Abstract

Rare earth elements are an integral part of modern industry. Although not “rare” in terms of crustal abundance, concentrations in natural deposits are rarely of economic benefit. Vital to high-tech sectors and sustainable technologies, such as renewable energy, electric transportation, military, and medicine, rare earths are traditionally produced with high environmental impact and complications of economic efficiency in separating 15 – 17 chemically similar metals that occur in tandem. Given the rapid growth projected for these metals, development is expected to increase around the globe and new deposits for rare earths is of interest. Recovering them from secondary sources, such as industrial and electronic wastes can be appealing from an economic and environmental point of view. This leaves governments and industry with difficult decisions around how to prioritize development. As technologies for extracting rare earths from secondary sources are mainly still at laboratory scale and primary extraction from ores is growing, understanding potential economic feasibility and environmental impacts to compare processes is important, but challenging. This dissertation aims to reduce this knowledge gap by providing decision makers with tools for evaluating rare earth processing techno-economics, potential revenue from deposits, and environmental impacts from secondary production. First, we show that traditional single sample Monte Carlo analysis as it is being used in technoeconomic analysis regarding rare earths is inappropriate because variability in prices is not captured realistically and this creates unnecessary uncertainty in economic modelling. Alternate uncertainty analysis methods are compared and time-intervals for sampling and forecasting are tested to show difference in outcome uncertainty. For a case study of recovering rare earths from hard drives, we quantify how choice of time-increment affects uncertainty in profitability arising from price uncertainties. Our conclusions are that mean-reversion methods are preferable, and that it is important to gather information on time scales of purchases and sales to accurately estimate uncertainty. Second, a key parameter for prioritizing development of REEs is comparison of potential revenue. Typically, deposits and projects are characterized for economics based on economic feasibility studies, however, these do not compare over different REEs resources. Basket prices have been used to compare mineral deposit value; however, these ignore ore grades. We formalize a relation between ore grades and revenue. We provide a comparison of potential revenue from developing REEs from several source materials. Results show that electronic waste such as batteries and magnets have the highest revenue potential and industrial waste such as coal ash and red mud have low potential. Revenue for industry waste sources of REEs is driven mostly by scandium content, whereas electronic waste revenue is driven mostly by neodymium. We also provide a mathematical relation between revenue and ore grades. This information can help regional decision-makers prioritize development of resources based on supply chains and market demands. Finally, life cycle analyses, which are used to measure environmental impacts for rare earth processing are relatively rare, and even more so for secondary sources. When they are available, they are difficult to compare due to many assumptions, complications from proprietary data, and differences in boundaries and functional units. This means that the environmental impact of most secondary production is largely uncharacterized. We provide an ordinal ranking framework to aid in qualitatively comparing environmental impacts from process pathways still in laboratory. This framework is used to highlight areas of further research where formal life cycle analysis methods can be applied to yield robust quantitative information useful to decision makers around prioritizing rare earth development from an environmental impacts point of view. Other important gaps identified include taking primary data for rare earth yields from processes still in laboratory, and how to scale yields to industrial level, and robust information of chemical reagent production and consumption, especially around reuse. This dissertation contributes novel data and modeling tools that can aid stakeholders and decision makers across the rare earth elements industry in making informed decisions in resource development, policy planning, and material recovery.

Library of Congress Subject Headings

Rare earth metals--Economic aspects; Electronic waste--Recycling--Economic aspects; Factory and trade waste--Recycling--Economic aspects

Publication Date

7-25-2023

Document Type

Dissertation

Student Type

Graduate

Degree Name

Sustainability (Ph.D.)

Department, Program, or Center

Sustainability (GIS)

Advisor

Gabrielle Gaustad

Advisor/Committee Member

Eric Williams

Advisor/Committee Member

Thomas J. Tarka

Campus

RIT – Main Campus

Plan Codes

SUST-PHD

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