Environmental benefits from the use of CO2 in the thermal disposal of cigarette butts

Abstract

As the global consumption of cigarettes has increased, the massive generation of cigarette butts (CBs) has led to critical environmental and health problems. Landfilling or incineration of CBs has been conventionally carried out, but such disposal protocols have suffered from the potential risks of the unwanted/uncontrolled release of leachates, carcinogens, and toxic chemicals into all environmental media. Thus, this study focuses on developing an environmentally dependable method for CB disposal. Littered CBs from filtered/electronic cigarettes were valorized into syngas (H2/CO). To seek a greener approach for the valorization of CBs, CO2 was intentionally considered as a reaction intermediate. Prior to multiple pyrolysis studies, the toxic chemicals in the CBs were qualitatively determined. This study experimentally proved that the toxic chemicals in CBs were detoxified/valorized into syngas. Furthermore, this work demonstrated that CO2 was effective in thermally destroying toxic chemicals in CBs via a gas-phase reaction. The reaction features and CO2 synergistically enhance syngas production. With the use of a supported Ni catalyst and CO2, syngas production from the catalytic pyrolysis of CBs was greatly enhanced (approximately 4 times). Finally, the gas-phase reaction by CO2 was reliably maintained owing to the synergistic mechanistic/reaction feature of CO2 for coke formation prevention on the catalyst surface.