Vegetable oil spills hurt environment, too

July 10, 2003 -- Petroleum spills may get most of the press, but vegetable oil spills also occur and can likewise damage the environment. Large tanks and pipelines carry vegetable oil for distribution, and when an accident occurs or storage tanks fail, large quantities of vegetable oil can spill into rivers, lakes and harbors.

When you think "oil spill" you think petroleum oil, but vegetable oil spills also occur and they can wreak environmental havoc. An environmental engineer at Washington University in St. Louis is experimenting with a method that uses clay to clean up vegetable oil spills.

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Brian Wrenn, Ph.D., assistant professor of civil engineering at Washington University in St. Louis, and his co-researchers have taken on the task of addressing bioremediation of floating vegetable oil spills.

"Although vegetable oils are not as acutely toxic as many petroleum products, uncontrolled releases can result in significant environmental damage," Wrenn said.

Aquatic birds and animals can become "oiled," the water's oxygen supply can become depleted, and hard or gummy coatings on oiled surfaces can persist for years, he explained.

The researchers have found that adding dry clay to spilled oil results in formation of oil-mineral aggregates that sink to the bottom of a body of water. This process is most efficient when dry clay contacts the floating oil; wetting of the clay with water reduces its ability to interact with the oil and increases the mass of clay needed to sink a unit mass of oil. Thus, this process works best under conditions of relatively low mixing energy.

Wrenn said sending vegetable oil to the bottom of a body of water can be an acceptable remedy for spills only if the oil can be biodegraded in the sediment. He and his group will continue to study this aspect of vegetable oil remediation.