A Review on Path Forward toward Sustainable Recycling of Waste Plastics through the Pyrolysis Route

Abstract

The relentless proliferation of plastic waste in landfills constitutes a profound environmental crisis, precipitating groundwater contamination, soil impoverishment, and ecological disequilibrium, while conventional recycling modalities remain prohibitively costly, energy-intensive, and environmentally deleterious. Pyrolysis, a thermochemical recycling route conducted under inert conditions, offers a promising alternative by converting diverse plastic feedstocks into fuels, chemicals, syngas, and hydrogen with energy yields comparable to those of conventional fuels. This review integrates mechanistic insights, kinetic modeling, and process simulations with a critical evaluation of sustainability bottlenecks that hinder industrial deployment of pyrolysis. Feedstock heterogeneity complicates product selectivity and requires advanced sorting and pretreatment. Catalyst deactivation from coke and impurities reduces long-term efficiency, while reactor scale-up faces challenges in heat transfer, residence time control, and fluid dynamics. Equally, misalignment between waste management and petrochemical industries limits integration of pyrolysis oils into existing cracker systems. Emerging solutions include pretreatment strategies to homogenize mixed plastics, bifunctional and mesoporous catalysts to enhance yields, and AI/ML-enabled reactor control to optimize nonlinear dynamics. Standardized data sets, life cycle assessments, and certification frameworks are emphasized as systemic enablers. By combining technical innovation, economic viability, and policy alignment, pyrolysis is positioned as a vital yet evolving technology for circular economy integration and sustainable plastic-waste valorization.