Parametric approach to life cycle assessment
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Life cycle assessment is a method to evaluate economic and environmental benefits and tradeoffs of technologies, human activities, and systems. Data gaps, variability, uncertainty, and weak generalizability are among the continuing challenges in life cycle assessment. As a way of resolving these issues, a parametric life cycle assessment framework is proposed and demonstrated, using case studies of vehicle electrification and decentralized power generation for buildings. The parametric life cycle assessment involves investigating governing equations; identifying overall relationships between input and output variables; evaluating characteristics and typology of input and output variables; assessing relative importance and contribution of individual input parameters; and developing a parametric form of life cycle assessment models. For medium- and heavy-duty vehicles electrification, the results from the parametric life cycle assessment indicate that electric vehicles provide positive social benefits for niche applications or locations, regardless of the variations and uncertainties in input conditions including future electric grid evolution and fuel prices changes. Beyond the niche applications or locations, however, electrifying medium- and heavy-duty vehicles is not expected to provide positive net social benefits in the near future, in comparison with conventional technologies powered by petroleum, biofuels, or natural gas. Vehicle operation strategy modifications or a moderate level of electrification such as micro-hybrid technology can provide more immediate benefits. Using the same parametric LCA approach, life cycle tradeoffs of decentralized power generation technologies for buildings are systematically evaluated, including natural gas-based hydrogen fuel cell and microturbine technologies. Combined cooling, heating, and power provides numerous benefits including more efficient and stable electricity provision compared to conventional building energy systems. From the life cycle perspective, cogeneration or trigeneration technologies, in particular, microturbines help reduce air emissions and water consumption but at the expense of energy efficiency. Although fuel cell and microturbine technologies tend to move air emissions sources from less-populated locations to population centers, overall air pollution impacts across the U.S. are lower than for conventional systems. Depending on the building types, overall social benefits of these alternative and distributed power production technologies can vary. In general, achieving electric grid independence and improving resilience against power outage requires up to 50% higher valuation of reliable power production.