Methodology for Comparative Analysis and Yield Optimization of Different Plastic Wastes via Thermal Pyrolysis

Abstract

The rapid increase in global plastic consumption has created significant environmental challenges. Only ~9% of the ~370 Mt of plastic waste generated annually is effectively recycled, underscoring the urgent need for alternative strategies. Thermal pyrolysis is a promising waste-to-fuel technology that converts mixed plastics into valuable hydrocarbon fuels under oxygen-limited conditions. Remarkably, thermal depolymerization processes (pyrolysis or hydrothermal liquefaction) can achieve plastic-to-oil conversions exceeding 90% under optimal conditions. For common plastics (LDPE, HDPE, and PP), liquid-oil yields ranging from 74–82% were experimentally obtained in this study under optimized thermal pyrolysis conditions, while literature reports indicate yields up to 90–95% under advanced catalytic conditions. In this study, a comparative methodology is developed to optimize yields from different plastic wastes. The effects of key parameters (temperature, catalysts, feedstock composition) on product distribution has been examined. Catalytic pyrolysis (using zeolites, CaO, red mud, etc.) is evaluated for its effect on oil quality. The study also discusses the future potential of integrating machine-learning techniques for pyrolysis process optimization. Results show that optimized pyrolysis of polyolefins produces predominantly liquid fuels with high calorific value (~46 MJ/kg) and minimal char, while capturing hazardous by-products (HCl) effectively. The findings demonstrate a viable pathway for converting waste plastics into energy, supporting sustainable waste management and a circular carbon economy.