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Researchers Found Precious Metals in the Last Place Anyone Would Think to Look

New research from the U.S. Geological Survey (USGS) may completely change the way we handle bodily waste — we might start mining it for precious and nuisance metals.

Over 7 million tons of biosolids end up in wastewater facilities each year, and samples suggest that it may all contain microscopic bits of metals that are ripe for extraction.

Withdrawing these metals would prevent them from entering the environment when the waste is repurposed as fertilizer or sent to a landfill, and could have a positive effect on the ecosystem.

Heather Lowers via EurekAlert!

Heather Lowers/USGS via EurekAlert!


Researchers analyzed random samples from across the U.S., and found a significant amount of valuable metals, including copper and vanadium, which are often used in electronic devices and alloys, as well as silver and gold.

By removing and selling these metals, the government could turn a profit while reducing the need for environmentally damaging mining operations.

Dana Kolpin via USGS

Dana Kolpin via USGS

Additionally, analysis showed the presence of less desirable elements, like lead, which “currently limit how much of these biosolids we can use on fields and forests,” according to the study’s head researcher Kathleen Smith.

As for how the metals got there, Smith says, “There are metals everywhere… in your hair care products, detergents, even nanoparticles that are put in socks to prevent bad odors.”

Likely, the miniscule bits of metal accumulate during treatment at municipal wastewater facilities after going down the drain.

To remove these metals, the research team is currently experimenting with the same chemicals used to extract metal from rock, called leachates. Although these chemicals have damaged the environment in the past, Smith claims they can be safe and effective when used in a controlled setting.

A separate study published in January, which also detected rare earth elements in municipal sewage, estimates that $13 million of metals can be found annually in the biosolids of a typical U.S. community of one million people.

While Smith agrees that monetizing the biosolids’ lucrative metals could be commercially feasible, she notes that this should be determined on a “case-by-case basis.”

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