The fact that the brine is preheated reduces costs and the energy footprint relative to conventional lithium production methods, Mr. Lowry said. Because the geothermal companies have an exemption from water laws, which allows them to pump their brine back into the ground, the process also spares Simbol potential cleanup or environmental mitigation costs. “We don’t want this stuff above ground because it would be impacting water tables,” said John Burba, Simbol’s chief executive since April 2013. “But this goes back into the formation where it came from.”

Mr. Burba is a co-inventor and lead developer for the basic lithium extraction technology that Simbol is using, which he helped develop while he was working for the chemical manufacturers Dow and FMC. Simbol now owns patents and pending applications on refinements of this filtering process.

Brian Jaskula, a lithium specialist with the United States Geological Survey in Reston, Va., said Simbol’s process was a well-guarded secret, making it hard to evaluate the technical merits. “If it does what they say it does, it seems promising,” Mr. Jaskula said.

What appears certain is that there are plenty of resources to be extracted. Brine from Southern California’s geothermal plants is rich in lithium, and in manganese, zinc and potassium, according to a hydrologist specializing in minerals contracted by Simbol. And geothermal energy production in the region is expanding.

Mr. Jaskula is optimistic about Simbol’s chances, even though several other emerging contenders hope to start producing lithium as soon as this year and could beat Simbol on price, as the company has not yet revealed a breakdown of its production costs. That is because a stable supply, not price, is the critical factor for battery manufacturers, Mr. Jaskula said. “Lithium is only 2 to 3 percent of the battery’s content as well as the price of the battery,” he said. “But it’s so important that the price doesn’t matter as much as having a variety of sources to ensure that they do not run out.”

Simbol says the plant will have the capacity to produce 15,000 metric tons of lithium annually. The permits are ready, Mr. Burba said, and Simbol has secured the water necessary to operate the plant — no small feat in dry California — from the Imperial Irrigation District, which has set aside water to attract industry.