A comprehensive life cycle impact assessment of rare earth elements mining, processing and consumption

Abstract

Rare earth elements (REE) play crucial roles in modern industry, technology applications, medical treatments and renewable energy system. Due to their unique physical and chemical properties, REE permanent magnets, alloys, phosphors, electronics and chemical catalysts have become indispensable components in a broad range of renewable energy technologies including wind turbines, electric vehicles (EV), photovoltaic (PV) thin films, and fluorescent lighting systems. The lack of comprehensive studies of current global REE supply chain severely limits our understanding of the comprehensive environmental burdens associated with the exploitation of these critical elements. There is an urgent need to establish a comprehensive and quantitative life cycle impact assessment (LCIA) based on robust REE mineral resources database and reliable rare earth elements (REE) processing information for global REE supply chain from the mining through refining to use stages which include impacts during production as well as benefits. In this way, the long-term future security of global REE supply can be modelled and assessed, thus ensuring sustainable REE uses. This thesis established a novel, systematic, comprehensive and transparent REE deposit geological classification system that covers all known and potential types of REE mineralization and deposit formation to categorize current available REE mineral resources. Then, based on this new classification scheme and mineral resources accounting, the first global REE mineral resources dataset based on statutory mining codes (e.g., JORC, NI43-101, SAMREC) has been compiled, which enables quantitative analyse the long-term REE resources availability and numerous key aspects (e.g. ore grade, mineral resources, principal mineralogy, by/co-products, deposit types, individual REE concentrations etc.) of future global REE supply. The results suggest REE geological scarcity is not an immediate problem. However, other issues such as associated environmental impacts, economic and social constraints will strongly influence the development of REE resources. Furthermore, a “cradle to gate” scale LCIA study based on 26 operating and potential REE mining projects in conjunction with their industrial reported REE mineral resources and processing data has been carried out. It showcases the possibility and necessity to systematically analyse the interconnections between critical aspects of REE production (e.g. project configurations, deposit types, ore grades, principal REE mineralogy, significant by/co-products) and consequent environmental impacts. Results suggest the development of cleaner REE refining technology based on project specific geological condition and mineralogy would be critical in optimizing the overall environmental performances long-term global REE supply chain. Finally, this thesis presents an indicative LCIA case study to assess future global REE demands and associated environmental implications in wind turbine industry, hence, It filled significant knowledge gaps between the comprehensive environmental benefits for REE consumption in downstream renewable energy system. The results suggest that the utilization of REE permanent magnet would not compromise but enhance the wind turbine’s sustainable performances. The consequential environmental benefits from wind energy generation significantly offset the environmental impacts for REE mineral production stages.