for world production at present. As shown, the main energy inputs for primary metallurgy today are coal for blast furnace reduction (6390 TWh), followed by electricity for Hall-Héroult aluminum (940 TWh) and natural gas for direct reduced iron (510 TWh). (a) Total cost is the sum of energy and non-energy costs, where aluminum has higher overall costs and a higher share of total cost from energy than steel. (b) Emissions intensity is the product of carbon intensity of energy and energy intensity of metal.