Lithium: A Sustainable Source in the Desert

:: Wednesday, October 13, 2021

A new revolutionary and environmentally conscious approach to producing lithium may be key to meeting the soaring demand for this critical mineral.

Our California lithium operations has developed a breakthrough process that enables lithium production from existing mine waste rock. We are operating a demonstration plant at our Boron mine, optimizing the process so we can produce lithium on a larger scale.

There’s no doubt more lithium is needed in the market today. Lithium is essential to manufacturing batteries for many modern products including computers, smartphones, and electric cars. The demand for these products is only expected to increase.

In August 2021, the U.S. president signed an executive order that sets an ambitious target in the fight to reduce carbon emissions: Half of all new vehicles sold in the United States need to be zero-emissions electric vehicles by 2030—and many of those vehicles will require lithium batteries.

Global and national initiatives like this one have led us to increased collaboration with the U.S. Department of Energy’s Critical Materials Institute (CMI), an energy innovation hub focused on developing solutions around the source and supply of critical minerals. With CMI’s help, Rio Tinto is at the forefront of innovation for investigating lithium sources to meet growing demand—propelling us toward a more sustainable energy future.

Boron and lithium: A natural synergy

Typically, boron—like lithium—is found in trace amounts throughout the world. It’s uncommon to find large deposits of either. However, when a deposit of one mineral is found, the other is likely to be nearby because both develop in similar geologies.

Our Boron operation in California is home to one of the richest borate deposits in the world. And part of the work of our world-class mine revolves around responsible management of the mine’s waste rock (also called “gangue material”). In the 1950s, our scientists examining that waste material found—among other useful materials—lithium. At the time, the mineral was a side note.

Then in 2016, when we were evaluating gangue for gold and critical materials, we realized the potential value of the lithium and saw promise in extracting it.

Our scientists used acid digestion followed by inductively coupled plasma mass spectrometry (ICP-MS) to isolate and analyze the lithium content of the gangue material. Then, we extended the research to determine the lithium content in all possible waste streams at the Boron site.

By the end of 2017, we had developed a new method for extracting lithium: Through a proprietary process, we mix roasting reagents into the gangue material, then feed the mixture into a roaster that converts the lithium to a leachable form. The roasted solids are leached and concentrated to remove certain impurities, then a crystallization step concentrates the lithium and removes other unwanted impurities. The concentrated lithium liquor is converted to lithium carbonate, then purified.

This breakthrough roasting and leaching process proved lithium extraction was feasible—and results in 99.5% pure, battery-grade lithium. While the potential was evident, significant challenges remained for efficiently extracting lithium and bringing it to the market. Through inclusive, close collaboration, our expert teams quickly made progress to ensure the process would be economically viable and scalable.

Confronting challenges: Producing battery-grade lithium at scale

To solve the challenges of scaling this new process, we drew on our long-term relationship with the CMI, whose technical experts have helped solve process issues and are working to radically change the process to decrease the cost of producing lithium.

One benefit we found is that our process does not require additional mining cost. The gangue material—which is produced as waste material in our primary process and boric acid ponds (BAPs)—was already there. The next hurdle was proving our ability to extract lithium in a cost-efficient way.

After our research team verified the process at laboratory scale, we moved quickly to build the current demonstration plant. The demonstration plant enables:

  • Collaboration among chemistry experts and process engineers working to optimize a future industrial-scale plant design
  • Learning from mistakes at an early stage in process development
  • Data collection to help with equipment design and process modelling for commercial-scale production

The demonstration plant is designed with the capacity to produce 10 tonnes of battery-grade lithium per year. During its first year, its operations will inform a feasibility assessment to enable development of a production-scale plant with an initial capacity of at least 5,000 tonnes per year. That’s enough lithium to make batteries for approximately 70,000 electric vehicles.

Lithium production: Powering a more sustainable future

Discovering an innovative new process for extracting and producing lithium from mine waste is a great step toward a more sustainable future.

As the world increasingly turns to renewable and sustainable energy sources, the work accomplished at our Boron site is an encouraging sign of what’s possible.

This recent lithium extraction project in Boron is just one of several of our ongoing initiatives to improve sustainability and maximize the responsible use of naturally occurring minerals.