One promising alternative to traditional mining is phytomining, a process in which plants absorb metals from soil and concentrate them in their tissues. Certain plant species can extract rare-earth elements even from polluted environments such as mine waste or contaminated soils. However, a major challenge has been determining how much of these metals plants actually accumulate—without destroying the plant during testing.

To address this challenge, the researchers developed a method based on fluorescence spectroscopy. This technique works by shining light on plant tissues and analyzing how different compounds absorb and re-emit that light.

“Rare-earth metals are essential for many technologies,” says Colleen Doherty, co-corresponding author of a paper on the work.

“These are not actually rare, it’s just that they are rarely found in high concentrations in the environment in their pure form. Right now, the U.S. obtains most of the rare-earth materials it needs from international sources, so there is a great deal of interest in identifying domestic sources of these critical materials.”

The research team focused on dysprosium because of its unique property: it continues to emit light longer than the natural fluorescence of plant tissues. This time-based difference allows scientists to distinguish the signal of the metal from the plant’s own background glow.

To enhance detection, the plants were treated with sodium tungstate, which amplifies the light emitted by dysprosium. A deep ultraviolet laser was then used to trigger fluorescence, and the emitted light was measured to determine the metal’s concentration accurately.

Although the study focused on dysprosium, the researchers believe the technique can be adapted to detect other rare-earth elements such as terbium, europium, erbium, and neodymium.

The development of a non-destructive method to measure rare-earth elements in plants marks a major step forward in sustainable resource extraction. By enabling efficient phytomining, this innovation could reduce dependence on traditional mining and foreign supply chains while promoting environmental restoration. As research continues, plant-based mining may emerge as a viable and eco-friendly solution to meet the growing global demand for rare-earth materials.

“Some plant species are capable of taking rare-earth elements out of polluted soil and concentrating it in their tissue,” says Doherty, who is an associate professor of molecular and structural biochemistry at North Carolina State University.

“In order to maximize this ‘plant mining’ technique, we wanted to find a way to detect and measure the concentration of rare-earth materials in these plants. This can inform not only which plants we want to use for these mining projects, but when the optimal time would be for harvesting those plants to maximize yield of rare-earth elements.”