Herein, CO2 is employed as a pyrolysis medium for thermal treatment (i.e., pyrolysis) of polyethylene terephthalate (PET) waste in an environmentally benign way. The CO2-assited pyrolysis provides a novel way to not only enhance energy recovery from the PET waste but also reduce acidic byproducts such as benzoic acid. The generation of carbon monoxide (CO) for pyrolysis of the PET waste in CO2 is similar to 5 times more than that in N-2. In addition to the enhancement of CO generation, the compositions of benzene derivatives, PAHs, and acidic compounds are lower in pyrolytic products in CO2 than that in N-2. This study suggests that the employment of CO2 in pyrolysis of PET waste would be a more environmentally friendly waste treatment process with enhancing energy recovery. (C) 2017 Elsevier Ltd. All rights reserved.