ZeroPM removal workshop: Enabling a PFAS free circular economy for sludge through source control and pyrolysis

o Enabling a PFAS free circular economy for sludge through source control and pyrolysis Hans Peter H. Arp Norwegian Geotechnical Institute (NGI) Norwegian University of Science and Technology (NTNU) Contact: [email protected] ZeroPM Third International Workshop Removal through Technical Solutions Mytilene, Lesvos, Greece. 7th -8th October, 2025 “Pyrolysis solves the issue with organic contaminants in sewage sludge”1 1) Buss (2021) ACS Sust Chem. Eng. https://doi.org/10.1021/acssuschemeng.1c03651 2) Moško et al (2021) Chemos https://doi.org/10.1016/j.chemosphere.2020.129082 Figure: Buss (2021) ACS Sust Chem. Eng. https://doi.org/10.1021/acssuschemeng.1c03651 Boiling points deciding factor  volatilized or decomposed2 Is this really true for PFAS and other persistent contaminants? PFAS/PMT substances in wastewater Current state: Pollutants spreading and circulating in a carbon inefficient system Wastewater treatment Contaminated Effluent contaminated drinking water supply Contaminated Raw water Drinking water treatment Water reservoir GHG emissions PFAS and pollutants in atmosphere Contaminated Run off Contaminated Food supply Very contaminated Sludge Accumulation of PFAS/PMT substances in a circular water/sludge system Very contaminated waste water) waste water treatment Cleaner drinking water supply Cleaner Raw water Cheaper drinking water treatment Water reservoir Carbon and pollutants in atmosphere Cleaner Run off Cleaner Food supply Cleaner biochar Pyrolysis biochar production Very contaminated sludge C sequestration Solution: Removing contaminants, while getting energy and char from sludge Now add sludge biochar… PFAS sorbent biochar What happens to PFAS and other organic contaminants in pilot scan dry pyrolysis? Source: Sørmo et al (2023) JHazMat Photo: NGI Reduction of PFAS by >98% in sludge biochar PFAS decreased by factors of 10 – 1000, more loss with increasing temp dependence (> 95% loss at > 500 C) 60-100% fewer congeners Shift towards long chain PFAS (>6xCF2) Digested sewage sludge (DSS-1 and DSS-2), limed sewage sludge (LSS), de-watered sewage sludge (DWSS), food waste reject (FWR), waste timber (WT), garden waste (GW), & wood chips from forestry (CWC) Source: Sørmo et al (2023) JHazMat Sørmo et. al. Journal of Hazardous Materials,454, 131447. Sludge biochar as a wastewater filter for PFAS 716/10/2025 Sørmo, et al. Science of the Total Environment,922, 170971. LCA Comparison of Alternative Treatment Options Positives  Negatives  DescriptionTreatment category Nutrient recycling Contamination of PFAS, metals and other persistent contaminants Sludge placed directly on farms No treatment Nutrient recycling and biogas generation Contamination of PFAS, metals and other persistent contaminants Sludge placed directly on farms after anaerobic digestion Anaerobic Digestion energy recycling, P can be extracted (struvite) Carbon is lost, ash and flue gas management, air emissions* Dedicated sewage sludge incinerators Monovalent Incineration C-sequestration, fuel, P recycling Heavy metals concentrate in fertilizer, air emissions Heating dry sludge with no oxygen Dry-pyrolysis Further reading: https://www.umweltbundesamt.de/en/publikationen/technical-guide-on-the-treatment-recycling-0 https://www.eureau.org/resources/news/545-key-to-a-circular-future * Incinerators and co-combusters (also pyrolyzers?) need to fulfill air emission regulations, such as Directive 2010/75/EU and Directive 2001/80/EC Energy production: Pyrolysis and Incineration result in power benefits 1.4 41.8 -7.1 -38.7 -106.4 -162.6 -70.5 -203.9 -250 -200 -150 -100 -50 0 50 100 C1 C2 C3 (low T) C3 (high T) C4 (low T) C4 (high T) C5 C6 Electricity consumption [kWh/t-DW-SS] Anaerobic digestion De-watering Biogas upgrading Incineration CHP benefits (power) Drying Pyrolysis Incineration benefits (power) Net Electricity pyrolysis Incineration No treatment Biogas Pyrolysis after biogas production Incineration after biogas production Thank-you! Acknowledgments 16 Thanks to funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101036756 and Horizon Europe Program under grant agreement 101112723 Thanks to the Research Council of Norway, through the joint-industry sustainability (BIA-X) project “Valorization of Organic Waste” (VOW) (NFR 299070) and the Miljøforsk project SLUDGEFFECT (NFR 302371); On safe ground