Plastic Valorization into Added-Value Products via Microwave and Conventional Pyrolysis: A Review

Abstract

Plastics are indispensable due to their versatility and low cost, but their accumulation poses major environmental challenges. Conventional waste management methods like landfilling, incineration, and mechanical recycling are inadequate, spurring interest in advanced valorization techniques. Pyrolysis offers a pathway to convert plastic waste into value-added products; however, traditional pyrolysis is energy-intensive, requiring high temperatures and long reaction times. Microwave-assisted pyrolysis (MAPP) has emerged as a superior alternative, enabling rapid heating (up to 50 °C/min), lower temperatures (≤500 °C), and shorter reaction times (∼10 min). MAP improves energy efficiency, yield, and selectivity toward valuable fractions such as bitumen, toluene, xylene (BTX), and medium-chain olefins. This review uniquely compares conventional pyrolysis and MAP for plastic waste conversion, analyzing process fundamentals, reactor designs, catalyst innovations (hierarchical, metal-modified, regenerable types), and product outcomes. Life cycle assessment data reveal MAP’s lower greenhouse gas emissions and water use compared to conventional pyrolysis, landfilling, and incineration. This work also highlights emerging applications, including hydrogen, jet fuel analogues, carbon nanotubes, and CO2 adsorbents from char, especially from underexplored plastics like PET, PS, and PVC. This work also systematically compares literature data across multiple studies, presenting the results in tabular form, while the identified gaps in catalyst standardization and product optimization delineate important directions for future research.