INSTITUTE OF TRANSPORTATION STUDIES- UC DAVIS
Background: Fuel combustion during vehicle operation has been, and continues to be, the overwhelmingly dominant source of greenhouse gas (GHG) emissions during passenger vehicle life cycles. Life cycle assessments (LCAs) of standard passenger vehicles have estimated use-phase or operation emissions at approximately 85-95% of total life cycle GHG emissions. Thus, previous standards addressing GHG emissions at the tailpipe (or fossil fuel consumption based on fuel economy) have functioned to effectively reduce vehicle life cycle emissions.
The current paradigm shift in vehicle architecture and energy carriers will, however, lead to an increasing proportion of vehicle emissions attributable to non-operation life cycle stages. This shift will occur both because of increased production-stage emissions due to the use of more advanced materials and technologies that have higher production-related emissions than their conventional counterparts, and because of greater efficiencies during the vehicle use phase.
In addition to shifts in vehicle GHG emissions toward the production stage, recent research on life cycle assessment (LCA) and carbon accounting methods show that early emissions in a product’s life cycle have greater global warming effects than later ones over analytical time horizons consistent with common GHG accounting practices (e.g. 100 years). The global warming effect caused by a GHG is the result of a cumulative process, so all else equal the sooner a long-lived GHG enters the atmosphere, the greater its global warming effect at some point in the future. Thus, not only are the production and disposal stages increasingly important when developing effective models for calculating vehicle life cycle emissions, but the timing of these emissions will further increase the importance of production-related emissions, and by the same logic, reduce the benefits of recycling that occurs at the vehicle end-of-life (EOL).
This report describes the implementation and results of a simplified GHG LCA for a hypothetical future vehicle, the high-development (HD) 2020 Toyota Venza, as described in Lotus Engineering Inc.’s 2010 report. In addition, a lower-development version of this vehicle that uses the body structure from a low-development (LD) vehicle (as described in the Lotus Engineering report) is modeled with a GHG LCA.
The LCAs are based on the reported bill of materials (BOM) for the HD and LD vehicles. This simplified LCA approach, where vehicle production is modeled by matching a BOM with life cycle inventory (LCI) data, allows us to test a potential streamlined approach to implementing GHG LCAs.
The complexity and burden of implementing regulations that address life cycle emissions is one of a number of potential barriers to incorporating life cycle emissions in vehicle standards. Generating life cycle GHG emissions estimates may introduce a considerable burden on OEMs and regulatory agencies, and may generate unintended consequences. This report aims to determine whether LCA approaches, and various enhancements to common LCA approaches, such as including emissions timing in global warming calculations should be made despite these complexities.
The Institute of Transportation Studies at UC Davis (ITS-Davis)
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