Microbial Recycling of Plastic-Polymer-Bonded Rare Earth Magnets

Project Overview

Rare earth elements (REE) are essential components of many military, industrial, and consumer products, but the U.S. domestic supply is threatened by limited availability and relies on overseas importations. Thus, strategies to recover and recycle REEs from end-of-life (EOL) products are necessary to help secure the domestic REE supply, while also reducing lifecycle costs and environmental impacts associated with current REE mining efforts. Rare earth permanent magnets (e.g., NdFeB) are a promising EOL source for REE recycling. However, efforts to recover REEs from these magnets requires unsustainable or hazardous processes.

The overall objective of this project was to enable effective REE recovery by bioprospecting for bacteria that can dissolve NdFeB magnets at ambient temperatures and semi-neutral pH. While our initial plan was to identify microbes that could degrade plastic polymers associated with magnets to boost REE recovery, initial efforts in this area yielded inconclusive results that did not demonstrate degradation of the following polymers: polyphenylene sulfide, epoxy, and nylon. However, the biodissolution of non-bonded and bonded NdFeB magnets by an enrichment culture was similar, indicating that the presence of polymers did not negatively impact microbial growth or dissolution rates. Therefore, we pivoted the project toward the identification of microbes that could dissolve magnets for direct utility in bio-based recycling and recovery of REEs. Microbes from an iron-rich pond were enriched under iron-oxidizing and -reducing conditions and subsequently exposed to NdFeB magnets and isolated. The top candidate was further evaluated to identify conditions that enhanced REE recovery and to understand the mechanisms behind dissolution. Consistent dissolution was observed over several days in minimal media and was comparable to the model microbe known for bioleaching, Gluconobacter oxydans. Moreover, compared to G. oxydans, our top candidate dissolved the NdFeB magnetat semi-neutral pH with no added nutrients (e.g., yeast extract, tryptone). The main mechanism behind dissolution likely involves microbially produced organic acids or chelators, with the potential for iron reduction. Overall, these results demonstrate that bioprospecting and bioleaching holds promise for sustainable REE recovery from rare earth magnets.

Mission Impact

This work contributed to Lawrence Livermore National Laboratory's (LLNL) mission by providing an innovative and sustainable solution for current national security concerns on critical raw materials by developing a proof-of-concept bio-based method for REE recovery and by providing fundamental and mechanistic understanding for biodissolution. Furthermore, this project strengthened the Core Competency, Bioscience and Bioengineering, by integrating experimental and computational tools for identifying microbial processes to utilize in a bio-based recycling approach for NdFeB magnets to recover REEs. This work builds upon established LLNL expertise in REE recovery and provides a new research direction by identifying sustainable microbial processes for dissolving NdFeB magnets. Overall, this research contributed to both strategic thrusts of LLNL's Core Competency Bioscience and Bioengineering ([1] integrating experimental and computational tools and [2] understanding cellular mechanisms). We also fostered new collaborations with Oak Ridge National Laboratory and continued collaborations with Arizona State University and the University of Southern California. Results from this research are relevant to several agencies, including DOE EERE and Office of Science (Energy Efficiency and Renewable Energy), DOD SERDP (Strategic Environmental Research and Development Program), CMI (Critical Materials Institute), and DOE ARPA-E (Advanced Research Projects Agency-Energy), all of which recently solicited proposals on REE recovery.

Publications, Presentations, and Patents

Thompson, Jaclyn, Casey Barr, Lydia Babcock-Adams, Lina Bird, Eugenio La Cava, Arkadiy Garber, Yuichi Hongoh, et al. "Insights into the Physiological and Genomic Characterization of Three Bacterial Isolates from a Highly Alkaline, Terrestrial Serpentinizing System." Frontiers in Microbiology 14 (2023): 1179857. https://doi.org/10.3389/fmicb.2023.1179857.

Merino, Nancy, Farah Merchant, Shalini Mabery, Parans Paranthaman, and Mimi Yung. "Bioprospecting for Microbial Dissolution of Rare Earth Magnets." Abstract accepted for presentation to American Geophysical Union 2023 Conference, San Francisco, CA. 2023.