In a nutshell, the energy needed to produce a vehicle's raw materials accounts for about 10 percent of a typical vehicle's carbon footprint during its total lifecycle, and that number is up from six percent because of advancements in fuel economy (fuel use is down to about 68 percent of total emissions from about 75 percent). Still, even with that higher material-extraction share, the fuel-efficiency gains from aluminum compared to steel will offset the additional vehicle-extraction energy in just 12,000 miles of driving, according to the study. That means that, from an environmental standpoint, aluminum vehicles are playing with the house's money after just one year on the road.
Aluminum-sheet construction got topical real quickly earlier this year when Ford said the 2015 F-150 pickup truck would go to a 93-percent aluminum body construction. In addition to aluminum being less corrosive than steel, that change caused the F-150 to shed 700 pounds from its curb weight. And it looks like the Explorer and Expedition SUVs may go on an aluminum diet next. Take a look at SAE International's synopsis of the Oak Ridge Lab's study below.
Advanced lightweight materials are increasingly being incorporated into new vehicle designs by automakers to enhance performance and assist in complying with increasing requirements of corporate average fuel economy standards. To assess the primary energy and carbon dioxide equivalent (CO2e) implications of vehicle designs utilizing these materials, this study examines the potential life cycle impacts of two lightweight material alternative vehicle designs, i.e., steel and aluminum of a typical passenger vehicle operated today in North America.
LCA for three common alternative lightweight vehicle designs are evaluated: current production ("Baseline"), an advanced high strength steel and aluminum design ("LWSV"), and an aluminum-intensive design (AIV). This study focuses on body-in-white and closures since these are the largest automotive systems by weight accounting for approximately 40% of total curb weight of a typical passenger vehicle. Secondary mass savings resulting from body lightweighting are considered for the vehicles' engine, driveline and suspension.
A "cradle-to-cradle" life cycle assessment (LCA) was conducted for these three vehicle material alternatives. LCA methodology for this study included material production, mill semi-fabrication, vehicle use phase operation, and end-of-life recycling. This study followed international standards ISO 14040:2006  and ISO 14044:2006 , consistent with the automotive LCA guidance document currently being developed .
Vehicle use phase mass reduction was found to account for over 90% of total vehicle life cycle energy and CO2e emissions. The AIV design achieved mass reduction of 25% (versus baseline) resulting in reductions in total life cycle primary energy consumption by 20% and CO2e emissions by 17%. Overall, the AIV design showed the best breakeven vehicle mileage from both primary energy consumption and climate change perspectives.