Acetolysis for epoxy-amine carbon fibre-reinforced polymer recycling

Nature (2025)Cite this article

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Carbon fibre-reinforced polymers (CFRPs) are used in many applications in the global energy transition, including for lightweighting aircraft and vehicles and in wind turbine blades, shipping containers and gas storage vessels1,2,3,4. Given the high cost and energy-intensive manufacture of CFRPs5,6,7, recycling strategies are needed that recover intact carbon fibres and the epoxy-amine resin components. Here we show that acetic acid efficiently depolymerizes both aliphatic and aromatic epoxy-amine thermosets used in CFRPs to recoverable monomers, yielding pristine carbon fibres. Deconstruction of materials from multiple sectors demonstrates the broad applicability of this approach, providing clean fibres from 2 h reactions. The optimal conditions were scaled to 80.0 g of post-consumer CFRPs, and demonstrative composites were fabricated from the recycled carbon fibres, which were recycled two more times, maintaining their strength throughout. Process modelling and techno-economic analysis, with feedstock cost informed by wind turbine blade waste generation8, indicates this method is cost effective, with a minimum selling price of US$1.50 per kg for recycled carbon fibres whereas life cycle assessment shows process greenhouse gas emissions around 99% lower than virgin carbon fibre production. Overall, this approach could enable recycling of industrial CFRPs as it provides clean, mechanically viable recycled carbon fibres and recoverable resin monomers from the thermoset.

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All data are available in the paper or the Supplementary Information. Materials synthesized for this study are available upon request through a Materials Transfer Agreement with the NREL. The materials provided by industrial partners are not available from the authors of this work as they were obtained through Materials Transfer Agreements with the respective industrial partners.

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We thank colleagues at INEOS Britannia, The Boeing Company and Yeti Cycles for providing scrap carbon fibre composite materials. We thank R. Murray and R. Beach at the National Renewable Energy Laboratory (NREL) for providing the scrap glass fibre composite. We thank J. Dietzel at the University of Delaware, L. Hamernik at NREL and members of the BOTTLE Consortium for helpful discussions. We thank R. DiPucchio for sharing synthesis methods for the model thermoset materials. This work was authored by NREL, operated by Alliance for Sustainable Energy, LLC, for the US Department of Energy (DOE) under contract no. DE-AC36-08GO28308. This work was performed as part of the BOTTLE Consortium, which is supported by the US DOE, Office of Energy Efficiency and Renewable Energy, Advanced Materials and Manufacturing Technologies Office (AMMTO) and Bioenergy Technologies Office. Additional funding was provided by AMMTO and BETO under agreement no. DE-FOA-0002245. 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.

Ciaran W. Lahive

Present address: Department of Materials, University of Manchester, Manchester, UK

These authors contributed equally: Ciaran W. Lahive, Stephen H. Dempsey

BOTTLE Consortium, Golden, CO, USA

Ciaran W. Lahive, Stephen H. Dempsey, Sydney E. Reiber, Ajinkya Pal, Katherine R. Stevenson, William E. Michener, Hannah M. Alt, Kelsey J. Ramirez, Erik G. Rognerud, Clarissa L. Lincoln, Ryan W. Clarke, Jason S. DesVeaux, Taylor Uekert, Nicholas A. Rorrer, Katrina M. Knauer & Gregg T. Beckham

Renewable Resources and Enabling Sciences Center, National Renewable Energy Laboratory, Golden, CO, USA

Ciaran W. Lahive, Stephen H. Dempsey, Sydney E. Reiber, Ajinkya Pal, Katherine R. Stevenson, William E. Michener, Hannah M. Alt, Kelsey J. Ramirez, Erik G. Rognerud, Clarissa L. Lincoln, Ryan W. Clarke, Nicholas A. Rorrer, Katrina M. Knauer & Gregg T. Beckham

Catalytic Carbon Transformation and Scale-up Center, National Renewable Energy Laboratory, Golden, CO, USA

Jason S. DesVeaux

Strategic Energy Analysis Center, National Renewable Energy Laboratory, Golden, CO, USA

Taylor Uekert

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Conceptualization: C.W.L. and G.T.B. Investigation: C.W.L., S.H.D., S.E.R., A.P., K.R.S., W.E.M., H.M.A., K.J.R., E.G.R., C.L.L., J.S.D. and T.U. Visualization: S.H.D., C.W.L., S.E.R., K.R.S. and J.S.D. Resources: W.E.M., H.M.A., E.G.R., C.L.L. and R.W.C. Funding acquisition: J.S.D., T.U., N.A.R., K.M.K. and G.T.B. Writing—original draft: C.W.L., S.H.D., S.E.R., A.P., K.R.S. and G.T.B. Writing—review and editing: all authors reviewed and approved the manuscript.

Correspondence to Gregg T. Beckham.

C.W.L., K.R.S., S.H.D., N.A.R., K.M.K. and G.T.B. have filed a patent application on this concept (US provisional patent 63/642,917).

Nature thanks Mikael Skrifvars and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Peer reviewer reports are available.

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Resin formulations were prepared from mixtures of the illustrated epoxies, diluents, and hardeners. The resulting cubes were subjected to acetolysis at 280 °C at ~250 mg scale in 20 mL acetic acid, and the mass balance recorded at 0.5, 1, 2, and 3 h after the products were dried in vacuo for 48 h. Images of the post-reaction liquors and solids are provided in Supplementary Fig. 5.

(a) Image of the downsized mountain bicycle CFRP, see top for 30 cm scale ruler. (b) Image of the post-reaction, dry rCF after washing once with an additional 400 mL of AcOH, twice with 2 L of 70 °C water, and air drying. (c) Demonstration image of a 10 g rCF mat prepared via manual wet-layup in a paper mold. (d) Image of the mold setup with orange silicone gasket that was used for panel fabrication. (e) Image of the sheet placed in the mold with 50 g resin mixture added. (f) Image of the press apparatus used to cure the panels where heat is applied from the bottom and the top. Optimal cure conditions were 20 psi at 80 °C for 2 h, with a 3 h post-cure at 80 °C in an oven. (g) Image of the disperse rCF composite post-fabrication showing the highly unaligned fiber structure visible through the matrix and few surface defects. For panel characterization data, see Supplementary Figs. 75-76 (h) Specific flexural strength (three-point bend) of the three generations of composites (data are mean ± s.d., with Gen1 n = 6, Gen2 n = 7, Gen3 n = 6) contrasted with steel and aluminum. Error bars represent the standard deviation. The three generations exhibit statistically equivalent properties at a 95% confidence interval, with unpaired two-tailed Student’s t-test results of 0.0807 for Gen1-Gen2 and 0.1480 for Gen1-Gen3. The larger deviation between samples for Gen1, and slightly lower average strength in Gen2, is likely explained by its production early in the process, as our fabrication skill increased over the course of the campaign and the composites became more consistent.

This file contains Supplementary Text, Figs. 1–85, Tables 1–15 and references.

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Lahive, C.W., Dempsey, S.H., Reiber, S.E. et al. Acetolysis for epoxy-amine carbon fibre-reinforced polymer recycling. Nature (2025). https://doi.org/10.1038/s41586-025-09067-y

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DOI: https://doi.org/10.1038/s41586-025-09067-y

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