Skip to main content

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

  • Article
  • Published:

Process innovations to enable viable enzymatic poly(ethylene terephthalate) recycling

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.

This is a preview of subscription content, access via your institution

Access options

Buy this article

Prices may be subject to local taxes which are calculated during checkout

Fig. 1: Extrusion, quenching, and chopping compared with extrusion and cryomilling as a PET amorphization method.
Fig. 2: Solution reuse for increased EG concentration in the enzymatic hydrolysis reactor and NH4OH base regeneration.
Fig. 3: Comparisons of EG recovery methods via distillation with MVR and RE/RD.
Fig. 4: Process modeling results for an improved PET enzymatic recycling process.

Similar content being viewed by others

Data availability

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.

References

  1. Garcia, J. M. & Robertson, M. L. The future of plastics recycling. Science 358, 870–872 (2017).

    Article  CAS  PubMed  Google Scholar 

  2. Martín, A. J., Mondelli, C., Jaydev, S. D. & Pérez-Ramírez, J. Catalytic processing of plastic waste on the rise. Chem 7, 1487–1533 (2021).

    Article  Google Scholar 

  3. Ellis, L. D. et al. Chemical and biological catalysis for plastics recycling and upcycling. Nat. Catal. 4, 539–556 (2021).

    Article  CAS  Google Scholar 

  4. Jehanno, C. et al. Critical advances and future opportunities in upcycling commodity polymers. Nature 603, 803–814 (2022).

    Article  CAS  PubMed  Google Scholar 

  5. Vidal, F. et al. Designing a circular carbon and plastics economy for a sustainable future. Nature 626, 45–57 (2024).

    Article  CAS  PubMed  Google Scholar 

  6. Uekert, T. et al. Technical, economic, and environmental comparison of closed-loop recycling technologies for common plastics. ACS Sustain. Chem. Engin. 11, 965–978 (2023).

    Article  CAS  Google Scholar 

  7. Postconsumer PET Recycling Activity in 2018 (National Association for PET Container Resources, 2019).

  8. Mohan, A. M. Untangling the thermoform recycling conundrum. Packaging World https://www.packworld.com/sustainable-packaging/recycling/article/22921860/thermoform-recycling-challenges-and-opportunities (2024).

  9. Allen, R. D. & James, M. I. in Circular Economy of Polymers: Topics in Recycling Technologies (eds Collias, D. I. et al.) Vol. 1391, Ch. 4, 61–80 (American Chemical Society, 2021).

  10. Klotz, M., Haupt, M. & Hellweg, S. Potentials and limits of mechanical plastic recycling. J. Ind. Ecol. 27, 1043–1059 (2023).

    Article  CAS  Google Scholar 

  11. The 50 States of Recycling (Eunomia Research & Consulting, 2023).

  12. Werner, M. N. A. et al. Closing the Plastics Circularity Gap (Google & AFARA, 2022).

  13. Peng, Z. S. T. J., Wallach, J., Youngman, A. Advanced Recycling: Opportunities for Growth (McKinsey & Co., 2022).

  14. The New Plastics Economy: Rethinking the Future of Plastics (The Ellen MacArthur Foundation, 2016).

  15. Herriot, A. Plastic Recycling Reimagined: A High-Level Overview of Non-mechanical Recycling (WRAP, 2023).

  16. Tournier, V. et al. An engineered PET depolymerase to break down and recycle plastic bottles. Nature 580, 216–219 (2020).

    Article  CAS  PubMed  Google Scholar 

  17. Wei, R. et al. Possibilities and limitations of biotechnological plastic degradation and recycling. Nat. Catal. 3, 867–871 (2020).

    Article  CAS  Google Scholar 

  18. Carniel, A., Waldow, Vd. A. & Castro, A. M. d. A comprehensive and critical review on key elements to implement enzymatic PET depolymerization for recycling purposes. Biotechnol. Adv. 52, 107811 (2021).

    Article  CAS  PubMed  Google Scholar 

  19. Bell, E. L. et al. Directed evolution of an efficient and thermostable PET depolymerase. Nat. Catal. 5, 673–681 (2022).

