Techno-economic and Life Cycle Analysis for Bioleaching Rare-Earth Elements from Waste Materials
A bioleaching process to extract rare earth elements (REE) from fluidized catalytic cracking (FCC) catalysts was optimized using a heterotrophic bacterium Gluconobacter oxydans to produce organic acids from glucose. Parameters optimized included agitation intensity, oxygen levels, glucose concentrations and nutrient additions. Biolixiviants from the optimized batch process demonstrated REE leaching efficiencies up to 56%. A continuous bioreactor system was subsequently developed to feed a continuous leach process and demonstrated leaching efficiencies of 50%. A techno-economic analysis showed glucose to be the single largest expense for the bioleach process constituting 37.8% of the total cost. The bioleaching plant described here was found profitable although the margin was small. Lower cost carbon and energy sources for producing the biolixiviant and improved leaching efficiencies would improve profitability as well as sourcing FCC catalysts with higher levels of REE. In conclusion, a life cycle analysis showed that electricity generation and glucose production required for the bioreactor had the largest potential for environmental impacts.