The Plan to Extract Rare Earth Metals from Coal Mining Waste

They say one person’s trash is another person’s treasure, and that could quite literally be the case for toxic coal mine waste. A group of researchers at West Virginia University is currently building a prototype treatment facility that will clean up runoff from old coal mines while simultaneously skimming out rare earth metals—the difficult-to-separate elements needed to make high tech products, including smartphones.

If they’re able to prove that this process can be done efficiently and affordably, it could open up a whole new world of opportunity for coal country and the rare earth metals industry in the US, all while keeping toxic messes out of our water.

“If we can assign a value to this material and turn it into a valuable commodity that people would buy, then we’re creating jobs in Appalachia, incentivizing people to treat mine drainage, and we’re finding a use for this waste product,” Dr. Paul Ziemkiewicz, director of West Virginia Water Research Institute and principal investigator on the project, told me over the phone.

The runoff being treated is called acid mine drainage (AMD), a byproduct of mining rocks like coal, gold, and silver. When you’re rifling through the dirt to extract hunks of rock, other subterranean substances get unearthed as well, including the mineral pyrite, a very common sulphide. When exposed to the air, pyrite becomes chemically unstable and starts to release matter including sulphuric acid, said Ziemkiewicz. When these substances leach out of the ground and into nearby water supplies, it poisons the water and turns it an impossible-to-ignore shade of rusty orange.

This pollution can be mitigated by treating the water with neutralizing minerals, such as lime, Ziemkiewicz said. Modern mining operations are required by law to treat the water, but the old, abandoned, unused mines that dot the Appalachian mountains aren’t really anyone’s responsibility. Instead, local volunteer conservation groups have taken up the task of cleaning the water. But if Ziemkiewicz and his team can prove their concept and the potential value of old mine waste, industry groups will be scrambling for the privilege of cleaning up this decades-old sludge.

Right now, US companies get all their rare earth metals and elements from other countries, primarily from toxic mines in Inner Mongolia. Globally, the rare Earth mine industry is dominated by Chinese companies. These metals are used for a variety of purposes in electronics; for example, neodymium is used in an iPhone’s speakers, and indium is used in touchscreens.

A few years ago, Ziemkiewicz had noticed that the sludge going into AMD treatment facilities tested high for many rare earth metals, but the clean water that came out was metal free. Sure enough, he was able to show that the untreated waste contains high concentrations of rare earth metals, including the rare and profitable metals such as scandium, used in aerospace materials, which at times has sold for $15,000 per kilogram. Those metals are extracted during the treatment process.

“We were finding the increase in concentration of rare earths [after treatment] was between 2,000 and 4,000-fold,” Ziemkiewicz said. “The sulphuric acid created by the weathering of the pyrite was leeching the rare earth elements out of the rock and then that was coming out in the acid mine drainage.”

Ziemkiewicz and his team have developed a number of different technologies that can extract and separate the rare earth metals from the treatment waste, and they have shown promising results in the lab. With the new treatment facility, being built with the help of with more than $3 million in government and industry funding, they’ll be able to determine once and for all if this is a feasible option for mining rare earth elements.

“I spent the last 30 years trying to make acid mine drainage go away,” Ziemkiewicz laughed. “In my weaker moments, now I sometimes wish we had more of it left.”

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