A study conducted by the US Geological Survey has found that gold and valuable material worth hundreds of millions of dollars could be extracted from human excrement.
Precious metals such as platinum, silver and gold have been discovered in treated waste by the team, which aims to discover exactly what else is contained in bodily waste.
Kathleen Smith of the US Geological Survey told AFP: "The gold we found was at the level of a minimal mineral deposit."
According to Smith, finding a method for extracting the materials is expected to reduce the need for mining and unwanted release of metals such as lead into the environment.
Annually, more than seven million tonnes of biosolids come out of US wastewater facilities and around half of that is used as a fertiliser for fields and forests, while the remainder is incinerated or sent to landfills.
As part of the study, Smith and her team are looking into eliminating some regulated metals from the biosolids that currently limit its use for land applications.
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Through a scanning electron microscope, the team observed minute quantities of gold, silver and platinum in excrement samples collected from small towns in the Rocky Mountains, rural communities and large cities, in order to evaluate the viability of mining sewage.
Separately, a recent study conducted by a different group of experts found that waste from one million Americans could contain as much as $13m of metals.