Life cycle assessment of enzymatic poly(ethylene terephthalate) recycling

Taylor Uekert, Jason, S. DesVeaux, Avantika Singh, Scott, R. Nicholson, Partrick Lamers, Tapajyoti Ghosh, John McGeehan, Alberta, C. Carpenter, Gregg T. Beckham

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Abstract

Enzymatic hydrolysis of poly(ethylene terephthalate) (PET) is a chemical recycling approach intended to enable a circular economy for polyester materials. To quantitatively compare this technology implemented at scale to other recycling and synthesis approaches for PET, it is critical to conduct rigorous and transparent process analyses. We recently reported a detailed process model that was used to conduct economic, energy, and greenhouse gas emissions analyses for enzymatic PET recycling (A. Singh et al., Joule 2021). Here, we expand upon this previous work by conducting a process-based life cycle assessment (LCA) of the same enzymatic hydrolysis system, to produce both terephthalic acid (TPA) and ethylene glycol (EG) for use in a closed-loop PET recycling scheme. This LCA shows that enzymatic hydrolysis currently performs either the same as or worse than virgin TPA and PET production across most impact categories, excepting ecotoxicity and fossil fuel depletion, with the top contributors to these impacts being PET flake processing, sodium hydroxide use, and electricity. Sensitivity analysis shows that improving yields throughout the recycling process and eliminating certain process steps, such as amorphization pre-treatment and reaction pH control, can reduce the overall environmental impacts of enzymatic PET recycling to levels statistically equivalent to virgin TPA and PET production, thereby highlighting crucial areas for further research and innovation.
Original languageEnglish
Number of pages13
JournalGreen Chemistry
Early online date2 Aug 2022
DOIs
Publication statusEarly online - 2 Aug 2022

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