Miners turn to unique leaching processes for copper extraction

Bacteria and newly developed chemicals provide an alternative to conventional leaching.

Edited by Josephine Patterson

Photo: Jetti Resources

Due to copper prices nearly doubling in the past two years, miners like Rio Tinto and Freeport-McMoRan have begun to use new leaching technologies to extract low concentrations of the in-demand product from waste rock, reported Reuters

Miners aim to use bacteria or other newly developed chemicals to extract even more copper from waste rock in a secondary leaching process. Rio Tinto and other companies that spoke with Reuters estimate that the piles of waste rock stored at their mine sites could contain as much as 100 million tonnes of copper. That could enable them to produce copper at concentrations of 0.5% or lower – compared with typical grades in mines of 0.6% to 1% or beyond – in an economic way, the companies told Reuters.

“It’s the equivalent of bringing on a new mine without having all the capital costs,” said Freeport President Kathleen Quirk.

These new processes also do not require fresh regulatory approval, noted the news agency, helping mining companies to avoid lengthy permitting delays as well as potential battles with environmentalists who have long worried that traditional leaching methods could lead to acids and other materials in drinking water supplies.

Rio Tinto tests ‘Nuton’

Rio Tinto, which said it has been studying leaching technologies for 30 years, has developed a bacteria that naturally produces heat when applied to certain types of rock, helping to extract copper.

The miner has inked deals with Canadian-based Lion Copper and Gold Corp. and Arizona Sonoran Copper Co. to test out the technology, which it has labeled “Nuton” – a play on Isaac Newton’s name.

“Our ambitions here are quite substantial,” said Rio Tino’s Adam Burley, who runs the Nuton program. “In order to capture the full size of the prize, both financially and socially, we need to deploy within and beyond Rio’s portfolio.”

Freeport invests in Jetti

Freeport has developed several new leaching technologies internally and with partners at its Morenci copper mine in Arizona. The miner has estimated that there are 19 billion pounds of copper unrecoverable by traditional leaching methods at the open-pit mining complex.

With the new leaching technologies, Freeport said that it could boost its annual copper production by at least 100 million lbs. within a few years, equivalent to roughly 2.6% of its output in 2021.

Last year, the miner invested in Boulder, Colo.-headquartered Jetti Resources, a technology-driven company that has developed a method to extract copper from low-grade primary sulfides. When the investment was announced, Josh Olmsted, Freeport’s president and chief operating officer – Americas, said: “We are pleased to partner with Jetti, as we pursue technologies to improve copper production from leach stockpiles, reduce our carbon footprint, and supply responsibly produced copper to a global market with increasing demand.”

“The mining industry is used to high capital budget projects that are hard to permit and have environmental drawbacks,” said Jetti founder and chief executive Mike Outwin. “Our proposition to the industry is cheaper.” The company charges its customers a per-pound royalty that is linked to the copper price.

Beyond copper, Reuters said technology firms are looking to boost the use of leaching for other minerals, including rare earths. For example, Massachusetts-based startup Phoenix Tailings said it has developed technology to leach several types of rare earth metals, including neodymium, from waste rock without using harsh chemicals. 

Phoenix Tailings’ process is still in lab testing, but the company hopes to begin commercial operations by 2025.

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