The energy benefit of stainless steel recycling

The energy used to produce austenitic stainless steel was quantified throughout its entire life cycle for three scenarios: (1) current global operations, (2) 100% recycling, and (3) use of only virgin materials. Data are representative of global average operations in the early 2000s. The primary energy requirements to produce 1 metric ton of austenitic stainless steel (with assumed metals concentrations of 18% Cr, 8% Ni, and 74% Fe) is (1) 53 GJ, (2) 26 GJ, and (3) 79 GJ for each scenario, with CO2 releases totaling (1) 3.6 metric tons CO2, (2) 1.6 metric tons CO2, and (3) 5.3 metric tons CO2. Thus, the production of 17 million metric tons of austenitic stainless steel in 2004 used approximately 9.0×1017 J of primary energy and released 61 million metric tons of CO2. Current recycling operations reduce energy use by 33% (4.4×1017 J) and CO2 emissions by 32% (29 million tons). If austenitic stainless steel were to be produced solely from scrap, which is currently not possible on a global level due to limited availability, energy use would be 67% less than virgin-based production and CO2 emissions would be cut by 70%. The calculation of the total energy is most sensitive to the amount and type of scrap fed into the electric arc furnace, the unit energy of the electric arc furnace, the unit energy of ferrochromium production, and the form of primary nickel.