Experimental and theoretical investigation of plastic waste pyrolysis for environmental management in Kinshasa, Democratic Republic of Congo

Abstract

Abstract This study examines the potential of pyrolysis as a method of converting plastic waste into fuel in Kinshasa, in the Democratic Republic of Congo (DR Congo), a city facing major environmental challenges due to plastic pollution and energy shortages. The research focuses on the pyrolysis of polyethylene terephthalate (PET), high-density polyethylene (HDPE) and polypropylene (PP) plastics, with the aim of producing clean, affordable energy while tackling the growing problem of plastic waste. The methodology involved collecting plastic waste from local rivers, followed by a slow pyrolysis process that yielded liquid products exhibiting physicochemical properties comparable to those of gasoline and diesel according to selected ASTM quality parameters. The results show that PP gives the highest oil yield, while mixed plastics show variable results depending on their composition. The physicochemical properties of the oils obtained were analysed, demonstrating their potential as alternative fuels. Engine performance evaluations of gasoline–pyrolysis oil blends demonstrated that partial gasoline substitution with crude pyrolysis oil increased brake torque while simultaneously reducing brake specific fuel consumption under the evaluated operating conditions. This study highlights the feasibility of using waste plastics through pyrolysis to contribute to a circular economy, reduce environmental pollution and provide sustainable energy solutions in Kinshasa. Further research is recommended to optimize the pyrolysis process and explore large-scale implementation. Theoretical calculations using quantum chemistry methods at the G4 and M06-2X levels showed that the pyrolysis of polyethylene and polypropylene is initiated by C–C bond scission, with associated energies ranging from 80 to 95 kcal/mol.