After discussing the basic methodology of life-cycle assessments and examining the choice of boundaries, design features, and input assumptions, this book compares several of the publicly available assessments of life-cycle emissions data for Canadian oil sands crudes against each other and against those of other global reference crudes. As congressional concern over the environmental impacts of Canadian oil sands production may encompass both a broad understanding of the global resource as well as a specific assessment of the proposed Keystone XL pipeline, the book surveys both the general scientific literature as well as the individual findings of the State Department's Keystone XL Project Environmental Impact Statement. As life-cycle assessments have become an influential, albeit developing, methodology for collecting, analysing, and comparing GHG emissions, this book concludes with a discussion of some tools for policy-makers who are interested in using these assessments to investigate the potential impacts of U.S. energy policy choices on the environment.