## 2 Solid Waste Degradation of Fluorinated Compounds
### Incineration of Fluoropolymers  
As discussed previously, the electronegativity and small radii of fluorine cause C-F bonds to be exceptionally strong and, therefore, require high temperatures for destruction. On 16 th May 2000, the EPA and 3M, which at the time was the only manufacturer of PFOS, announced the phase out of PFOS because it was considered toxic, bioaccumulative, and persistent [88]. Research concerning potential precursors of toxic PFAS since this announcement has grown substantially as studies have been completed on commercial products treated with fluorinated polymers such as fabrics, non-stick cookware, and microwave popcorn bags [33; 89]. Studies have also been completed on the incineration or combustion of common fluorinated compounds to determine degradation products [2; 34; 35; 36; 37; 38; 39; 90]. [PERSON] et al., determined the unimolecular reaction rates to show that CF\({}_{4}\) molecules require 1440 \({}^{\circ}\)C for greater than 1 s to achieve 99.99% destruction [91]. Therefore, CF\({}_{4}\) molecules are a reference for the destruction removal efficiency (DRE) testing on the required temperatures, times, and turbulence during incineration [92]. Despite the ease of removing or oxidizing the polar functional groups such as decarboxylation, the resulting products of incomplete combustion (PIC) are not well understood [92]. A technique to better understand the PIC products of PFAS combustion was utilized during thermal treatment by direct- and indirect-fired thermal oxidation mitigation through a bypassing flame and packed bed reactor with Ca(OH)\({}_{2}\) to form CaF\({}_{2}\)[47] This approach provided a way to manage the hydrofluoric acid, carbon monoxide and carbon dioxide generated during decomposition in an elevated pH media to investigate and characterize the reaction products. A recent study by [PERSON] et al., 2015, showed that PFAS can be created from the waste handling of fluoropolymers at the end of useful life, specifically as a result of the municipal incineration of PTFE [47]. While PTFE is inert in the environment due to its high chemical and thermal stability, [PERSON] et al., 2014 found that municipal waste incinerators operating with a mean gas temperature of 1000 \({}^{\circ}\)C over the effective length of the reactor can be used to decompose PTFE [39]. Recently in 2019, [PERSON] et al., built upon this prior study and evaluated the potential formation of 31 PFAS compounds from the waste incineration of PTFE--one of the most common fluoropolymers used in industry [45]. This study also attemptedto validate that PTFE almost entirely transforms fluorine into hydrofluoric acid and a number of trace PFAS species ranging in concentration from 0.3 to 24 \(\upmu\)m/m\({}^{3}\) using incineration under standard municipal waste conditions [45]. The biggest challenge from the experiment was the probability of producing false positive results. To reduce their probability of false positive results using liquid chromatography with mass spectrometry (LC-MS/MS) detection methods, the experiment was scaled up to pilot plant incineration levels, meaning the solid combustion material input was orders of magnitudes larger than in lab-based simulations. Input materials were selected to minimize external contaminates, and paired t-testing was used to identify the presence of statistical differences between blank and PTFE spiked conditions. The 31 compounds selected were based on previous literature citations, occurrence in the environment, and availability of validated methods from commercial laboratories. A constant mass flow of wood pellets was utilized while adding PTFE to the reactor to maintain a consistent thermal profile, as shown in Figure 1. To analyze PFAS concentrations, they collected flue gas samples to test for compounds of interest after they cooled from roughly 850 to 1000 \({}^{\circ}\)C to below 300 \({}^{\circ}\)C, allowing for potential condensation reactions to occur.