Recently, there’s been a lot of talk in the energy world about the minerals needed by clean-energy technologies and whether mineral supply problems might pose a threat to the clean-energy transition.

To hold warming to less than 1.5 degrees Celsius over preindustrial levels, the world must cut greenhouse gas emissions in half by 2030 and reach net-zero emissions by 2050. To do that, it must radically ramp up production of solar panels, wind turbines, batteries, electric vehicles, electrolyzers for hydrogen, and power lines.

Those technologies are far more mineral-intensive than are the equivalent fossil fuel technologies. ​“A typical electric car requires six times the mineral inputs of a conventional car,” writes the International Energy Agency (IEA), ​“and an onshore wind plant requires nine times more mineral resources than a gas-fired plant of the same capacity.” (The IEA uses the simplified term ​“minerals” to refer to the entire mineral and metal value chain, and I do the same in this post.)

Power transmission and distribution require aluminum and copper. Batteries and EVs require cobalt, lithium and nickel. Wind turbines require rare earth elements. And so on.

In a previous article, I offered a broad overview of the problems related to minerals needed for the clean-energy transition. To recap:

• Clean-energy technologies are more minerals-intensive to build than their fossil-fuel counterparts.
• The growth of clean energy will rapidly raise demand for a set of key minerals.
• Mining and processing of those minerals are geographically concentrated, often in countries with weak labor and environmental protections.
• Mineral mines and processing facilities often pollute water, scar landscapes and impoverish communities.
• Production may not be able to expand fast enough to keep up with demand, which could cause supply constrictions and price fluctuations and slow the transition away from fossil fuels.

That’s the big picture.

In this article, I want to take a closer look at some of the biggest clean-energy technologies and the minerals required to build them. Specifically, I’ll cover batteries, solar PV, wind, geothermal, concentrated solar, and carbon capture and storage. I’m not going to get too deep into any one of these — just a quick tour.

I’ll be drawing heavily on a 2020 World Bank report that projects demand for key minerals under rapid decarbonization scenarios from the International Energy Agency — specifically the RTS (reference technology scenario, or current policy), 2DS (2-degree scenario) and B2DS (beyond 2-degree scenario, which aims to limit warming to 1.5 degrees Celsius). (The World Bank and IEA use the simplified term ​“minerals” to refer to the entire mineral and metal value chain, and I do the same in this post.)

This tour will reveal which minerals are expected to be most in demand — which ones are certain to be needed and which depend on the direction taken by particular technologies. It will help focus attention on possible supply stress points.

It will also reveal that there is enormous uncertainty about the pace and scale of demand growth for key minerals both specifically and generally. Much depends on unpredictable developments in technology, policy and politics. Epistemic humility is called for, along with policy focused on resilience. (More on policy in the next post.)

One fact that is certain: The more ambitious the world’s decarbonization efforts, the higher mineral demand will rise.

Here’s an overview table of energy sources and technologies and the key minerals they use:

The United States needs a domestic source of lithium that can be extracted using renewable energy. Lithium is a key element in the batteries that will enable us to decarbonize the power grid and vehicles. 

The superheated brine trapped deep under the earth beneath California’s Salton Sea offers both lithium and renewable energy — and investors are starting to take notice. 

Since the 1980s, geothermal plants south of the state’s largest lake have tapped this subsurface source of steamy brine to drive turbines that generate carbon-free power. The brine contains many elements, including metals iron, zinc, manganese — and lithium.

In recent years, researchers and developers have been working on technology to extract this lithium from the brine after it’s used by the region’s geothermal power complex. Proving out a cost-effective way to extract lithium from this brine could create a sustainable U.S.-based source of this key component in lithium-ion batteries and create much-needed employment in a lower-income region, Southern California’s Imperial Valley. It could also improve the economics for geothermal energy projects in the area, which produce clean power around the clock. 

“A buildout of this vision could be amazing,” V. John White, executive director of the California-based Center for Energy Efficiency and Renewable Technology, said in a recent phone interview.

Private investors agree — and some are starting to put serious money behind it. One firm working on lithium extraction for a geothermal plant near the Salton Sea, Lilac Solutions, announced in late September that it had raised $150 million from Lowercarbon Capital, Bill Gates’ Breakthrough Energy and others. In July, General Motors, which will need lots of lithium to execute on its multibillion-dollar electric vehicle plans, announced an investment of undisclosed size in Controlled Thermal Resources, the geothermal developer that’s working with Lilac on the project. 

