Aluminum Stock and Flows in U.S. Passenger Vehicles and Implications for Energy Use
In this article, a methodology to model the annual stock and flows of aluminum in a key end‐use sector in the United States—passenger vehicles—from 1975-2035 is described. This dynamic material flow model has enabled analysis of the corresponding energy embodied in automotive aluminum as well as the cumulative aluminum production energy demand. The former was found to be significant at 2.6 × 109 gigajoules (GJ) in year 2008 under baseline assumptions. From 2008-2035, the cumulative energy required to produce aluminum to be used in vehicles is estimated at 7.8 × 109 GJ. Although the automotive aluminum stock is expected to increase by 1.8 times by 2035, the corresponding energy embodied is not expected to grow as rapidly due to efficiency improvements in aluminum processing over time. The model's robustness was tested by checking the sensitivity of the results to variations in key input assumptions, including future vehicle sales, lifetimes, and scrap recovery. Sensitivity of energy embodied in automotive aluminum to changes in aluminum production efficiency and aluminum applications within the vehicle were also explored. Using more recycled aluminum or improving the energy efficiency of aluminum production at a faster rate can lower production energy demands. However, aggressive and sustained changes are needed beginning today to achieve meaningful reductions. This may potentially be countered by increased use of stamped aluminum in vehicles.