While there is still controversy over coal for energy, a new study says that rare earth elements widely used in smartphones, computers and other electronics could soon be extracted cleanly and inexpensively from United States coal, which would decrease the nation's dependence on Chinese production of those elements (REEs).

Currently, China is responsible for producing 85 percent of Earth's REEs and the U.S. cranks out a little over 6 percent, according to the United States Geological Survey (USGS). The USGS also estimates that REE demand worldwide will grow by more than 5 percent each year through 2020.

"We have known for many decades that rare earth elements are found in coal seams and near other mineral veins," Sarma Pisupati at Penn State said in a release. "However, it was costly to extract the materials and there was relatively low demand until recently.

Because coal is abundant in the U.S. and, of course, in Pennsylvania, Penn State researchers wanted to take a closer look in their study at extracting REEs from domestic coal. In that research, they used byproducts of coal production from the Northern Appalachians, finding out whether the chemical process of ion exchange could extract the REEs safely.

In the past, research looked at the process called "roasting," which uses more energy and requires contact with concentrated acids. In comparison, ion exchange needs less energy and is a more environmentally friendly choice, with its process of rinsing coal with a solution that brings out the REEs bound to the coal.

The team's findings were recently reported in the journal Metallurgical and Materials Transactions E. This included the information that ammonium sulfate succeeded in deriving the highest portion of REEs and was environmentally friendly. Being able to extract 2 percent of the REEs that are available would help companies financially, says the report.

"We were able to very easily extract 0.5 percent of REEs in this preliminary study using a basic ion exchange method in the lab," Pisupati said in the release. We are confident that we can increase that to 2 percent through advanced ion exchange methods."

The researchers are working with several Pennsylvania coal-mining companies to look into a possible commercial operation to extract REEs.

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-Follow Catherine on Twitter @TreesWhales