In 2020, just after Winslow and Laura Robinson bought a farm in Maine, they were surprised to learn that sewage sludge had been used as fertilizer there decades earlier—and that the sludge had left behind “forever chemicals” that remained in the soil.
Farmers in Maine have been at the forefront of uncovering a problem that exists on farmland across the country. Sewage sludge from wastewater treatment plants has been widely used on farms since the 1970s, both to keep it out of landfills and provide cheap fertilizer to farmers. (“Biosolids” are also sold in some garden stores as home fertilizer, which you might unwittingly be using in your own backyard.) But the sludge can contain high levels of PFAS, so-called forever chemicals that don’t break down and can move from soil into food. While the impacts of PFAS in food aren’t yet fully understood, the chemicals have been linked to liver disease, cancer, and other illnesses.
After testing, the Robinsons found a safe area of their farm to begin growing organic produce. But like other farmers, they didn’t have a good solution for the contaminated fields they’d discovered. A new study from Yale University, published in the Proceedings of the National Academy of Sciences, suggests a low-cost way that farms can clean up the problem and simultaneously help fight climate change.
A cheaper way to tackle forever chemicals
Existing methods for PFAS remediation are extremely expensive—sometimes $1 million per acre—and typically used only at sites like airports or military bases. They also involve removing soil. Cleaning up millions of acres of American farmland just isn’t feasible.
Noah Planavsky, a geochemistry professor at Yale who studies soil health, decided to work on the problem after learning about the issue from farmers. “Farmers were deeply concerned about this, felt like they weren’t getting good information, and felt like this was a massive problem where they were being ignored or gaslit,” Planavsky says.
The study tested a simple approach for treating contaminated soil. Farmers plant crops known to absorb PFAS quickly, such as hemp and sunflowers. The farmers also add crushed alkaline rocks to the soil to raise the pH level, which helps the plants take up more of the chemicals. When the crops are harvested, they’re heated to very high temperatures without oxygen, which breaks down the PFAS.
“Although they are forever chemicals— very sturdy and robust chemicals—they can be destroyed at higher temperatures, and that is something that has been well documented,” says Planavsky. The process creates biochar, which can be added back to the soil to help trap more PFAS. The scientists estimate that in some cases, the method could bring contamination down to a safe threshold within a decade.
There’s another challenge: In most states, sewage sludge is still being used on some farms. It’s not surprising that it’s been commonly used historically. “Farmers are barely making ends meet,” says Laura Robinson, the organic farmer from the Maine farm, who participated in the Yale study. “There’s not much profit in farming. So if you’re being offered free fertilizer for acres and acres of hay fields, you’re going to take it. The powers that be [were] saying that it’s safe.”
Maine, which has moved faster than others to tackle the problem after farmers raised the alarm, banned the use of sewage sludge on farms in 2022. The first step is to stop its use broadly. Under the Trump administration, the EPA has backed away from regulating sewage sludge as fertilizer. States may move more quickly, though, and the study’s new cleanup method comes at a time when farmers are looking hard for solutions.
Could cleanup be affordable at scale?
The scientists’ approach is an order of magnitude cheaper than other methods for PFAS cleanup. And it has a second advantage: Adding crushed rocks to soil helps capture carbon dioxide. (Planavsky also researches this type of carbon removal, called enhanced rock weathering, and cofounded a startup called Lithos that separately works with rock dust on other farms.) In theory, selling carbon removal credits could help fund the PFAS cleanup.
“We need billions of tons of carbon dioxide removal to meet our climate goals,” he says. “And there’s also scientific consensus that having PFAS in the food system is something that poses real health concerns at a broad public scale . . . I think most folks would say that we have inadequate funding moving to both of these.”
Litigation could also potentially help fund PFAS remediation on farms. The number of lawsuits is growing; the State of New York, for example, recently sued major PFAS manufacturers for allegedly hiding what they knew about the health and environmental harms of the chemicals. Previous settlements have sent billions of dollars to communities to begin removing PFAS from drinking water.
Outside funding is critical, farmers say. “If this solution is going to work, it’s going to have to be something that’s funded,” says Robinson, the organic farmer. And, she says, it’s something that needs to happen. “My big takeaway from all of this is that this is a problem that is absolutely everywhere. Towns, states, countries—everybody needs to be paying attention to it and putting money towards it. . . . It’s a huge public health problem, because it’s going to affect everybody. We all need to eat.”