Getting PFAS out of biosolids isn’t easy. Some companies are trying,
A dairy farm in Arundel, Maine, triggered an alarm in 2016 when high levels of perfluorooctanesulfonic acid (PFOS) were detected on the property in a monitoring well for a public drinking-water system. The chemical hasn’t been produced in the US since 2002 but is one of many per- and polyfluoroalkyl substances (PFAS), often called forever chemicals, that persist in the environment.
The farmer reached out to the Maine Department of Agriculture, Conservation and Forestry (DACF) and asked, “What does this mean for my animals? They’re drinking this water as well,” says Meagan Hennessey, the department’s director of PFAS response. The farmer agreed to have milk from the cows tested for PFAS.
After finding high levels of PFOS in the milk, the department began working with a toxicologist at the Maine Center for Disease Control and Prevention to set a limit for PFOS in milk sold in Maine. PFOS has been linked to human health effects (PDF), including some cancers and adverse effects on the immune system, reproduction, and development.
The source of the PFOS contamination on the Arundel farm was likely fertilizer made from industrially contaminated sewage sludge, also called biosolids, spread decades ago on the land where the cows grazed, according to an investigation by the Maine Department of Environmental Protection. PFOS in sewage sludge applied to land accumulates in soil and seeps into groundwater. The cows were eating hay grown on tainted soil and drinking PFOS-laden water.
The contamination led the farm to cease its dairy operations. It also prompted Maine to begin testing retail milk for PFOS contamination. In 2020, milk from two more dairy farms in the state was found to be contaminated with PFOS.
Two years later, Maine banned land application of biosolids-based fertilizers. Other states are also grappling with PFAS contamination on farms. Five states have enacted regulatory limits, and five have advisory levels for at least one PFAS in biosolids, according to a compendium of state PFAS actions (PDF) published by the Environmental Council of the States in April.
States are stepping in because the US Environmental Protection Agency (EPA) has yet to regulate PFAS in biosolids applied to land. The agency released a draft risk assessment, the first step toward regulating PFAS in biosolids, in January during the final days of the Biden administration. The draft assessment concluded that PFOS and perfluorooctanoic acid (PFOA) in biosolids applied to land pose health risks to people who live on or near the land.
It is unclear when or if the EPA will finalize that evaluation. Republicans in the House of Representatives are hoping to stop the EPA from doing so by cutting funding for the effort. A provision in the House version of the Interior, Environment, and Related Agencies appropriations bill for fiscal year 2026, released July 14, states, “None of the funds made available by this or any other Act may be used to finalize, implement, administer, or enforce the draft risk assessment titled ‘Draft Sewage Sludge Risk Assessment for Perfluorooctanoic Acid (PFOA) and Perfluorooctane Sulfonic Acid (PFOS).’”
Removing PFAS from biosolids is not straightforward. A few companies are optimizing technologies, such as gasification and pyrolysis, that can destroy PFAS in biosolids and create hydrogen gas and biochar as valuable by-products. It remains to be seen whether wastewater treatment plants will adopt such methods and how they will pay for the costs of a high-energy PFAS-destruction system.
In the meantime, some rural communities are turning to the courts to pursue liability claims and secure funding for cleanups. Class-action settlements in a few states have provided some relief to people with PFAS-contaminated water supplies. Other cases against chemical manufacturers and the Department of Defense are pending. And in a case that could set a precedent for future litigation, farmers are suing a company that makes biosolids-based fertilizers.
But few options are available for disposing of PFAS-contaminated biosolids. About 53% of biosolids in the US are applied to land as nutrient-rich fertilizer and soil amendments, according to 2018 data reported by biosolids industry groups and compiled by the National Biosolids Data Project. The rest are either landfilled or incinerated.
It’s unclear exactly where the 53% of biosolids are spread. The data are hard to get your hands on, says Jared Hayes, senior policy analyst at the Environmental Working Group (EWG), an environmental group. The 2018 industry data suggest that nearly 70 million acres of farmland in the US could be contaminated with PFAS from biosolids-based fertilizers, he says.
Farmers go to court
In June 2024, Public Employees for Environmental Responsibility (PEER), an advocacy group, sued the EPA on behalf of five Texas farmers (PDF), claiming that the EPA has failed “to perform its non-discretionary duty to identify and regulate toxic pollutants in sewage sludge” under the Clean Water Act.
The EPA has detected more than 350 hazardous chemicals in biosolids but has regulated only 9, all of which are metals, says Laura Dumais, staff counsel and environmental case manager at PEER. In their lawsuit against the EPA, the Texas farmers specifically point out that 18 PFAS are “present in sewage sludge in concentrations that may affect public health and the environment based on their toxicity, persistence, concentration, mobility, or potential for exposure.”
