Sustainable Recycling of Critical Materials for Clean-Energy Applications
AuthorChowdhury, Nighat Afroz
Life cycle assessment
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PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
EmbargoRelease after 12/01/2028
AbstractCritical materials are considered the backbone for a decarbonized energy infrastructure. These materials include cobalt, lithium, nickel, and manganese used in lithium-ion batteries (LIBs) for electric vehicles, and rare earth elements (REEs) used in neodymium-iron-boron (NdFeB) magnets for energy-storge technologies. The heightened implementation of clean-energy applications is escalating the global demand of critical materials and has rendered them vulnerable to supply risks due to their limited geographical availability. Moreover, the mining of these materials presents serious ethical, economic, and environmental concerns. Fueled by the imperative for net-zero carbon goals and national security imperatives, there is a growing inclination towards adopting recycling practices for the recovery of critical materials from secondary sources. This shift is prompted by a substantial growth of end-of-life LIBs and NdFeB magnets predicted within the next decade. Recycling could ensure a secondary supply reducing the pressure on mining, close the supply chain loop ensuring circular economy, conserve resources, and minimize landfill waste. While numerous novel recycling processes are emerging, their primary focus has historically been on metal extraction efficiency. However, it is crucial to prioritize the assessment of economic and environmental impacts to ensure sustainability, technology commercialization, and industry standardization. This study aims to apply technoeconomic analysis (TEA) and life cycle assessment (LCA) to evaluate the economic and environmental sustainability of three innovative recycling technologies designed for value recovery of critical materials from secondary sources. TEA is dedicated to appraising the economic prospects of a process, whereas LCA plays a crucial role in comprehensively gauging the environmental impacts, thereby offering a more holistic perspective on sustainable technological advancements. The first technology under consideration is electrochemical leaching to extract critical materials out of LIBs. LCA was conducted to compare its environmental impacts with traditional peroxide-based leaching and another emerging technology – SO2-based leaching. The results showed that electrochemical leaching reduces the global warming potential by 80%−87% compared to peroxide-based leaching due to a lower acid consumption, avoidance of hydrogen peroxide, and regeneration of reducing agent iron (II) sulfate and compares well with SO2-based leaching in most impact categories. The analysis suggested that electricity was one of the environmental hotspots and integrating the proposed technology with renewable energy sources could further reduce the carbon footprint by 45%. The second study presents a novel acid-free dissolution technology that utilizes copper nitrate to dissolve REEs in NdFeB magnet swarf and subsequently recover ~97% of them as mixed rare earth oxides (REOs) of purity ≥99.5%. TEA and LCA quantified the economic and environmental impacts of adopting the proposed technology, projecting a net profit margin of 10–80% and a global warming impact reduction by up to 73% compared to the prevailing REO production routes. As copper nitrate is the single largest contributor to the cost and environmental footprint, recycling of copper nitrate was investigated as well as using alternative copper salts (e.g., copper acetate), revealing significant improvements in TEA and LCA results. Dysprosium was a major revenue source, highlighting the importance of targeting electric vehicle magnets that are rich in dysprosium. As the REO market is volatile, a sensitivity analysis was employed to evaluate the profitability of the proposed technology under different REO prices over the last eleven years. Apart from chemical pathways, bio-based technologies stand out as a compelling avenue for recuperating critical materials from end-of-life and low-grade sources. Therefore, a third study was undertaken that delves into the economic and environmental potential of an innovative bioaccumulation method designed to extract REEs from NdFeB magnet swarf. The proposed process exceled in reclaiming REEs as 90% pure REE-phosphates, achieving a 70%–84% recovery yield. Extending the system boundary to REO production, TEA demonstrated a total cost of $23–54/kg of mixed REO, with a net profit margin of 44%–76% when compared to the prevailing REO market price of approximately $96/kg. Moreover, LCA reveals a 55%–93% reduction in carbon footprint compared to conventional routes. A comprehensive scenario analysis was integrated with static TEA-LCA model to predict dynamic sustainability aspects based on current REE market and simulate the future possible sustainability pathways. Overall, these compelling outcomes emphasize the economic feasibility and environmental merits of the three proposed technologies. They offer a promising pathway for critical materials recycling, addressing sustainable resource management and the development of advanced technologies, while reflecting the dynamic characteristics of the critical materials market.
Degree ProgramGraduate College
Systems & Industrial Engineering