Research Paper
Turning wastewater waste into value: Pilot‑scale phosphorus recovery with biosolids biochar
Researchers at the Environmental Research Institute (ERI) have published new findings demonstrating how biochar produced from wastewater biosolids can be used to recover phosphorus (P) from wastewater effluent, while generating a nutrient‑enriched material suitable for reuse. The study provides a proof of concept for a pilot‑scale P recovery system that supports circular‑economy approaches across the water and agricultural sectors.
The paper, “Pilot-scale phosphate recovery with biosolids biochar: Performance, phosphorus bioavailability and biochar quality assessment” was led by Dr Sabolc Pap with Scottish Water through his IBioIC Feasibility Fund and has been published in the journal Separation and Purification Technology (Volume 395, 2026).
The research explored the performance of biosolids‑derived biochar (SSB‑O) as an adsorbent for P removal from final wastewater effluent, with a particular focus on meeting the stringent discharge limits introduced under the revised EU Urban Wastewater Treatment Directive. Using a pilot filtration unit packed with approximately 17 kg of biochar, the team assessed P removal under environmentally relevant conditions over an extended operational period.
In addition to treatment performance, the researchers evaluated the quality and reuse potential of the spent biochar. The P‑loaded material contained approximately 8% P₂O₅ and was enriched with beneficial macro‑nutrients such as calcium and potassium. Comprehensive chemical analyses showed that trace metals, polycyclic aromatic hydrocarbons (PAHs), and flame retardants (PFAS/PFOS) were present at concentrations well below limits set by the European Biochar Certificate and World Biochar Certificate guidelines.
Results indicated limited immediate P release and minimal risk of metal leaching, suggesting environmental compatibility. While additional studies are required to confirm long‑term nutrient‑release behaviour and agronomic value, the findings support the safe reuse of P‑enriched biochar in secondary applications.
Read the full paper:
Pap, S., Thompson, T., Gronbjerg, P.J., Kennedy, T., Cakin, I., Taggart, M.A., 2026. Pilot-scale phosphate recovery with biosolids biochar: Performance, phosphorus bioavailability and biochar quality assessment. Separation and Purification Technology, p.137760.
