Gunnison Copper Corp (TSX:GCU, OTCQB:GCUMF) announced that Rio Tinto Ltd (LSE:RIO, ASX:RIO, OTC:RTNTF) has produced the first copper from the Johnson Camp mine in Arizona using its Nuton bioleaching technology, marking the initial commercial-scale output from the process.
The first copper cathode was produced last month following more than three decades of research and development, according to the companies, Gunnison said on Thursday.
The technology package deployed at Johnson Camp includes a heap leach pad designed to target about 30,000 tonnes of refined copper over a four-year demonstration period.
Rio Tinto said it is in discussions with potential US customers as it works to support the domestic copper supply chain.
"The first production of Nuton copper at Johnson Camp is the culmination of exceptional teamwork between Gunnison Copper and Rio Tinto's Nuton team,” Gunnison CEO Stephen Twyerould said in a statement.
“Achieving this level of performance in such a short time frame shows what is possible when innovation, operational excellence, and a shared vision come together. With Nuton copper now entering the US supply chain, this milestone underscores the critical role we can play in strengthening domestic access to cleaner, low-carbon copper."
Rio Tinto copper chief executive Katie Jackson said the Nuton technology is designed to allow faster and more efficient copper production.
"Nuton has designed a modular system deployed as a technology package integrating biology, chemistry, engineering, and digital tools, allowing it to be rapidly scaled and tailored to different ore bodies, unlocking resources that have historically been considered uneconomic or challenging,” Jackson said.
According to Gunnison, the Nuton process uses naturally occurring microorganisms to extract copper from primary sulphide materials.
These microbes, grown in proprietary bioreactors, accelerate mineral oxidation in the heap, allowing copper to dissolve into solution before being processed into 99.99% pure copper cathode. Recovery rates can reach up to 85%.
Gunnison and Rio Tinto said the process eliminates the need for traditional concentration, smelting and refining, and may allow operators to extract value from materials that would otherwise be considered waste. They also reported expected reductions in water use and carbon emissions compared with conventional methods.
At Johnson Camp, Nuton aims to produce copper with what the companies say is the lowest carbon footprint in the United States.
Rio Tinto said it has purchased 134,000 Green-e Energy certified renewable energy certificates to match all electricity use at the site. The resulting copper is expected to have a mine-to-metal carbon footprint of 0.82 kilograms of CO₂-equivalent per kilogram of copper.
The next phase for the project will focus on confirming long-term technical performance, including multi-year testing, third-party verification, and internal review by Rio Tinto.
Shares of Gunnison added 2.7% in early Thursday trading in Toronto at C$0.38.