    Article  CAS  Google Scholar 

  20. Arnal, G. et al. Assessment of four engineered PET degrading enzymes considering large-scale industrial applications. ACS Catal. 13, 13156–13166 (2023).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  21. Tournier, V. et al. Enzymes’ power for plastics degradation. Chem. Rev. 123, 5612–5701 (2023).

    Article  CAS  PubMed  Google Scholar 

  22. Oda, K. & Wlodawer, A. Development of enzyme-based approaches for recycling PET on an industrial scale. Biochemistry 63, 369–401 (2024).

    CAS  Google Scholar 

  23. Chen, S. et al. Biochemical characterization of the cutinases from Thermobifida fusca. J. Mol. Cat. B 63, 121–127 (2010).

    Article  CAS  Google Scholar 

  24. Sulaiman, S. et al. Isolation of a novel cutinase homolog with polyethylene terephthalate-degrading activity from leaf–branch compost by using a metagenomic approach. Appl. Env. Microbiol. 78, 1556–1562 (2012).

    Article  CAS  Google Scholar 

  25. Yoshida, S. et al. A bacterium that degrades and assimilates poly(ethylene terephthalate). Science 351, 1196–1199 (2016).

    Article  CAS  PubMed  Google Scholar 

  26. Danso, D. et al. New insights into the function and global distribution of polyethylene terephthalate (PET)-degrading bacteria and enzymes in marine and terrestrial metagenomes. Appl. Env. Microbiol. 84, e02773–02717 (2018).

    Article  CAS  Google Scholar 

  27. Sonnendecker, C. et al. Low carbon footprint recycling of post-consumer PET plastic with a metagenomic polyester hydrolase. ChemSusChem 15, e202101062 (2021).

  28. Erickson, E. et al. Sourcing thermotolerant poly(ethylene terephthalate) hydrolase scaffolds from natural diversity. Nat. Commun. 13, 7850 (2022).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  29. Seo, H. et al. Landscape profiling of PET depolymerases using a natural sequence cluster framework. Science 387, eadp5637 (2025).

  30. Then, J. et al. Ca2+ and Mg2+ binding site engineering increases the degradation of polyethylene terephthalate films by polyester hydrolases from Thermobifida fusca. Biotechnol. J. 10, 592–598 (2015).

    Article  CAS  PubMed  Google Scholar 

  31. Shirke, A. N. et al. Stabilizing leaf and branch compost cutinase (LCC) with glycosylation: mechanism and effect on PET hydrolysis. Biochemistry 57, 1190–1200 (2018).

    Article  CAS  PubMed  Google Scholar 

  32. Son, H. F. et al. Rational protein engineering of thermo-stable PETase from Ideonella sakaiensis for highly efficient PET degradation. ACS Catal. 9, 3519–3526 (2019).

    Article  CAS  Google Scholar 

  33. Hong, H. et al. Discovery and rational engineering of PET hydrolase with both mesophilic and thermophilic PET hydrolase properties. Nat. Commun. 14, 4556 (2023).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  34. Lu, H. et al. Machine learning-aided engineering of hydrolases for PET depolymerization. Nature 604, 662–667 (2022).

  35. Cribari, M. A. et al. Ultrahigh-throughput directed evolution of polymer-degrading enzymes using yeast display. J. Am. Chem. Soc. 145, 27380–27389 (2023).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  36. Singh, A. et al. Techno-economic, life-cycle, and socioeconomic impact analysis of enzymatic recycling of poly(ethylene terephthalate). Joule 5, 2479–2503 (2021).

    Article  CAS  Google Scholar 

  37. Uekert, T. et al. Life cycle assessment of enzymatic poly(ethylene terephthalate) recycling. Green Chem. 24, 6531–6543 (2022).

    Article  CAS  Google Scholar 

  38. Wei, R. et al. Biocatalytic degradation efficiency of postconsumer polyethylene terephthalate packaging determined by their polymer microstructures. Adv. Sci. 6, 1900491 (2019).

