Scientists have discovered that a readily available substance can help remediate hazardous soil.
Biochar — the remnants of organic matter burned without oxygen — adheres to contaminants and improves soil health, enabling unusable land to be farmed again. A study by Chalmers University of Technology in Gothenburg, Sweden, showed earthworms in soil polluted with dichlorodiphenyltrichloroethane (DDT) absorbed half as much of the toxin if the soil was amended with biochar, as Phys.org relayed.
DDT was used for decades as an insecticide before it was banned in Sweden in 1970. It remains widely prevalent around the world because of its stability in soil and water, and it bioaccumulates in animals, meaning species atop the food chain are most affected. It infamously pushed bald eagles to near extinction in the United States.
The study provides hope that biochar can be used widely to ameliorate potentially harmful conditions, though DDT-contaminated soil must be addressed because of ecological regulations and not risks to crops or plants.
As much as 70% of the soil in the European Union is unhealthy, and pollution is a major factor, Phys.org noted. But it would require a massive undertaking to deal with the 2.8 million potentially contaminated sites on the continent. Sweden has thousands of DDT-tainted areas.
"Treating contaminated soil in large volumes is costly and complicated. A common solution is to dig out the soil and then transport it to a landfill for hazardous waste, but that means destroying good quality soils and is not a reasonable solution for large contaminated areas," first author Paul Drenning said.
"Treatment with biochar on site could thus make the land useful instead of being left uncultivated or degraded, and also at a significantly lower cost for both the landowner and for the environment."
Biochar holds long-term carbon-storage potential; helps soil retain water, air, and nutrients; and it is slow to decompose. That means treatments could remain effective for decades, the researchers reported.
Their next steps are to continue testing soil samples from the former tree nursery where they conducted the study and to try to scale up the process so biochar amendments don't necessitate the removal of soil.
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Not enough time ⏳ "There is a great interest in using biochar for stabilization of both DDT and various other contaminants in soils, such as metals and polyaromatic hydrocarbons," Drenning said.
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