Critical Minerals Don’t Belong in Landfills – Microwave Tech Offers a Cleaner Way to Reclaim Them from E-waste
Right now, just a few countries, including China, control most of the mining, processing and recovery of these materials, making the U.S. vulnerable if those countries decide to limit exports or raise prices.
These materials aren’t cheap, either. For example, the U.S. Geological Survey reports that gallium was priced between US$220 to $500 per kilogram in 2024. That’s 50 times more expensive than common metals like copper, at $9.48 per kilogram in 2024.
Revolutionizing Recycling with Microwaves
At West Virginia University’s Department of Mechanical, Materials and Aerospace Engineering, I and materials scientist Edward Sabolsky asked a simple question: Could we find a way to heat only specific parts of electronic waste to recover these valuable materials?
If we could focus the heat on just the tiny specks of critical minerals, we might be able to recycle them easily and efficiently.
The solution we found: microwaves.
This equipment isn’t very different from the microwave ovens you use to heat food at home, just bigger and more powerful. The basic science is the same – electromagnetic waves cause electrons to oscillate, creating heat.
In our approach, though, we’re not heating water molecules like you do when cooking. Instead, we heat carbon, the black residue that collects around a candle flame or car tailpipe. Carbon heats up much faster in a microwave than water does. But don’t try this at home; your kitchen microwave wasn’t designed for such high temperatures.
In our recycling method, we first shred the electronic waste, mix it with materials called fluxes that trap impurities, and then heat the mixture with microwaves. The microwaves rapidly heat the carbon that comes from the plastics and adhesives in the e-waste. This causes the carbon to react with the tiny specks of critical materials. The result: a tiny piece of pure, sponge-like metal about the size of a grain of rice.
This metal can then be easily separated from leftover waste using filters.
So far, in our laboratory tests, we have successfully recovered about 80% of the gallium, indium and tantalum from e-waste, at purities between 95% and 97%. We have also demonstrated how it can be integrated with existing recycling processes.
Why the Department of Defense Is Interested
Our recycling technology got its start with help from a program funded by the Defense Department’s Advanced Research Projects Agency, or DARPA.
Many important technologies, from radar systems to nuclear reactors, depend on these special materials. While the Department of Defense uses less of them than the commercial market, they are a national security concern.
We’re planning to launch larger pilot projects next to test the method on smartphone circuit boards, LED lighting parts and server cards from data centers. These tests will help us fine-tune the design for a bigger system that can recycle tons of e-waste per hour instead of just a few pounds. That could mean producing up to 50 pounds of these critical minerals per hour from every ton of e-waste processed.
If the technology works as expected, we believe this approach could help meet the nation’s demand for critical materials.
How to Make E-waste Recycling Common
One way e-waste recycling could become more common is if Congress held electronics companies responsible for recycling their products and recovering the critical materials inside. Closing loopholes that allow companies to ship e-waste overseas, instead of processing it safely in the U.S., could also help build a reserve of recovered critical minerals.
But the biggest change may come from simple economics. Once technology becomes available to recover these tiny but valuable specks of critical materials quickly and affordably, the U.S. can transform domestic recycling and take a big step toward solving its shortage of critical materials.
Terence Musho is Associate Professor of Engineering, West Virginia University. This article is published courtesy of The Conversation.
