GM and CTR’s Salton Sea venture marks a shift to responsible lithium production

Lawrence Berkeley National Library

Earlier this month, General Motors announced a “strategic investment and commercial collaboration” with Controlled Thermal Resources (CTR) to procure lithium from Southern California’s Salton Sea, said to hold a third of the world’s supply in lithium, through a relatively new process that seeks to minimize the environmental impacts of traditional lithium mining.

While the battery-electric vehicles (BEV) that will ultimately benefit from this partnership produce no major environmental impacts locally, the same isn’t necessarily true of lithium mining strategies. The most common processes involve hogging the stuff out of the earth in surface mines to process ore or pumping underground brine into evaporation ponds before processing off the remaining mixture of heavy metals and salts to extract the lithium. GM’s SoCal investment isn’t significant simply because the OEM is securing its own vertical in battery production; it’s a major step in the right direction for the lithium mining industry to address its most glaring hypocrisy: the environmental casualties of its processes.

If you spend any amount of time on social media, no doubt you’ve seen the photos of the stair-stepped craters in Australia and China. Surface mining (also called “hard rock” or “open pit” mining) is nothing new: stripping the land in a methodical dig that chases ore veins by cutting down to them from above instead of boring into the land with underground mining. The process can be fast and affordable, and compared to underground mining it’s also much safer for workers.

However, there’s nothing environmentally protective about erasing whole hilltops. The regions where lithium tends to collect—usually around areas of historical volcanic activity and marble formation—are often in barren and arid parts of the world, so the average person won’t become aware of the dramatic consequences until they come across an image in the news or in some weaponized meme; but a lack of public awareness hardly removes the need for sustainable practices with minimal environmental impacts.

Lithium Production Brine Ponds Aerial
Pablo Cozzaglio/AFP via Getty Images

As an alternative to surface mining, companies have chosen to pump underground brine—salt water that is rich in various precious minerals—into giant above-ground pools. Over the course of months, depending on temperature and rainfall, the water evaporates, leaving behind salts that are rich in potassium, manganese, and borax. Lithium, ironically, is still very sparse in the remaining salts, only accounting for a few percent of the total materials processed out of the brine. Another disadvantage of this process is that it demands vast amounts of water: Evaporation pools in Chile account for 65 percent of the region’s water usage. Those pools can also leech these materials—the mined salts and the acids used to separate them— back into topsoil, causing problems for local populations and ecosystems. And have we talked about the land use yet? To promote evaporation, the pools must be large and shallow, with maximum surface area to absorb sunlight.

While the evaporation process isn’t nearly as costly to the earth as surface mining is, it’s a highly inefficient method if you’re primarily interested in harvesting lithium. These pools can’t reliably support future demand for lithium, which is sure to be voracious, and they still require more real estate than the direct-extraction method that GM and CTR are exploring.

Controlled Thermal Resources

Direct Lithium Extraction (DLE) is essentially a closed-loop brine system that replaces the evaporation ponds with a manufacturing process to separate lithium from the brine before injecting the spent brine it back into the ground to support further extraction. That re-injection of the brine is what makes this process unique; that excess water isn’t being evaporated off while local resources are simultaneously sucked dry to support the pumping of those evaporation ponds. Eliminating the ponds means that DLE facilities won’t have a massive footprint, since underground drilling and pumping have minimal impact at the surface.

This investment isn’t just about the mining of lithium, either. GM and CTR are lining up every bird they can throw a stone at with the Hell’s Kitchen operation, which will also produce geothermal steam power. We need to mine lithium and we need a more robust power-generation infrastructure to charge it, and this SoCal operation offers a promising solution to this sustainability paradox. The Salton Sea is an active geothermal area, meaning that high temperatures below the surface create a significant amount of steam pressure, which can be harnessed during the brine extraction to drive turbine-generators while the liquid brine is processed for lithium. While geothermal energy production is already common around the Salton Sea, none of it has been yet adapted for mining.

GM and CTR aren’t the only players in DLE mining—Tesla is chasing similar mining processes—but the two are among the first OEMs to commit to the technology at this scale. We’re excited to see the fruits of the venture.

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