When 930 kg of traditional steel in the body structure, doors, hood, body structure, closures (doors, hood/bonnet, liftgate/boot), suspension, and subframe is replaced with 630 kg of Aluminium or 698 kg of Advanced High-Strength Steel, which one is better for the environment in terms of vehicle emissions reduction and fuel savings?
This case study examines the effect that various automotive materials can have on total life cycle Greenhouse Gas (GHG) emissions for a Sport Utility Vehicle (SUV) class. A Life Cycle Assessment (LCA) shows that Advanced High-Strength Steel (AHSS) materials used for lightweighting lowered total life cycle emissions, as well as decreased fuel consumption.
The case study uses the Automotive Materials Energy and GHG Comparison Model (UCSB Model), developed by Dr. Roland Geyer of the University of California Santa Barbara Bren School of Environmental Sciences. It investigated whether or not an AHSS-intensive design would result in fewer emissions than an aluminium-intensive design when looking at the entire vehicle life, from material production and manufacturing, to fuel production, vehicle use and vehicle end-of-life recycling and disposal. The UCSB Model also projects fuel consumption savings.
In this best case scenario (lowest total emissions) , which shows total life cycle GHG emissions, substituted aluminum to reduce fuel consumption, but compared to the conventional steel baseline, reduced the total life cycle emissions by less than 1,000 kg. The best scenario for the AHSS design, however, reduced emissions compared to the baseline by over 3,000 kg.
In fact, in all of the 5,000 iterations, the AHSS-intensive design results in lower GHG emissions than the Aluminium-intensive design, 100% of the time.
For a fleet of 200,000 vehicles, this means an AHSS-intensive SUV design saves approximately 600,000 metric tonnes of CO2e total life cycle emissions over the aluminium-intensive vehicle.
According to fuel consumption estimates, the aluminum SUV owner can expect to save 1/5 of one fuel fill up per year over the steel owner (based on 26-gallon fuel tank and 12-year vehicle lifetime).
Download the study Executive Summary and/or the full technical reports below to find out more. Without a life cycle assessment to guide the design process, decisions will be made that could result in unintended consequences: a complete shift of the emissions problem to the manufacturing of the vehicle, with no impact or even an increase in total lifetime emissions reduction. This case study shows why LCA is so critical to truly reduce transportation emissions impacts on the environment.
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