Low-Pressure Hydrothermal Processing of Disposable Face Masks into Oils

A total of 5.4 million tons of face masks were generated worldwide annually in 2021. Most of these used masks went to landfills or entered the environment, posing serious risks to wildlife, humans, and ecosystems. In this study, batch low-pressure hydrothermal processing (LP-HTP) methods are developed to convert disposable face masks into oils. Three different materials from face masks were studied to find optimal processing conditions for converting full face masks into oil. The oil and gas yields, as well as oil compositions, depend on the feedstock composition, particle size, and reaction conditions. Yields of 82 wt.% oil, 17 wt.% gas, and minimal char (~1 wt.%) were obtained from full masks. LP-HTP methods for converting face masks have higher oil yields than pyrolysis methods in the literature and have lower operating pressures than supercritical water liquefaction. LP-HTP methods for face masks can increase net energy returns by 3.4 times and reduce GHG emissions by 95% compared to incineration. LP-HTP has the potential to divert 5.4 million tons of waste masks annually from landfills and the environment, producing approximately 4.4 million tons of oil.