11. Pyrolysis of Plastic Wastes Towards Achieving a Circular Economy: An Advanced Chemistry and Technical Approach

The increasing use of plastics has led to increased dump heaps of industrially and domestically generated plastic waste in the environment due to poor plastic waste disposal management, which are sources of serious environmental pollution due to associated non-renewable fossil sources. The limited nature of fossil fuels, which are the major source of plastic, have made circular economy approaches more attractive, which bring about sustainability via plastic waste reduction, recycling, and reuse. Pyrolysis of plastic in a thermal reactor free from O₂ interference at a temperature range of 300–800 °C degrades larger polymeric chains in plastics into lighter and higher-value-added oil derivatives, which could serve the purpose of domestic or industrial fuel and raw materials for making new plastics. Pyrolysis releases less environmental pollutants as compared to conventional methods of waste management (combustion, incineration, and landfilling). The present study provides a comprehensive analysis of the complex composition of plastic waste and the consequential ramifications for conventional waste management methodologies. The paper explores the fundamental principles of pyrolysis, emphasising the significance of temperature, reaction medium, and catalysts in increasing product yields and pyrolysis oil quality. This study provides a comprehensive insight of advanced analytical methods, including spectroscopy, chromatography, and microscopy, that are used for the characterization of pyrolysis products. The utilisation of these techniques allows for a more profound comprehension of reaction pathways. Moreover, this study discusses the several pyrolysis products that arise from the process of plastic pyrolysis, including liquid fuels, gases, and solid wastes, and highlights their possible utilisation in a wide range of sectors. The adaptability of pyrolysis technology and its contribution to resource efficiency are shown by its emphasis on transforming waste plastics into chemicals, fuels, and feedstocks via the process of upcycling. Economic feasibility and environmental impacts are also evaluated, considering energy consumption, emissions, and life cycle assessments to provide a holistic perspective on the sustainability of pyrolysis-based circular economy solutions. This paper underscores the importance of regulatory frameworks and policy incentives to foster the integration of pyrolysis technologies into existing waste management systems. Additionally, challenges related to feedstock variability, scale-up, and technology optimisation are discussed alongside ongoing research efforts and potential future directions.