Responsible sourcing of rare earth elements
Date: 21 October 2019
University of Exeter
PhD in Mining and Minerals Engineering
Rare earth elements (REE) are considered to be critical raw materials due to the combination of their high importance in a range of low-carbon technologies and the concentration of supply, which is dominated in China. The REE industry has a legacy of environmental damage and the mining, processing, and separating out of the REE requires ...
Rare earth elements (REE) are considered to be critical raw materials due to the combination of their high importance in a range of low-carbon technologies and the concentration of supply, which is dominated in China. The REE industry has a legacy of environmental damage and the mining, processing, and separating out of the REE requires a significant quantity of energy and chemicals. Life cycle assessment (LCA) is a method to quantify the environmental impacts of a product or process and can be applied to the raw materials production sector. This thesis presents how LCA can be applied for REE projects in development. The results can help identify environmental hotspots for a project, and analyse alternatives to help reduce the environmental impacts of REE production. Mineral processing simulation are commonly used in REE project development and data generated from these studies can be used to carry out a LCA. This approach was presented with the Songwe Hill REE project in Malawi. The mineral processing simulation output data which includes energy and chemical flows is used as the life cycle inventory data (LCI) and calculated with characterization factors to generate life cycle impact assessment (LCIA) results such as global warming potential. This data can inform future engineering studies or process simulations. REE projects, like all mining projects, can last decades and extract different ore compositions throughout this life-time. A method is presented to generate tempo- rally explicit LCA results. The Bear Lodge REE project, which is in the prefeasibility stage of development and located in the United States, is used as a case study. LCIA results highlight that grade and mineralogy can influence the LCIA results. The relationships between environmental impacts and grade and mineralogy are explored. Thirdly, a method is presented to include LCA data in the mine scheduling pro- cess. LCIA data can form an environmental block model alongside the economic block model for a deposit. These spatially explicit data can then be used as a constraint within long-term mine scheduling simulations. The results indicate that significant reductions in global warming impact can be achieved at a small economic cost. Finally advances to the current resource depletion impact categories are achieved, advancing the previous methods which neglect socio-economic, regulatory and geopolitical aspects, nor do they include functionalities such as material recycling or reuse that control the supply of raw materials. I examine the economic scarcity potential (ESP) method and make advances based on recent developments in material criticality. ESP criticality scores for 15 REE with the addition of Au, Cu, platinum-group metals (PGM), Fe and Li are measured and a case study is presented to for the inclusion of REE ESP scores for the materials that form a NdFeB permanent magnet. This thesis has a focus on utilising LCA in a proactive manner and incorporating it into the planning stages of REE projects to encourage responsible production of REE.
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