The Salton Sea geothermal field in California potentially holds enough lithium to meet all of the US’ domestic battery needs, with even enough left over to export some of it. (Earlier post.)

There are currently 11 commercial plants at the Salton Sea field producing geothermal energy, a process in which hot fluids are pumped up from deep underground and the heat is then converted to electricity. Normally the cooled fluid would simply be reinjected underground, but the idea is to first extract the lithium from the brine before injecting it back.

The hot brine that comes up from the subsurface as part of geothermal power production at the Salton Sea in California is a rich stew of minerals, including iron, magnesium, calcium, sodium, and lithium. Using various extraction techniques, lithium chloride can be extracted from the brine, then processed into other forms for battery production. (Credit: Jenny Nuss/Berkeley Lab)

However, questions remain about the size of the resource, the potential rate of decline, the potential for regeneration, and sustainability of production.

With nearly $1.2 million in support from DOE’s Geothermal Technologies Office, scientists from Lawrence Berkeley National Laboratory (Berkeley Lab), UC Riverside, and Geologica Geothermal Group, Inc. will work together to both quantify and characterize the lithium in this hypersaline geothermal reservoir.

The project is the first comprehensive scientific effort to map out California’s “Lithium Valley” and attempt to gain a detailed understanding of the mineral-rich underground brine at the Salton Sea geothermal system. Using an electron microscope and other advanced analytical tools, for example, the scientists hope to learn the mineral sources of lithium and whether the rocks will “recharge” the brine with lithium after it has been extracted from the produced fluids.

The project team will also investigate potential environmental impacts—to quantify how much water and chemical usage is needed for lithium extraction, air quality during the extraction process, and potential induced seismicity from the associated geothermal energy production.

The Salton Sea geothermal system is the primary potential geothermal resource for lithium in the United States, and it’s a world-class resource. But there is a wide range of estimates in terms of the size of the resource, and also not a great understanding of where the lithium comes from, the rate at which it would decline over time with extraction of lithium from the geothermal brines, and whether it would be replenished by the remaining lithium in the host rocks.

—Pat Dobson, the Berkeley Lab scientist who is leading the project

Currently, most of the world’s lithium supply is either mined from open pit mines, which are common in China and Australia, or extracted from salar deposits, or salt lake flats, in South America. Lithium is obtained from these huge deposits (the largest salar, located in Bolivia, is the size of the “Big Island” of Hawaii) simply by pumping up the shallow groundwater and letting it sit for a year or two while the sun evaporates the water.

Both of these methods have serious environmental issues associated with them.

We think geothermal lithium is one of the least environmentally impactful ways of obtaining lithium. We want to understand how to mitigate any environmental side effects to make it even more benign.

—Pat Dobson

California established the Lithium Valley Commission last year to research and write a report on the opportunities. (Earlier post.)

UC Riverside geochemist Michael McKibben, who has been studying the Salton Sea geothermal field since the 1970s, agrees with the potential.

If you do a back-of-the-envelope calculation, you can convince yourself there’s somewhere between 1 and 6 million metric tons of lithium in that field. That would be the largest brine source of lithium in the world, bigger than any individual South American salar deposit. So, it’s a big number, and it means the potential is there for—again, back-of-the-envelope calculations—something like 50 to 100 years’ worth of lithium production.

—Michael McKibben

McKibben, a professor emeritus, and Maryjo Brounce, an assistant professor in the Department of Earth and Planetary Sciences, lead the UC Riverside effort in this project. Brounce, a petrologist by training, will use instrumentation to map out where the lithium is located within the reservoir rocks, and what form it’s in. This geochemical characterization will then be incorporated into models to assess the rate of resupply of lithium to geothermal fluids.

We’ll look at how quickly might you expect the resource to be regenerated—is it centuries? Decades? Those chemical reaction rates will depend on where in the rock lithium is stored pretty strongly, so it can help create a predictive tool.

—Maryjo Brounce

This work will complement geochemical studies being conducted by researchers in Europe, who are also investigating the potential of geothermal brines for supplying lithium.

Several companies have started pilot operations at the Salton Sea to extract lithium, including Berkshire Hathaway Energy (BHE) and Controlled Thermal Resources. (Berkeley Lab has projects with both under grants from the California Energy Commission.) For this new project, Berkeley Lab and UC Riverside will use data from companies active in the area as well as published documents and field data from the state of California’s Geologic Energy Management (CalGEM) databases.

We need better data on the chemistry of the brines and their lithium content and how it’s distributed in terms of position and depth in the geothermal field. We’ve asked the geothermal companies to share their brine data with us. Pat and his group will put that in a database. Then if we can use the database to correlate lithium concentration with things like temperature, chlorinity, and other physical and chemical parameters, we can actually predict how much lithium might be in brine in parts of the field that haven’t been completely drilled out yet.

—Michael McKibben