Expanding cerium magnet deployment for balanced and sustainable use of light rare earths

Rare earth elements (REEs) are geologically co-existed and co-produced but are used in highly differentiated downstream markets. The rapid expansion of NdFeB magnet use has made neodymium (Nd) and praseodymium (Pr) the primary drivers of light REEs production, while resulting in the large and growing surplus of lanthanum (La) and cerium (Ce) that have very limited application. However, cerium magnet, an important alternative to NdFeB magnet, is rapidly developing and has substantial potential to expand cerium use. Here, we develop a material flow analysis framework to quantify China’s historical and future cerium surplus and evaluate the mitigation potential of cerium magnets under nine scenario combinations of NdFeB demand pathways and cerium magnet adoption levels. We find that cerium surplus increased from 2 kt to 51 kt during 1990–2025. Under a scenario in which cerium magnet deployment remains limited, the surplus is projected to expand to 244–295 kt by 2050. China’s cerium magnet demand could reach 163–453 kt by 2050 across all scenario combinations, mitigating 25% (conservative cerium magnet adoption and aggressive NdFeB demand scenario) to 97% (aggressive cerium magnet adoption and moderate NdFeB demand) of projected cerium surplus. Under the moderate scenario, cerium magnets could mitigate 25% of projected Ce surplus through direct Ce utilization in cerium magnet production and an additional 44% by partially substituting NdFeB magnets and avoiding co-produced Ce supply. This study reveals the structural elemental imbalance embedded in co-produced REE systems and demonstrates how demand-side technological substitution can rebalance material flows.