Researchers utilizing agricultural waste to remediate soil polluted by Agent Orange
In the 1960s and ’70s, the United States military used an herbicide and defoliant chemical called Agent Orange as part of the war effort in Vietnam to kill plants in the rural parts of the country, which were largely covered by impenetrable jungle. More than 40 years later, the destructive chemicals are still wreaking havoc.
“More than 30,000 tons of Agent Orange were spread across the country, and the unfortunate legacy is widespread contamination with dioxins,” said UIC Professor Karl Rockne of civil, materials, and environmental engineering.
In an effort to rectify the damage, Rockne is collaborating with Professor Dang Thuong Huyen at Vietnam National University to investigate new technologies for the contamination reversal of more than 12,000 square miles throughout Vietnam.
“The project is focused on the bioremediation of soil polluted by Agent Orange using plant-based biochars sourced from agricultural waste stocks,” Rockne said. “Our proposed research represents an interesting symmetrical approach to the problem of Agent Orange by using plant-based products to facilitate the treatment of polychlorinated dibenzodioxins/furans [environmental pollutants] resulting from the use of plant defoliants.”
Biochars have a lot of exceptional properties, and they are often used as soil amendments. They also have the ability to absorb hydrophobic organic pollutants.
“At the surface interface of biochars, electrons can be transferred across these surfaces because of its chemical structure. It turns out that this interface between the solid and the liquid, and sometimes the gas phases can be inhabited by micro-organisms (bacteria), and facilitate the transport of electrons to chemicals that are also absorbed at this interface,” he said.
Under the appropriate conditions, the bacteria can respire chlorine, which is abundant in dioxin, and the chlorine can act as the electron acceptor to respire organic matter.
“In this approach we have literally traded places between the target and the pollutant by using biochar, a product derived from plants, to destroy the pollution caused by the use of defoliants to kill the plants,” Rockne said.
Another goal the researchers want to achieve is the creation of a green circular economy, which can be accomplished by mimicking nature and repurposing agricultural waste products within Vietnam to create the biochar.
“We will look at which byproducts do the best job. We’re going to be conducting detailed chemical scientific analysis of this process, and investigating different ways to produce the biochars,” he said.
In addition to working with researchers, Rockne will be going to Vietnam to teach short courses and seminars, and help disseminate knowledge in a broad field of environmental engineering. The research is made possible by a three-year grant titled “Biochar Facilitated Bioremediation: A Green Solution for Dioxin/Furan Pollution” from USAID Partnerships for Enhanced Engagement in Research program.