Sustainable Bioleaching of Rare Earth Elements from Industrial Waste Materials Using Agricultural Wastes

Agricultural waste was used as substrate for fermentation by Gluconobacter oxydans to produce lixiviant for rare earth element (REE) recovery from industrial waste materials, i.e., spent fluid catalytic cracking (FCC) catalysts. Biolixiviant generated from potato wastes performed comparably to that generated from refined glucose (25.7% +/- 0.2 and 25.1% +/- 1.1 REE recovered, respectively). Corn stover yielded a slightly less effective biolixiviant (23.3% +/- 0.3 REE recovered) but may serve as a better industrial substrate since collection systems for stover are already in development and have been implemented in several locations. Techno-economic analysis indicated that the use of agricultural waste carbon could lead to a more cost-effective bioleaching process than refined glucose. Analyses suggested that a corn stover-based bioleaching plant would have 22% lower total costs than a potato wastewater-based plant, and a potato wastewater-based plant should have 17% lower total costs compared to a glucose-based plant. An environmental life cycle analysis showed no clear winner among the three alternatives when ten impact categories were considered simultaneously. However, a corn stover-based process generally showed less environmental impact than a potato wastewater-based process or a refined glucose-based process. Our studies indicate that using agricultural wastes as substrates for biological production of lixiviant provides a profitable means for recovering critical metals from recyclable waste materials.