Upcycling of waste plastics: strategies, status-quo, and prospects

The exponential growth in plastic production over the last fifty years has not only propelled global economic growth but also led to an alarming environmental dilemma: plastic pollution. As reliance on plastics, particularly single-use packaging, intensifies worldwide, the imperative to enhance waste plastic recycling emerges as a critical global issue for sustainable resource utilization and ecological conservation. In 2019, the production of plastics worldwide reached 353 million tons, with 67% (238 million tons) allocated to single-use applications, predominantly in packaging and consumer products. Prominent single-use plastics, such as polyethylene terephthalate (PET), polyethylene (PE), polypropylene (PP), and polystyrene (PS), constitute over 70% of the global plastic market. Despite their ubiquitous presence, a significant majority of these plastics remain unrecycled, leading to severe environmental impacts. A substantial portion is burned to recover energy, generating 37.5 gigatons of CO2 in 2018—equivalent to 2% of global CO2 emissions. Moreover, over half of plastic waste ends up in landfills, where it breaks down into microplastics, introducing persistent risks to ecosystems and human health. The existing recycling techniques are frequently inefficient, costly, and environmentally damaging, thus aggravating economic challenges and ongoing pollution issues. This necessitates the development of more effective technologies, strengthened legislation, and enhanced waste management systems. This review examines the significant policy initiatives and technological progress in China’s fight against plastic pollution, within the context of its circular economy. Over the past 30 years, the Chinese government has enacted robust policies targeting plastic waste, including comprehensive legal frameworks for solid waste management. These measures have contributed to notable advances in the recycling sector, ecological safeguards, and waste recovery. Today, China is recognized as having the largest recycling capacity in the world, supported by a robust waste plastic transportation infrastructure and a strong technological foundation for industrial upgrades. The implementation of the 14th Five-Year Plan, featuring initiatives such as the Circular Economy Development Action Plan and the Plastic Pollution Control Action Plan, has reinforced the objective of refining plastic management. This includes shifting away from inefficient landfilling, enhancing the sustainability of plastic incineration, and advocating high-value utilization (upcycling) of plastic waste. Upcycling/recycling, an increasingly prominent interdisciplinary field, bridges chemistry, economics, engineering, and policy. The development of sustainable chemical techniques is central to these efforts, and recent years have seen a variety of innovative recycling methods. This review examines several advanced upcycling and recycling approaches, including thermal, electrical, photochemical, and biological methods, which facilitate the effective conversion of plastics into valuable chemicals. For instance, the use of tandem catalytic strategies has facilitated the transformation of plastic waste into fine chemicals and pharmaceutical precursors, greatly enhancing their economic value. Despite these advances, challenges persist in achieving a balance between conversion efficiency, effectiveness, economic feasibility, and environmental impact. Notably, much of the research has concentrated on laboratory-grade plastics and after-use plastics, while the upcycling of real-life plastic wastes is still largely unexplored. The presence of impurities in everyday plastic waste presents a distinct challenge for upcycling processes, necessitating further research to comprehensively understand how these impurities influence conversion and to refine processing conditions to reduce their impact on the effectiveness and efficiency of upcycling processes. Addressing these challenges is essential for harnessing the full potential of waste plastic upcycling technologies. Enhancements in legislation, logistics, and process optimization will be critical for promoting a more sustainable and circular plastic economy. Ultimately, the success of these efforts will hinge on the ability to balance economic, ecological, and technological considerations in the transition towards a more sustainable future.