Criticality of Byproduct Materials: Assessing Supply Risk, Environment Impact, and Strategic Policy Response for Tellurium

Creating a more sustainable future will require a transition toward more clean energy technologies. As technology shifts, the portfolio of materials needed to support the energy sector will shift as well. To prevent resource scarcity challenges, it is necessary to investigate multifaceted risks for energy materials. In recent years, a tool known as criticality assessment has been used for this purpose, identifying economic vulnerabilities for key energy, defense, and electronic technologies. These studies intend to guide strategic response to reduce risk; however existing methodologies lack a comprehensive systems perspective necessary to inform decisions. This is particularly true for materials supplied from byproduct mining. Byproduct minerals (e.g. tellurium, indium, gallium) are unintended minor joint products generated while mining and refining major metals (e.g. aluminum, iron, copper). They contribute only marginally to profit, so their extraction is justified strictly by association with the carrier metal ore, linking their supply, both physically and economically, to the system of materials being produced by the joint process. This level of interconnection is not well captured by the single-product focus characteristic of existing criticality assessments, potentially misrepresenting risks for byproducts. This dissertation aims to inform more appropriate policy response by addressing key gaps in criticality assessment and mitigation for byproduct minerals through the application of various systems modeling tools, including dynamic material flow analysis (dMFA), life cycle assessment (LCA), and scenario-based uncertainty analysis. Resulting contributions address the following specific challenges: (a) supply risk assessment neglects carrier metal production dynamics, (b) environmental risk assessment is sensitive to variability in impact allocation assumptions, and (c) standard, static result metrics are poorly matched for development of dynamic risk mitigation policy. Novel methodologies are demonstrated throughout using a case study of tellurium, a byproduct of copper refining critical to rapidly-growing CdTe thin-film photovoltaics.

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http://scholarworks.rit.edu/theses/9025/