Abstract
Enzymatic depolymerization of poly(ethylene terephthalate) (PET) has received considerable attention for closed-loop polyester recycling. However, current approaches for enzymatic PET recycling face challenges to achieve commercial viability with lower environmental impacts compared with virgin polyester manufacturing. Here we present multiple process innovations for enzymatic PET recycling that enable economic and environmental feasibility. We show that substrate amorphization through extrusion and quenching is energy-efficient and enables near-quantitative enzymatic conversion in 50 h. Using ammonium hydroxide for pH control and thermolysis of the isolated diammonium terephthalate salt reduces the acid and base consumption by >99%, lowering annual operating expenses by 74%. Fed-batch processing increased ethylene glycol concentration, leading to a 65% reduction in energy consumption for ethylene glycol recovery. These improvements were modeled in an optimal process, with recycled PET estimated to be US$1.51 kg−1 relative to US domestic virgin PET at US$1.87 kg−1 and eliminating key life cycle obstacles to scale this technology.

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The authors declare that the data supporting the findings of this study are available within the Article and its Supplementary Information. Source data are provided with this paper.
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Acknowledgements
Funding for N.P.M., S.H.D., J.S.D., T.U., B.N.-B., E.L.B., C.A.S., J.E.M. and G.T.B. was provided by the US Department of Energy (DOE), Office of Energy Efficiency and Renewable Energy (EERE), Advanced Materials and Manufacturing Technologies Office (AMMTO) and Bioenergy Technologies Office (BETO). 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 AMMTO and BETO under contract no. DE-AC36-08GO28308 with the National Renewable Energy Laboratory (NREL), operated by Alliance for Sustainable Energy, LLC. Funding to N.P.M., J.S.D., A.C.C., M.J.S. and G.T.B. was also provided by the US DOE EERE offices, AMMTO and BETO, under contract no. DE-FOA-0002029, and to N.P.M., J.S.D., B.N.-B. and G.T.B. by the Department of Energy (DOE) Technology Commercialization Funding (TCF), administered by the DOE Office of Technology Transitions. A.R.P. was supported by Research England through the Expanding Excellence in England (E3) scheme, and by BBSRC grants BB/X011410/1 and BB/Y007972/1. The views expressed in the Article do not necessarily represent the views of the DOE or the US Government. The US Government retains and the publisher, by accepting the Article for publication, acknowledges that the US Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this work, or allow others to do so, for US Government purposes.
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Conceptualization: N.P.M., S.H.D., J.S.D., A.R.P., J.E.M., M.J.S. and G.T.B. Investigation: N.P.M., S.H.D., J.S.D., T.U., A.C.C., S.M., B.N.-B., E.L.B. and C.A.S. Visualization: N.P.M., S.H.D. and J.S.D. Resources: M.A., H.M.A. and K.J.R. Funding acquisition: J.E.M., A.R.P., M.J.S. and G.T.B. Writing—original draft: N.P.M., S.H.D., J.S.D. and G.T.B. Writing—review and editing: all authors have reviewed and approved of the manuscript.
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N.P.M., S.H.D., J.S.D., A.R.P. and G.T.B. have filed pending US provisional application numbers 63/642,940 and 63/668,257, covering ethylene glycol and terephthalate salt recovery from polyethylene terephthalate enzymatic hydrolysis. G.T.B. is a member of the advisory board of Samsara Eco. The other authors declare no competing interests.
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Extended data
Extended Data Fig. 1 Process flow diagram of the enzymatic PET recycling process, adapted from Singh et al.36.
Individual sub-processes are shown as labeled: feedstock pre-treatment of PET subdivided into flake preparation and micronization, enzymatic hydrolysis to EG and TPA; monomer and co-product recovery as subdivided into product clarification, TPA crystallization, and EG distillation; and repolymerization to rPET from EG and TPA. A summary of economic results is provided in Supplementary Table 9.
Extended Data Fig. 2 Univariate sensitivity analysis for the proposed enzymatic hydrolysis process.
a. Percent change in the process MSP for rPET across various process parameters. The 5-year average US market price of $1.87/kg for vPET production36,51 is shown for reference as a dashed gray line. b. Percent change in the GHG emissions for rPET across various process parameters. The emissions for vPET production are shown for reference as a dashed gray line. Figure data are provided in Supplementary Tables 23–24.
Extended Data Fig. 4 Sankey diagram for percent utility consumption in the proposed process.
Steam generated in the recrystallization and compression processes is reused in the evaporation and distillation operations. The final utility percentages include the energy flow in steam generation.
Supplementary information
Supplementary Information
Supplementary Figs. 1–24, Tables 1–27 and discussion.
Supplementary Data 1
Conversion profiles for the bioreactor runs, data used for concentration determinations, and complete reactive extraction dataset.
Source data
Source Data Fig. 1
Numerical values for the graphs in Fig. 1.
Source Data Fig. 2
Numerical values for the graphs in Fig. 2.
Source Data Fig. 3
Numerical values for the graphs in Fig. 3.
Source Data Fig. 4
Numerical values for the graphs in Fig. 4.
Source Data Extended Data Fig. 1
Summary of discounted cash flow analysis for the base-case process shown in Extended Data Fig. 1.
Source Data Extended Data Fig. 2
Numerical values for the graphs in Extended Data Fig. 2.
Source Data Extended Data Fig. 3
Numerical values for the graphs in Extended Data Fig. 2.
Source Data Extended Data Fig. 4
Numerical values used to generate the Sankey diagram in Extended Data Fig. 4.
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Murphy, N.P., Dempsey, S.H., DesVeaux, J.S. et al. Process innovations to enable viable enzymatic poly(ethylene terephthalate) recycling. Nat Chem Eng 2, 309–320 (2025). https://doi.org/10.1038/s44286-025-00212-y
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DOI: https://doi.org/10.1038/s44286-025-00212-y
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