A Unified Classification of Waste Plastic Chemical Recycling: Pyrolysis, Gasification, Depolymerization, and Dissolution.

Waste plastic valorization has become a critical challenge in achieving global circular economy goals and mitigating climate change. However, the field suffers from fundamental inconsistencies in terminology and classification that impede scientific communication, technology development, and policy formulation. This study critically analyzes existing classification frameworks for waste plastic valorization technologies and identifies major sources of confusion: (i) ambiguous classification of dissolution processes across physical and chemical recycling categories; (ii) conflation of dissolution with chemical depolymerization despite their distinct mechanisms and products; (iii) inconsistent definitions of pyrolysis and gasification that blur the distinction between fundamentally different thermochemical processes; (iv) arbitrary temperature-based subcategorization of pyrolysis lacking scientific basis; and (v) misleading designation of energy recovery as "thermal recycling." I propose a coherent classification scheme based on process-type logic: dissolution is repositioned within chemical recycling based on its operational characteristics, chemical recycling and feedstock recycling are explicitly differentiated, and energy recovery is divided into direct (combustion of waste plastic) and indirect (combustion of thermochemically-derived fuels) pathways. This unified framework aims to establish a common foundation for education, research, and evidence-based policymaking in sustainable waste plastic management.