Scientists Turn Oily Soil Into Reclaimed Fertile Ground

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Rice University scientists are cleaning soil contaminated by oil spills in a way that saves energy and reclaims the soil’s fertility. They use a process known as pyrolysis, which involves heating contaminated soils in the absence of oxygen. The approach is said to be much better for the environment than standard incineration techniques for fast remediation, said Rice environmental engineer Pedro Alvarez.

“Our original goal was to speed the response to oil spills, but our aspiration was to turn contaminated soil into fertile soil,” added the George R. Brown professor and chairman of Rice’s Civil and Environmental Engineering Department. The work is explained by Alvarez and his colleagues at Rice University in the American Chemical Society journal Environmental Science and Technology.

Offshore oil spills get the most attention, but 98% of spills—more than 25,000 a year—occur on land. Industry and governments worldwide spend more than $10 billion annually to clean up oil spills. The Rice team found that pyrolysis of contaminated soil for three hours not only reduced the amount of petroleum hydrocarbons left to well below regulatory standards, typically less than 0.1% by weight, but also enhanced the soil’s fertility by turning the remaining carbon into beneficial char.

The researchers successfully grew lettuce in reclaimed soil. “There’s no one plant officially accepted as the standard for testing petroleum toxicity, but lettuce has been accepted by the community as very sensitive to toxins, especially petroleum,” said Rice graduate student Julia Vidonish, the paper’s lead author. Noted is that reclaimed soil may not necessarily be used to grow food, but it certainly could be used for re-greening—planting grass to minimize erosion and to restore vegetation.

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