Mechanistic Insights Into PFAS Distribution And Leaching In Compost-An Unique Environmental Matrix

North Dakota State University Fargo, Fargo ND

Investigators

Abstract

Composting is a widely used method for managing organic waste and producing nutrient-rich fertilizers. About 35% of U.S. households use compost for gardening. However, recent studies have found that compost can contain PFAS — a group of harmful, long-lasting chemicals. These chemicals can accumulate and move through compost piles in unexpected ways, eventually ending up in soil and water when compost is applied. This project will investigate how PFAS behave in compost under different environmental conditions. By understanding the factors that influence PFAS movement through compost, the project will help make composting safer. The findings will support public health, guide regulatory decisions, and raise awareness through outreach to communities, students, and composting facilities. The project focuses on understanding the fate and transport of per- and polyfluoroalkyl substances (PFAS) in compost, a unique and environmentally relevant matrix used in organic waste management. Unlike relatively static matrices such as soil or sediment, compost exhibits dynamic physicochemical properties—including high porosity, elevated levels of dissolved organic matter (DOM), temperature gradients, and variable hydraulic conductivity—that evolve with feedstock type and compost maturity. To develop a mechanistic understanding of PFAS fate and transport in compost, the project will pursue three integrated objectives: (1) elucidate how compost temperature gradients, physicochemical characteristics, and hydraulic properties influence precipitation-induced PFAS leaching; (2) investigate PFAS leaching mechanisms under freeze-thaw conditions; and (3) evaluate the role of PFAS molecular isomerism on leaching behavior. Laboratory experiments will be conducted, including batch desorption studies, saturated column tests, and large-scale unsaturated column experiments using mature composts derived from different feedstocks (e.g., yard waste, food waste). PFAS leaching potential will be evaluated under realistic environmental conditions, including simulated precipitation events and seasonal freeze-thaw cycles. The research will employ advanced analytical techniques such as fluorescence excitation-emission matrix spectroscopy to characterize DOM composition, molecular weight fractionation to assess DOM size distribution, and isomer-specific PFAS quantification. Extractable organic fluorine (EOF) and total oxidizable precursor (TOP) assays will complement targeted PFAS analyses, offering a broader perspective on known and unknown PFAS pools. Air–water interfacial partitioning behavior will be measured to assess the impact of compost porosity on PFAS retention, particularly in unsaturated conditions. Flow-interruption tracer studies and non-reactive tracer modeling will provide insights into kinetic limitations and mass transfer phenomena relevant to PFAS mobility. The findings will support the development of mitigation strategies such as compost washing and help shape future regulatory frameworks. The project will include targeted outreach to industry and regulatory stakeholders, public education campaigns at composting sites, and hands-on training for undergraduate and graduate students, fostering PFAS literacy and improved public health. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.