The five Texas farmers claim that their soil and water were contaminated with PFAS when a neighboring farmer spread a biobased fertilizer on crops. The contamination led to significant health consequences for the plaintiffs and caused devastating damage to their livestock, including stillborn calves with extremely high levels of PFOS in their livers, they allege.
The EPA filed a motion to dismiss the case in December, claiming that it has discretion under the Clean Water Act on whether to regulate toxic chemicals in sewage sludge. The court has yet to rule on that motion.
The five Texas farmers also filed a lawsuit against Synagro Technologies, which produced and sold the biobased fertilizer in question. The case, initially filed in the Circuit Court of Baltimore County in February 2024, was dismissed over jurisdiction issues and refiled this past February in the US District Court for the Northern District of Texas (case no. 3:25-cv-00445-K). Synagro disputes the plaintiffs’ claim that the PFAS contamination on their farms came from their neighbor’s use of a Synagro fertilizer product.
Synagro hired the engineering firm Parsons and Linda Lee, an agronomy professor and PFAS expert at Purdue University, to look for PFAS in its Granulite fertilizer and in water and soil samples from the plaintiffs’ farms.
In March, Synagro announced in a press release that the results show that the biosolids-based fertilizer spread on the farm could not have been the source of the PFAS found in fish and animals on the neighboring farms. Synagro has not made the results public.
The company claims that perfluoropropanoic acid (PFPrA) was found in every sample from the adjacent farms but not in the Granulite fertilizer spread on the farm. PFPrA data for the ponds, wells, and soils from the adjacent properties suggest another PFAS source, not Granulite fertilizer, Synagro says in the press release.
Kyla Bennett, director of science policy at PEER, disagrees with that conclusion. PFPrA is a degradation product “of all these other PFAS that were found in the biosolids,” she says. “They are forever chemicals, but they can change form.”
Synagro has sought to dismiss the case, which is one of the first lawsuits seeking to hold a biosolids-based-fertilizer company liable for PFAS contamination on farmland. The case could set a precedent for future litigation. But the widespread presence of PFAS in the environment has made proving causation difficult in such PFAS lawsuits.
To prevent further contamination of land from the application of biosolids, the EPA should require companies to filter PFAS from industrial discharges before they enter wastewater treatment plants, the EWG’s Hayes says. “The vast majority of PFAS found in biosolids is going to be from these industrial uses of PFAS that are entering into the waste stream.” After that, the EPA should address household sources of PFAS in wastewater and ban nonessential uses of PFAS in consumer products, he says.
Under the Biden administration, the EPA proposed a rule to regulate PFAS in industrial discharges. On day one of President Donald J. Trump’s second term, the White House Office of Management and Budget scrapped it. The withdrawal was part of an executive order to freeze rules that had not yet been finalized.
Patchwork of state action
In the absence of federal regulations, states have taken different approaches to managing PFAS in biosolids. Maine, where some of the first reports of PFAS contamination on dairy farms occurred, stopped allowing biosolids to be applied to land in 2022. Landfills in the state that accept biosolids are quickly filling up, and the state is searching for other solutions to deal with biosolids waste. A small fraction of it is shipped out of state.
In 2021, Maine’s legislature provided money to support the cost of testing milk for PFAS, Hennessey says. The state legislature also established a fund for testing soil and groundwater for PFAS at sites where biosolids were historically applied.
The Maine DACF has tested soil and groundwater for PFAS at about 150 agricultural sites in Maine, and as of May 30, 93 of them are considered impacted, Hennessey says. The state defines impacted as soil levels exceeding 6.4 ppb PFOS and water exceeding the state's interim drinking water standard of 20 parts per trillion for the sum of six PFAS.
Most of the 93 farms are still able to produce commercial products, despite the PFAS contamination. The impact of the contamination depends on the size of the farm, what they’re producing, and whether they can modify their operations, Hennessey says. Some farms didn’t need to modify operations at all, she notes. That’s because some crops take up more PFAS from soil or water than others do.
In addition to testing soil and groundwater, since 2021, the Maine DACF has conducted an intense sampling effort on farms to better understand how much PFAS to expect in crops like hay, corn, lettuce, and garlic for a given soil concentration, Hennessey says. “Today, we can focus primarily on testing the soil and any particular new irrigation source or water source of concern,” she says. “That can give us a really good understanding of what to expect in the crops and the vegetation without necessarily having to test those specific products every time.”
