New resource assessment characterization factors for rare earth elements: applied in NdFeB permanent magnet case study

Abstract

Rare earth elements (REEs) are among the most critical raw materials with a high supply risk. Despite their criticality, REEs are not covered by any resource Life Cycle Impact Assessment (LCIA) methods. The main purpose of the current study is to tackle the issue of missing characterization factors (CFs) for REEs in Life Cycle Assessment (LCA). The development of resource depletion characterization factors for REEs in this study are based on two widely used resource assessment methods, Abiotic Depletion Potential (ADP) and ReCiPe. ADP is based on the use-to-stock ratio, while ReCiPe focuses on the additional cost that society has to pay as a result of extraction. To develop the CFs, a wide range of data is gathered from USGS archives and specific mining reports for 11 large deposits worldwide. The characterization factors for 15 REEs, following the ADP and ReCiPe, are provided in this article. A comparison of the developed CFs with other resources confirms their compatibility. All REE CFs, except ADP for dysprosium (among the 25% highest CFs), are placed among the highest 50 to 75% available CFs for both methods. The significant difference between the results, whether including REE CFs or not, highlights the possible misinterpretation of LCA results. The results reveal that REEs have a relatively high resource impact; therefore, they should be included in the assessment of resources. In addition, applicability of the provided CFs is checked in a NdFeB permanent magnets case study, and some recommendations are provided for the practice. The proposed CFs can be used for both the further update of methods and readily implementation in main LCA software, such as Simapro and GaBi, to address the resource depletion of REEs.