84,000 gallons of crude oil are glugging their way across an Arkansas community right now, putting the spotlight on the transport of tar sands oil across the United States. While Exxon is claiming it’s just “heavy” oil, the naming is a matter of semantics, because the oil comes straight from Canada’s infamous tar sands. It’s not the only recent spill involving oil from this region; in 2010, 877,000 gallons of oil were released in Michigan, for example. With more tar sands oil being transported, the frequency of such spills is only going to increase, and worse, there are signs that tar sands oil is more prone to spills than its conventional counterpart.
To understand why this is, it helps to understand a little bit of the chemistry behind tar sands oil. It’s made by extracting bitumen, an extremely thick petroleum product that’s about the consistency of peanut butter at room temperature. As you can imagine, forcing peanut butter through an oil pipeline wouldn’t work out very well, so it’s thinned with chemical agents, producing a product called diluted bitumen or dilbit. Even diluted, the oil needs to be transported in a warmed pipeline to ensure it won’t clog, and the pressure of the pipeline needs to be increased to keep it flowing.
Warmer temperatures can increase corrosion rates and stress on joints, while the increased pressure can make a spill more likely in a pipe that’s under stress. This means that the very conditions needed to move dilbit around can increase the risk of a spill. Internal corrosion with dilbit appears to be worse because of its chemical composition, which compounds the problems with moving it around.
Furthermore, pressure changes inside a pipeline carrying dilbit can cause a phenomenon known as column separation, where tiny bubbles of natural gas liquids develop in the fluid. These can mimic a leak on detection systems, and pipeline monitors have trouble telling the difference between true leaks and column separations. Consequently, oil may continue to flow for hours before a leak is detected. The infamous Enbridge spill in Michigan started with a misdiagnosed column separation.
As if all this wasn’t bad enough, dilbit is also harder to clean up once it gets into the environment. It tends to separate into its components, and conventional oil spill response techniques are typically not adequate for controlling it. Consequently, it leads to much greater damage, and it’s more expensive to clean up. Meanwhile, manufacturers, transporters, contractors and governments wrangle over the economic liability for handling spills.
Already, the United States is working with aging oil pipeline infrastructure that’s vulnerable to leaks even with the prized light sweet crude oil companies prefer. With the push to transport more tar sands oil, the risk of spills is likely to increase, and that poses a serious risk to the environment. It also presents a significant argument to move away from petroleum products and on to renewable resources, and to address the seriously outdated oil infrastructure in the United States to make it safer to move oil around when it does need to be moved.
That includes updating infrastructure to cope with the unique conditions posed by tar sands oil, including developing more sensitive and effective equipment for identifying column separation versus leaks, as well as better inspection equipment that can catch corrosion and internal pipeline damage before pipelines rupture, rather than after. The high environmental costs associated with tar sands oil also need to be weighed in discussions about corporate liability and establishing plans to ensure that governments aren’t left holding the bag when it comes to costly oil cleanups.
This has especially important ramifications for the forthcoming decision on the Keystone XL pipeline; could the dangers of dilbit be the nail in the coffin when it comes to authorizing the highly controversial project?
Photo credit: chesapeakeclimate