A study, “A New Paradigm in Automotive Mass Benchmarking,” provided insights into the lightweighting of production model vehicles. Since then, we conducted a follow up Life Cycle Assessment (LCA) case study, the focus of this article. LCA is a methodology that considers a vehicle’s entire life cycle, from the manufacturing stage (including material production and vehicle assembly) through the use stage (including production and combustion of fuel) to the end of life (EOL) stage (including end of life disposal and recycling).
What were the findings of the initial study?
Using statistical benchmarking methodology developed by Dr. Don Malen,, research scientist University of Michigan, we identified the most efficient (the lightest for the same size and performance) designs from a database of over 200 production vehicles. In our initial study, we compared efficient steel and efficient aluminium components for doors, hoods, hatchbacks, decklids and bumpers. Interestingly, we uncovered some startling findings:
- There is a wide variation in efficiency among steel components in vehicles on the road today.
- When aluminium closure components, such as doors, bumpers, hatchbacks, and decklids, are compared to efficient steel components of similar size and performance, the 40 percent mass savings currently accepted as a standard measure of aluminium lightweighting capability is not nearly reached.
- While use of aluminium may achieve mass savings at the component level, that mass savings is lost when an entire system is measured.
What were the findings of our follow-up case study that considered a vehicle total life cycle?
Using data and mass estimation models from the initial study, we next investigated the life cycle GHG impact of three principal categories of material usage in the Body Structure subsystems for A/B vehicle class cars that were represented in the vehicle benchmarking data (provided by A2Mac1, a global benchmarking company.) The following are the three categories of material usage we examined:
- An average steel design;
- An efficient steel design based on 17 of the most efficient body structures in the database;
- An efficient aluminium design, which was derived from the most efficient aluminium structures.
The results of the LCA case study show that the aluminium body structure, though lighter, will result in a +1% increase in GHG emissions over its total life cycle. The steel body structure would result in a -1% decrease in GHG emissions.
Why? If a weight savings is achieved, shouldn’t the car be more environmentally efficient?
This question highlights the reason LCA is so important to improving vehicle environmental performance. Because the primary production of steel emits seven times less GHG emissions than aluminium, vehicles made of steel, using efficient, optimized designs, may be lower in emissions when considering the vehicle total life cycle.
Following are our results in an infographic summary (click the image to enlarge). Download the Case Study to review all parameters that we used in the model and the detailed results. The estimation of life cycle GHG emissions was conducted using the UCSB Automotive Materials Energy Model. The UCSB Model was designed to quantify the energy and GHG impacts of automotive material substitution on a total vehicle life cycle basis, under a broad range of conditions and in a completely transparent fashion. The Model has been peer-reviewed and uses current data for material emissions and other parameters.
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