Gray, Xu, and Masliyah reply: In our article we presented both the underlying science of the operations and a summary of the environmental issues that the oil-sands industry faces. Mining and processing of the oil sands results in greenhouse gas emissions “from well to wheels”—that is, from production through to the vehicle tailpipe—of around 108 grams of carbon dioxide emissions per megajoule of gasoline, compared with 95–105 g CO2e/MJ for a range of conventional crude oils imported into the US. 1 Due to the energy required to heat the underground formations, the well-to-wheels emissions from an in situ process are higher: approximately 115 g CO2e/MJ for both California heavy oil and for bitumen sent from the oil sands to US refineries. In comparison, the highestemission technology is coal conversion to liquid fuels, at approximately 200 g CO2e/MJ. Used on a large scale in South Africa, coal-conversion technology is also under development in China and is proposed for use in the US.
Any feasible scenario for growth in production of renewable sources of transportation fuels, in combination with conservation measures, will still require use of petroleum for many years. In our opinion, oil-sands processing is an essential component of a secure energy supply for North America. The oil sands are valuable for the production of transportation fuels, not for combustion for their energy content alone. Natural gas is a much more favorable alternative for generating electricity.
The issue of CO2 emissions from any use of petroleum is very real, but several environmental groups have targeted the oil-sands industry by combining incorrect information with extreme extrapolation to create alarming scenarios. The most egregious of those claims is the projected impact on migratory birds. By considering the total population of migratory birds crossing northern Alberta, the total area of oil-sands deposits, and unsupported estimates of bird deaths in the tailings ponds, they have projected Armageddon for migrating songbirds and waterfowl. As we wrote in our article, only a small fraction of the total oil-sands resource can be mined. The total area approved for mining is 1520 km2, out of Alberta’s 661 848 km2 area; the approved area represents 0.04% of the Canadian boreal forest. In that zone, the current area of the tailings ponds is approximately 60 km2. In contrast, Alberta wetlands make up 139 000 km2. Remediating the existing tailings ponds and minimizing their future use are essential, but grossly exaggerated claims of impact should not be credited by trained scientists.
