PFAS characterization and behavior in Waste-to-Energy technologies

PFAS (per- and polyfluorinated alkyl substances) are a group of anthropogenic organic chemicals comprising more than 4,700 different substances that are highly persistent in the environment and in the human body. Due to their peculiar physico-chemical characteristics and properties (e.g., water-, oil- and dirt-repellent, flame retardant or non-flammable, high thermal stability) thousands of PFAS are largely applied as additives in commercial products (e.g., textiles, paper, firefighting foams) and end up among the waste feed to WtE plants. Even if combustion is indicated as one of the process alternatives applicable for effective destruction of a large variety of PFAS, the very strong C-F bonding pose a challenge both in terms of the possibility of incomplete mineralization than in the formation of parent compounds, even at trace levels commonly detected in feedstocks. The study reports the principal results of a scientific literature analysis conducted to obtain an overview of most significant issues related to PFAS in the field of waste-to-energy processes, including the occurrence of PFAS compounds in wastes and related European regulatory framework, combustion of PFAS containing waste in WtE plants and general measurement issues regarding their content in gaseous, liquid and solid samples, with a final review on technical and research gaps still to be filled out. Major conclusions of review show PFAS thermal destruction as an efficient alternative at the conventional operating condition of WtE plants; nevertheless, the wide spectra and variability of compounds potentially present in waste streams and the limited availability of standard measurement methods for the compounds still result in poorly documented investigations on real-world WtE plant experimental evaluations and on the corresponding emissions of PFAS and related by-products.