The latest step toward a more sustainable future may involve extracting lucrative minerals from seaweed.
The science behind it comes out of Pacific Northwest National Laboratory, an outfit of the Department of Energy.
“Minerals known as rare earth elements, like neodymium, are some of the most important ingredients in our electronics, vehicles, and buildings and are traditionally mined underground,” PNNL reported. But the ocean — and its seaweed — is the next frontier.
Researchers have long known that the sea is home to such minerals, but they are too diluted to be harvested efficiently. Seaweed, however, can hold concentrations over a million times greater than those of the water. And PNNL scientists have been growing the organisms in water from Sequim Bay in Washington.
Different species host different minerals, but these substances are ingrained in the tissue. The researchers found that they can use an acidic liquid to break the bonds holding them together. This lixiviant, used to extract minerals from rock in mining, separates the valuable inorganics from the seaweed.
The researchers are varying their methods so they can retrieve 50% of the minerals, trying to find the least energy-intensive combination as well as the most cost-efficient. They no longer heat-dry the seaweed first, for example, and they have used waste acids to reduce the expense associated with lixiviant.
“The ocean is the single largest source of a lot of critical minerals we need for high-tech applications,” principal investigator Michael Huesemann said. “If we’re able to tap seawater and do it in a way that’s responsible, that potentially allows for a domestic source of critical materials.”
After the scientists grind the seaweed into a paste, they mix it with lixiviant to break the chemical bonds holding the minerals in the seaweed. They then treat the plants at high temperatures to break more chemical bonds. The last two steps are repeated as necessary.
If the process can be scaled, it would signal a massive shift in the process of mining minerals, which creates pollution without enabling a fully circular economy. Recycling facilities for smartphones and other devices made with rare earth elements are helping to create a cleaner future, but the prevalence of e-waste shows there’s a long way to go.
Still, Earth.com reported that recovering less than 1% of these minerals “could transform supply.” Boosting recovery while creating a new source via biomining might be revolutionary.
The PNNL researchers also noted the remaining seaweed could be used as biofuel feedstock or in plastics, building materials, and adhesives. The organism grows fast, too, without the need for fresh water.
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