Precious finds in solid waste

If recent research has prompted you to strain your sewerage in search of the latest big find, you can probably think again.

A report from the US Geological Survey and companion study by Arizona State University suggested commercial, albeit low-grade quantities of precious metals could be recovered from solid waste.

The research also argued organised extraction could limit the release of harmful metals back into the environment.

But WASM Adjunct Professor Bill Staunton said while the findings were not surprising, anyone looking down the drain in search of riches was probably misguided.

"We've known for a long time that you can get a concentration of metals out of sewage as you process it," Prof Staunton said.

"In one or two places in the developing world, in situations where you'll find a row of goldsmiths for instance - people survive buy scouring the drainage systems of those streets for the little bits of gold the smiths accidentally release.

"But it's not usually considered an economic resource in any real sense of the word."

The ASU study found a good-sized city flushed an estimated $US13 million down the drain each year - with the metals concentrated as the waste water moved through the processing stages.

While it may be easy to think we're somehow ingesting gold and silver, the contamination comes from the ubiquitous nature of precious metals in everyday items, with miniscule dust and grains being swept into the sewer system.

Professor Staunton said the overall money on offer paled in comparison to available resources.

"The industry produces about 2800 tonnes of gold a year at about $50 million per tonne -- one or two million would be nice to have in your pocket, but you'd probably spend four or five million getting it out," he said.

"By the time you've got rid of the water, extracting the metals from what is a very complex chemical mixture is not an easy process."

"The USGS survey described the grade as equivalent to low-grade ore. Well, we have lots of low grade ore now that isn't full of s…, and lots more of it."

But we left the final word on this possible new cottage industry to the Chamber of Minerals and Energy's Holly Phillips, who said it was always great to see new innovations and research playing a role in the resources sector.

"I'm not confident there will be a big crowd lining up to go prospecting though," Ms Phillips said.