    Article  Google Scholar 

  39. Brizendine, R. K. et al. Particle size reduction of poly(ethylene terephthalate) increases the rate of enzymatic depolymerization but does not increase the overall conversion extent. ACS Sustain. Chem. Eng. 10, 9131–9140 (2022).

    Article  CAS  Google Scholar 

  40. Chang, A. C. et al. Understanding consequences and tradeoffs of melt processing as a pretreatment for enzymatic depolymerization of poly(ethylene terephthalate). Macromol. Rapid Commun. 43, e2100929 (2022).

    Article  PubMed  Google Scholar 

  41. Thomsen, T. B., Hunt, C. J. & Meyer, A. S. Influence of substrate crystallinity and glass transition temperature on enzymatic degradation of polyethylene terephthalate (PET). N. Biotechnol. 69, 28–35 (2022).

    Article  CAS  PubMed  Google Scholar 

  42. Colachis, M. et al. An efficient and scalable melt fiber spinning system to improve enzyme-based PET recycling. Chem. Eng. J. Adv. 19, 100624 (2024).

    Article  CAS  Google Scholar 

  43. Patel, A. et al. Melt processing pretreatment effects on enzymatic depolymerization of poly(ethylene terephthalate). ACS Sustain. Chem. Eng. 10, 13619–13628 (2022).

    Article  CAS  Google Scholar 

  44. Sherwood, T. K. Mass Transfer between Phases (Pennsylvania State Univ., 1959).

  45. Rudzki, H. S. Purification of terephthalic acid. US patent 2,829,160 (1974).

  46. Panasyuk, G. P., Azarova, L. A., Budova, G. P. & Izotov, A. D. Synthesis and characterization of ammonium terephthalates. Inorg. Mater. 38, 385–389 (2002).

    Article  CAS  Google Scholar 

  47. Murdoch, W. S. Production of terephthalic acid and ethylene glycol from polyethylene terephthalate by ammoniolysis. US patent 6,723,873 B1 (2004).

  48. Kubic Jr, W. L. & Tan, E. C. Reactive extraction process for separating 2,3-butanediol from fermentation broth. Ind. Eng. Chem. Res. 62, 5241–5251 (2023).

  49. Recycling Markets https://www.recyclingmarkets.net/ (2024).

  50. Average Freight Revenue per Ton-Mile (Bureau of Transportation Statistics, 2024); https://www.bts.gov/content/average-freight-revenue-ton-mile

  51. USA Trade Import and Export Data (US Census Bureau, 2024); https://usatrade.census.gov/

  52. Uekert, T., Walzberg, J., Wikoff, H. M., Doyle, M. M. & Carpenter, A. C. Strategies for considering environmental justice in the early-stage development of circular economy technologies. ACS Sustain. Chem. Eng. 12, 8307–8312 (2024).

    Article  CAS  PubMed  PubMed Central  Google Scholar 

  53. EPA toxic release inventory (TRI) | Basic search. US Environmental Protection Agency https://guideme.epa.gov/ords/guideme_ext/f?p=guideme:chemical-list-basic-search (2024).

  54. Toto, D. & February, E. D. PET Bale Prices Continue to Climb (Recycling Today, 2024).

  55. Chemical Recycling: Making Fiber-to-Fiber Recycling a Reality for Polyester Textiles (GreenBlue, 2017).

  56. Duijn, H. V. et al. Sorting for Circularity, Europe: an Evaluation and Commercial Assessment of Textile Waste across Europe (Textile Exchange, 2022).

  57. Scaling Textile Recycling in Europe—Turning Waste into Value (McKinsey & Company, 2022).

  58. Alt, H. M. B. et al. Analysis of ethylene glycol and 1,4-butanediol by HPLC-RID. protocols.io https://doi.org/10.17504/protocols.io.6qpvr8wrplmk/v1 (2024).

