Life Cycle Greenhouse Gas Emissions Study Reveals No Conclusive Evidence that Aluminium-Intensive Vehicles Reduce Greenhouse Gas Emissions
The study compares aluminium-intensive vehicles to ULSAB-AVC AHSS optimized vehicles
Buenos Aires, 03 Oct. 2006 — A study presented today at the World Steel Association Annual Conference in Buenos Aires gives evidence to dismiss the claim that aluminium-intensive vehicles produce less greenhouse gases (GHG) than steel vehicles, based on attributional life cycle assessment (LCA). Dr. Roland Geyer of the Donald Bren School of Environmental Science and Management, University of California at Santa Barbara, disclosed the results of a year-long university study.
The report emphasizes the importance to include all phases of the vehicle life cycle in order to adequately assess vehicle GHG impact: a) materials production and vehicle manufacturing, b) use phase, and c) end-of-life disposal/recycling. And it recommends conducting consequential LCA to assess vehicle GHG accurately.
“Based on attributional LCA, there is no conclusive evidence that aluminium-intensive vehicle designs offer any GHG emission savings relative to optimized AHSS-intensive vehicles designs currently in production,” said Dr. Geyer.
Study Scope and Findings
The study encompassed a review of nine different studies comparing aluminium with conventional steel vehicle designs, including a report by the International Aluminium Institute (IAI), completed in 2000, that claims 25.3 kg CO2eq (carbon dioxide equivalent) emissions are saved during the vehicle use phase for every kg of aluminium that replaces steel in components.
The Life Cycle Greenhouse Gas Emissions study created a model that replicated the findings of the previous reports. Using data for the UltraLight Steel Auto Body Advanced Vehicle Concepts (ULSAB-AVC), which are optimized Advanced High Strength Steel (AHSS)-intensive designs, the study reveals that only between 1.9 and 8.5 kg CO2eq are saved during vehicle use phase for every kg of aluminium that replaces steel. The ULSAB-AVC vehicle was used since it more closely matches vehicles on the road today than the older designs cited in the previous studies.
Further, when the entire vehicle life cycle is considered, including the GHG impacts of material production, manufacturing yields, as well as prompt and end-of-life scrap recycling , many data and modeling assumptions show that AHSS-intensive vehicles produce less GHG than aluminium-intensive vehicles.
“Material selection decisions usually involve trade-offs,” notes Dr. Henrik Adam, chairman of World Steel Association’s Automotive Group, WorldAutoSteel. “Use of lower density materials instead of steel may provide some mass savings, but, there also are environmental and economic costs. As auto companies continue to change from former designs with little high-strength and advanced high-strength steels to ULSAB-AVC-type designs, there are no significant trade-offs.” Automakers may find that the cost premium for using aluminium may not be worth the small or negligible gain.
Allocation Method Dramatically Impacts Results
However, lowest level GHG emissions shift between aluminium- and steel-intensive vehicles, depending on which model input data and allocation methods are used.
One reason for this disparity of results has to do with the choice of allocation method for material recycling, to which the results are extremely sensitive. This essentially means that the accounting assumptions for vehicle scrap recycling are critical for the life cycle GHG attributable to light weight vehicle designs.
“All of the existing studies that compare life cycle GHG emissions (or energy consumption) of steel- and aluminium-intensive vehicles use attributional LCA methodology,” said Dr. Geyer. “This is not the most appropriate methodology to assess the GHG emission impacts of the diffusion of light weight materials in vehicle production.” Dr. Geyer’s report recommends evaluating vehicle GHG using a consequential life cycle assessment, which could prove valuable for the industry and the LCA community in advancing vehicle LCA methodologies.
“There have been long debates in the LCA community on the right allocation procedure for material recycling. There is no one right allocation, therefore, a variety of methods must be used to accurately assess results,” Dr. Geyer said. Consequently, his study uses a variety of allocation methods for open loop recycling, in accordance with the ISO 14041 standard for life cycle assessment.
Powertrain and Fuel Alternatives
Increase Benefits of Steel Use
Other efforts to reduce GHG emission from the vehicle use phase, like use of alternative powertrains and less GHG-intensive fuels, strengthen the position of AHSS-intensive designs relative to aluminium-intensive designs. This is largely due to the significantly lower emissions during material production. Steel production at integrated mills emits between 2.3 to 2.7 kg CO2eq (carbon dioxide equivalent) per kg of material, while primary aluminium production emits between 13.9 and 15.5 kg CO2eq per kg of material, depending on the production methods and energy sources used. As well, the production of steel does not generate the potent perfluorocarbons (PFC) as does the production of primary aluminium or sulphur hexafluoride (SF6), emitted during magnesium production.
As use phase vehicle emissions are reduced (i.e., through hybrid electric powertrains or biofuels), GHG generated during materials production dominate a larger percentage of the total vehicle life cycle emissions. Choice of materials will become far more impactful.
“It is critical to choose materials that not only reduce weight in vehicle structures for use phase savings, but also have low GHG emissions during their production,” said Edward Opbroek, WorldAutoSteel Director. The ‘well-to-wheels’ approach used for automotive fuels needs to be complemented by a ‘mine-to-wheels’ approach for automotive materials in addition to consideration of end-of-life recycling issues. This will ensure that savings gained during the use phase are not compromised through the use of GHG-intensive materials.
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World Steel Association Automotive Group, WorldAutoSteel, a global steel industry organisation, continually explores steel innovation that demonstrates and communicates the value of steel in automobiles to industry and society. Its member companies from around the world pool global resources within and beyond the steel industry to deliver vital research that is central to effective steel automobile applications. WorldAutoSteel continues to lead the materials revolution through projects like the UltraLight Steel Family of Research: ULSAB, ULSAC, ULSAS, and ULSAB-AVC (Advanced Vehicle Concepts) that help the world’s automotive industry improve the safety, affordability and environmental impact of its products. To learn more about these and other WorldAutoSteel projects, visit www.worldautosteel.org.
ULSAB-AVC and its sister research projects, the UltraLight Steel Auto Body (ULSAB), UltraLight Steel Auto Closures (ULSAC), UltraLight Steel Auto Suspensions (ULSAS), were completed over the course of the last nine years. The international, consortia that spearheaded the projects were comprised of steel companies, representing 22 countries and 35 steel producers. Comprehensive reports on the ULSAB family of research can be found at World Steel Association’s automotive applications website, www.worldautosteel.org. ULSAB-AVC and the ULSAB family of research projects revolutionized the kinds of steels normally applied to vehicle architectures, as well as demonstrated cutting edge steel vehicle design. ULSAB-AVC concept demonstrations have been credited with bringing the potential for safe, affordable, fuel efficient vehicles that are environmentally responsible to near-term reality. This family of research represents over €50 million in private investment by the world’s sheet steel producers.
