M.V. Evans, B. Webster, M. Heinrichs
Keywords: critical minerals, rare earth elements, REE, technoeconomic, coal ash, economic viability
Summary:There is significant need for the U.S. to secure domestic supply chains for critical materials, including rare earth elements (REE). REE are used widely in strong magnets, semiconductor materials, and optoelectronic devices, and are vital for both green energy technology development and defense purposes. Despite their wide and important uses, REE are challenging to mine, process, and refine, making the supply chain establishment difficult and expensive. There has been increased interest in recovering REE from non-ore based unconventional feedstocks, such as coal ash, acid mine drainage, mine tailings, e-waste, and more, as these feedstocks are readily available waste streams. However, the economic viability of these feedstocks is questionable and depends on feedstock matrix, REE concentrations, saleable byproducts, and waste disposal considerations. Prior to the application of funding and organizational labor for significant research and development (R&D) efforts, technoeconomic efforts can be employed as a “go-no go” decision maker depending on the economic viability. Battelle previously developed and utilized technoeconomic analyses for pilot scale recovery of REE from coal ash using acid digestion and solvent extraction processes. This platform has since been employed in determining the economic viability of applying a similar process to other feedstocks such as municipal solid waste, and for other extraction processes such as bioleaching of coal ashes. Our results have informed R&D directions and directed where additional R&D is needed to eliminate process bottlenecks, minimize operational costs, and maximize recovery efficiency.