Gabrielle Gaustad

Economic and environmental characterization of an evolving Li-ion battery waste stream.

While disposal bans of lithium-ion batteries are gaining in popularity, the infrastructure required to recycle these batteries has not yet fully emerged and the economic motivation for this type of recycling system has not yet been quantified comprehensively. This study combines economic modeling and fundamental material characterization methods to quantify economic trade-offs for lithium ion batteries at their end-of-life. Results show that as chemistries transition from lithium-cobalt based cathodes to less costly chemistries, battery recovery value decreases along with the initial value of the raw materials used. For example, manganese-spinel and iron phosphate cathode batteries have potential material values 73% and 79% less than cobalt cathode batteries, respectively. A majority of the potentially recoverable value resides in the base metals contained in the cathode; this increases disassembly cost and time as this is the last portion of the battery taken apart. A great deal of compositional variability exists, even within the same cathode chemistry, due to differences between manufacturers with coefficient of variation up to 37% for some base metals. Cathode changes over time will result in a heavily co-mingled waste stream, further complicating waste management and recycling processes. These results aim to inform disposal, collection, and take-back policies being proposed currently that affect waste management infrastructure as well as guide future deployment of novel recycling techniques.

Prioritizing material recovery for end-of-life printed circuit boards.

THIS work explores environmental and economic metrics for prioritizing the recovery of materials from end-of-life printed circuit board (PCB). Data from various PCB component and product types, primary and scrap commodity market prices, and virgin and secondary embodied energy was collected and statistically sampled. Initial results will be used to inform and develop optimal recycling technologies.

Recycling single-wall carbon nanotube anodes from lithium ion batteries

Large scale incorporation of nanomaterials into industrial systems and commercial products is relatively new, and therefore little attention has been given for options when these products reach their end-of-life. During the course of this study, the ability to recycle end-of-life (EOL) single-wall carbon nanotubes (SWCNTs), recovered from lithium ion battery electrodes, was investigated. Specifically, SWCNT–Li+ coin cells were forced to their EOL though extended cycling at high charge rates and recycled using a series of acid and thermal treatments originally developed for the purification of as-produced SWCNT material. The recycling treatments were successful in removing the EOL byproducts (e.g. solid electrolyte interphase, lithium) and upgrading the SWCNT material to its pre-cycling functionality. The material was characterized at each step in the recycling process through a combination of scanning electron microscopy, thermogravimetric analysis, Raman spectroscopy, and optical absorption spectroscopy. The energy required for each of the recycling procedures was measured and compared to the energy of SWCNT synthesis. The recycled-SWCNT material was successfully incorporated into Li+ battery coin cells with insertion and extraction capacities of 650 mA h g−1, comparable to the virgin pure-SWCNT electrodes. Therefore, the ability to refunctionalize “used” SWCNTs from a device, through chemical processing, to their initial purity and functionality has been demonstrated. The direct energy required to refunctionalize the SWCNTs was measured and is less than half of the direct energy required to synthesize new material. Thus, the ability to preserve the nanoscale properties of SWCNTs with reduced impact offers new opportunities for end-of-life management.

Targeting high value metals in lithium-ion battery recycling via shredding and size-based separation.

Development of lithium-ion battery recycling systems is a current focus of much research; however, significant research remains to optimize the process. One key area not studied is the utilization of mechanical pre-recycling steps to improve overall yield. This work proposes a pre-recycling process, including mechanical shredding and size-based sorting steps, with the goal of potential future scale-up to the industrial level. This pre-recycling process aims to achieve material segregation with a focus on the metallic portion and provide clear targets for subsequent recycling processes. The results show that contained metallic materials can be segregated into different size fractions at different levels. For example, for lithium cobalt oxide batteries, cobalt content has been improved from 35% by weight in the metallic portion before this pre-recycling process to 82% in the ultrafine (<0.5mm) fraction and to 68% in the fine (0.5-1mm) fraction, and been excluded in the larger pieces (>6mm). However, size fractions across multiple battery chemistries showed significant variability in material concentration. This finding indicates that sorting by cathode before pre-treatment could reduce the uncertainty of input materials and therefore improve the purity of output streams. Thus, battery labeling systems may be an important step towards implementation of any pre-recycling process.

Comparative Analysis of Supply Risk-Mitigation Strategies for Critical Byproduct Minerals: A Case Study of Tellurium

Materials criticality assessment is a screening framework increasingly applied to identify materials of importance that face scarcity risks. Although these assessments highlight materials for the implicit purpose of informing future action, the aggregated nature of their findings make them difficult to use for guidance in developing nuanced mitigation strategy and policy response. As a first step in the selection of mitigation strategies, the present work proposes a modeling framework and accompanying set of metrics to directly compare strategies by measuring effectiveness of risk reduction as a function of the features of projected supply demand balance over time. The work focuses on byproduct materials, whose criticality is particularly important to understand because their supplies are inherently less responsive to market balancing forces, i.e., price feedbacks. Tellurium, a byproduct of copper refining, which is critical to solar photovoltaics, is chosen as a case study, and three commonly discussed byproduct-relevant strategies are selected: dematerialization of end-use product, byproduct yield improvement, and end-of-life recycling rate improvement. Results suggest that dematerialization will be nearly twice as effective at reducing supply risk as the next best option, yield improvement. Finally, due to its infrequent use at present and its dependence upon long product lifespans, recycling end-of-life products is expected to be the least effective option despite potentially offering other benefits (e.g., cost savings and environmental impact reduction).

