Recycling of so-called rare earth elements could ease global concerns about a reliable supply of the substances now mined mostly in China, researchers say.

Writing in the journal Environment Science & Technology, scientists say the dozen or so rare earth elements, or REEs, have unique physical and chemical properties making them essential for defense applications, computers, cellphones, electric vehicles, batteries, appliances, fertilizers, liquid crystal displays and other products.

But having only one major source supply, China, is a worry, they say.

"Since 1990, China has played a dominant role in REE mining production; other countries are almost completely dependent on imports from China with respect to rare earth resources," the researchers wrote.

Researchers say a "recycle and reuse" strategy could lessen that dependence.

They say they've done the first-ever analysis of the amount of REEs available in in-use products in the United States, Japan and China, the major users of the materials.

They found nearly 99,000 tons REEs were included in products manufactured in 2007.

This "invisible" stock, equivalent to more than 10 years of mining production, "suggests that REE recycling may have the potential to offset a significant part of REE virgin extraction in the future ... and minimize the environmental challenges present in REE mining and processing," the researchers said.