Environmental impact of PFAS incineration

Abstract

A first-order thermodynamic model for the incineration of poly- and per-fluorinated alkyl substances (PFAS) in aqueous film-forming foam (AFFF) in a rotary kiln incinerator (i.e., a typical hazardous waste disposal) as well as decomposition at lower temperatures used in waste-to-energy incineration processes is used to discuss the global warming potential (GWP) impact of such incineration. Approximate orders of magnitude of tons of CO₂ per ton of AFFF combusted are determined based on AFFF disposal data from a survey on the incineration of the US military’s AFFF supplies for complete and incomplete combustion of the AFFF wastewater. The model suggests that incomplete combustion of fluorosurfactants at low temperature will result in the release of high GWP waste products such as CF-alkanes. The risk of incomplete PFAS combustion may be amplified with diluted AFFF streams as the net reaction will be endothermic, potentially depressing the reactor temperature and promoting the formation of high-GWP byproducts. For more complete combustion cases evaluated, the estimated emission is on the order of 2 metric tons of CO₂ per ton of AFFF combusted. In the worst-case scenario with CF-alkane release, the expected emission is between 439 and 537 metric tons of CO₂ per ton of AFFF combusted. In this scenario, the incineration impact of 10,007 metric tons of AFFF combusted is equivalent to the emissions resulting from firing an average coal-fired power plant for approximately 3.6 years or the annual emissions of approximately 1 million automobiles.