The Fertilizer That Wasn’t Safe: PFAS-Laden Biosolids and the Agricultural Crisis
For decades, municipal wastewater treatment plants have produced biosolids—nutrient-rich sludge remaining after wastewater treatment—and distributed them to farmers as fertilizer under a regulatory framework premised on their safety and value. This practice, governed by EPA’s Part 503 regulations, was considered environmentally beneficial: recycling nutrients, diverting waste from landfills, and improving soil organic matter. The discovery that biosolids are massively contaminated with PFAS has revealed a fundamental flaw in this regulatory framework and exposed thousands of American farms to chemical contamination of potentially permanent consequence.
How PFAS Concentrate in Biosolids
PFAS entering municipal wastewater treatment systems—from industrial dischargers, household product use, and commercial sources—are not destroyed by biological treatment. Instead, PFAS partition between the liquid effluent stream and the solid biosolids. Longer-chain PFAS with stronger hydrophobic character preferentially concentrate in biosolids; shorter-chain more water-soluble PFAS pass through to the effluent. The net result is that biosolids are significantly enriched in certain PFAS compounds—particularly PFOS, PFOA, and related long-chain compounds—relative to wastewater influent.
Studies of biosolids from treatment plants across the United States have found total PFAS concentrations ranging from hundreds to tens of thousands of micrograms per kilogram (dry weight)—concentrations that, when biosolids are applied to agricultural land at recommended rates over multiple years, produce soil PFAS accumulations that can exceed crop uptake thresholds, contaminate underlying groundwater, and persist in agricultural soils for decades to centuries. The EPA’s preliminary determination that essentially all biosolids in the United States contain PFAS was a landmark acknowledgment of the scale of this contamination pathway.
Maine as Ground Zero: The State’s Biosolids Crisis
Maine’s dairy farm community has become the most visible face of the biosolids-PFAS crisis. Several Maine dairy farms that received biosolids applications over decades have documented PFAS contamination of well water, soil, crops, and livestock tissue at levels requiring farm closure. The Stoneridge Farm in Arundel, Maine—where PFAS from biosolids contaminated well water, cow milk, and family members’ blood—became a nationally publicized example of the human and economic consequences of biosolids-PFAS contamination. Several other Maine farms followed with similar findings, triggering state testing programs that identified dozens of farms with actionable PFAS contamination from biosolids applications.
Maine’s legislative response included the establishment of a PFAS fund providing direct payments to affected farmers, a statewide moratorium on new biosolids applications pending further assessment, and development of PFAS soil action levels for agricultural land. Maine has become a national model for biosolids-PFAS policy response, with other states including Michigan, Wisconsin, North Carolina, and Vermont developing or accelerating their own biosolids PFAS programs informed by Maine’s experience.
Federal Response and the Path Forward
The EPA has initiated a risk assessment for PFAS in biosolids that will inform potential revisions to the Part 503 regulations. Preliminary findings suggest that the current biosolids regulatory framework—developed without consideration of emerging contaminants like PFAS—needs substantial update to protect farms, farmers, and communities that receive biosolids applications. The cost implications of any restrictions on biosolids land application are significant: prohibiting or limiting land application would require alternative disposal pathways (landfilling, incineration, advanced treatment) that are far more expensive and would dramatically increase water utility costs. The regulatory challenge is balancing the environmental benefit of nutrient recycling against the unacceptable risk of PFAS contamination of agricultural land—a balance that EPA has not yet publicly resolved.