	Introduction

Recent congressional interest in U.S. energy policy has focused in part on ways through which the United States could secure more economical and reliable petroleum resources both domestically and internationally. Many forecasters identify petroleum products refined from Canadian oil sands as one possible solution. Increased production from Canadian oil sands, however, is not without controversy, as many have expressed concern over the potential environmental impacts. A number of key studies in recent literature have expressed findings that GHG emissions per unit of energy produced from Canadian oil sands crudes are higher than those of other crudes imported, refined, and consumed in the United States. Hence, the 2014 Final EIS made similar findings to the 2011 Final EIS, including the following:
1. Canadian oil sands crudes "are more GHG-intensive than the other heavy crudes they would replace or displace in U.S. refineries, and emit an estimated 17% more GHGs on a life-cycle basis than the average barrel of crude oil refined in the United States in 2005," and 2. The second section of the report, " Results of Selected Life-Cycle Emissions Assessments ," compares several of the publicly available assessments of life-cycle GHG emissions data for Canadian oil sands crudes against each other, against those of other global reference crudes, and against those of other fossil fuel resources. For a specific analysis of the GHG emissions attributable to the proposed Keystone XL pipeline, see CRS Report R43415, Keystone XL: Greenhouse Gas Emissions Assessments in the Final Environmental Impact Statement , by [author name scrubbed] . As reported in NETL 2008, discounting the final consumption phase of the life-cycle assessment (which can contribute up to 70%-80% of Well-to-Wheels emissions), Canadian oil sands emit an estimated 80% more GHGs on a Well-to-Tank (i.e., "production") basis than the weighted average of transportation fuels sold or distributed in the United States (in reference year 2005). Design Factors and Input Assumptions for Life-Cycle Assessments of Canadian Oil Sands Crudes

Most published and publicly available studies on the life-cycle GHG emissions data for Canadian oil sands crudes identify two main factors contributing to the difference in emissions intensity relative to other reference crudes:
1. oil sands are heavier and more viscous than lighter crude oil types on average, and thus require more energy- and resource-intensive activities to extract; and 2. oil sands are chemically deficient in hydrogen, and have a higher carbon, sulfur, and heavy metal content than lighter crude oil types on average, and thus require more processing to yield consumable fuels by U.S. standards. Extraction Process. Compared to selected energy- and resource-intensive crudes, Well-to-Wheels GHG emissions from gasoline produced from a weighted average of Canadian oil sands crudes are found to be "within range" of those produced from heavier crudes such as Venezuelan Bachaquero and Californian Kern River, as well as lighter crudes that are produced from operations that flare associated gas (e.g., Nigerian Bonny Light). Individual estimates of WTW GHG emissions from Canadian oil sands crudes from the primary studies listed in Table 1 range from 9% to 19% more GHG-intensive than Middle Eastern Sour, 5% to 13% more GHG-intensive than Mexican Maya, and 2% to 18% more GHG-intensive than various Venezuelan crudes (including both Venezuelan Conventional and Bachaquero). Some studies suggest that GHG emissions intensities of Canadian oil sands crudes should be measured against a global average in order to assess the full environmental impacts of the resource.
Canadian Oil Sands and Climate Change
Recent congressional interest in U.S. energy policy has focused in part on ways through which the United States could secure more economical and reliable petroleum resources both domestically and internationally. Many forecasters identify petroleum products refined from Canadian oil sands as one possible solution. Increased production from Canadian oil sands, however, is not without controversy, as many have expressed concern over the potential environmental impacts. These impacts include emissions of greenhouse gases (GHG) during resource extraction and processing. A number of key studies in recent literature have expressed findings that GHG emissions per unit of energy produced from Canadian oil sands crudes are higher than those of other crudes imported, refined, and consumed in the United States. The studies identify two main reasons for the difference: (1) oil sands are heavier and more viscous than lighter crude oil types on average, and thus require more energy- and resource-intensive activities to extract; and (2) oil sands are chemically deficient in hydrogen, and have a higher carbon, sulfur, and heavy metal content than lighter crude oil types on average, and thus require more processing to yield consumable fuels by U.S. standards.
Selected Findings from the Primary Published Studies
CRS surveyed the published literature, including the U.S. State Department-commissioned studies for the Keystone XL pipeline project in both the 2011 Final Environmental Impact Statement and the 2014 Final Supplementary Environmental Impact Statement. The primary literature reveals the following:
Canadian oil sands crudes are generally more GHG emission-intensive than other crudes they may displace in U.S. refineries, and emit an estimated 17% more GHGs on a life-cycle basis than the average barrel of crude oil refined in the United States; compared to selected imports, Well-to-Wheels GHG emissions for Canadian oil sands crudes range from 9% to 19% more emission-intensive than Middle Eastern Sour, 5% to 13% more emission-intensive than Mexican Maya, and 2% to 18% more emission-intensive than various Venezuelan crudes; compared to selected energy- and resource-intensive crudes, Well-to-Wheels GHG emissions for Canadian oil sands crudes are within range of heavier crudes such as Venezuelan Bachaquero and Californian Kern River, as well as lighter crudes that are produced from operations that flare associated gas (e.g., Nigerian Bonny Light); discounting the final consumption phase of the life-cycle assessment (which can contribute up to 70%-80% of Well-to-Wheels emissions), Well-to-Tank (i.e., "production") GHG emissions for Canadian oil sands crudes are 9%-102% higher than for selected imports; the estimated effect of the Keystone XL pipeline on global GHG emissions remains uncertain, as some speculate that its construction would encourage an expansion of oil sands investment and development, while others suggest that the project would not substantially influence either the rate or magnitude of oil extraction activities in Canada or the overall volume of crude oil transported to and refined in the United States.
Scope and Purpose of This Report
Congressional interest in the GHG emissions attributable to Canadian oil sands crudes has encompassed both a broad understanding of the resource as well as a specific assessment of the proposed Keystone XL pipeline. This report focuses on the broader resource. It discusses the methodology of life-cycle assessment and compares several of the publicly available studies of GHG emissions data for Canadian oil sands crudes against each other and against those of other global reference crudes. For a detailed analysis of the GHG emissions attributable to the proposed Keystone XL pipeline, and the findings from the State Department's Final Environmental Impact Statement, see CRS Report R43415, Keystone XL: Greenhouse Gas Emissions Assessments in the Final Environmental Impact Statement.