Current developments in the chemical upcycling of waste plastics using alternative energy sources

The management of plastics waste is one of the most urgent and significant global problems now. Historically, waste plastics have been predominantly discarded, mechanically recycled, or incinerated for energy production. However, these approaches typically relied on thermal processes like conventional pyrolysis, which are energy-intensive and unsustainable. In this Minireview, we discuss some of the latest advances and future trends in the chemical upcycling of waste plastics by photocatalytic, electrolytic, and microwave-assisted pyrolysis processes as more environmentally-friendly alternatives to conventional thermal reactions. We highlight how the transformation of different types of plastics waste by exploiting alternative energy sources can generate value-added products such as fuels (H2 and other carbon-containing small molecules), chemical feedstocks, and newly functionalized polymers, which can contribute to a more sustainable and circular economy. Agency for Science, Technology and Research (A*STAR) Ministry of Education (MOE) National Research Foundation (NRF) Accepted version H.S.S. acknowledges that this project is supported by A*STAR under the AME IRG grants A2083c0050, A1783c0003, and A1783c0002. H.S.S. is also grateful for the Singapore Ministry of Education Academic Research Fund Tier 1 grant RT 05/19. H.S.S. and X.Y.K. acknowledge that this research is supported by the Singapore National Academy of Science (SNAS) and the National Research Foundation (NRF) Singapore under its SNAS ASEAN Postdoctoral Fellowship (NRF-MP-2020-0001) program.