Lithium from geothermal brine could help meet growing demand for raw material and make geothermal power more cost efficient
Electric vehicles are expected to be essential to reducing greenhouse gas emissions. As more of them roll off production lines and onto roads, the world will need two things: more lithium, the key element in the batteries that power them, and carbon-free power to charge those batteries.
Using computational modeling, researchers at Idaho National Laboratory say geothermal power generation may significantly address both challenges.
Annual passenger electric vehicle sales are predicted to more than quadruple by 2025, according to Bloomberg New Energy Finance. Industry experts estimate that lithium demand will rise nearly twentyfold, from 75,000 metric tons in 2020 to 1.41 million metric tons per year by the end of the decade.
In the journal Resources, Conservation & Recycling, Ange-Lionel Toba, an INL systems modeling researcher, and his colleagues Ruby Thuy Nguyen and Ghanashyam Neupane suggest that lithium from U.S. geothermal plants could meet up to 8% of the world’s demand. Extracting lithium from the brine before cycling it back into the ground might also offset geothermal capital costs, making electrical generation from geothermal more cost competitive.
By itself, lithium is a light, chalky powder that must go through a chemical conversion process to become lithium carbonate and lithium hydroxide. These compounds are combined with materials such as graphite, silicon, cobalt, nickel and manganese to make cathodes and anodes, which are used in individual battery cells. Thousands of cells may be combined to create a battery pack for an electric vehicle.
Currently, the United States imports most lithium-ion batteries used in vehicles and consumer goods, as well as the lithium for domestic battery manufacturing. With demand expected to skyrocket, policymakers are asking: How much more can be found domestically and what sources can be tapped?
One plentiful source may lie below the earth’s surface in the circulatory systems of geothermal power plants. While producing heat and carbon-free electricity, geothermal plants extract hot, briny water that is loaded with minerals, including lithium.
Where does today’s lithium come from?
Mineral companies most commonly get lithium by drilling into mineral-rich brine in lakes on high-altitude salt flats, pumping it into evaporation pools on the surface where it is left for months at a time to dry out. These operations are widespread in South America and China.
Lithium can also be mined, usually from clay deposits. Even though the United States has large reserves, the country today has only one large-scale lithium mine, Silver Peak in Nevada, which first opened in the 1960s and produces roughly 4,500 metric tons a year – less than 2% of the world’s annual supply.
U.S. Department of Energy research has shown that we could get roughly three times that much from a green energy source. As much as 15,000 metric tons per year of lithium carbonate could be recovered from a single geothermal power plant in the California’s Salton Sea area, the most mineral-rich brine source in the U.S. Located about 160 miles southeast of Los Angeles, the area has attracted attention lately from companies such as General Motors and Berkshire Hathaway Energy Renewables.
How does geothermal energy work?
Geothermal generation requires water or steam at high temperatures – 300° to 700°F – and power plants must be built where geothermal reservoirs are located. A power station pumps hot subsurface brine to make steam that turns turbines to power electrical generators. Once the cycle is completed, the brine goes back into the ground to be reheated. Observing the large concentrations of lithium within, DOE researchers, with support from the Critical Materials Institute, developed an absorbent material to extract lithium.
What’s the new finding?
With a viable extraction process available, Toba and his co-authors posed three key research questions:
- What is the economic potential of lithium extraction from U.S. geothermal resources?
- Is geothermal lithium extraction technology a viable investment in the U.S.?
- What is the potential supply chain impact of lithium supply from U.S. geothermal sources?
Using simulation and modeling software, they probed data sets that included county-by-county estimates of U.S. geothermal lithium potential, supply/demand dynamics of lithium extraction and estimates of projected demand in the battery market.
The researchers ran two sets of experiments. One compared the capital costs of a lithium extraction project to the energy capacity of the geothermal plant – in other words: Could the plant sell enough electricity to justify an investment in lithium recovery? The other examined whether the cost of daily operations could be covered, given that both lithium prices and yield would vary over time.
As with almost any commodity, the economic potential is linked closely to supply and demand. Lithium-ion battery prices started dropping in 2014 because of oversupply and improvements in manufacturing. Prices are still low, which has dampened investors’ enthusiasm for any new projects. But with electric vehicle manufacturing on the rise, demand for lithium is expected to rise exponentially.
The results of the team’s simulations showed the benefits could be substantial. “(This) provides not only a viable option to meet demand in the long term but also a reliable source for lithium extraction domestically,” Toba said. “The technology risk is apparent, but the upside is worth exploiting.”
DID YOU KNOW?
Annual sales of passenger electric vehicles are forecast to rise to 10 million in 2025, 28 million in 2030 and 56 million by 2040, according to a 2019 report from the research organization Bloomberg New Energy Finance.
The Critical Materials Institute (CMI) is a Department of Energy Innovation Hub led by the U.S. Department of Energy’s Ames Laboratory and supported by the Office of Energy Efficiency and Renewable Energy’s Advanced Manufacturing Office, which supports early-stage applied research to advance innovation in U.S. manufacturing and promote American economic growth and energy security. CMI seeks to accelerate innovative scientific and technological solutions to develop resilient and secure supply chains for rare-earth metals and other materials critical to the success of clean energy technologies.
