Techno-Economic and Environmental Impact Assessment of Phytomining for Extracting Rare Earth Elements in the Northwestern United States

Abstract Demand for rare earth elements on a global scale is increasing daily due to the surging demand from various sectors (e.g., renewable energy and consumer electronics). Bio-ore, a product from pyrolysis conversion of biomass feedstocks obtained through phytomining, is a promising solution to address challenges faced by sustainable rare earth extraction, such as minimal land disturbance and soil erosion. This study explores the sustainability benefits of producing bio-ore at a critical materials rich site via a portable refinery unit and transporting it to an extraction plant. Techno-economic and environmental impact assessments are performed on a case study in the Northwestern United States. Total bio-ore production cost is estimated utilizing a life cycle costing model as part of the techno-economic analysis. Life cycle assessment is used to explore the global warming potential and other environmental impacts of the proposed bio-ore production pathway. Total cost of bio-ore production through phytomining ranges from $156–$197 per metric ton, depending on key parameters (e.g., mobile refinery capacity and hyperaccumulator water content). Total greenhouse gas emission is 11–35 kg CO2 eq. per metric ton of bio-ore. On-site production rate and biomass water content are the two key parameters that are examined in a sensitivity analysis to reduce bio-ore unit price and environmental impacts. This study concluded that the proposed phytomining-to-bio-ore approach provides a cost effective and economically feasible rare earth element extraction pathway.