Fate of per- and polyfluoroalkyl substances through commercial composting facilities

Rising concerns about solid waste management globally necessitate the adoption of sustainable practices, particularly in dealing with organic waste, which constitutes a significant portion of municipal solid waste (MSW). Composting is an effective waste management strategy that can reduce both the environmental impact and greenhouse gas emissions of organic wastes, while producing valuable organic material (compost) for soil enhancement. However, the presence of persistent contaminants such as per- and polyfluoroalkyl substances (PFAS) in compost poses environmental and human health risks, challenging the sustainable management of organic wastes. This study investigates the fate of 33 PFAS compounds in two composting systems-windrow and in-vessel-focusing on the transformation and persistence of these compounds through the composting process, with the aim of collecting information which will support the identification of strategies to mitigate PFAS contamination in composting practices. The findings indicate significant reductions in total PFAS concentrations after composting, with reductions of 88.3% and 86.3% in the windrow and in-vessel systems, respectively. Notably, certain PFAS compounds, such as PFBS, appeared after composting, while PFPeA, became undetectable, suggesting potential leaching or transformation. Across both leachate and dust samples, PFAS concentrations were relatively low, with only a few compounds detected in each matrix. The final compost products met Australia's proposed NEMP 3.0 guidelines. However, considering the variation in PFAS content within similar categories of waste (feedstock), compliance with regulatory limits may vary. These results highlight the need for continued research into PFAS behaviour during composting and the development of best practices to mitigate contamination risks.