Two other companies — Berkshire Hathaway Energy Renewables and EnergySource Minerals — are also working on lithium recovery in the region. 

If the technology can be refined and proven effective, lithium extraction from brine could be ​“game-changing,” the National Renewable Energy Laboratory reported in July, ​“potentially delivering 10 times the current U.S. lithium demand from California’s Salton Sea known geothermal area alone.”

The potential scope of the region’s lithium supply is staggering. The California Energy Commission estimates that up to 150,000 metric tons of lithium per year would be recoverable from existing geothermal projects at the Salton Sea — enough to meet nearly half the current annual global demand of 300,000 metric tons. A 2020 report from the commission estimated the Salton Sea could produce more than 600,000 tons of lithium per year if more geothermal plants were built there. If that lithium were sold at a price of $12,000 per ton — roughly the midpoint of global lithium prices over the past two years, according to NREL — it would add up to $7.2 billion per year. 

But the success of this effort will depend on moving beyond pilot projects to full-scale commercial production. 

A ​“whole other level of complexity”

Much of the lithium now used in lithium-ion batteries is produced by destructive hard-rock mining, predominantly in Australia, and then refined in China. Other major producers of lithium — in Argentina, Bolivia and Chile — extract it from brine that they push to the surface and evaporate in immense pools, a process that uses large amounts of groundwater and has led to soil contamination and other kinds of degradation, according to a 2020 United Nations report.

The lithium-extraction technologies being tested out south of the Salton Sea, in contrast, require just a fraction of the land and water used by other methods, and they are powered by geothermal energy, so they’re less carbon-intensive. The Salton Sea in Southern California is also physically closer to potential major lithium buyers than other sources of the element.

The Salton Sea is an accidental lake created in 1905 when an irrigation channel fed by the Colorado River flooded, and it’s been steadily shrinking ever since. It lies within a former volcanic area where geothermal activity heats briny underground water to an average temperature of 500 degrees Fahrenheit. 

This brine contains every mineral in the periodic table, said Elisabeth de Jong, program administrator for the California Energy Commission’s Geothermal Grant and Loan Program. While the amount of lithium in the brine is relatively small, about 200 milligrams per liter, the geothermal plants use so much brine that ​“it makes sense to recover” lithium from it, she said in a September interview. For example, Berkshire Hathaway Energy Renewables, which operates 10 of the 11 geothermal plants in the area and is working on lithium-extraction pilot projects, processes 50,000 gallons of brine per minute.

But the process of extracting lithium from this mineral brew is highly complex, according to Will Stringfellow, a Lawrence Berkeley National Laboratory environmental engineer and expert in industrial and agricultural wastewaters. Compared to wastewater left behind by oil and gas production, ​“geothermal brines are a whole other level of complexity,” he said last year. They contain up to 30 percent solids and a stew of dissolved metals and minerals, only a few of which are valuable. 

Even so, ​“we are involved in this because we think it can work,” Stringfellow said in a phone interview last month. ​“Everyone is waiting with bated breath to see if it works at scale.”

Three competing efforts to extract lithium from brine

There are several different processes that can be used to extract lithium from brine. Those being piloted at the Salton Sea have centered on more modern adsorption technologies made possible by advances in materials science. 

Berkshire Hathaway Energy Renewables has two lithium-extraction demonstration projects in the works. Its subsidiary CalEnergy owns and operates 10 geothermal plants along the Salton Sea with 345 MW of capacity, which have been online for at least 35 years. 

BHE started building the first of the demonstration projects in April, funded by a $6 million state grant matched with $6 million from the company and expects it to start operating in March 2022. The project will test the technical and commercial feasibility of recovering lithium in the form of lithium chloride from one of its geothermal power plants. It will use an ion-exchange process, which is essentially a molecular sieve that captures only the tiny bits of suspended lithium, Jonathan Weisgall, BHE vice president of government affairs, said in a September interview.

Next year the company plans to start building a second project, funded by a $15 million grant from the U.S. Department of Energy, that will convert the lithium chloride into lithium hydroxide. 

Both lithium carbonate and lithium hydroxide are used in lithium-ion batteries, but hydroxide is emerging as the preferred resource because it provides ​“more bang for the buck,” Weisgall said. 

If BHE’s pilot projects pan out, construction of a commercial-scale plant would begin in 2024. Weisgall estimates that 90,000 metric tons of lithium will be recovered per year, a little less than one-third of current annual global demand.