Abstract In this study, CO2 was used as a reaction medium in the pyrolysis of printed circuit boards (PCBs), thus providing a novel route to mitigate the evolution of harmful chemical species during the thermal degradation of PCBs. For example, this study showed that CO2 acts as an effective carbon scavenger during the pyrolysis of PCBs. CO2 facilitated the thermal cracking of volatile organic compounds (VOCs) that evolved from the thermal degradation of PCBs. As a result, CO2 mitigated the evolution of various harmful pollutants such as phenol and benzene derivatives, PAHs and brominated pollutants, which resulted in the increased generation of syngas (H2 and CO). This study indicates that using CO2 as a reaction medium could lead to the development of a more environmentally benign process for the thermal treatment of PCBs and other harmful and/or refractory wastes.