Historical trends in greenhouse gas emissions of the Alberta oil sands (1970–2010)

Abstract

There has been increased scrutiny of the Alberta oil sands due to their high carbon intensity (CI) relative to conventional crude oil. Relying entirely on public and peer-reviewed data sources, we examine historical trends in the CI of oil sands extraction, upgrading, and refining. Monthly data were collected and interpolated from 1970 to 2010 (inclusive) for each oil sands project. Results show a reduction in oil sands CI over time, with industry-average full-fuel cycle (well-to-wheels, WTW) CI declining from 165 gCO 2 e MJ −1 higher heating value (HHV) of reformulated gasoline (RFG) to 105 (−12, +9) gCO 2 e MJ −1 HHV RFG. 2010 averages by production pathways are 102 gCO 2 e MJ −1 for Mining and 111 gCO 2 e MJ −1 for in situ. The CI of mining-based projects has declined due to upgrader efficiency improvements and a shift away from coke to natural gas as a process fuel. In situ projects have benefitted from substantial reductions in fugitive emissions from bitumen batteries. Both mining and in situ projects have benefitted from improved refining efficiencies. However, despite these improvements, the CI of oil sands production (on a pathway-average basis) ranges from 12 to 24% higher than CI values from conventional oil production. Due to growing output, total emissions from the oil sands continue to increase despite improved efficiency: total upstream emissions were roughly 65 MtCO 2 e in 2010, or 9% of Canada's emissions.

Energy consumption and greenhouse gas emissions in the recovery and extraction of crude bitumen from Canada’s oil sands

“…Fig. 4 shows a comparison of electricity estimated by this research to electricity consumption reported by major SAGD operators against the SOR of the projects [49,50]. As can be observed, the electricity intensity estimated by this research is representative of electricity intensity reported by majority of SAGD operators.…”

“…The natural gas consumed in the process also depends on the amount of coproduced gas. Produced gas in SAGD ranges from 1 to 89 m 3 /m 3 of bitumen [44,49,50]. Most of the produced gas is conserved and utilized so as to reduce the natural gas demand of the plant while a portion of it is flared.…”

“…Most of the produced gas is conserved and utilized so as to reduce the natural gas demand of the plant while a portion of it is flared. Based on production weighted average of produced gas consumption and flaring data [49,50], a default value 13.1 m 3 /m 3 is utilized for consumption of produced gas and 7.4 m 3 /m 3 for flaring of produced gas in SAGD plants. The GHG emissions from crude bitumen batteries (emissions from bitumen storage systems) are taken into account and an average of five years (2007-11) has been obtained from [50].…”

“…Based on production weighted average of produced gas consumption and flaring data [49,50], a default value 13.1 m 3 /m 3 is utilized for consumption of produced gas and 7.4 m 3 /m 3 for flaring of produced gas in SAGD plants. The GHG emissions from crude bitumen batteries (emissions from bitumen storage systems) are taken into account and an average of five years (2007-11) has been obtained from [50]. The energy content of co-produced gas varies widely depending on the composition of the produced gas and can be one-third to equal of the energy content of natural gas [44,51,52].…”

“…GHG emissions from crude bitumen batteries form a significant portion and amount to approx. 2.1 gCO 2 eq/MJ of bitumen [50].…”