For the past eight years, North Dakota state geologists have been sampling lignite coal seams in the western part of the state and testing the coal for rare earth elements.
The sought-after elements are used in a wide range of electronic devices from computer disk drives to electric vehicle motors to medical devices.
Most of these rare earth elements are now mined in China.
The U.S. Department of Energy suggests the concentration of these elements in coal needs to exceed 300 parts per million to make extraction feasible.
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“Three-hundred parts per million is probably only about twice as high as the dirt outside in your lawn,” said Levi Moxness, a geologist with the North Dakota Geological Survey.
Most coal in the U.S. has much lower concentrations, below 100 parts per million.
“And so finding something like our highest concentrations of 2,570 parts per million, that starts to get us a little bit excited,” said Moxness.
More exploration is needed to better understand the extent of the area of higher concentration of the valuable elements.
Focus on west-central N.D.
The area of focus is called the Bear Den Member of the Golden Valley Formation, covering 340 square miles in west-central North Dakota.
The formation was created during the Paleocene-Eocene thermal maximum more than 50 million years ago. The rare earth minerals leached from rocks and soil into the coal where it concentrated, said Moxness.
The 1,700 samples tested so far represent only a small fraction of the estimated 25 billion tons of lignite in North Dakota. But Moxness said the research has helped geologists understand areas where the concentrated rare earth elements are most likely to be found.
Finding these critical minerals in significant concentrations is only a first step.
“No one has produced rare earths from coal before at a commercial scale, but the U.S. Department of Energy seems pretty serious about making it a reality,” said Moxness. “North Dakota is on a short list of locations where it really could be viable.”
The U.S. Department of Energy recently awarded grants to the University of North Dakota and West Virginia University to develop methods for extracting rare earth elements from coal.
“If you can do raw ignite, it really releases its rare earths very easily,” said Moxness. “And so that is one of the the big selling points for lignite and North Dakota.”
The state that first proves a viable extraction method is in line for $120 million in federal funds to build a commercial scale plant and tap in to a growing demand for rare earth elements.