Quantifying variability in well-to-wheel greenhouse gas emission intensities of transportation fuels derived from Canadian oil sands mining operations

摘要

How oil sands bitumen is produced (through mining or in situ methods) and how the crude is processed (either upgraded to synthetic crude oil, SCO, or diluted to produce dilbit) result in a range of crude properties with distinct downstream emissions. Previous life cycle studies of the greenhouse gas (GHG) intensities of transportation fuels derived from oil sands bitumen have not accounted for this downstream variability. We quantify, on a project basis as well as across the industry, variability in well-to-wheel (WTW) GHG intensities of transportation fuels from mined oil sands bitumen using detailed upstream, crude transport, and refinery models. Across projects, the mining project producing dilbit has lower median WTW GHG intensity per MJ (low heating value basis) gasoline (median: 96; 80% confidence interval: 93-101 g CO(2)eq/MJ gasoline) versus SCO projects (median: 108-114; 80% confidence interval across all SCO projects: 106-123 g CO2eq/MJ gasoline) but is strongly influenced by assumptions regarding refinery configuration and allocation to refinery products. Intraproject variability exceeds interproject variability, with 80% confidence intervals for individual projects varying up to 16 g CO2eq/MJ, and is driven in approximately equal proportions by the upstream and refining stages, although their relative contributions vary across projects. Compared to the U.S. EPA baselines, the mining project producing dilbit has a WTW GHG intensities that range from 1% (lower) to 8% (higher) and 2% (lower) to 6% (higher) for gasoline and diesel, respectively (80% confidence intervals). Across mining projects producing SCO, WTW GHG intensities range from 10 to 32% higher and 2-25% higher than the U.S. EPA baselines for gasoline and diesel, respectively. We show how downstream modeling decisions (e.g., allocation of refinery emissions to products such as gasoline) influence WTW GHG intensity distributions, compare mining and in situ bitumen production methods' GHG intensities, and discuss implications for meeting intensity-based targets. (C) 2020 Elsevier Ltd. All rights reserved.