Riley Coulthard

Riley Coulthard

Riley Coulthard

Yale University, Ph.D. 
Fiessinger Doctoral Scholar 2016

Carbon Nanotube Enabled Technology for Reclamation of Rare Earth Elements from Coal Combustion Residues

Project Description:
The goal of this project is to develop a technology to extract rare earth elements (REEs) from large volume solid wastes, specifically targeting coal combustion residuals (CCRs). With support from the EREF, Riley will pursue a nanomaterial-enabled device that leverages electrochemical precipitation to recover valuable components, even those that occur at trace levels, from CCRs. The ability to recover REEs from this “waste" stream will create economic incentive for diverting coal ash  to a novel material resource.

REEs are increasingly used in electronics, clean energy technologies, and defense applications, but the supply of REEs is generally restricted to non-U.S. sources or is not economically competitive in the US. As a result, some REEs have been identified as critical materials by the U.S. Department of Energy. Further, because REEs are diffuse, they are often dilute components of mixed ores and their extraction is challenging. However, REEs are enriched in CCRs. With approximately 100 million metric tons generated annually, CCRs are one of the largest industrial solid waste streams in the country. Almost half of the coal ash is recycled as cement or drywall, whereas more than half remains as stored waste. This can leach toxic metals into the groundwater or, in some cases, fail catastrophically, releasing the ash into local surface waters. Since coal ash presents a viable source of REEs, Riley seeks to utilize CCRs as an alternative resource of REEs. The development of technology to purify REEs from coal ash would increase the economic benefit of coal ash treatment and reuse, and that is the primary goal of this work.

Riley graduated Summa Cum Laude with a B.A. in Chemistry from Lewis and Clark College in Portland, OR and is a Barry Goldwater Scholar. Inspired by the solid wastes generation at her prior job as a barista, Riley volunteered at Free Geek, an electronics recycling facility, and sought research opportunities to begin to address the global challenge of solid waste management.  Riley spent two summers researching at Lawrence Livermore National Lab in the Materials Science Division, working on the optimization of nanoparticle synthesis and the utilization of those nanoparticles in homeland security and energy applications.

Currently, Riley works to improve nanotechnology for the reclamation and recycling of rare earth elements (REEs) from coal combustion products and leverages electrochemically-induced metal nanoparticle crystal growth to do so. In the future, Riley plans to adapt this technology to other sectors in order to ensure the supply of REEs for electronics, renewable energy, and national defense applications. She is also interested in minimizing the release of REEs into the environment during waste processing and disposal.  She would like to recruit others to her cause by expanding research opportunities to community college students and educating the public about waste management and recycling technologies in order to facilitate greater public participation in recycling.

Riley is pursuing her Ph.D. in Environmental Engineering at Yale University. Her hope is that by creating an economic incentive to improve recycling, she will be able to redefine the notion of “waste” and generate resources from some of the country’s largest solid waste streams.