Estimating direct human health impacts of end-of-life solar recovery

Studies have found that recycling photovoltaics at their end of life has significant potential for energy pay-back time reduction, resource savings, and environmental impact reduction. However, most of these studies do not consider the complexities of PV recycling resulting from lack of collection infrastructure, unavailability of advanced recovery technologies, and the geo-spatial dependence of both of these issues. This work combines geo-spatial modelling and statistics, collection logistics optimization, and environmental impact assessment in order to quantify the impacts resulting from collection, processing, and recovery of PV materials given current US solar installations, municipal solid waste and landfill infrastructure, and the networks between them. Results show that previous work may have underestimated certain environmental impacts due to transportation by an order of magnitude for the US case study. The treatment of a recycling resource credit significantly impacts these results. Using the avoided burden approach results in a net negative SO2 and NOx emissions of up to 0.57 g SO2 per kWh and 0.039 g NOx per kWh. Cumulatively, the avoided burden approach results in an net negative 14.5 PM10 eq g per kWh. If the assumption of the avoided burden approach are true, then recycling cancels out lifecycle emissions.

Price volatility in PV-critical material markets: Perspectives for solar firms, consumers, and policy makers

Price volatility in byproduct material markets, such as tellurium and indium, create economic uncertainty for technologies that use them, e.g. CdTe and CIGS solar PV. This uncertainty is of interest to multiple stakeholders since it can affect, for example, firm profitability and consumer rate of return on investment; however, this issue has not yet been addressed in the literature. The present work seeks to fill this gap by probing sensitivity of key decision metrics, namely profit margin for firms and payback time for consumers, to changes in input material price on par with recently observed volatility. The results of the previous two analyses are used to provide a broad perspective on potential insights for policy makers looking to most effectively promote clean energy adoption.

Dissipative Use of Critical Metals in the Aluminum Industry

To improve properties such as weldability, corrosion resistance, strength, etc. the aluminum industry, in recent years, has enhanced functionality of aluminum alloys by increasing diversity of metals being used for alloying. These metals often include critical ones i.e. those that are geologically scarce, highly prone to supply bottleneck and/or highly demanded with no known substitute. A logical solution to the above-mentioned identifiers would be the recovery of these critical materials from the finished products at their end of life. Unfortunately, the yield of the critical metals, on recovery, is too low for feasible economic recovery and therefore they are dissipatively lost. This work quantifies the impacts of such losses using material flow analysis and life-cycle assessment in order to suggest best practices to minimize these impacts. Results show circular economy strategies can be effective for mitigating criticality risk in the aluminum industry.

Potential for Handheld Analyzers to Address Emerging Positive Material Identification (PMI) Challenges

Positive material identification (PMI) is a challenge in the metals secondary industry that remains persistent as products are designed with increasing complexity. Strategies in the automotive industry to improve fuel efficiency include development of lightweight wrought aluminum and magnesium alloys to replace heavier steel components in vehicles. These alloys have tight compositional requirements and the traditional equipment for sorting and identifying this scrap (i.e. a magnet, file, and/or grinding wheel) is inadequate. Handheld analyzers that utilize X-ray fluorescence and spectroscopy technology may offer technological assistance that is helpful for PMI. This work tests the performance of these units under the challenging conditions present in yards (contaminated, unpolished, comingled scraps). As the costs of these units have decreased substantially over time, results have shown there are more opportunities for quicker return on investment under a variety of scenarios; yard volume, incoming grades, and diversity of suppliers have the largest impact on pay-off.

Portfolio Optimization of Nanomaterial Use in Clean Energy Technologies

While engineered nanomaterials (ENMs) are increasingly incorporated in diverse applications, risks of ENM adoption remain difficult to predict and mitigate proactively. Current decision-making tools do not adequately account for ENM uncertainties including varying functional forms, unique environmental behavior, economic costs, unknown supply and demand, and upstream emissions. The complexity of the ENM system necessitates a novel approach: in this study, the adaptation of an investment portfolio optimization model is demonstrated for optimization of ENM use in renewable energy technologies. Where a traditional investment portfolio optimization model maximizes return on investment through optimal selection of stock, ENM portfolio optimization maximizes the performance of energy technology systems by optimizing selective use of ENMs. Cumulative impacts of multiple ENM material portfolios are evaluated in two case studies: organic photovoltaic cells (OPVs) for renewable energy and lithium-ion batteries (LIBs) for electric vehicles. Results indicate ENM adoption is dependent on overall performance and variance of the material, resource use, environmental impact, and economic trade-offs. From a sustainability perspective, improved clean energy applications can help extend product lifespans, reduce fossil energy consumption, and substitute ENMs for scarce incumbent materials.