Alfalfa pulls rare earth metals out of coal ash waste
Douglas I, Mohanty M, Abbasi B
Phytoremediation
If you've got a compost pile or raised bed near industrial fill, this is a reminder that some common forage plants are surprisingly good at pulling specific metals out of the ground and concentrating them in their leaves and stems.
Researchers grew alfalfa in pots of soil mixed with different amounts of coal fly ash, a leftover from burning coal that happens to contain rare earth metals like europium and neodymium. They found the alfalfa actually absorbed these metals from the ash and, as the plants matured, moved more and more of it from the roots up into the shoots. That's a big deal because it hints alfalfa could someday be used to harvest rare earth elements from waste material instead of mining them from the ground.
Key Findings
Europium accumulation peaked at 304.44 µg/g (combined shoot and root) under 20% coal fly ash amendment at 120 days
Translocation factors exceeded 1 for europium and praseodymium across all fly ash treatments by 180 days, meaning more metal ended up in shoots than roots
Bioaccumulation factors were actually highest in the unamended control, showing that fly ash loading reduced uptake efficiency, likely due to pH-driven immobilization of the elements
chevron_right Technical Summary
Alfalfa grown in soil mixed with coal fly ash soaked up rare earth elements like europium, neodymium, and praseodymium, moving much of it up into the shoots rather than leaving it in the roots. This points to alfalfa as a potential tool for extracting valuable rare earth materials from waste ash, though timing and ash amount both matter a lot.
Abstract Preview
Original paper
Bioaccumulation and translocation of rare earth elements in Medicago sativa L. grown in coal fly ash-amended substrates.
A greenhouse pot experiment investigated the bioaccumulation and translocation of Cerium (Ce), Erbium (Er), Europium (Eu), Neodymium (Nd), and Praesodymium (Pr) in Medicago sativa L. grown in a sub...
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Alfalfa, lucerne, Medicago sativa is a perennial flowering plant in the legume family Fabaceae. It is cultivated as an important forage crop in many countries around the world and is used for grazing, hay, and silage, as well as a green manure and cover crop. It has also been cultivated as livest...