Who would have thought it but sewage sludge and landfills could be the venue for the next gold rush. Multiple ones, in every city in the world. Researchers from Arizona State University have estimated that $13m worth of gold, silver and other metals end up in the sewage sludge of a million-person city. That includes $2.6 million in silver and gold.
Their findings are in the journal Environmental Science & Technology and Warren Cornwall wrote a piece for the layman in Science magazine.
The metals find their way into the sewage generated by a multitude of factory activities – mining, electroplating, electronics, jewelry manufacturing.
According to the Science magazine piece, the Japanese have already started extracting the gold from sludge. “In Suwa in Nagano Prefecture, a treatment plant near a large number of precision equipment manufacturers reportedly collected nearly 2 kilograms of gold in every metric ton of ash left from burning sludge, making it more gold-rich than the ore in many mines,” it said.
Clearly mining landfills and sludge may be the revenue sources of tomorrow.