The renewable energy revolution including solar panels, wind turbines, and electric vehicles is largely dependent on the extraction 17 rare earth elements (REE). Indeed, sales of electric vehicles (EVs) have surged in recent years, with a 35% increase in 2023. However, extracting the REE needed to produce EVs and green energy can be very damaging to the environment. In response, a new study published in Frontiers in Earth Science examined the potential of extracting REE from already degraded landscapes – coal mines.
Scientists at the University of Utah collected samples of coal and surrounding rock from active and inactive coal mines as well as coal waste piles in Colorado and Utah. The U.S. Department of Energy considers concentrations of rare earth minerals over 300 parts per million (ppm) to be economically viable for mining. However, for this study, the researchers set a threshold concentration of 200ppm or more.
Their analysis showed that the amount of rare earth elements present varies with the type of rock. For instance, samples of coal alone had very little REE. However, up to 45% of shale and siltstone samples near coal seams had high concentrations.
Furthermore, 100% of igneous, or volcanic, rock samples they examined contained REE at concentrations greater than 200 ppm. Igneous rock and impure volcanic-ash-rich coal are commonly a waste byproduct in coal mining, the researchers note. They suggest that those products could instead be processed for rare earth elements, providing an economic and environmental benefit for coal companies.
“The coal itself is not enriched in rare earth elements,” Michael Vanden Berg, study’s co-author and Energy and Minerals Program Manager at the Utah Geological Survey, said in a statement. “There’s not going to be a byproduct from mining the coal, but for a company mining the coal seam, could they take a couple feet of the floor at the same time? Could they take a couple feet of the ceiling? Could there be potential there? That’s the direction that the data led us.”
This approach could have the additional benefit of creating new jobs in coal country, where the transition away from coal has hurt local economies.
Previous studies have also found rare earth elements associated with coal in various parts of the U.S. These discoveries suggest that the U.S. has great potential for extracting REEs, the study’s authors write. Today, China supplies most of the world’s REEs.
The U.S. Department of Energy has invested more than 17 million dollars in research for extracting rare earth elements from coal mines. Along with research teams across the country they are now working out best practices for finding and extracting REEs from coal mines. The goal is to quickly reduce greenhouse gas emissions through renewable energy and electric vehicles while also reducing the environmental impact associated with mining these essential elements needed for the energy transition.
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