A new Yale-led study finds that removing forever chemicals from farmlands could become far cheaper using hemp, rock dust, and biochar, potentially cleaning contaminated soils within a decade.
Removing Per- and Polyfluoroalkyl Substances (PFAS) from farmlands could soon become far cheaper and far less destructive. A new Yale-led study outlines a three-step process using plants, rock dust, and biochar. Researchers say it could work within a single decade.
The chemicals in question are often called “forever chemicals.” They resist breaking down and have built up in soil for decades. Much of that contamination traces back to sewage sludge once used as fertilizer.
Removing forever chemicals from farmlands matters because these chemicals do not simply fade away on their own. Once present in soil, they can persist for generations without intervention. That persistence is part of why the chemicals earned their nickname in the first place.
The study estimates PFAS have contaminated roughly 1.2 million hectares of U.S. cropland. Some Maine farms have already shut down after soil tests exceeded safety limits. Exposure to these chemicals has been linked to certain cancers, thyroid problems, and fertility issues.
Health researchers have also linked long-term PFAS exposure to weakened immune response. These risks make removing forever chemicals from farmland a public health priority, not just an environmental one. Farmers directly exposed to contaminated soil and water face some of the highest risks.
Conventional cleanup methods of removing forever chemicals from farmlands usually means excavating and burning contaminated soil entirely. That approach can cost an estimated $1.6 million per hectare. Scaled nationally, the total bill could reach roughly $8 trillion.
The Yale team’s model instead starts with basalt rock dust spread across farmland. This dust shifts soil pH in a way that sounds counterproductive at first. It actually makes PFAS more available for uptake by nearby plants.
Hemp and certain perennial grasses then draw the loosened PFAS out of the soil. Rock dust sped up removal of one compound, called PFOS, by 20-40%. Researchers call PFOS the higher regulatory priority of the two chemicals studied.
Harvested plants next go through a heating process to make biochar. That heat destroys much of the remaining chemical structure left in the plant tissue. Spreading the finished biochar back onto contaminated fields could cut chemical runoff by 95%.
A Yale-developed process for removing forever chemicals from farmlands uses basalt rock dust to loosen chemical bonds in contaminated soil, allowing hemp (photo above) and perennial grasses to draw pollutants up through their roots before harvesting and heating the plants into biochar that, spread back onto fields, could cut PFAS runoff by 95%. Photo by Mark Stebnicki on Pexels.
Postdoctoral researcher Jake Thompson led the study alongside professor Noah Planavsky at Yale. Planavsky, who comes from a farming family, says farmers urgently need better tools to address this problem. Thompson notes that small and organic farms were often hit hardest by past PFAS-laden fertilizer use.
Combined, researchers project these steps could bring soils below safety thresholds within a decade. Estimated costs come in at around $1,460 per hectare each year. That figure is a tiny fraction of traditional excavation and burning costs.
The rock dust and biochar processes also carry an added climate benefit. Both methods help pull carbon dioxide out of the atmosphere over time. Scaled nationwide, researchers estimate the approach could remove 10.5 million metric tons of carbon dioxide each year.
Unlike excavation, this method would let farmers keep working their land throughout the process. Researchers note that removing forever chemicals from farmlands is a global issue beyond the United States. In parts of Europe and the UK, most sewage sludge still gets applied directly to farmland.
Europe alone spreads about 10 million tons of sewage sludge onto cropland each year. The United Kingdom applies sludge to roughly 70% of its farmland. China follows a similar pattern, researchers say, making the contamination problem a shared one worldwide.
So far, the findings come from computer modeling built on real farm data rather than full field trials. The research team now hopes to test the approach on partner farms across different soil types.
Real-world results of removing forever chemicals from farmlands through this approach will show whether these modeled gains hold up outside the lab. If they do, hemp, rock dust, and biochar could offer struggling farmers a genuine way forward. For land written off as unusable, that alone would count as real progress.
