Ames Lab Researchers Turn To Corn Stover For Electronics Recycling

By Dan Mika, Staff Writer

Researchers at the Ames Laboratory and other Department of Energy labs have demonstrated a way to use corn stover left over from harvest to help recycle strategically significant metals from outdated electronics.

The process, researched at the Ames Laboratory on the Iowa State University campus and carried out by other Department of Energy sites in Idaho, California and at Purdue University, uses leftover corn stover to feed a strain of bacteria that is attracted to rare-earth metals and separates them from residual materials.

Rare-earth metals, a group of 17 elements found naturally occurring on the planet, are extensively used in electronics and manufacturing for various magnetic properties.

Alex King, director of the Critical Materials Institute at the Ames Lab, said researchers in Ames previously discovered the bacteria, known as Gluconobacter, by accident several years ago while looking for a bacteria that wouldn’t be poisoned by those materials. The bacteria not only survived exposure to the metals, but stripped them to their base elemental state.

“We’re essentially using biological mining for these elements that are invaluable,” he said.

Although Gluconobacter is effective at collecting the metals, it requires sustenance to continue mining. Researchers previously fed them refined glucose, a type of sugar. It worked, but the cost of the glucose made it too expensive to be used at larger scales.

Under the new process announced this past week, researchers believe they can use the sugars found in corn stover to feed industrial levels of bacteria without breaking the bank.

“It’s not quite as good as glucose, but it’s much, much cheaper,” he said.

The vast majority of rare-earth metals are produced in China, which by one estimate controlled up to 80 percent of the world’s supply last year. In 2010 and 2011, China began to restrict rare-earth exports, citing environmental concerns, forcing other countries to begin research into rare-earth alternatives and recycling.

Despite the name, the metals are fairly common across the Earth, but there are only a handful of areas where the material is pure enough to mine.

At the moment, the process has only been demonstrated at the laboratory level. The next step is scale experiments to an industrial level to see if the bacteria still strip the metals effectively. If that works, the Lab will license the technology to a private company for its own use.

A successful licensing could lead to a major “economic boon” for Iowa as a whole due to the opening of a new market for local farmers, he said.

King said while the process can be used to recycle rare-earth metals from old electronics, it could potentially be developed to a scale where it can be used to purify rare-earth metals extracted from mines diluted with other material.

“It’s kind of a game changer,” he said.

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