Rio Tinto’s lithium-from-waste-rock demonstration plant is located at the company’s Boron site in California. Current plans are to run the 10-t/d plant throughout 2021, allowing the company to assess the feasibility of enlarging the facility to a production-scale operation.

Rio Tinto has begun production of battery-grade lithium from waste rock at a lithium demonstration plant at the company’s Boron mine site in California, USA. The plant is the next step in scaling up a breakthrough lithium production process developed at Boron, to recover the critical mineral and extract additional value out of waste piles left from 90 years of mining at the operation.

According to the company, an initial small-scale trial in 2019 successfully proved the process of roasting and leaching waste rock to recover high grades of lithium. The current demonstration plant has a design capacity of 10 metric tons per year of battery-grade lithium. It will run throughout 2021 to optimize the process and support Rio Tinto’s feasibility assessment for progressing to a production scale plant with an initial capacity of at least 5,000 mt/y — enough to make batteries for approximately 70,000 electric vehicles.

Rio Tinto Minerals Chief Executive Sinead Kaufman said, “This is a valuable next step in scaling up our production of lithium at the Boron site, all from using waste material without the need for further mining. It shows the innovative thinking we are applying across our business to find new ways to meet the demand for emerging commodities like lithium, which are part of the transition to a low-carbon future.”

Rio Tinto’s lithium pipeline includes the Jadar lithium-borate project in Serbia, for which a feasibility study is expected to be completed by the end of 2021.

Rio Tinto said development of the lithium project at Boron draws on its long-standing partnership with the U.S. Department of Energy’s Critical Materials Institute (CMI), which is focused on discovering ways to economically recover critical mineral byproducts from existing refining and smelting processes. CMI experts worked alongside Rio Tinto technical leads to help solve a number of key processing challenges to produce battery-grade lithium at Boron.

At the Bank of America SmartMine 2.0 conference in June, Mark Davies, group executive–safety, technical and projects for Rio Tinto, said in addition to the lithium project, the company also is developing methods for waste-stream extraction of tellurium at its Kennecott Copper mine in Utah and scandium oxide at Rio Tinto Fer et Thane in Canada.

Rio Tinto also recently announced a partnership with Heliogen to pilot their solar technology at the Boron site.  Heliogen will use solar heat to generate and store carbon-free energy to power the mine’s industrial processes. The two companies will begin detailed planning and securing government permits for the project, with the aim of starting operations from 2022. The companies will also use the Boron installation to begin exploring the potential for deployments of Heliogen’s technology at Rio Tinto’s other operations to supply process heat, which accounted for 14% of Scope 1 and 2 emissions from the group’s managed operations in 2020.

Heliogen said its high-temperature solar technology is designed to cost effectively replace fossil fuels with sunlight for a range of industrial processes, including those used in mining. At the Boron mine, the company’s technology will use AI to control a network of mirrors that concentrate sunlight to capture energy used to make steam. Heliogen’s system will also store the captured energy in the form of heat, allowing it to power nighttime operations and provide the same uninterrupted energy stream offered by legacy fuels.

The Boron site currently generates steam using a natural gas cogeneration plant and natural gas-fired boilers. Heliogen said its installation will supplement these energy sources by generating up to 35,000 lb/h of steam to power operations, with the potential to reduce carbon emissions at the Boron site by around 7%. Rio Tinto will also assess the potential for larger scale use of the technology to reduce the site’s carbon footprint by up to 24%.