Water can be filtered to remove PFAS, but so far, no viable option exists for farmers to remediate soil that is contaminated with PFAS, Hennessey says. Changing crops, avoiding certain areas, and building raised beds with clean compost can help growers stay in business, she says. “Thankfully, we do have some resources to provide financial assistance to help folks as they're trying to make those sorts of changes,” she adds.
A few states have put limits on certain PFAS in biosolids applied to land. Maryland, Michigan, Minnesota, and New York have all adopted tiered approaches.
Under Michigan’s policy, implemented in January 2024, biosolids with PFOS or PFOA levels at or above 100 ppb are considered industrially impacted and cannot be applied to land. Wastewater treatment plants with industrially impacted biosolids must notify the state’s water-resource department, arrange for alternative treatment and disposal, sample source effluent, and investigate potential sources of PFOS and PFOA to the wastewater and biosolids.
Biosolids with PFOS or PFOA levels of 20–99 ppb are considered elevated and trigger a different set of requirements, including reducing land application, sampling source effluent, and investigating potential sources. Biosolids with PFOS or PFOA levels of less than 20 ppb can be applied without restrictions.
Michigan’s approach focuses on identifying significant sources of PFAS to municipal wastewater treatment plants and stopping that pollution at the source, before it gets to the treatment facility, says Stephanie Kammer, emerging pollutants section manager at the Michigan Department of Environment, Great Lakes, and Energy.
Michigan began investigating PFAS in biosolids in 2017 after finding PFOS in effluent from a chrome-plating facility. The facility had not used PFOS in more than a decade but was still discharging the chemical in its wastewater.
Following that discovery, in 2018, Michigan began requiring wastewater treatment plants in the state to determine which industrial users have the potential to discharge wastewater contaminated with PFAS and to sample wastewater from those users.
“Initially, we found five treatment plants that were industrially impacted,” Kammer says. The sources turned out to be a chrome-plating facility, firefighting foam used on a military base, and a fire truck leaking foam, she says. Those sources of contamination have since been remediated, she notes.
Engineering a solution
In some cases, major sources of PFAS are obvious and can be eliminated. But identifying sources of PFAS is not always easy for wastewater treatment plants because the chemicals are so prevalent in the environment and persist for decades. State regulations and the fear of litigation are driving some municipal facilities to consider installing technologies on-site at wastewater treatment plants to remove PFAS from their biosolids.
3 ways to destroy PFAS in biosolids
Gasification
Heartland’s HelioStorm: Voltage is applied across electrode pairs, creating a plasma with temperatures of 3,000–10,000 °C. Organic chemicals, including per- and polyfluoroalkyl substances (PFAS), in biosolids break apart in the active plasma field. The process makes synthesis gas, also called syngas, which can be used as fuel to generate electricity or as chemical precursors. Minerals are left behind in char, which can be used as building material. Before biosolids can be treated by gasification, they should be dried to 5–10% moisture.
Pyrolysis
CHAR Technologies’ high-temperature pyrolysis process: Solid materials are indirectly heated to over 800 °C in the absence of oxygen. Organic chemicals, including PFAS, break apart. Gases generated by the process can be used to produce natural gas or hydrogen, and char can be used as a soil amendment or building material.
Supercritical water oxidation
General Atomics Electromagnetic Systems’ PERSES: Solid materials must be ground to a particle size of 2–300 μm and prepared as a liquid slurry. The slurry is heated to 650 °C under a pressure of 4,000 psi. Under those conditions, organic chemicals, including PFAS, break apart. The process creates carbon dioxide and water. Halogens such as fluorine are ionized and immediately react with hydrogen to form acid, which is then immediately neutralized with sodium hydroxide. Sodium fluoride precipitates as a salt.
Such technologies are energy intensive, but they can also produce energy sources such as hydrogen gas. One technique ready for commercial-scale destruction of PFAS is gasification.
Heartland, a waste transformation company, is optimizing a gasifier to destroy PFAS in biosolids and create valuable products, like hydrogen gas and char, the latter of which can be used to make cement or asphalt. The company plans to deploy the system at a wastewater treatment plant in the next 12 to 18 months, says Catharine Reid, chief marketing officer at the firm. She declined to say where that plant is located.
The system, called HelioStorm, was initially developed by Peter Kong and colleagues at the US Department of Energy’s Idaho National Laboratory to create nanoparticles for research purposes. It evolved into a waste-to-energy gasifier, which was licensed to Cogent Energy Systems. Heartland acquired Cogent Energy Systems in 2022 with plans to optimize the gasification system for destroying PFAS in biosolids.
