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. The researchers will look to nature for possible solutions. Diatoms, sea sponges, and certain plants use biological molecules and organic scaffolds to capture dissolved forms of silicon and assemble them into intricate silica structures under relatively mild conditions. By adapting these mechanisms, the team aims to develop lower-energy methods that break down the silica-rich components of industrial waste, convert the silica into useful materials, and free rare earth elements and other critical minerals trapped within the substances. The project brings together expertise in biology, geochemistry, materials science, metallurgy, engineering, computational chemistry, and artificial intelligence. Researchers will use advanced computational modeling and artificial intelligence to design specialized biomolecules, predict how those molecules will interact with silicon-rich waste, and accelerate the identification of promising pathways for mineral recovery and materials manufacturing. As lead principal investigator, Tao will oversee the project’s management and coordination while leading research on biosilicification, the process through which organisms form silica materials, and bio-enabled metallurgy for recovering rare earth elements from silicon-rich wastes. Eggleston, a professor in the Department of Civil, Environmental, and Architectural Engineering with expertise in geochemistry, will lead efforts to identify, understand, and optimize the chemical reactions involved in breaking down and rebuilding silicate materials. His work will examine the pathways and reaction rates associated with silicate dissolution, repolymerization, carbonation, glass formation, and silicone synthesis. Wang, the William B. Smith Professor of Mechanical and Materials Engineering and a widely recognized pioneer in battery recycling and sustainable manufacturing, will lead the development of bioengineered processes for recovering rare earth elements and other critical minerals. The team will also evaluate the economic and practical feasibility of scaling the technologies for industrial applications. If successful, the research could create new pathways for transforming large volumes of industrial waste into marketable products, reducing reliance on newly mined resources, lowering the environmental footprint of materials production, and strengthening domestic supplies of critical minerals and rare earth elements. WPI graduate and undergraduate students will be involved in the multiyear project as part of the university’s immersive STEM experience. The interdisciplinary research sits at the intersection of sustainability, biotechnology, materials science, data science, and artificial intelligence. This project also aims to cultivate a broader bioengineered, silicon-based materials ecosystem by connecting researchers, industry partners, policymakers, educators, and future innovators across disciplines and sectors.
