Researchers Suggest That Although CCS and Other Technologies Could Reduce Oil Sands GHG Emissions to Near Zero, That Strategy May Not Make Sense
| Examples of emerging oil sands related technologies and trade-offs. Credit: ACS, Bergerson and Keith. Click to enlarge. |
Although it is technically possible to make deep reductions
in oil sands well-to-tank greenhouse gas emissions through the use of technologies such as carbon capture and storage (CCS) and the co-firing of biomass with fossil fuels for process heat or hydrogen, it is unclear if such a strategy
makes sense, Joule Bergerson and David Keith at the University of Calgary suggest in a paper published online 12 August in the ACS journal Environmental Science & Technology.
The paper is an examination of how various choices about the
scale of the life cycle analysis applied to oil sands (i.e., system boundaries) determine the emissions estimates, the technologies available to reduce
emissions, and perspectives and strategies of stakeholders. Bergerson and Keith pay particular attention to CCS, showing how divergent views about its cost effectiveness emerge from divergent choices about the scale of analysis.
| “Debate about the future of oil sands development is so contentious that even the name of the resource is disputed: proponents typically use oil sands while opponents use tar sands. We use oil sands not to express our views on the debate, but because tar is technically incorrect because tars are products of biomass combustion and are chemically distinct from bitumen. The source material is neither oil nor tar but bitumen, but is most generally described as an example of ultraheavy oil.” |
| —Bergerson and Keith |
The authors note that while some sources claim that the oil sands are up to 5 times more emissions intensive than conventional oil, others claim that they are as low as 10% more intensive. Both those claims can be defended, with the discrepancies arising “from an artful choice of the scale of analysis.”
The core of the discrepancy is whether or not the energy intensity and GHG
emissions are measured from the well-to-tank (WTT) or over
the full life cycle (well-to-wheels [WTW], from extraction of
the resource through to the use of the fuel in a vehicle). About 60-80% of full life cycle emissions result from driving/operating a vehicle; if only the extraction
emissions (WTT) are examined, oil sands will deliver a relatively high value.
A recent study by Bergerson and Keith’s group at the university (Charpentier 2009) reviewed published literature and concluded that while the extraction energy intensity and GHG emissions associated with oil sands are typically higher than those of conventional production, “it is not inconceivable that an oil sands pathway
may perform better than a conventional oil pathway, under
certain circumstances”.
They also note that if the scale of analysis is that of the entire economy, the
value commonly referenced for economy wide emissions is
that oil sands constitute ~5% of Canada’s emissions. However, this only
accounts for the processing that occurs in Canada and
therefore excludes much of the refining and transport
emissions. Nor does this estimate include the use of
transportation fuels in vehicles, which occurs throughout
North America (NA); approximately two-thirds of oil sands
products end up in the US. All told, they wrote, the well-to-wheel (WTW) emissions
of oil sands products constitute roughly 2% of total emissions
in Canada and the US.
While oil sands emissions have more than doubled from 1990 to 2006, the absolute increase in emissions from oil sands over the same period is less than the absolute increase in Canadian electric or transportation sector emissions, and far less than
the increases in these sectors on a North American basis, they note
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Tags: acs journal, greenhouse gas emissions, oil sands development
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