Phytomining of rare earth elements using native hyperaccumulator plants and surface soils from Idaho, USA

Phytomining is a sustainable mineral extraction method that employs metal-tolerant hyperaccumulator plant species to recover metals from surface soils. Our preliminary study explored the survivability and effectiveness of rare earth element (REE) hyperaccumulators of 45 species when grown in naturally occurring REE-rich soil sourced from Idaho, finding that Idaho native grass Pseudoroegneria spicata is an effective REE hyperaccumulator. This study then evaluated the REE hyperaccumulation ability of P. spicata and Phalaris arundinacea, assessing the performance of seven varieties within each species. Plants were grown in a greenhouse and harvested biomass was ashed or pyrolyzed, acid digested, and characterized by elemental analysis. Results showed that P. spicata and P. arundinacea accumulated an average of 26,044 and 27,761 μg/g total mixed REEs in their shoot tissues, respectively. Species and variety were found to mostly have a significant effect on dry biomass yield while tissue type (root vs. shoot) significantly impacted internal plant REE concentration, with roots accumulating more than shoots. This study concludes that using these hyperaccumulating grass species, especially P. spicata, for Idaho-based phytomining has promise and should be further studied and developed.