Tackling PFAS Contamination of Farm Land in Unity, Maine Using Biochar

Biochar Delivery at Hunter Farm, June 2024

pROJECT OVERVIEW

Unity, Maine has become the center of a groundbreaking research project aimed at introducing biochar into PFAS-contaminated soil to reduce crop uptake and leaching of PFAS into groundwater, as well as improving soil health. Northern Tilth, LLC, working with Hunter Farm and Purdue University, is leading the study, which has been actively underway since October 2023 and is expected to conclude in June 2026. The research explores the utilization and effectiveness of biochar incorporation into PFAS-contaminated soil at Hunter Farm, aiming to reduce PFAS uptake and improve overall soil health. The project is titled “Biochar Use to Reduce Crop Uptake of PFAS and Improve Soil Health.”

PFAS Contamination Background

Per- and polyfluoroalkyl substances (PFAS), also notoriously known as “Forever Chemicals,” are a group of human-produced pollutants that have contaminated soil and water sources for decades. PFAS have been used widely in industrial and consumer products since the 1940s for their resistance to grease, oil, water, and heat. Originally implemented for their water-repellent properties, they are commonly used in various consumer products. Widespread use in the environment has led to the contamination of organic matter-based soil amendments, resulting in the PFAS contamination of agricultural soil, water sources, and waste such as compost. This problem has become especially apparent in Maine, where an increasing number of farms are finding their fields unfarmable. Grass feed for cattle and, subsequently, dairy products are especially at risk, as studies have shown certain grass species have higher rates of PFAS transfer from soil to crop. PFAS may lead to adverse health effects if consumed. Although some PFAS have been phased out from commercial use,  they continue to linger in the environment due to an abundance of historical application. 

Utilizing Biochar for PFAS Remediation

Biochar is a carbon-dense material produced by the pyrolysis of organic matter such as wood or manure. Biochar has a unique ability to sequester carbon, reducing the emission of climate-changing chemicals called greenhouse gasses. The study’s hypothesis is that biochar may have the ability to lock PFAS in place and reduce leaching and uptake of plants, due to its ‘adsorptive’ ability to hold onto qualities and cation exchange capacity (via a negative electrical charge that makes it ‘sticky’), which prevent crops from absorbing the chemical through contaminated water. By sequestering carbon back into the soil and increasing the soil’s maximum water retention, it reduces the mobility of harmful chemicals like PFAS in soil and groundwater. 

Boiochar has a strong affinity for organic chemicals which may allow it to adsorb PFAS at an increased level. Amongst a variety of benefits that biochar can deliver to sustainable agriculture, biochar is generally considered safe to use as it is produced from organic materials like woody biomass and there are no expected health risks involved with the application of biochar. 

Presenting the Study at Hunter Farm

Historical application of sludge has left many agricultural fields in Maine useless. Farmers are losing valuable land and resources to PFAS contamination. The study taking place in Unity, Maine, aims to explore various ways to tackle PFAS contamination and explores how biochar can be incorporated into affected soil with the goal of reducing PFAS uptake and improving soil health to restore farmland. Northern Tilth has had experience using biochar-like material in the past to successfully sorb pesticides in pesticide-contaminated composts.  Based on practical, field-based experience and based on the ability of activated carbon to filter organic compounds out of water and air, it seems probable that this same phenomenon could take place in a soil environment.

The research at Hunter’s farm will complement statewide efforts to characterize the extent of issue in Maine. The progressive response led by the state of Maine has brought together several agencies, including the Department of Agriculture, Conservation and Forestry (DACF), and the Department of Environmental Protection; food system leaders such as the Maine Organic Farmers and Gardeners Association and the Maine Farmland Trust; and scientists across UMaine.

Until recently, Hunter cultivated organic vegetable crops and forage for dairy cows on approximately two-thirds of the 150-acre property. The farm’s business screeched to a halt in early 2022 when a neighboring farmer who purchased hay from Hunter said that it tested positive for PFAS. At Hunter and her son Keith’s request, Northern Tilth  methodically collected dozens of soil and water samples to find out where and how much PFAS had accumulated on the farm. Lab results from Northern Tilth arrived in April 2022, and they were jarring. Most of the property was contaminated, including the unfarmed wetlands and groundwater used for irrigation and drinking water.

“It was devastating, it really was,” Hunter says. “We’re farmers, and we love our land. We love this place. It’s home to us. I’ve been a farmer since I was 17 years old.” Once the PFAS was identified on the farm, Hunter started to study the results. She noticed that soil contamination levels varied widely between parcels and wondered if that may make the property well-suited for conducting experiments about PFAS. She reached out to Nancy McBrady, deputy commissioner of the Maine DACF, who, in turn, connected Hunter with Diane Rowland at the University of Maine.

“The property is perfectly suited to the types of questions that we need to ask and answer about PFAS,” says Rowland, dean of the College of Natural Sciences, Forestry, and Agriculture and director of the Maine Agricultural and Forest Experiment Station, who also serves on the state PFAS Fund Advisory Committee. “Setting up an experimental condition with variable PFAS levels and past data collection like Sue has on her farm would take millions of dollars and decades to create. Farmers like Sue are extremely brave to come forward and turn a tragic situation into an opportunity to accelerate vital research on this issue.”

The site access agreement between Hunter and UMaine will provide researchers access to the farm’s land, water, and equipment to study PFAS bioaccumulation factors in natural and farm settings.The study will be conducted over a two field season timeframe and will include several field trials on Hunter Farm. The biochar will be used to treat two fields with different PFAS levels, as well as a control plot for both, in which only tilling will take place. Soil from each plot, including the control plots, will be collected at random before the treatments are applied.  Grass samples seeded in the plots will be sampled four times over the two field seasons.  Both the soil and the grass will be analyzed in a lab for PFAS contamination levels. Purdue University will conduct the PFAS analysis, while the University of Maine’s soil testing services will analyze the soil for soil health parameters, pH levels, and nutrient composition.

Approximately 60 cubic yards of biochar, produced by Standard Biocarbon, a biochar facility located in Maine, was introduced as one of three biochar types being evaluated. Grass will be planted in the soil and harvested the following season. This will be repeated for the following growing season. The soil itself will also be collected and analyzed both before and after biochar incorporation.

Expected Outcome of the Study

The study hopes to achieve significant changes in the PFAS levels of contaminated soil and analyze the effects biochar can have in treating PFAS contamination. The goal is for farmers to utilize the study results to treat PFAS contamination effectively.

Conclusion

Conducting this study at Hunter Farm may uncover innovative ways for farmers to utilize biochar to affordably reduce PFAS contamination while continuing to farm their land. Demonstrating biochar's unique ability to reduce PFAS uptake and improve soil health, this project aims to add to a growing body of evidence that biochar can play an important role addressing the critical challenge of removing toxins from agricultural soils.