Coal ash, red mud, and mine tailings are typically viewed as environmental liabilities. But locked inside these massive waste streams are valuable silica, rare earth elements, and other critical minerals. A Worcester Polytechnic Institute (WPI)-led research team has received a $3.3 million award from the National Science Foundation’s Growing Convergence Research program to explore whether lessons from diatoms, sea sponges, and plants could help recover those resources using less energy and fewer harsh chemicals.
The five-year, two-phase project is led by Mingjiang Tao, associate professor in the WPI Department of Civil, Environmental, and Architectural Engineering, with Professors Carrick Eggleston and Yan Wang serving as co-principal investigators. Researchers from George Mason University, the University of California San Diego, the University of Massachusetts Amherst, and the University at Buffalo will also be involved.
“Recovering critical minerals is only part of the opportunity,” Tao said. “We want to develop a process that uses as much of each waste stream as possible, separating strategically important elements while converting the remaining material into useful products. That whole-material approach could fundamentally change how industries manage waste and obtain essential resources.”
The research addresses two interconnected challenges. Producing many silicon-derived materials used in concrete, glass, ceramics, semiconductors, and silicones can require high temperatures, substantial energy, and intensive chemical processing. At the same time, industries generate enormous quantities of silicon-rich waste, including coal ash residue, red mud, mine tailings, concrete debris, waste glass, and metallurgical slag. Much of this waste is stored in landfills, ponds, impoundments, and large waste piles, even though it contains valuable silicon, critical minerals, and rare earth elements (REE). For example, the estimated 11 million tons of REEs trapped in U.S. coal ash landfills is worth $8.4 billion—nearly eight times the nation’s current raw domestic reserves. These materials are essential for electronics, clean-energy technologies, transportation, and national security.
