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Rio Tinto (ASX, LON, NYSE: RIO) has at a plant located at a borates mine it controls in California.

The demonstration facility is the next step in scaling up a breakthrough lithium production process developed at the Boron mine. The method allows Rio Tinto to recover the critical mineral and extract additional value out of waste piles from over 90 years of mining at the operation.

An initial small-scale trial in 2019 successfully proved the process of roasting and leaching waste rock to recover high grades of the metal, vital in the production of batteries that power electric vehicles (EVs) and most high tech electronics.

Rio’s discovery of lithium at Boron was a fluke. The miner was actually testing Boron’s tailings to see whether the presence of gold was significant and found instead traces of lithium at a concentration higher than domestic projects under development.

“We were looking for gold… but we found something better than gold: battery-grade lithium – and the potential to produce a lot of it,” Alex Macdonald, senior engineer at the plant, .

The project comes at a time when the US is pushing to both encourage the electrification of vehicles and reduce the country’s dependence on China for rare earths, lithium and other minerals needed for EV batteries.

The Biden administration has promised to convert the entire  — about 640,000 vehicles — to EVs. If the plan is successful, the total number of EVs in the US would increase by more than 50%.

Major leagues

Rio Tinto invested $10 million to build the pilot plant that will be able to produce 10 tonnes a year of lithium-carbonate. By the end of the year, and based on the trial’s results, it will decide whether or not to spend a further $50 million in an industrial-scale plant with annual capacity of 5,000 tonnes a year — enough for around 15,000 Tesla Model S batteries.

The projected production would be roughly the same as the capacity of Albemarle ’s Silver Peak mine in Nevada, which is currently the only lithium-carbonate producing asset in the country, according to the US Geological Survey. 

Until now, the global miner’s incursion in the lithium market has been mostly limited to its 100%-owned lithium and borates mineral project in Jadar, Serbia. A feasibility study for the proposed mine is expected to be complete by the end of 2021, Rio said.

Rio has produced borates — a group of minerals used in soaps, cosmetics and other consumer goods — for nearly a century in the Mojave Desert, about 195 km (120 miles) north of Los Angeles.

The world’s second-largest miner announced in March an agreement with renewable energy firm Heliogen to explore the deployment of solar technology at the mine.

Rio Tinto is not alone in its quest to produce lithium in the US.

Lithium Americas (TSX, NYSE: LAC) is also advancing a major project that received final federal approval in January.  The Thacker Pass lithium mine in Nevada is expected to generate 20,000 tonnes a year of the battery metal, once operational in 2023.

The plant at Boron is one the company’s latest attempts latest to extract valuable materials from waste rock or by-products – including , as well as  and  from its aluminum operations.