Environmental Life Cycle Impact and Complexity Assessment of Rare Earth Production
Rare Earth Elements (REEs) find applications in clean energy technology, including wind turbines, electric vehicles, and high efficiency lighting therefore, as the renewable energy market expands, demand of REEs is anticipated to rise. However, it is well known that the production of REEs carries large environmental burden and as a result, reducing environmental footprints of REE production becomes critical. The first action towards reducing the environmental degradation during production of REEs is the thorough examination of the energy requirements and environmental emissions. To date, Life Cycle Assessment (LCA) is the standard methodology to evaluate the environmental performance of a system, process, or product and this method comprehensively considers all life cycle stages and their associated resource consumption and environmental emissions. There are limited LCA studies on REEs production. Unfortunately, even these limited studies have issues: they comprise a small fraction of the REE life cycle, suffer from low data quality, and may not represent typical production practice. Moreover, for many life cycle steps and processes, no datasets are available and surrogates are frequently utilized. Given the importance of REEs in clean energy technologies, a new life cycle inventory database that is well documented, easily accessible, and open to customization while covering typical REEs production pathways is highly desirable. Therefore, two major REE production pathways in China were covered in this study: 1) bastnasite/monazite open-pit mining, beneficiation, cracking, separation via solvent extraction; and 2) in-situ leaching of ion adsorption clay followed by solvent extraction. Production of REE metals and alloys were also modelled. Since LCA develops a network of flows of resources or emissions, it is likely that emissions or resource flows in life cycle networks can provide additional insights such as resilience and vulnerability regarding the sustainability of products or systems which is presently not captured by any of the aggregated metrics. Hence, this investigation used the network analysis approach as popular technique for the study of several complicated systems to investigate life cycle networks of rare earth elements to investigate the utility of network analysis for obtaining advantageous information from LCA networks. The carbon dioxide emission networks were obtained from the Ecoinvent database as well as new database compiled based on Chinese production. In the current study, network metrics of indegree and outdegree strength, betweenness centrality, closeness centrality, and eccentricity were utilized to study the complexity of REEs production networks. The result of this research greatly improves our ability to identify the most environmentally impactful materials and energy flows within REEs’ production and helps us develop new sustainable products or processes to meet the expanding demand for rare earth elements while improving their environmental performance more effectively.
Zhao, Purdue University.
Off-Campus Purdue Users:
To access this dissertation, please log in to our