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Chemical and biological catalysis for plastics recycling and upcycling

Abstract

Plastics pollution is causing an environmental crisis, prompting the development of new approaches for recycling, and upcycling. Here, we review challenges and opportunities in chemical and biological catalysis for plastics deconstruction, recycling, and upcycling. We stress the need for rigorous characterization and use of widely available substrates, such that catalyst performance can be compared across studies. Where appropriate, we draw parallels between catalysis on biomass and plastics, as both substrates are low-value, solid, recalcitrant polymers. Innovations in catalyst design and reaction engineering are needed to overcome kinetic and thermodynamic limitations of plastics deconstruction. Either chemical and biological catalysts will need to act interfacially, where catalysts function at a solid surface, or polymers will need to be solubilized or processed to smaller intermediates to facilitate improved catalyst–substrate interaction. Overall, developing catalyst-driven technologies for plastics deconstruction and upcycling is critical to incentivize improved plastics reclamation and reduce the severe global burden of plastic waste.

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Fig. 1: Annual global market size of commodity plastics in MMT yr−1.
Fig. 2: Substrate characterization flowchart.
Fig. 3: Simplified model to illustrate thermodynamic and kinetic control in polymer upcycling.
Fig. 4: Opportunities in polyolefin upcycling via the olefin-intermediate process.
Fig. 5: Depolymerization of C–N- and C–O-linked polymers for closed-loop recycling or open-loop upcycling.
Fig. 6: Opportunities in biological processes for deconstruction and upcycling of polymers.

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Acknowledgements

Funding for N.A.R., L.D.E., K.P.S., Y.R.-L., and G.T.B. was provided by the US Department of Energy’s Office of Energy Efficiency and Renewable Energy, Advanced Manufacturing Office and Bioenergy Technologies Office. This work was performed as part of the Bio-Optimized Technologies to Keep Thermoplastics out of Landfills and the Environment (BOTTLE) Consortium and was supported by the Advanced Manufacturing Office and Bioenergy Technologies Office under contract number DE-AC36-08GO28308 with the National Renewable Energy Laboratory, operated by the Alliance for Sustainable Energy. The BOTTLE Consortium includes members from the Massachusetts Institute of Technology, funded under contract number DE-AC36-08GO28308 with the National Renewable Energy Laboratory. J.E.M. was supported by Research England through the Expanding Excellence in England (E3) scheme. N.W. acknowledges funding from the European Union’s Horizon 2020 research and innovation programme under grant agreements 863922 (MIX-UP) and 887711 (Glaukos). The scientific activities of the Bioeconomy Science Center were financially supported by the Ministry of Culture and Science within the framework of the NRW Strategieprojekt BioSC (number 313/323-400-002 13; PlastiCycle). We thank R. Clare for help with figure preparation. We thank colleagues in our research groups and collaborators for helpful discussions that have influenced many of the perspectives put forward here.

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L.D.E., N.A.R., K.P.S., and G.T.B. wrote the first draft of the manuscript, which was edited and approved by all authors. All authors contributed to the intellectual efforts for the review; specifically, M.O., J.E.M., and N.W. contributed to the biological catalysis component of the review and Y.R.-L. contributed to the chemical catalysis component of the review.

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Correspondence to Gregg T. Beckham.

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Ellis, L.D., Rorrer, N.A., Sullivan, K.P. et al. Chemical and biological catalysis for plastics recycling and upcycling. Nat Catal 4, 539–556 (2021). https://doi.org/10.1038/s41929-021-00648-4

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