Thermochemical processing for the sustainable disposal of spent filter waste

High-efficiency particulate air filters are widely used for indoor air purification. Spent filter waste (SFW), which can trap infectious and toxic substances, is primarily treated via incineration. This method causes environmental concerns, particularly regarding the generation of carbon dioxide (CO₂) and other air pollutants. To cope with these issues, this work proposes the pyrolysis of SFW using CO₂ as a sustainable alternative to conventional incineration. The introduction of CO₂ enhanced reactivity during pyrolysis, potentially offering a more sustainable process. The SFW consisted of filtered particles and two distinct filter/support layers, and the presence of toxic chemicals and primary polymer constituents was characterized. While CO₂ had a minimal impact on enhancing syngas production, owing to its slow reaction rate during SFW pyrolysis, adding a nickel-based catalyst significantly improved CO₂ reactivity. This resulted in a 649.7% increase in carbon monoxide (CO) production compared to that in pyrolysis under N₂. The potential of this pyrolysis system for reducing CO₂ emissions was evaluated against that of conventional incineration. Overall, this study presents a promising method for the pyrolytic conversion of SFW into combustible gases, particularly CO, while leveraging CO₂ utilisation to mitigate global warming.