New research identifies how to design biochar for removing “forever chemicals” from irrigation water
image: Biochar selection for removal of perfluoroalkyl substances from reclaimed water for agricultural irrigation
Credit: Pia Ramos, Michael P. Schmidt, Richeng Xuan & Daniel J. Ashworth
A new study shows that carefully designed biochar can effectively remove harmful “forever chemicals” from recycled water used in agriculture, offering a promising and sustainable solution to protect food systems and public health.
Per- and polyfluoroalkyl substances, known as PFAS, are a group of persistent chemicals widely found in water, soil, and living organisms. Because they do not easily break down, they can accumulate in crops and enter the human food chain. Recycled water used for irrigation is one of the main pathways through which PFAS can reach agricultural systems.
In a new study published in Biochar, researchers conducted one of the most comprehensive evaluations to date of how biochar properties influence PFAS removal.
“Biochar has strong potential as a low-cost and sustainable material for removing PFAS from water, but not all biochars perform the same,” said lead author Pia Ramos. “Our goal was to understand which properties matter most so we can design or select biochars that work reliably in real-world conditions.”
Biochar is a carbon-rich material produced by heating organic waste such as wood, crop residues, or manure in low-oxygen conditions. It has already been widely studied for soil improvement and carbon sequestration, but its role in water treatment is rapidly gaining attention.
In this study, the team analyzed 24 different biochars made from agricultural waste materials including pine wood, grass clippings, walnut shells, and cattle manure. These biochars were produced at different temperatures and characterized using 17 physicochemical properties, such as surface area and elemental composition.
The researchers then tested how well each biochar removed a range of PFAS compounds from water. They found that performance varied widely depending on the material’s properties.
Long-chain PFAS compounds such as PFOS were removed very effectively, often exceeding 90 percent removal. Short-chain PFAS, which are typically harder to capture, showed more variable removal rates but could still be significantly reduced under the right conditions.
The study identified key factors that control PFAS removal, including specific surface area and the ratios of carbon, nitrogen, and oxygen in the biochar. These properties influence how strongly PFAS molecules attach to the biochar surface.
Using these insights, the researchers developed predictive models that estimate PFAS removal based on measurable biochar characteristics. These models were then used to select a commercial biochar that demonstrated excellent performance across multiple PFAS compounds, including those that are typically difficult to remove.
Importantly, the study also tested performance in treated municipal wastewater, which more closely resembles real irrigation water. While many biochars showed reduced performance in complex water conditions, the optimized biochar maintained high removal efficiency, highlighting its practical potential.
The researchers further explored regeneration strategies and found that simple thermal treatment could restore or even improve biochar performance over repeated use. In some cases, removal of short-chain PFAS increased two to five times after treatment.
“These findings show that biochar can be engineered not only to remove PFAS effectively, but also to remain functional over multiple cycles,” said co-author Daniel J. Ashworth. “That is critical for scaling up this technology for agricultural water treatment.”
The results provide a framework for selecting or designing biochars tailored for PFAS removal, supporting the development of low-cost filtration systems for irrigation water.
As concerns over PFAS contamination continue to grow, this research highlights a pathway toward practical and sustainable solutions that protect both environmental and human health.
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Journal Reference: Ramos, P., Schmidt, M.P., Xuan, R. et al. Biochar selection for removal of perfluoroalkyl substances from reclaimed water for agricultural irrigation. Biochar 7, 56 (2025).
https://doi.org/10.1007/s42773-025-00436-4
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About Biochar
Biochar (e-ISSN: 2524-7867) is the first journal dedicated exclusively to biochar research, spanning agronomy, environmental science, and materials science. It publishes original studies on biochar production, processing, and applications—such as bioenergy, environmental remediation, soil enhancement, climate mitigation, water treatment, and sustainability analysis. The journal serves as an innovative and professional platform for global researchers to share advances in this rapidly expanding field.