A bacterium contained in drainage from old mines can enrich copper to the level of copper ore, a research team said.
The discovery could lead to a more efficient system of collecting copper from scrapped electric appliances and other goods at a time when the metal is in high demand but limited in supply.
The study started after Satoshi Mitsunobu, 45, a professor at Ehime University’s Graduate School of Agriculture specializing in environmental microbiology, found a high concentration of copper in drainage sediment at an old copper mine in Ehime Prefecture about two years ago.
A detailed examination showed a bacterium that lived on energy produced when iron is oxidized. The iron-oxidizing bacterium created iron rust, which absorbed copper in the drainage water, producing the sediment.
Normally, copper accounts for roughly 0.7 percent of the weight of mined copper ore.
But the deposits contained up to 2 percent, according to the researchers.
The team will work on establishing a system to use the newly found bacterium to collect copper from smartphones and other scrap sources more efficiently than current technologies.
Kazuya Tanimoto, 24, a graduate student at Ehime University, was a member of the team.
Researchers from the Riken scientific research institute, the Japan Atomic Energy Agency and Kyushu University’s Graduate School also participated in the joint research.
Mitsunobu, who has been studying soil and drainage from old mines for micro-organisms, took note of the geological characteristics of the Shikoku region.
The Median Tectonic Line, Japan’s largest fault, stretches for about 1,000 kilometers and runs directly under the main Shikoku island. The line is dotted with the ruins of many metal mines.
According to the economy ministry, copper, a highly conductive and easy-to-process metal, is used for transmission cables, connectors of communication equipment and many other purposes.
Copper demand has grown rapidly in recent years for electric vehicles, artificial intelligence and other technologies.
However, large-scale copper mines are increasingly difficult to find, and metal producers are banking on new deposits found at existing mines.
“We are at a stage where we have just found out the principle of an application to collect copper,” Mitsunobu said. “Because there is a high possibility that copper will be in short supply, we want to study further to contribute to a stable supply.”
The team’s findings were published on Nov. 30 in Environmental Microbiology, an international scientific journal issued in the United States.