Life Cycle Assessment studies of rare earths production - Findings from a systematic review

Rare earth elements (REEs) are one of the most important elements used for transformation of the fossil era into a decarbonized future. REEs are essential for wind, electric and hybrid vehicles, and low-energy lighting. However, there is a general understanding that REEs come along with multiple environmental problems during their extraction and processing. Life cycle assessment (LCA) is a well-established method for a holistic evaluation of environmental effects of a product system considering the entire life cycle. This paper reviews LCA studies for determining the environmental impacts of rare earth oxide (REO) production from Bayan Obo and ion adsorption clays (IAC) in China, and shows why some studies lead to over- and underestimated results. We found out that current LCA studies of REE production provide a good overall understanding of the underlying process chains, which are mainly located in China. However, life cycle inventories (LCI) appear often not complete. Several lack accuracy, consistency, or transparency. Hence, resulting environmental impacts are subject to great uncertainty. This applies in particular to radioactivity and the handling of wastewater and slurry in tailing ponds, which have often been neglected. This article reviews 35 studies to identify suitable LCAs for comparison. The assessment covers the world's largest REO production facility, located in Bayan Obo, as well as in-situ leaching of IACs in the Southern Provinces of China. A total of 12 studies are selected, 8 for Bayan Obo and IACs each. The LCIs of these studies are reviewed in detail. The effects of over- and underestimated LCIs on the life cycle impact assessment (LCIA) are investigated. The partly controversial results of existing LCAs are analyzed thoroughly and discussed. Our results show that an increased consistency in LCA studies on REO production is needed.