MANY MINDEDA soil cleanup for 'forever chemicals' that could cost a fraction of today's methods
Researchers led by Jake Thompson of Yale University published in PNAS a method for stripping PFAS — the persistent 'forever chemicals' — from contaminated soil at far lower cost than existing options. The team estimates current PFAS removal from US farmland runs roughly $800,000 to $1.6 million per hectare, an $8 trillion problem nationally. Their proposed method is estimated at about $29,000 per hectare if repeated for up to 20 years.
The approach works in stages. Crushed alkaline rock, such as basalt or limestone, is applied to raise soil pH toward 7, which increases the mobility of PFAS. Plants like hemp and perennial grasses that accumulate the compounds are grown, harvested, and pyrolyzed into biochar; that biochar, reapplied, can lock down residual contamination. The researchers estimate national adoption could also draw down 10.5 million metric tons of carbon dioxide per year.
Contamination is widespread: millions of dry metric tons of sewage biosolids are spread on US soils annually, much of it carrying PFAS, and the carbon-fluorine bond means these chemicals persist for thousands of years. A cheaper remediation route matters for the shared environment and for the farmland that feeds people, turning an unaffordable cleanup into a possibly practical one.
The honest limits: this is a modeled, US-focused study, with cost and carbon figures dependent on following the process exactly. PFAS behavior during pyrolysis carries many unknowns, and a recent study suggests temperatures of at least 800°C may be needed. The projected contamination trajectories are modeled with confidence intervals, not observed field results.
Source: ScienceAlert