Bringing rare earths into the circular economy
In an ironic twist, the rare-earth elements that are key to many clean energy technologies are produced by material- and energy-intensive processes that tend to be heavily polluting. At Purdue, we’re developing a comprehensive environmental profile of these elements using life cycle analysis (LCA), which considers the environmental impacts of a product from raw material extraction through manufacturing, transportation, use, and end of life. The goal is to clean up the process and usher these vital elements into the circular economy.
Rare earth elements are a group of 17 metals with similar and unique physical and chemical properties that make it very difficult to find substitutes without sacrificing performance. For example, neodymium and dysprosium are used to make permanent magnets for electric vehicle motors and wind turbine generators. Terbium and yttrium are needed to make phosphors for high-efficiency lighting. Cerium and lanthanum have a vital role in making catalysts.
Life cycle analysis can help quantify the environmental performance of any product or process. It helps avoid the potential shifting of environmental burdens from one life cycle stage to another, one medium to another, or one location to another. LCA is the starting point for an environmental sustainability initiative, but existing studies on rare earth production are limited, riddled with obsolete and/or generic data and lots of simplifications and assumptions.
We developed the first open-source software tool for documenting rare earth production pathways with data collected from sites in China. In addition, we worked with researchers at the Critical Materials Institute — a U.S. Department of Energy Innovation Hub that supports early-stage research to advance innovation in U.S. manufacturing — to provide environmental hotspot information that can be used to guide the development of “greener” processes. We released the tool in 2018 and have since received hundreds of inquiries from researchers around the world.
Now we’re expanding our software to cover additional critical materials like lithium, cobalt, graphite, indium and gallium. We’re also working on recycling lithium-ion batteries and hard disk drives to recover their critical materials, with support from the DOE’s Critical Materials Institute. Our collaborators include the Oak Ridge National Laboratory, the Idaho National Laboratory, Case Western Reserve University and the University of Arizona.
There are huge amounts of rare-earth-containing products currently in use. We believe recycling can play an important role in securing the supply of these critical materials in the United States while minimizing environmental impacts. Compared with virgin production, recycling could reduce the environmental impacts of rare earths production by up to 80 percent. Ideally, one would expect to see a circular economy in rare earths, requiring minimal virgin materials to sustain production. Developing a viable infrastructure and technologies for recycling is key.
We can’t continue business as usual and expect to address the supply risk and environmental impacts of rare earths, as doing nothing new may hinder the wide deployment of green technologies. Disciplines like environmental and ecological engineering attack the problem at the source — rather than cleaning up afterward — through development of greener processes and recycling, as well as system and life cycle analysis to support policymaking.
Associate Professor of Mechanical Engineering and Environmental & Ecological Engineering
College of Engineering, Purdue University
Purdue Engineering Podcast: “Urban Sustainability” with Fu Zhao