In 1925, nowhere in the United States produced more crude oil than the Smackover oil field in southern Arkansas. At the time, wildcatters flocked to the region in pursuit of liquid gold. 

The boom was short-lived. But what industry left behind — salty brine water from oil drilling — could be the key to boosting domestic lithium production 100 years later. 

That’s because a critical trove of lithium is located roughly 2 miles underground in southwestern Arkansas, containing between 5 and 19 million tons of reserves, according to a recent U.S. Geological Survey study. If this resource can be recovered commercially, it could power nine times the number of electric vehicles projected to be in demand globally in the year 2030.

“When we went into south Arkansas, we knew the lithium was high already. Industry has been interested in this topic for many years,” said USGS hydrologist Katherine Knierim. “The oil and gas industry typically has these brines co-produced when they are extracting these other resources, and they’re often seen as a waste stream, something that has to be disposed of.”

Because these wells have already been drilled and are largely not used for oil production anymore, lithium extraction is more viable.

“You have to piggyback on the work done by oil people,” said JP Nicot, a professor at the University of Texas at Austin. “The only way to get into the subsurface is to drill a well for oil,” he said. “Otherwise, it’s too expensive.”

While the underground Smackover formation, which dates back to the Jurassic period, stretches from east Texas to Florida, industry is focused on southern Arkansas and east Texas, according to Nicot. Samples from the region have shown roughly 300 to 500 milligrams of lithium per liter. 

“Those are high concentrations,” he said.

The trick is finding the most effective extraction technique to successfully remove the metal from the brine.

“There’s still a lot of chemistry, a lot of potential environmental issues,” he said. “There is no free lunch.”

There are multiple developing techniques for what’s called direct lithium extraction. One uses a membrane to filter lithium from the brine to isolate and enrich it, while another uses a sorption process, which involves adding a material that sticks to the lithium.

Companies like Standard Lithium, ExxonMobil and TerraVolta are investing in direct extraction of Smackover lithium. And in September, the U.S. government announced nearly half a billion dollars in grants to companies for lithium projects in southern Arkansas.

This investment in U.S. battery production comes as the popularity of electric vehicles grows globally, according to analyst Lukasz Bednarski of S&P Global Commodity Insights. 

“In the last years, lithium demand and supply broke through this 1 million tons mark,” he said. “It was a relatively small industry in comparison to other commodity industries, but the growth is really strong and in 2024 we were already at 1.2 million tons of lithium demand.”

He predicts global demand will reach 2 million tons by 2027. 

Despite growing demand, little lithium is extracted within American borders. “Compared to the rest of the world, the mining production in the U.S. doesn’t even register,” Bednarski said. 

While the U.S. has ample lithium resources, he said, the challenge is that most are unconventional, which means they are difficult to mine and cannot be commercially unearthed at a large scale with today’s technology.

And when it comes to direct lithium extraction in the Smackover specifically, there are questions about commercial viability as well as environmental ones — like how much water these projects might end up using.

“Lithium has never been mined in this way,” Bednarski said. “It will be great if they succeeded because then we will have a new source of lithium globally. But there’s still a lot of question marks whether they will succeed in this or not.”

John Shaw, a University of Arkansas geosciences professor, expressed optimism about what direct lithium extraction could mean for his state.

“You always say this with a little bit of trepidation of something scaling up really large, but I think it can be done in a safe way and a generally beneficial way,” he said.

Starting with the 1920s Smackover oil discovery, the state has gone through several energy booms, Shaw said. “Then in the 2010s, there was big natural gas being produced from the Fayetteville Shale in northern Arkansas. And that’s disappeared.”

It might just be lithium in the Smackover that pushes Arkansas back into the energy economy.