WorldAutoSteel case studies stress need for life cycle mindset in vehicle emissions regulations

Detroit-based WorldAutoSteel, the automotive group of the World Steel Association, has released findings of two new case studies that examine the effect various automotive materials can have on total life cycle greenhouse gas (GHG) emissions for light-duty truck and SUV classes. By conducting a life cycle assessment (LCA) of each vehicle class, the studies showed that advanced high-strength steels (AHSS) lowered total life cycle emissions and decreased fuel consumption.

The case studies used 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. They investigated whether an AHSS-intensive design would result in fewer emissions than an aluminum-intensive design, compared to a conventional steel baseline, when looking at the entire vehicle life.

“Numerous iterations of the model were conducted to simulate the many possible conditions a vehicle might see,” said Russell Balzer, technical director, WorldAutoSteel. “In each vehicle’s best performance (lowest emissions) case, the steel design showed decreased total life cycle emissions over the aluminum vehicle by 3 percent for the light-duty truck and 5 percent for the SUV.”

The UCSB model also projects fuel savings by considering driving cycles, engines, fuel types, and the effects of lightweighting. Results showed that fuel consumption was not substantially decreased when substituting aluminum for steel. The AHSS and aluminum designs reduced structural weight (includes body structure, doors, and hood, as well as truck bed for trucks and liftgate, suspension, and subframe for SUVs) by 25 percent and 35 percent, respectively.

For both the truck and SUV cases, the AHSS designs were within 70 kg of the aluminum weight savings. Fuel cost savings were about $25 to $35 per year with aluminum. However, efforts to lower weight with aluminum to reduce fuel consumption resulted in an increased environmental footprint at a potential cost of three times that of steel.

“On a life cycle basis, the AHSS-intensive vehicles produce fewer emissions than the aluminum-intensive one,” said Balzer. “Steel performs better in these vehicle cases because the primary production of steel, including AHSS, produces seven to 20 times fewer emissions than other materials such as aluminum, magnesium, and carbon fiber-reinforced plastics.”

The UCSB model is designed to quantify the energy and GHG impacts of automotive material substitution on a total vehicle life cycle basis, under a variety of conditions in a completely transparent fashion. The model methodology has been peer-reviewed by members of the LCA community and the aluminum industry.

Visit www.worldautosteel.org/life-cycle-thinking/case-studies/light-duty-truck-case-study/ to review the complete findings of the light-duty truck case study and www.worldautosteel.org/life-cycle-thinking/case-studies/sport-utility-vehicle-a-case-for-life-cycle-assessment/ for the complete findings of the SUV case study.