Electric blanket boils PCBs from soil.

Engineers have long been able to destroy polychlorinated biphenyls (PCBs) and other organic pollutants.

The challenge has been how to separate them cost-effectively from the material they contaminate. Scientists now report having solved that problem for soil by cooking it with an intensely hot electric blanket to vaporize the pollutants. In the November Environmental Science & Technology, William A. Edelstein of General Electric Corporate Research & Development in Schenectady, N.Y., and his coworkers offer results from day-long tests at an abandoned U.S. drag strip. Decades ago, PCB-laced oil had been sprayed there to control dust.

The researchers' prototype blanket, shown here, is edged with electric wires and partially folded back from a treated area. Operated at temperatures up to 925#161#C, it eventually brought the top 15 centimeters of soil to 200#161#C. A vacuum pulled the pollutant vapors that formed under the blanket into a flameless thermal oxidizer, which broke down the PCBs. The contamination-initially as high as 2,000 parts per million (ppm)-fell to less than 2 ppm over each 9 square meters treated. In follow-up tests, the researchers achieved comparable cleanup to depths of 16 inches at an even more heavily tainted area.

On Aug. 1, the Shell Oil Co. of Houston created a subsidiary, TerraTherm, to commercialize such blankets for the removal of dioxins, solvents, pesticides, and perhaps heavy metals such as mercury, cadmium, and lead.