A vast and largely overlooked source of rare earth metals, materials critical for clean energy, could be in our homes, sitting in the back of our cabinets and junk drawers.

A new study from researchers in China and the Netherlands estimates that reusing or recycling rare earth metals from old cellphones, hard drives, electric motors and turbines could meet as much as 40 percent of the demand for the metals in the United States, China and Europe by 2050.

It’s a promising prospect, particularly for the United States, which relies heavily on imports of these materials, often just called rare earths. That reliance, industry experts say, can make American supply chains vulnerable to disruption and geopolitical risks.

Rare earths are essential for green technology, like electric vehicles and wind turbines, which have a critical role in moving the world away from burning fossil fuels. They’re also used in industries like aircraft, missile and satellite manufacturing.

Reusing and recycling rare earths can cut down on the need for mining, which can pollute soil and water with toxic heavy metals like arsenic. Rare earth mining operations have also become embroiled in local conflicts and human rights violations.

Being able to tap already-mined rare earths would be another advantage of switching to renewable energy from burning fossil fuels, which drives global warming, said Peng Wang, a researcher at the Institute of Urban Environment at the Chinese Academy of Sciences and lead author of the study, which was published this month in Nature Geoscience.

“Unlike fossil fuels, which are ‘burnt out’ and permanently lost once consumed,” he wrote, rare earths “can be ‘recovered’ as alternative supply.”

The idea of reusing or recycling rare earths isn’t new. In the 1980s, Japanese researchers coined the term urban mining to describe collecting rare metals from discarded appliances and electronic devices, rather than from the earth.

Common metals like iron, copper and aluminum are already widely recycled. But only about 1 percent of rare earths in old products are reused or recycled, researchers estimate. The world instead relies on mining for its supply of rare earths, about 70 percent of which comes from China, according to the U.S. Geological Survey.

For the latest study, researchers used modeling to forecast how reusing and recycling rare earths could change that. The scientists found that the United States, the European Union and Japan could eventually accumulate rare-earth stockpiles in their old electronics and other products that far exceed what they would find mining the earth.

Based on their modeling, the researchers predicted that, globally, reuse and recycling could reduce the need to mine neodymium, a rare earth element used in wind turbines, by 60 percent in 2050 compared to a business-as-normal base line. For dysprosium, also used in wind turbines, that figure was 67 percent.

The opportunity is there, but some big challenges remain.

Rare earths are often combined with other metals, so extracting them can be difficult. Some rare-earth recycling methods require hazardous chemicals and lots of energy. Extracting the few grams, or even milligrams, of rare earths that are present in each old product can be a daunting task. And there aren’t many systems in place to collect old electronics and other items.

Scientists, though, are working to advance recycling techniques. Researchers at the Department of Energy’s Critical Materials Innovation Hub at Idaho National Laboratory, for example, are developing ways to use microbes instead of toxic chemicals to pull rare earths from old products. Companies like Apple are developing robots that help to recover critical materials, including rare earths, from old iPhones. Twenty-five U.S. states and the District of Columbia already have recycling laws that mandate the collection of some used electronics, though most rare earths in those electronics aren’t being recycled.

“We already have a supply right now. But we’re land-filling a lot of it, or it’s sitting in people’s houses, in cellphones in a drawer somewhere,” said David Reed, a scientist who leads research into reuse and recycling at the Idaho National Laboratory.

“The challenge is gathering it and processing it, and I don’t know if there’s going to be a silver bullet,” he said. “But there’s a lot of research going on, a lot of interest.”

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