Charcoal-type additives lock forever chemicals into sewage sludge fertiliser before it reaches soil
Arab M, Navarro DA, Smernik R, Kabiri S
Biochar
If you buy or receive compost-style biosolids for your beds, the biochar you already use in the garden belongs to the same family of materials shown to hold PFAS in place instead of letting them seep into soil and groundwater.
Sewage sludge is often spread on farmland as fertiliser, but it can carry long-lasting industrial chemicals called PFAS that wash out into soil and water. Researchers mixed in a small amount of activated carbon or biochar (a charcoal made from plant waste), and it trapped most of those chemicals. Activated carbon worked slightly better, and the heavier, longer-chain PFAS were held most tightly.
Key Findings
Across 22 Australian biosolids, 22 PFAS compounds were detected, with PFOS the most abundant at 11.3-107 µg/kg.
Adding 1% (w/w) granular activated carbon or biochar significantly cut PFAS leaching, with PFOS immobilisation above 85% in 80% of biosolids tested.
Activated carbon was slightly more effective than biochar, and long-chain PFAS were stabilised better than short-chain ones; pharmaceutical leaching also dropped, depending on the compound.
chevron_right Technical Summary
Mixing just 1% activated carbon or biochar into sewage sludge fertiliser locks up most of the 'forever chemicals' (PFAS) that would otherwise wash out. That could make land-applied biosolids safer for soil and water.
Abstract Preview
Original paper
Stabilisation of PFAS in biosolids by activated carbon and biochar: Implications for leaching control.
Biosolids, the major by-products of wastewater treatment plants (WWTPs), are widely applied to agricultural land as cost-effective fertilisers and soil amendments. However, they have emerged as a s...
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