Rare Earth metals are becoming expensive, because they are found in only a few places on Earth.

In addition, extraction methods are costly and damage the environment.

In a new study, Japanese researchers have discovered a less expensive and more eco-friendly way to recycle rare Earth metals as an alternative.

For the study, the researchers use the DNA in salmon sperm as an extraction tool.

The reason the researchers at the University of Tokyo are using this unlikely tool is because of the chemical structure of DNA.

While studying the adsorption properties of rare Earth metals, Yoshio Takahashi observed that on bacterial cell surfaces that the site containing a phosphate molecule was important for binding metal ions. This is what led them to consider DNA which also has a phosphate site.

Since most DNA samples are soluble in water, they need to have a solid substrate attached to them.

However, salmon sperm is solid and insoluble. It is also inexpensive. The Japanese fishing industry disposes of thousands of tons of salmon sperm each year.

In the study, the salmon sperm was turned into a powder with a solution containing neodymium, dysprosium and trivalent iron which are the main metals used in neodymium magnets.

The researchers found that metal ions were highly attracted to the phosphate in the powder. They were able to recover the metal ions using centrifugation.

"The idea of relying on cheap salmon sperm to adsorb and separate rare Earth elements from iron in scrap magnets is quite interesting and, although the proposed protocol does not suppress dissolving the magnets in strong acid, it deserves attention," said Jean-Claude Bunzli, a rare Earth metal researcher at the Swiss Federal Institute of Technology in Lausanne.

This process could be used to remove rare Earth metals from electronic circuits, mobile phones and hard disk drives, Bunzli added.

The research was published in the journal PLOS ONE.