Once, coal was king in Pennsylvania. Black rock from Northern Appalachia heated buildings, powered trains, and fueled the growth of a nation.
As other fossil fuels—oil and natural gas—came for coal’s crown, the industry faded. Jobs disappeared and environmental scars remained.
Decades later, on the cusp of an apparent green energy revolution, the nation is again turning to its coal region.
In a twist of fate, coal and its byproducts represent a source of critical minerals like rare earth elements (REE), a group of seventeen minerals that are building blocks in a wide array of modern technology, including in electric vehicles, wind turbines, and other parts of a green economy.
REEs may not have household names—names like scandium, yttrium, gadolinium—but their importance in batteries, display screens, alloys, and powerful magnets has made them a backbone of modern electronics and essential for health care and military applications.
“Rare earths aren’t exactly rare,” said Barbara Arnold, professor of practice in mining engineering. “They’re found everywhere. But they’re rarely found in high concentrations, so mining for them often isn’t economically viable.”
Even as demand for products like hybrid cars and solar panels rises, the United States finds itself with a shortfall of critical minerals. The country currently imports nearly its entire supply due to the high financial and environmental costs of harvesting the materials.
“If we are moving toward renewable energy, buying cars with rechargeable batteries, we need to know where the materials are going to come from,” Arnold said. “It’s been stated that we can’t recycle enough to meet this challenge, so we need to mine more.”
The answers may lie in buried in landfills and acid mine drainage retention ponds in the coal region. These mining waste streams feature elevated concentrations of REEs and other critical minerals like aluminum and cobalt. And Penn State scientists are leading the charge to try and unlock these materials to help industry develop domestic supply chains.
“The Appalachian region has a rich history in mining, and because of this we have a lot of resources often left behind as waste streams,” said Sarma Pisupati, professor of energy and mineral engineering “We at Penn State can help industry produce valuable materials while also remediating some of the environmental problems caused by these waste streams.”
Penn State researchers, through the Center for Critical Minerals, have innovated new methods to extract REEs in higher concentrations. And the scientists are leading a new consortium of academia and industry, aimed at taking stock of the REEs resources available in the northern Appalachian region. The consortium is part of a broader national effort funded by the U.S. Department of Energy (DOE) to produce domestic supplies of critical minerals.
“The very same fossil fuel communities that have powered our nation for decades can be at the forefront of the clean energy economy by producing the critical minerals needed to build electric vehicles, wind turbines, and so much more,” Secretary of Energy Jennifer M. Granholm said when the funding was announced. “By building clean energy products here at home, we’re securing the supply chain for the innovative solutions needed to reach net-zero carbon emissions by 2050—all while creating good-paying jobs in all parts of America.”
No stone unturned
Machines rumble and thump in the laboratory. Inside, rocks are crushed and then collected and smashed again into ever smaller pieces. A powder is fed through a water table that shakes and separates the material by weight, down to the finest grains. Taking some of the slurry in a pan, Arnold sees familiar golden flecks emerge.
She and her team are panning for gold in Hosler Building. More accurately, pyrite, or fool’s gold, sparkles back at her. The yellow mineral, commonly found in coal, is a dead giveaway that these samples are leftovers from coal mining—rocks and clays found in the seam and discarded as waste because of their low value. But Arnold knows something worth much more could be hiding in her pan.
Now its Arnold’s job to find potential sources of these materials in mining waste.
Arnold, managing director of the Consortium to Assess Northern Appalachian Resource Yield (CANARY) of Carbon Ore, Rare Earth Elements, and Critical Minerals (CORE-CM), is leading the search for these products in waste streams in northern Appalachia—from Kentucky through New York. The two-year, $1.2 million project, funded by the DOE, is part of a broader, nationwide effort to jumpstart domestic production of advanced carbon products and critical minerals.
Arnold and her rock crusher have been busy. She’s spent parts of the past year testing samples collected in the field and sent to her by industry collaborators.
“These first two years are a fact-finding mission,” she said. “We want to know where these waste streams exist, what’s the best way to get them out and process them. All of the information we find is going into our database. We are really digging into the history of mining—not just coal mining—in Pennsylvania and beyond.”
Penn State and its collaborators are tasked with assessing and cataloging northern Appalachian-basin critical mineral resources and waste streams; developing strategies to recover the materials from these streams; and identifying potential supply chain or technology gaps that will need to be addressed.
“The central goal is to develop the science and technology to fill any gaps and help industry take off as quickly as possible,” said Pisupati, principal investigator of the project, director of CANARY and of the Center for Critical Minerals. “The idea is to catalyze economic growth in places like Pennsylvania by developing new technologies and training the workforce that will do these jobs.”
Cleaning up
Winding between Centre and Clearfield counties, Moshannon Creek runs red. A reddish-orange tint stains the stream banks and rocks—a visible sign of acid mine drainage pollution from nearby coal mines.
Acid mine drainage, a common pollution issue in coal communities, occurs when pyrite unearthed by mining activity interacts with groundwater and air and then oxidizes, creating sulfuric acid. The acid then breaks down surrounding rocks, causing toxic metals to dissolve into the water.
“In a lot of these places, the coal was mined sixty, seventy, or eighty years ago,” Arnold said.
“Now we can go back in, reclaim some of these waste products, and put the materials back better so we don’t have things like acid mine drainage occurring.”
Materia USA and Texas Minerals Resource Corporation (TMRC), developers of rare earth and critical mineral projects, have produced conceptual plant designs for the recovery of rare earth minerals from coal waste streams like those in Central Pennsylvania and in the anthracite fields, respectively.
Penn State is partnering with the companies, and researchers have identified elevated levels of REEs in coal overburden and underclays from the areas.
“It’s reclamation of land and water,” Pisupati said. “That’s the idea. We can clean up the land, clean up the water, and reclaim various valuable resources from waste streams and reduce the foreign dependency for these critical minerals for sustainable growth.”
Liberate and separate
The DOE estimates there are millions of metric tons of critical minerals in the country’s coal waste streams.
But for projects like the Materia USA or TMRC plant to be competitive in the open market, scientists must continue to improve how we extract or separate the valuable materials from waste streams.
Penn State researchers with the Center for Critical Minerals, for example, have developed an innovative process that recovers more rare earth elements and aluminum from acid mine drainage while using a small amount of chemicals.
Adding carbon dioxide to acid mine drainage already being collected in retention ponds produces chemical reactions that result in solid minerals called carbonates forming and precipitating out of the water. The process results in a sludge from which critical minerals can be harvested.
“The success and scale-up of these processes, with collaboration between the Center for Critical Minerals and our industry partners, can result in unlocking significant secondary sources for critical minerals,” said Mohammad Rezaee, assistant professor of mining engineering. “We can help address U.S. needs for these materials, improving the environment by re-mining and treating the waste streams, promoting advanced technology and manufacturing, ensuring national security, and providing significant job opportunities.”
The Center for Critical Minerals unites over twenty-five faculty members across Penn State’s departments and colleges- geosciences, energy and mineral engineering, materials science and engineering, chemistry, chemical engineering, and energy business and finance who conduct cross disciplinary work addressing various challenges around critical minerals.
“This had to be Penn State,” Arnold said. “This is our history. This is what we do. This is what we have done. We should be the ones doing this given our rich history in geosciences and mining. That’s how Penn State started.”