This project is designed to evaluate gasification at a bench/laboratory level for ex situ thermal treatment and complete destruction of per- and polyfluoroalkyl substances (PFAS) in spent treatment system media, source zone soils, and aqueous film-forming foam (AFFF) concentrate. The objective is to collect field-impacted PFAS samples, process the samples using gasification, generate data using laboratory analytical methods to calculate destruction removal efficiency (DRE), and compare the DRE to 99.99% to evaluate effectiveness. Total fluorine, target PFAS, and non-target PFAS analyses will be completed to further understand PFAS degradation, transformations, byproducts formed during treatment, and the relationship of chemical concentration and treatment efficiency. This project will also measure the composition of synthesis gas (syngas) generated during gasification testing and evaluate the off-gas suitability for beneficial use, including compatibility with an advanced catalytic methanation technology that creates substitute natural gas (SNG) from the gasifier syngas. This project also aims to assess the syngas for emission control requirements, such as the extent of acid gas formation, and identify an analytical approach that adequately measures PFAS in air emissions.
First, go/no go testing will be conducted to measure the gasification DRE of target PFAS. Because field-impacted media may contain precursors and PFAS not currently targeted with available analytical methods, initial go/no go tests for the study will use samples spiked with target PFAS. This go/no go approach will provide a higher level of accuracy on PFAS DRE calculations and total fluorine mass balance by avoiding unknown PFAS potentially concentrated in field-impacted media. Following go/no go testing, if target PFAS are found to be 99.99% destroyed by gasification, similar testing will be conducted using field-impacted field media. During this step in the evaluation, additional analyses on co-occurring chemicals of concern and non-target PFAS will be conducted to evaluate an analytical approach that better evaluates the full destruction of PFAS and co-occurring chemicals of concern instead of select/targeted PFAS.
PFAS in the environment and the use of AFFF containing PFAS are a major concern, requiring investigations, controls, and cleanup of regulated PFAS and removal, disposal, and replacement of legacy AFFF once suitable replacement(s) are certified. Due to the stability of the carbon-fluorine bond in PFAS, the most common method to dispose and degrade PFAS is high temperature thermal incineration, making thermal destruction technologies a significant value. A better understanding of exhaust treatment requirements and an analytical approach to adequately measure PFAS in air emissions is of interest. Also, alternative and cost competitive thermal technologies are needed, particularly if the technology provides mobile treatment that can heat to known PFAS destruction temperatures and can process a wide range of PFAS-impacted matrices.
Mobile and fixed gasifiers are commonly used to provide high energy syngas using indirect heating on a diverse range of feed/fuels to temperatures greater than documented PFAS destruction temperatures. Gasification is immediately transferable to PFAS destruction for use as a commercially available thermal technology with resiliency to irregularities (e.g., heterogeneous material), high moisture content, and liquids that commonly impede other thermal technologies. In addition to rapid technology transfer, gasification will meet a variety of needs, most specifically for the small-scale, mobile, or large-scale treatment of field-impacted spent treatment system media and full destruction of PFAS and co-occurring chemicals of concern. Beneficial use of syngas generated during the gasification of PFAS-impacted matrices, such as the production of hydrogen fuel, methane, or other SNG, provide additional advantages, including an alternative energy option for remote locations where power and SNG pipeline distribution systems are not available.