DOI: http://dx.doi.org/10.1065/ehs2003.03.008
Intention, Goal, Scope, Background. Life Cycle Assessment (LCA) involves some subjectivity and uncertainty, especially with new technologies and future scenarios. With the intention of analyzing the life cycle impacts of future fuel cell vehicles and fuels, the Fuel Cell Vehicle Modeling Program at the Institute of Transportation Studies developed a very robust and interesting model - the Fuel Upstream Energy and Emission Model (FUEEM). In order to demonstrate the process adopted, three different fuel cell vehicle technologies (direct hydrogen, indirect methanol, and indirect hydrocarbon) were analyzed for the South Coast Air Basin (SCAB) of California (Los Angeles) in the year 2010. The analysis covered topics such as the energy sources requirement, the emissions of CO2 and other greenhouse gases, and also the emissions of several criteria pollutants generated within SCAB and within other regions.
Objective. The objective of this paper is to present the main results obtained from this example as well as the benefits of explicitly recognize the uncertainties.
Methods. The FUEEM process, among other things, quantifies the uncertainties using variables as probabilistic curves and propagating them through the calculation by means of Monte Carlo simulation. On the other hand, it explicitly involves the interested parties in the entire analysis process, not only in the critical final review phase.
Results and Discussion. The results show that the hydrogen option has the potential to present the most efficient energy life cycle for the SCAB, followed by the methanol and finally by the Fischer-Tropsch naphtha option. On the other hand, the uncertainty analyses show that this conclusion is not always true and that in most cases there are possibilities of the results being different. A similar behavior is observed for the greenhouse gas emissions. The results showing the criteria pollutants emitted within SCAB highlight a great potential for each fuel cell vehicle technology to improve air quality in urban areas.
Conclusions. This project demonstrates that explicit recognition and quantitative analysis of the inherent uncertainty in the LCA process generates richer information, explains many of the discrepancies between results of previous studies, and enhances the robustness and credibility of LCA analyses.
Recommendation and Outlook. The FUEEM method should be viewed as an additional and interesting tool to help the improvement of LCA, and as a basis for constant improvement. |
