Environmental evaluation of rare earth elements: Processing, products, and pathways
Rare earth elements (REEs) are a group of 17 elements with similar chemical properties; 15 of the elements are from the lanthanide group, and yttrium and scandium are also REEs. Due to their unique physical and chemical properties, REEs have gained increasing importance in many new energy technologies and systems that contribute to reduced greenhouse gas (GHG) emissions and fossil fuel depletion. However, it is well know that production of REEs is far from environmentally sustainable as it requires significant material and energy consumption while generating large amounts of air/water emissions and solid waste. Although life cycle assessment (LCA) has been accepted as the most comprehensive approach to quantify the environmental sustainability of a product, process, or policy, to date there have been only very limited LCA studies on the production of REEs. With the continual growth of renewable energy and energy efficient technologies, global production of REEs will increase. Therefore, reducing environmental footprints of REE production becomes critical and identifying environmental hotspots based on a holistic and comprehensive assessment of environmental impacts serves as an important starting point. After providing an overview of LCA methodology and a high-level description of the major REE production routes used from the 1990s to today, this thesis reviews the published LCA studies on the production of REEs. To date, almost all the LCA studies are based on process information collected from the operation of Mountain Pass facility in the U.S. in the 1990s and the operation of facilities in Bayan Obo, Inner Mongolia, China. However, the ion adsorption clays of southern China are an important REE pathway. For this thesis, knowledge gaps are identified and future research efforts are suggested to advance understanding on environmental impacts of REE production from a life cycle perspective.
Zhao, Purdue University.
Mechanical engineering|Environmental engineering
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