Historically, fuel economy regulations have been an effective mechanism for improving vehicle fuel economy and reducing greenhouse gas (GHG) emissions associated with fuel combustion. As these regulations become more stringent, automakers are looking to additional solutions, such as reducing the mass of vehicles to decrease fuel consumption, commonly referred to as “lightweighting.” The materials used as part of this strategy may include advanced high-strength steels (AHSS), aluminum, and in some cases carbon fiber composites or magnesium. Each of these materials can contribute to vehicle lightweighting to improve fuel economy; however, each does so at different manufacturing cost levels and environmental impacts.
While the focus of federal regulations typically has been on the vehicle use phase (tailpipe emissions), the true GHG profile of a vehicle is only evident by considering the entire life cycle. A vehicle’s life cycle has three parts (or phases): production, use (driving) and end-of-life (recycling and/or disposal).
TOTAL VEHICLE LIFE CYCLE =
(PRODUCTION PHASE) + (USE PHASE) + (END-OF-LIFE PHASE)
The Importance of the Production Phase in Vehicle Life Cycle GHG Emissions
As automakers move to lightweighting as a significant component of their strategy to meet increasingly stringent CAFE regulations, it becomes critically important to look beyond the tailpipe, and instead consider the full life cycle emissions of vehicles. This paper has shown the use of aluminum-intensive vehicles for lightweighting can result in higher life cycle GHG emissions of 0.6 percent to nearly 7 percent, and higher production-phase GHG emissions of 19 percent to over 40 percent. When scaled to an entire annual fleet of sedans, SUVs or pickup trucks, the conversion to an aluminum-intensive option versus AHSS results in a net increase in GHG emissions of about 1.5 billion kg for each vehicle class.
The concept is not unlike what has happened in the construction industry over the last several years. Initially, the focus of green building standards and rating programs was on operational energy improvement, as it was the dominant phase in the life cycle of buildings. However, as a building’s use phase has become increasingly more efficient, the focus is now shifting to building materials and the construction process through the incorporation of new assessment methods, including whole building life cycle assessment and environmental footprinting of building products. Similarly in automotive design, regulators and engineers have been doing an excellent job improving use-phase fuel economy, but now need to consider the emissions from production of the materials that comprise every vehicle, in order to lessen the automotive sector’s overall impact on our environment with certainty. Since automakers will likely use some high production-phase emissions materials as part of their strategy to meet CAFE regulations, these emissions must be accounted for in any regulation, to avoid the unintended consequence of actually increasing overall GHG emissions.