A Life Cycle Assessment (LCA) of the potential for biofuels to reduce greenhouse gas emissions and fossil fuel consumption: Comparative assessment of two regions in Ontario, Canada.

摘要

The production of ethanol from cereal grains for use in transport fuels has received considerable attention as a measure to reduce greenhouse gas (GHG) emissions and to reduce fossil fuel consumption, but a thorough and systematic assessment of this potential remains elusive. Life Cycle Assessment (LCA) provides a framework to account for all stages of fuel production and to estimate net reductions, but biofuel LCA work to date has largely ignored regional variations in ethanol production processes. In this investigation, LCAs were completed for the ethanol-gasoline blend fuel E5 and for pure gasoline in two regions of the Province of Ontario (Canada), southern and eastern Ontario. These regional assessments were also compared to a third more generalized province-wide assessment.;Producing grain corn for ethanol in the southern Ontario regional case was estimated to require 80% less fossil fuel and emit 65% fewer GHG than the eastern Ontario case, but blending with gasoline derived from oil-sand crude oil brought into the region, causes E5 from the southern region to have approximately 10% higher estimated overall fossil fuel use and emit 5% more GHG emissions than E5 from the less agriculturally productive eastern region. The main findings from the second type of comparison (regional vs. provincial) were that provincial LCA assessments are adequate for a preliminary estimate of fossil fuel and GHG reductions; but that the more refined regional LCA assessments better delineate processes to help optimize biofuel GHG and fossil reduction potential. Furthermore, the results from the regional assessments introduce the possibility that, within Ontario, some E5 fuels require more fossil fuel and emit more GHG than some gasoline fuels.;Overall this research has extended the understanding of the potential for biofuels generally and for E5 fuels specifically to address societal concerns regarding climate change mitigation and energy alternatives. This thesis suggests that E5 fuels will have at best a modest role in mitigating climate change and substituting for fossil fuel resources. Regional factors (e.g. corn yield) and factors external to the region (e.g. source of crude oil) alter the potential for biofuel to reduce fossil fuel use and GHG emissions, particularly as the proportion of ethanol in the biofuel blend increases. Finally, despite challenges to the application of LCA to biofuels, LCA provides a powerful framework to capture not only the long production chain of the biofuel commodity but also regional dimensions within that production chain.