The HelioStorm gasifier consists of modular hybrid plasma reactors. Each system is about the size of a single-family refrigerator. Voltage is applied across electrode pairs within three zones, creating a plasma with temperatures of 3,000–10,000 °C throughout the reactor. Biosolids pass through the active plasma field. The process breaks apart organic chemicals, including PFAS, and produces synthesis gas, also called syngas, which can be used as fuel to generate electricity or as chemical precursors. Minerals are left behind in char, which can be used as building material.
Before biosolids can be treated by gasification, they should be dried to 5–10% moisture, says Brandon Davis, director of engineering gasification and biosolids at Heartland. The system can handle a higher moisture content, but that is not the most efficient way to evaporate water, he says. Most dewatered biosolids from sewage treatment plants contain 80–85% moisture, he notes.
Heartland engineers have been busy this year demonstrating the capabilities of a commercial-scale version of the HelioStorm to wastewater treatment operators at the company’s warehouse-sized technology center in Murfreesboro, Tennessee. Heartland plans to lease land from municipal facilities where it can install and operate the system to destroy PFAS in municipal biosolids. The company would charge a fee based on the amount of biosolids processed.
“The business model is build, own, operate,” Reid says. “So Heartland would keep ownership of the unit itself.” The company would build the system off-site and deliver it in shipping containers that are lifted into place on-site and interconnected, she says.
“We hear from customers that they are getting future ready,” Reid says. State regulations limiting PFAS in biosolids, especially in the northeastern US, are coming into play. Wastewater treatment plants are preparing for regulations coming down the line and considering options for adopting PFAS destruction into their processes and businesses, she says.
In a May 6 press release, Synagro also says it is taking a proactive approach to address the future needs of wastewater treatment plants. As part of the Water Environment Federation’s Residuals and Biosolids and Innovations in Treatment Technology joint conference held at the Baltimore Convention Center in early May, the company demonstrated a commercial-scale pilot pyrolysis process developed by CharTech Solutions at Baltimore’s Back River Wastewater Treatment Plant.
CharTech’s system indirectly heats solid materials in the absence of oxygen. Synagro and CharTech are planning to test the effectiveness of the process and optimize it for destroying PFAS in biosolids at the Baltimore facility through December, according to the press release. Synagro did not respond to a request for an interview or a demonstration of the pyrolysis process in time for this article.
Another PFAS-destruction technology, supercritical water oxidation (SCWO), is also amenable to treating biosolids. San Diego–based General Atomics Electromagnetic Systems announced in 2023 that its industrial SCWO system had successfully destroyed PFAS in biosolids provided by two Southern California waste-management facilities.
Called PERSES, the system was initially developed in the early 2000s to destroy propellants and explosives, says John Follin, director of strategic development for industrial supercritical water oxidation technologies.
About 4 years ago, the EPA came to General Atomics for help destroying PFAS in firefighting foam. The company has since had several contracts related to destroying PFAS in granular activated carbon, ion-exchange-resin beads, and firefighting foam, Follin says. Granular activated carbon and ion-exchange resins are commonly used to filter PFAS out of drinking water. The material eventually gets saturated with PFAS and needs to be replaced. Methods like SCWO can destroy PFAS in the spent material and keep the chemicals out of landfills.
The PERSES system operates at 650 °C and 4,000 psi. Under those conditions, organic compounds are ripped apart, Follin says. The process creates carbon dioxide and water. Halogens such as fluorine are ionized and immediately react with hydrogen to form acid. “But within microseconds at the very bottom, we introduce sodium hydroxide” to neutralize the acid and precipitate the halogens as salts, Follin says. Fluorine precipitates as sodium fluoride, the compound added to toothpaste to prevent dental cavities, he adds.
Solid materials like biosolids need to be ground up and prepared as a liquid slurry before they can be treated with the PERSES system. A particle size of 2–300 μm is generally acceptable, Follin says. “We want to make sure that everything that gets inside our reactor vessel comes out destroyed,” he says.
It remains to be seen whether municipal wastewater treatment plants will adopt technologies like gasification, pyrolysis, or SCWO and how they will pay for them.
Farmers have used biosolids as an inexpensive option for fertilizer for the past 30–40 years. “But now, with all this information that's coming out about PFAS and how dangerous it is in biosolids, farmers are seeing the writing on the wall and aren't going to want to purchase it anymore,” says Hayes at the EWG. “So wastewater treatment plants aren't going to have the same amount of customers that they had in years prior, and they're going to have to find some kind of other solution.”