Ex-Ante Comparative Life Cycle Assessment of Membrane Distillation-Crystallization for Lithium Extraction
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Lithium is an energy-critical-element (ECE) that is a fundamental component of lithium-ion batteries which are projected to surge in demand in the coming years to meet the rising demand for battery electric vehicles (BEVs), variable renewable energy storage systems(RESS) and personal electronics. Supplying the projected amount of lithium for lithium-ion batteries in the near future is challenging due to the geographical concentration of lithium reserves and resources, complexity of recovering lithium from brines and the environmental impacts associated with lithium extraction in general. Several emerging technologies are being investigated to determine if they can provide additional lithium production capacity with improved efficiency and applicability to varying brine chemical compositions. In this study, membrane distillation-crystallization (MCr) is investigated as a potentially environmentally preferable alternative to the current lithium extraction process from continental brines. An ex-ante life cycle assessment (LCA) was conducted to measure the potential environmental impacts of using MCr as an alternative to the brine inspissation process. The midpoint impact assessment methodologies used were global warming potential (GWP), water use, acidification potential (AP), resource use (metals and minerals) and cumulative energy demand (CED). To conduct the study, an early-stage lab study of MCr by (Cerda et al., 2021) for lithium recovery was scaled using processing modeling at the Advanced Mining Technology Center in Chile to create a life cycle inventory (LCI) of MCr in addition to an annual operational mass and energy balance. The MCr LCI was coupled with existing datasets for Li2CO3 production to model a theoretical MCr-Li2CO3 production facility and measure the environmental impacts associated with producing the functional unit (FU) of 1 ton Li2CO3. Additionally, a narrative literature review was conducted to determine the current environmental impacts associated with brine inspissation in the Salar de Atacama, Chile. A second narrative literature review was conducted to determine the criteria upon which an improved lithium extraction technique can be measured. Lastly, the land use, land use intensity (LUI) and production intensity of the current brine inspissation route and the MCr route were explored. The most salient results of this study indicate that an MCr lithium extraction facility has the potential to produce the equivalent of 100 kilotons Li2CO3, 76 kilotons of potassium chloride (KCl) and 14 megatons of freshwater per year with an annual raw brine input of 22 megatons per year. This results in a 64% water recovery efficiency and 75% lithium recovery efficiency. However, the main drawbacks are the exceptional amount of energy required which amounts to 5.43 TWh per year and would require approximately 50 km2 of land if powered by solar photovoltaic (PV) energy. The other main drawback found was that the MCrLi2CO3 production route had 4.5 times the amount of GWP than the brine inspissation route and 2.5 times the GWP when using 100% solar PV for electricity supply. Lastly, considering MCr uses 94% less water than the brine inspissation route, it is a trade-off worth further evaluation and future research.