This proof-of-concept project aims to demonstrate that radical initiated hydrothermal liquefaction (RI-HTL), a newly developed radical initiated version of hydrothermal liquefaction, will destroy per- and polyfluoroalkyl substances (PFAS) in aqueous film-forming foam (AFFF) concentrates with simultaneous conversion of the principal foam components (glycols, hydrocarbon surfactants etc.), into renewable fuels. This project will serve as the scientific foundation for future development of RI-HTL as part of a PFAS removal method during AFFF concentrate conversion into renewable fuels. 

Specific objectives of this project include the following:

1. Demonstrate that RI-HTL can be used to convert AFFF concentrates into useable hydrocarbon fuels (biocrude). This will serve as the baseline for biocrude carbon yield.
2. Develop sample preparation approaches so chemical analytical tools can characterize and quantify PFAS and fluoride in firefighting foams and the multiple products from RI-HTL treatment.
3. Assess the performance of RI-HTL for removal of PFAS during AFFF conversion to biocrude and determine the percent PFAS reductions possible by attempting a fluorine mass balance.
4. Use multiple non-target analytical tools to investigate and determine the fate of PFAS through the RI-HTL process, investigate the formation of potential fluorinated organic intermediates formed during PFAS breakdown, and evaluate potential reaction mechanisms.

This study is focused on evaluating the ability of RI-HTL to mineralize PFAS during the process of converting AFFF concentrates to biocrude oil, a precursor to renewable fuels such as renewable diesel and sustainable aviation fuel. The objectives are to (1) determine the percent reduction in PFAS concentrations achievable by adjusting RI-HTL conditions, (2) quantify production of usable hydrocarbons during AFFF treatment, and (3) balance energy input to the RI-HTL process with the energy recovered as hydrocarbon product. The aims are to make an initial attempt to close a fluorine mass balance demonstrating percent reductions of PFAS and extent of mineralization by measuring achievable reductions in PFAS concentrations and increases in fluoride. Achieving PFAS mass balance closure and tracking the fate of PFAS during the RI-HTL process will be enabled by the application of multiple non-target chemical analytical methods. A combination of target and non-target analytical methods will be applied to quantify PFAS on two types of AFFF and in the resulting fuels, water, ash/char, and gaseous emissions. 

Under this project, a PFAS treatment method will be developed to convert AFFF concentrate wastes into a valuable fuel product through RI-HTL. The potential benefit is two-fold, with PFAS destruction and repurposing of organics in AFFF to be used as diesel or jet fuel, ultimately leading to improved PFAS treatment options that will protect the warfighter and installation communities. (Anticipated Project Completion - 2026)