Study models a lower-cost approach to PFAS in farmland

What you need to know

• The approach links three steps: rock amendments to raise soil pH and support plant uptake, plants to draw PFAS from the soil, and thermal treatment of the harvested biomass. The resulting biochar may then be returned to the soil. 12
• The study’s median estimate is about US$1,460 per hectare per year when carbon-removal value is counted. Without carbon crediting, the estimate rises to about US$4,200 per hectare per year, so the lower figure is not independent of assumptions about carbon revenues. 1
• The paper describes a possible 20-year programme. These are projected costs and timings, rather than results from a completed clean-up programme using the full method. 12
• The analysis focuses mainly on PFOS and PFOA. Its remediation estimates draw on modelling informed by soil data and published relationships between plants and PFAS uptake, rather than a field trial of the combined system. 1
• The paper also estimates that national deployment in the US could remove about 10.5 million tonnes of carbon dioxide per year. This is a modelled potential, not an observed result, and depends on the proposed approach being deployed at scale. 1

Why this matters

The proposal addresses PFAS in farmland with a treatment pathway that could, according to the study’s estimates, cost less than conventional clean-up. For practitioners assessing remediation options, the distinction between projected savings and demonstrated performance is important. 123

What happens next

Field demonstrations would need to test whether the modelled removal rates, costs and timelines hold across different soils and contamination levels. Further evidence is also needed on biochar’s long-term performance and on the products and fluorine balance of thermal treatment. 1

What we know

• The proposed treatment combines alkaline rock amendments, plant uptake of PFAS and thermal processing of harvested biomass, with possible reapplication of the resulting biochar. 12
• The analysis focuses primarily on PFOS and PFOA and uses modelling informed by soil data and published plant-uptake relationships. 1
• The estimated annual cost is about US$1,460 per hectare with carbon-removal value included, compared with about US$4,200 without carbon crediting. 1
• The paper estimates potential carbon removal of about 10.5 million tonnes of CO₂ per year under national deployment in the US; this is a projection, not a measured outcome. 1

What we don't know

• It is not yet established whether field demonstrations will confirm the projected PFAS removal rates, treatment times and costs across different soils and contamination levels. 1
• The long-term stability of PFAS immobilisation by biochar under field conditions remains uncertain. 1
• A complete fluorine mass balance for the thermal treatment has not been demonstrated, leaving questions about how reliably the process handles PFAS and its treatment products. 1
• It is unclear whether carbon-removal revenues will be available at the assumed value to support the lower cost estimate. 1

Read the reporting

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