Average carbon intensity of oil sands production has dropped ~36% in last 40 years; still 12-24% higher than conventional oil CI
|Trends in well-to-wheel pathway-specific CI. In situ production began in 1974, so no value is computable for 1970. Click to enlarge.|
The carbon intensity (CI) of Alberta oil sands production has significantly decreased over the last 40 years, according to a new study by a team from Stanford University published as an open access paper in the journal Environmental Research Letters.
Relying entirely on public and peer-reviewed data sources for the period from 1970 to 2010 (inclusive), the team found that industry-average full-fuel cycle (well-to-wheels, WTW) CI declined about 36% from 165 gCO2e MJ-1 higher heating value (HHV) of reformulated gasoline (RFG) to 105 (-12, +9) gCO2e MJ-1 HHV RFG. 2010 averages by production pathways are 102 gCO2e MJ-1 for mining and 111 gCO2e MJ-1 for in situ production.
Despite these improvements, they noted, the CI of oil sands production (on a pathway-average basis) ranges from 12 to 24% higher than CI values from conventional oil production.
Further, due to growing output, total emissions from the oil sands continue to increase despite the reduced CI; total upstream emissions were roughly 65 MtCO2e, or 9% of Canada’s emissions, in 2010.
The dataset the team used contained energy consumption and production quantities reported monthly to the Alberta Energy Regulator (AER, formerly Energy Resources Conservation Board).
|System boundary for mining & upgrading pathway. Englander et al. Supplementary Information. Click to enlarge.|
The system boundary for their lifecycle analysis included direct consumption of all primary fuels and electricity at production sites; processing of gas for H2 generation; emissions associated with direct land-use change; flaring from upgraders; emissions from tailings ponds (for mining); upstream emissions from natural gas production; emissions from crude bitumen batteries from in situ production; and emissions from directly producing the fuels in both mining and in situ production. The system boundary did not include emissions from embodied capital such as well pads, trucks, upgraders, etc.
They examined the oil sands industry as a whole, with aggregated results reported by extraction method (either mining or in situ) on a production-weighted-average basis. The mining method includes pathways in which mined bitumen is sent directly to refineries (as a synbit or dilbit); in situ includes pathways where in situ produced bitumen is sent to upgraders.
In assessing their results, they observed that the most substantial efficiency gains in oil sands production over the last 40 years have occurred in separation and upgrading. Process optimization and heat-recovery improvements within the upgrading process are other possible sources for increased efficiencies, although detailed accounts of such changes are not publicly available. Additional significant efficiency increases were achieved in refining.
… since the largest efficiency improvement in the oil sands operations has occurred in the processing and upgrading processes, the shift toward increased capabilities of refineries to handle oil sands bitumen, as well as the increasing share of in situ production, suggest that upgrading will be less relevant to future emissions profiles.
For in situ pathways, industry-wide steam to oil ratios (SOR)—which are a key driver for efficiency in in situ production—have been generally stable over the last 20 years. Potential technologies on the horizon to reduce SORs include solvent co-injection with steam. Steam generation technology is relatively mature, with less room for improvement then technology such as upgrading. … Reducing stack losses (such as through adoption of air preheat or condensing economizers), or reducing the pressure of steam required for SAGD (through use of downhole pumps enabling low-pressure-SAGD) have both been proposed as means to improve SAGD efficiency. Energy efficiency improvements of perhaps 20% have been suggested. The incentive for adoption of these technologies is uncertain when natural gas prices are low.
On the whole, these trends suggest that near-term oil sands CI is not likely to be significantly lower than today’s production on an industry-wide basis. In the longer term, technologies on the horizon could potentially allow for significant reductions in emissions from oil sands operations. Carbon capture and storage at large upgrading and refining facilities (e.g., the Shell Quest project) could result in significant reductions in oil sands CI. Advanced in situ technologies also may hold promise for longer term reductions (e.g., thermal recovery with low carbon electric resistive heating).—Englander et al.
Jacob G Englander, Sharad Bharadwaj and Adam R Brandt (2013) “Historical trends in greenhouse gas emissions of the Alberta oil sands (1970–2010),” Environ. Res. Lett. 8 044036 doi: 10.1088/1748-9326/8/4/044036