Regionalized life cycle assessment of lithium carbonate production from brines
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2024
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Doctoral Thesis
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Abstract
As lithium (Li) powers the transition to a low-carbon society through the expansion of energy storage technologies, it is crucial to understand its environmental impacts. This thesis examines the environmental impacts of Li extraction and processing. Meeting the soaring demand for Li requires substantial increases in primary and secondary supply. The global supply is concentrated in a few countries and is dominated by pegmatites (57 %) and brines (43 %) due to the limited secondary Li supply (< 1 %). Brines represent 2/3 of Li resources while pegmatites represent 1/3 of the Li resources. Thus, brines are expected to become the dominant suppliers. Current capacity and expansion plans are not sufficient, driving exploration of untapped deposits. However, environmental concerns exist, particularly regarding South American salt lakes. Water-intensive production in arid areas with fragile ecosystems, such as the Salar de Atacama, has attracted public attention. Additionally, the use of fossil fuels in Li production results in substantial greenhouse gas emissions. The brine chemistry is characterized by the environmental and geological conditions, making it unique and determining environmental impacts through the applied technology. The conventional technology, applied at most existing mines, is based on evaporation ponds and purification steps using chemicals to obtain lithium carbonate (Li2CO3). This, however, is often no longer sufficient, as the chemical composition of future brines with lower Li-concentration leads to poorer extraction results. Direct Lithium Extraction (DLE) creates conditions to address this while potentially reducing environmental damage from production. However, DLE is also discussed in terms of energy- and water-intensive processes, because, among other reasons, the brine must be pretreated for the selective Li extraction. Thus, the potential reduction of impacts needs thorough evaluation. Geothermal brines are promising Li sources. They diversify Li value chains and prevent supply chain disruptions. At the same time, they produce geothermal energy. This results in a great potential to cause less environmental damage than the current production. However, geothermal brines rely on the DLE technology and are challenging to treat due to the complex brine chemistry, elevated temperatures, and uncertain development of Li concentrations. This leads to high uncertainties regarding future production, and environmental impacts are therefore difficult to quantify. Life Cycle Assessment (LCA) literature mainly focuses on a few sites, without acknowledging substantial technological differences between sites. The comparability between studies is impeded by different methodological choices. The results can therefore not be globally generalized. There is a need to systematically quantify environmental impacts, taking into account site-specific characteristics. Only in this way it is possible to create comparability between locations and discuss results on a global level. This thesis provides a systematic framework (Chapter 2) for assessing site-specific life cycle impacts of Li2CO3 production from brines. It provides guidance for defining the goal and scope of the LCA and discusses choices in allocation and system boundaries. Life cycle inventories (LCI) are obtained based on literature with a focus on patents and company reports. Climate change impacts and regionalized water scarcity impacts as well as particulate matter-related human health impacts are assessed. The framework is applied to five cases in South America and China, covering a major share of current production from brines with Salar de Atacama being the largest brine operator. In Chapters 3 and 4, the framework is used as a baseline and further expanded. Chapter 3 specifically addresses the high uncertainties related to future Li2CO3 from geothermal brines by parameterizing brine chemistry, adsorption yield, drilling and energy inputs and evaluating life cycle impacts in > 3500 scenarios. In Chapter 4, the two approaches are combined which is necessary to cover LCA of existing and future Li2CO3 production from brines and to provide a fully parameterized and regionalized LCA model that can be expanded in future. Chapter 4 covers 90 % (300 kilotons) of the current Li2CO3 production from brines are assessed. Potential future production (forecasted 315 kilotons) is covered by assessing early- and late-stage exploration sites. This thesis reveals that life cycle impacts substantially vary between sites and are underestimated in background databases. The applied technology depends on the site’s characteristics (e.g., brine chemistry) and is a key influencing factor of life cycle impacts. The Li-concentration of the brine and the extraction efficiency influence the amount of brine required to produce Li2CO3, which is reflected in the impacts. Purification processes are crucial regarding the environmental performance, as impurity concentrations determine the type and scale of purification pathways. The LCA on geothermal brines illustrates the relevance of pre- and post-treatment processes due to site-specific brine chemistry. While Li-concentrations at Salton Sea and Upper Rhine Graben are similar, the impurity concentrations are 100 times higher at Salton Sea, resulting in substantially higher life cycle impacts. Chapter 4 emphasizes there is a substantial shift in terms of extraction technologies from current conventional technologies towards DLE technologies. In terms of climate change impacts, sites using DLE have 6-fold higher climate change impacts than sites using conventional technologies, on average. Water scarcity impacts of DLE sites are twice the impacts of sites using conventional technologies. Additionally, regionalized impact categories also contribute to the complexity and variability of life cycle impacts. The results underscore the necessity of linking regionalized LCI to characterization factors whenever is possible. Furthermore, this thesis highlights the relevance process-specific parameters and how they differ between identified technology groups in Chapter 4. With the provided LCA model, mitigation strategies such as the implementation of renewable energies are tested and provide new insights in site-specific reduction potentials. This thesis specifically addresses the sensitivity of process parameters in relation with the applied technology for the impacts of Li2CO3 production. With the enhanced knowledge on existing and future Li2CO3 production, the implications on the energy storage sector are discussed in detail. Finally, Chapter 5 sets the findings of the thesis into a broader context, highlights limitations and provides an outlook for research directions. This thesis aims to assess Li2CO3 production from brines on a global level while maintaining site-specific characteristics. A framework had to be created that allows for comparison between locations and supports LCA practitioners. Moreover, the high-resolution LCI can be integrated LCI databases, thereby improving the assessment of downstream industries, such as Li-ion battery manufacturing. Policy-makers are informed and supported by the transparent and systematic evaluation of environmental impacts and the associated uncertainties. Environmental and social impacts, along with political interests, should be holistically assessed and discussed in the future to enable a sustainable transition towards a low-carbon society.
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ETH Zurich
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Life Cycle Assessment; Mining; Lithium-ion batteries; Regionalization
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03732 - Hellweg, Stefanie / Hellweg, Stefanie
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