An American-led team of bum brownie boffins say we’re flushing a fortune down the drain as sewage sludge contains traces of gold, silver and platinum at levels that would be seen as commercially viable by traditional prospectors.
And they argue that by filtering faeces we could help the environment by reducing the level of harmful metals such as lead in fertilisers as well as the amount of toxic sewage that has to be buried or burnt.
“The gold we found was at the level of a minimal mineral deposit,” said Kathleen Smith, of the US Geological Survey, quoted in The Guardian. “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.
Precious metals are used in many everyday products including shampoos, detergents and even clothes, and waste containing these products ends up being funnelled through sewage treatment plants. A previous study by Arizona State University estimated that a city of one million people flushes about £8.7m worth of precious metals down toilets and sewers every year.
The latest eight-year study found that 1kg of sludge contained about 0.4mg of gold, 28mg of silver, 638mg of copper and 49mg of vanadium. These could be extracted at a sewage plant without the same high level of ecological risk posed when powerful chemicals are used at traditional gold mines.
But anyone tempted to painstakingly sift through their own poop is likely to be on an abortive quest for stools’ gold. The individual quantities of precious metals are microscopic, so there’s no point hitting the laxatives in expectation of a gold rush.