  59. Humbird, D. et al. Process Design and Economics for Biochemical Conversion of Lignocellulosic Biomass to Ethanol: Dilute-Acid Pretreatment and Enzymatic Hydrolysis of Corn Stover. Report No. NREL/TP-5100-47764 (National Renewable Energy Laboratory, 2011).

  60. Franklin Associates. Life Cycle Impacts for Postconsumer Recycled Resins: PET, HDPE, and PP (The Association of Plastic Recyclers, 2018).

  61. U.S. Life Cycle Inventory Database. National Renewable Energy Laboratory https://www.lcacommons.gov/lca-collaboration/National_Renewable_Energy_Laboratory/USLCI_Database_Public/datasets (2021).

  62. Steubing, B., de Koning, D., Haas, A. & Mutel, C. L. The Activity Browser—an open source LCA software building on top of the brightway framework. Softw. Impacts 3, 100012 (2020).

    Article  Google Scholar 

  63. Mutel, C. Brightway: an open source framework for Life Cycle Assessment. J. Open Source Softw. 2, 236 (2017).

  64. Huijbregts, M. A. J. et al. ReCiPe2016: a harmonised life cycle impact assessment method at midpoint and endpoint level. Int. J. Life Cycle Assess. 22, 138–147 (2017).

    Article  Google Scholar 

  65. Advancing Sustainable Materials Management: 2018 Tables and Figures (US Environmental Protection Agency, 2020).

  66. Nicholson, S. R. et al. The critical role of process analysis in chemical recycling and upcycling of waste plastics. Annu. Rev. Chem. Biomol. Eng. 13, 301–324 (2022).

    Article  CAS  PubMed  Google Scholar 

  67. NAPCOR’s 2022 PET Recycling Report Demonstrates Bottle-to-Bottle Circularity Continues on the Rise (National Association for PET Container Resources, 2023).

  68. Ho, J. et al. Regional Energy Deployment System (ReEDS) Model Documentation (Version 2020) (2021).

  69. Bolinger, M., Wiser, R. & O’Shaughnessy, E. Levelized cost-based learning analysis of utility-scale wind and solar in the United States. iScience 25, 104378 (2022).

    Article  PubMed  PubMed Central  Google Scholar 

  70. Cost and Performance Characteristics of New Generating Technologies, Annual Energy Outlook 2022 (US Energy Information Administration, 2022).

  71. Milbrandt, A., Bush, B. & Melaina, M. Biogas and Hydrogen Systems Market Assessment (National Renewable Energy Laboratory, 2016).

  72. Study on the Use of Biofuels (Renewable Natural Gas) in the Greater Washington, D.C. Metropolitan Area (ICF Resources, 2020).

Download references

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.

Author information

Authors and Affiliations

Authors

Contributions

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.

Corresponding authors

Correspondence to Margaret J. Sobkowicz or Gregg T. Beckham.

Ethics declarations

Competing interests

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.

Additional information

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

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.

Source data

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 2324.

Source data

Extended Data Fig. 3 Waterfall plot for a. the minimum selling price and b. the GHG emissions impact under decarbonized scenarios for unchanged, renewable electricity, and renewable heat and electricity scenarios.

The grid mix for renewable electricity represents the ReEDS mid-case scenario with 95% decarbonization68 at $0.03/kWh69,70 and decarbonized steam and hot oil from renewable natural gas at $12.40/GJ71,72. Figure data and life cycle inventories are provided in Supplementary Tables 2527.

Source data

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.

Source data

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.

Rights and permissions

Springer Nature or its licensor (e.g. a society or other partner) holds exclusive rights to this article under a publishing agreement with the author(s) or other rightsholder(s); author self-archiving of the accepted manuscript version of this article is solely governed by the terms of such publishing agreement and applicable law.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

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

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue date:

  • DOI: https://doi.org/10.1038/s44286-025-00212-y

This article is cited by

Search

Quick links

Nature Briefing: Translational Research

Sign up for the Nature Briefing: Translational Research newsletter — top stories in biotechnology, drug discovery and pharma.

Get what matters in translational research, free to your inbox weekly. Sign up for Nature Briefing: Translational Research