MAR 24, 2015 10:57 AM PDT

There's gold in them there biosolids!

The alchemists got it wrong. The irony cannot be overstated. The alchemists thought they could turn lead into gold. Maybe they should have focused on baser material.

As reported in the guardian.com, "Gold in faeces 'is worth millions and could save the environment'."

The article, which reported on findings presented at the 249th National Meeting & Exposition of the American Chemical Society in Denver, goes on to explain:

Fortunes could be saved from going down the drain by extracting gold and precious metals from human excrement, scientists suggest.

Sewage sludge contains traces of gold, silver and platinum at levels that would be seen as commercially viable by traditional prospectors. "The gold we found was at the level of a minimal mineral deposit," said Kathleen Smith, of the US Geological Survey.

Smith and her colleagues argue that extracting metals from waste could also help limit the release of harmful metals, such as lead, into the environment in fertilisers and reduce the amount of toxic sewage that has to be buried or burnt.

"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," she said.

A previous study, by Arizona State University, estimated that a city of 1 million inhabitants flushed about $13m (£8.7m) worth of precious metals down toilets and sewer drains each year.

The task of sifting sewage for microscopic quantities of gold may sound grim, but it could have a variety of unexpected benefits over traditional gold mining. The use of powerful chemicals, called leachates, used by the industry to pull metals out of rock is controversial, because these chemicals can be devastating to ecosystems when they leak into the environment. In the controlled setting of a sewage plant, the chemicals could be used liberally without the ecological risks.

Precious metals are increasingly used in everyday products, such as shampoos, detergents and even clothes, where nanoparticles are sometimes used to limit body odour. Waste containing these metals all ends up being funnelled through sewage treatment plants, where many metals end up in the leftover solid waste. "There are metals everywhere," Smith noted.

More than 7m tonnes of "biosolids" come out of US sewage treatment plants each year, about half of which is burned or sent to landfill and half used as fertiliser on fields and in forests. In the UK, about 500,000 tonnes of dry sewage solids are used as fertiliser each year. The amount of waste that can be converted into fertiliser is limited, in part, by the high levels of some metals.

"We're interested in collecting valuable metals that could be sold, including some of the more technologically important metals, such as vanadium and copper that are in cell phones, computers and alloys," Smith said.

To assess the viability of mining sewage, the team collected samples from small towns in the Rocky Mountains, rural communities and big cities, and used a scanning electron microscope to observe microscopic quantities of gold, silver and platinum.

In findings presented on Monday at the 249th National Meeting & Exposition of the American Chemical Society in Denver, the scientists showed that the levels of the precious levels were comparable with those found in some commercial mines.

The eight-year study, which involved monthly testing of treated sewage samples, found that 1kg of sludge contained about 0.4mg gold, 28mg of silver, 638mg copper and 49mg vanadium.

A sewage treatment facility in Tokyo that has already started extracting gold from sludge has reported a yield rivalling those found in ore at some leading gold mines.

Elsewhere, sewage plants are removing phosphorus and nitrogen, which can be sold as fertiliser. A Swedish treatment plant is testing the feasibility of making bioplastics from wastewater. Earlier this year, Bill Gates demonstrated his confidence in a radical sewage purification system by drinking a glass of clean water extracted from human waste.
About the Author
You May Also Like
NOV 29, 2018
Microbiology
NOV 29, 2018
Bacteria may Explain the Symbiotic Relationship of Anemones & Clownfish
Sea anemones normally kill and eat fish. But clownfish can nestle into anemones without getting stung....
DEC 10, 2018
Plants & Animals
DEC 10, 2018
Urbanized Tungara Frogs Have Developed Sexier Mating Calls, But Why?
Animals of all kinds change their behavior to adapt to urbanized settings, and tungara frogs are no different. New research published this week in the jour...
DEC 12, 2018
Earth & The Environment
DEC 12, 2018
Bioenergy crops are hurting global biodiversity
New research published in the Proceedings of the National Academy of Sciences suggests that bioenergy crop production may not be as eco-friendly as once th...
DEC 31, 2018
Plants & Animals
DEC 31, 2018
Conservationists Are Trying to Give the Elusive Madagascar Pochard a Second Chance
The Madagascar pochard is a duck species so elusive that conservationists once thought it was extinct. But in 2006, a team happened upon a small population...
DEC 31, 2018
Earth & The Environment
DEC 31, 2018
The Low-down on the Green New Deal
What is the Green New Deal? This is a term that has been thrown around a lot in recent months, equally in the political sphere as in the environmental sphe...
JAN 05, 2019
Microbiology
JAN 05, 2019
The Gut Microbiome can Help Shield Against Arsenic Toxicity
The microbes in our gut are intricately related to our health and well-being, and scientists continue to gain insight into that relationship....
Loading Comments...