Toward Sustainable Rare Earth Element Production: Key Challenges in Techno-Economic, Life Cycle, and Social Impact Assessment.

Rare earth elements (REEs) are 17 critical minerals used in many clean energy technologies like wind turbines and electric vehicles. Conventionally, we produce REEs from mining in a few, geopolitically restricted regions. Developing systems that utilize new technologies and unconventional feedstocks provides an opportunity to meet increasing demand while improving sustainability. Techno-economic analysis (TEA), life cycle assessment (LCA), and social LCA (sLCA) are commonly used tools to assess the sustainability performance of these systems. However, analyses of REE systems encounter challenges, including system scope, data availability, technology scale-up, and uncertainty. In the reviewed literature, systems served multiple functions beyond producing REEs, including circularizing production and waste remediation, leading to discrepancies in scope. Further, the instability of REE prices led to high uncertainty due to different revenue, costs, and impact allocation. Therefore, these analyses leave decision makers with an incomplete understanding of the current landscape of REE production, inhibiting intelligent and efficient identification of future research and policy goals. In this narrative review, we conducted a comprehensive overview of the literature, synthesized studies from each pillar of sustainability (economic, environmental, and social), highlighted the challenges and limitations in each field, and recommended directions for future work developing sustainable REE production systems.