About 40% of the total energy input to the steel industry is used to chemically reduce iron ore to liquid pig iron in the blast furnace. The majority of the energy input to the blast furnace is in the form of coke (made from coal in coke ovens), although supplemental fuels can be injected. Another 25% of the energy is used in process heating, including electric arc furnaces and reheating furnaces. Natural gas and byproduct gases (coke oven gas and blast furnace gas) are combusted in boilers to generate process steam. Electricity is used to power equipment (including casting machines and rolling mills) and to heat, light, and cool facilities. [DOE 1996]