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Dilbit Sinks in Enbridge Oil Spill, but Floats in Its Lab Study

Scientists say the 1.3 gallon spill in the lab tank omitted real-world factors that made dilbit sink in Michigan’s million-gallon Kalamazoo River spill.

Mar 14, 2013
The Dilbit Disaster

A recent industry-backed study of diluted bitumen, the Canadian crude oil that would be shipped through the proposed Keystone XL pipeline, contradicts what environmentalists have said for years—that diluted bitumen, or dilbit, sinks in water and is much more difficult to clean up than conventional crude oil.

Instead, the study found that dilbit floats when it spills into water, a claim that contradicts what happened during a major dilbit spill in Michigan's Kalamazoo River in 2010. The cleanup of that spill already has cost more than $810 million, and the Environmental Protection Agency is still struggling to figure out how to remove the submerged oil.

The study is important because there is little scientific research on how dilbit reacts in water, and because the Keystone would cross thousands of U.S. waterways, including the critically important Ogallala aquifer in Nebraska.

But five scientists interviewed by InsideClimate News say the study was so narrowly constructed that it shouldn't be used to draw conclusions about dilbit. The experiment's laboratory conditions didn't reflect most real-life situations, they said, and the study ignored the consequences of the Michigan spill.

"One single study doesn't answer very much at all," said Merv Fingas, a retired scientist from Environment Canada, the Canadian equivalent of the EPA, who studied dilbit in the 90's. "You really need a much more detailed study ... to explain the science behind all of this."

Fingas said Environment Canada tested different kinds of dilbit in the 1990s and found that they "all sank in freshwater." But the research was abandoned before it could be broadened, he said.

Dilbit is produced by diluting bitumen—a thick, heavy crude mined from Canada's tar sands region—with a cocktail of light liquid chemicals that allows the bitumen to flow through pipelines. About two weeks after the Michigan spill, the EPA discovered that the liquid chemicals were evaporating, leaving the bitumen to sink slowly to the river bottom.

The recent study was commissioned by Enbridge Inc., the Canadian pipeline operator responsible for that accident. It was conducted by SL Ross Environmental Research, an Ottawa-based consulting firm.

Ian Buist, an SL Ross engineer who was part of the study team, said they didn't take into account any of the findings from the Kalamazoo spill "because we weren't asked to. It wasn't part of the contract."

Buist declined to discuss how the experimental setup compared to a real life spill environment. He referred questions about the scope of the study to Enbridge.

In an email, Enbridge spokesman Todd Nogier said the study was done "to evaluate whether diluted bitumen would sink due to weathering processes alone. We attempted to simulate the conditions that exist in the environment that contribute to weathering of oil in a [water] setting such as UV lights, surface mixing and wind."

The SL Ross researchers poured 1.3 gallons of dilbit into a metal tank holding about 900 gallons of freshwater. They used a fan and UV light to simulate wind and sun, and circulated water from the bottom of the tank to create currents. After 11 days, they said no oil had sunk to the bottom of the tank. Most of the oil remained on the surface, with less than 5 percent suspended in the water.

No Sediment in the Tank

Several of the scientists InsideClimate News interviewed—none of whom worked on the study—said SL Ross has a reputation for conducting good research. But they also said there's a lot of room for improvement.

"What the experiment did is what I would say a good start, or maybe a place to consider the outcome and how you might be able to make it more sophisticated," said Chris Reddy, a geochemist at Woods Hole Oceanographic Institution who studies the fate and transport of crude oil in water. "I don't want to discount laboratory experiments. But you have to recognize that Mother Nature is a much more complex [environment] than what is found in a laboratory."

It's difficult to capture the variations in temperature, currents and organic matter found in a real river, he said. "To me, if you want a really good [experiment], you go to a site that's been impacted," like the Kalamazoo.

The scientists said the study didn't consider a crucial element—suspended material such as sediment and organic matter—found in virtually every body of water. Sand, clay and floating plant matter can drag down floating oil.  Even conventional crude oil, which is almost always lighter than water, will sink if enough suspended material sticks to it. Heavier oils, like bitumen, can sink even faster.

"Once it starts to pick up the sediment, it begins to get heavier and heavier," said Rich Gaudiosi, president of the Delaware Bay and River Cooperation, a nonprofit coalition of oil response companies. The oil "may not sink all the way to the sea bottom or river bottom, but it will hang below the surface, which makes it obviously harder to clean up because you don't know where it is."

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