We’re Losing Our Minds: Scientists Will Mine Human Waste for Gold

Microscopic gold-rich and lead-rich particles in a municipal biosolids sample. Image: Heather Lowers, USGS Denver Microbeam Laboratory
Microscopic gold-rich and lead-rich particles in a municipal biosolids sample. Image: Heather Lowers, USGS Denver Microbeam Laboratory

Every year, Americans are flushing a fortune down the toilet. Literally. More than 7 million tons of biosolids—treated sewage sludge—pass through US wastewater facilities annually. Contained within our shit are surprisingly large quantities of silver, gold, and platinum.

But our days of wasting human waste may be numbered, if Kathleen Smith of the US Geological Survey has anything to say about it. She’s leading a new research program that’s examining the feasibility of extracting precious metals from sewage. As Smith will explain Tuesday at a press conference at the annual meeting of the American Chemical Society, recovering metals from waste could reduce the need for environmentally-destructive mining programs, and make biosolids a safer source of fertilizer to boot.

“There are metals everywhere,” Smith said in a statement. “If you can get rid of some of the nuisance metals that currently limit how much of these biosolids we can use on fields and forests, and at the same time recover valuable metals and other elements, that’s a win-win.”

At treatment plants, raw sewage is processed by a series of physical, biological and chemical processes and transformed into treated water and biosolids. Roughly 60 percent of biosolids are applied as fertilizer to fields and forests. The rest are either incinerated or buried. While biosolids are routinely screened for hazardous heavy metals including lead, arsenic, and cadmium, few studies have tested our waste for anything as valuable as, say, gold or platinum.

But that’s starting to change. Earlier this year, a study led by Paul Westerhoff at Arizona State University profiled over 50 metals in biosolid samples from 94 wastewater treatment plants across the US. Most samples were substantially enriched in rare and precious platinum-group metals, silver, and gold. Extrapolating from their data, the authors worked out that the waste produced annually by a million Americans could contain as much as 13 million dollars worth of metals. That’s over four billion dollars worth of gold coming out of our collective arses every year.​

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SOURCE: MADDIE STONE
Motherboard / Vice

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