More studies will be needed to allay public concerns about potential environmental impacts from using chemical dispersants to help clean up offshore oil spills, a National Academy of Sciences committee examining the use of dispersants was told on Aug. 7. A forthcoming study should not be considered the last word on the subject, said one of its authors, Christopher M. Reddy, a senior scientist specializing in marine science and geochemistry at the Woods Hole Oceanographic Institution.
The paper, which is undergoing peer review before its upcoming publication in Proceedings of the NAS, suggests that dispersants deployed following the 2010 Macondo deepwater well blowout and spill helped improve air quality as response teams worked on the Gulf of Mexico’s surface.
“We’re very wary that this will be viewed as a unilateral stamp of approval. It’s not,” Reddy said. “It’s simply something that’s on one side of the ledger. Two other fine reports already have been issued. But even now, we can’t get work done without answering questions about dispersants. There are more questions about them than about oil spills.”
One committee member quickly agreed. Gina Coelho, who was chief scientist on the monitoring of subsurface dispersant injection during the Macondo spill cleanup and was a scientific liaison on dispersant issues for BP PLC, the well’s operator, during and after the spill response, said the company tried to hold public meetings to address concerns over dispersants, but no one came.
“The big question is how to expand your audience,” Reddy told the committee. “I don’t understand why there are so many negative views about dispersants. I don’t know why this is happening.”
Spill conditions, behavior vary
More studies are necessary because other offshore crude oil spills occur under different conditions, Reddy said. The priority immediately following the Macondo well blowout was to keep the situation from getting worse, but this should not keep scientists from exploiting other research opportunities, Reddy said.
A second speaker agreed. “Subsea dispersants are being implemented in Norway as a response option,” said Per Johan Brandvik, a senior research scientist at SINTEF Ocean AS in Trondheim. “We have an ongoing program to test various injection techniques. But the oil companies want to implement dispersant injections as a response option, so the time is running short.”
Dispersants can be effective because they shrink large crude oil drops that would race to the ocean’s surface to a size where they linger below before forming a thin layer that is easier to collect, Brandvik said. Following tests at Trondheim with support from Oceaneering International, SINTEF moved its studies to the Ohmsett National Oil Spill Response & Renewable Energy in Leonardo, NJ, where tests can be done in conditions closer to an actual ocean, he said.
SINTEF also has done work at the Southwestern Research Institute in San Antonio, which the American Petroleum Institute helped finance, Brandvik said. “An early response is important,” he said. “The dispersant needs to bond with the oil at the ocean floor before it rises to the turbulent zone, where it turns into droplets. We’re working with different release scenarios and different ways to inject the dispersant.”
Dealing with accident crude releases where natural gas also is involved is more difficult, the speakers agreed. The Macondo blowout should be considered more a petroleum fluid than a crude oil spill for that reason, Reddy said. “The gas actually was the star of the show,” he observed.
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