Correspondence/Rebuttal pubs.acs.org/est
Comment on “Variability and Uncertainty in Life Cycle Assessment Models for Greenhouse Gas Emissions from Canadian Oil Sands Production”
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A
dam Brandt’s recent article1 contains a serious analytic error that invalidates its conclusions, specifically, the recommendation for using a crude inappropriate model to generate industry average GHG emissions values. Industry professionals, economists, and financial analysts use refinery optimization models with multiple constraints for analyzing refining operations, economics, and capital requirements. Refinery optimization models are detailed, engineering representations of refining processes and the material flows between processes that are required to produce a given product slate from a proposed crude oil mix. Such modelsnot econometric models or regression analyses of refinery inputs and outputsare the appropriate methods for analyzing the relationships between crude oil quality, various types of refinery energy used, output of multiple products, and refinery CO2 emissions. Brandt recommends using an inappropriate model citing earlier related analysis by Greg Karras.2 Other authors have also uncritically cited the Karras article. Unfortunately, along with using an inappropriate model, Karras employs a highly suspect base assumption when he calculates the increase in carbon dioxide emissions from refineries processing heavy oil and oil sands oil. Karras assumes that heavy oils and oil sands would globally displace all other oils, concluding that “a switch to heavy oil and tar sands (oil sands) could double or triple refinery emissions and add 1.6−3.7 gigatons of carbon dioxide to the atmosphere annually from fuel combustion to process the oil.” Full replacement of conventional oils is not a near-term possibility, nor would it likely happen any time this century, if ever. If one assumes heavy oil and oil sands oil replace other oils at the rate implied by their 2009 share of world liquid fuel supplies (2.6%) compared with their projected share for 2035 (5.6%), it would take 846 years until full replacement. (See ref 3, Tables 1 and 3.) Before this near-millennial period of time elapses, the rate of displacement could, of course, change, but then so will all energy technology. Karras has provided a meaningless calculation, irrelevant to the real world. Other commentators and policymakers need to be aware of the shortcomings of both the Brandt and Karras articles. Any influence they might have over near-term policy and regulatory action could be undeserved and harmful.
REFERENCES
(1) Karras, G. Variability and uncertainty in life cycle assessment models for greenhouse gas emissions from Canadian oil sands production. Environ. Sci. Technol. 2012, 46, 1253−1261. (2) Brandt, A. R. Combustion emissions from refining lower quality oil: What is the global warming potential?Environ. Sci. Technol. 2010, 44, 9584−9589. (3) U.S. Energy Information Administration. International Energy Outlook 2011. http://www.eia.gov/forecasts/ieo/index.cfm (accessed).
Robert Greco*
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Downstream Group Director, American Petroleum Institute, Washington, DC
AUTHOR INFORMATION
Corresponding Author
*E-mail:
[email protected] . Notes
The authors declare no competing financial interest. © 2012 American Chemical Society
Published: February 15, 2012 4253
dx.doi.org/10.1021/es300130f | Environ. Sci. Technol. 2012, 46, 4253−4253
