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Human poo a mine of precious metals

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A study has identified gold in human waste from American sewage treatment plants at levels which if found in rock could be worth mining

A study has identified gold in human waste from American sewage treatment plants at levels which if found in rock could be worth mining

A study has identified gold in human waste from American sewage treatment plants at levels which if found in rock could be worth mining

Never was the expression "where there's muck there's brass" more appropriate.

Scientists have discovered a literal goldmine of precious metals in human poo.

The US researchers are investigating ways of flushing out the valuable minerals, including gold, silver and rare elements such as palladium and vanadium.

So far the group has already identified gold in waste from American sewage treatment plants at levels which if found in rock could be worth mining.

The microscopic nuggets were observed using a scanning electron microscope.

Lead scientist Dr Kathleen Smith, from the US Geological Survey, said: "The gold we found was at the level of a minimal mineral deposit."

She added: "There are metals everywhere - in your hair care products, detergents, even nanoparticles that are put in socks to prevent bad odours."

The metals find their way into the body and end up being excreted and going down the toilet. At sewage treatment plants they are concentrated in left-over "biosolids", more than seven million tons of which are produced in the US each year.

Half the biosolids are used as fertiliser on fields and in forests while the other half are incinerated or buried at landfill sites.

Dr Smith said: "We have a two-pronged approach. In one part of the study, we are looking at removing some regulated metals from the biosolids that limit their use for land application.

"In the other part of the project, 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."

Taking a lesson from industrial mining, the scientists are experimenting with chemicals called leachates that are used to pull metals out of rock.

Some of these chemicals have a bad reputation for damaging ecosystems when they leak or spill into the environment. But in controlled conditions, they could safely be used to recover metals from treated solid waste, Dr Smith claims.

"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.

The researchers described their work at the 249th national meeting of the American Chemical Society in Denver, Colorado.

A previous study published in the journal Environmental Science and Technology estimated that the waste from one million Americans could contain as much as 13 million dollars (£8.7 million) worth of metals.

PA Media