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Last year, Tesla Motors, the maker of all-electric luxury sedans, to open a $5 billion battery factory, the world’s largest. The idea is to mass-produce the lithium-ion batteries it needs to reach its goal of making 500,000 electric cars a year by 2020.

To make it work, the company has to find enough lithium, the lightest of all metals found on earth and the hidden power behind modern gadgets, like cellphones, laptops and a new generation of electric cars.

The trouble is, there’s nowhere near enough battery-grade lithium currently being mined to meet the sudden demand, and it’s spurring a race to find new sources in the remotest corners of the world, from the wilds of northern Tibet to distant salt plains in South America.

But the solution could come from an unlikely source: geothermal power plants, including the one operating on the Big Island.

An emerging technology is making it possible to extract lithium from the hot, mineral-rich brine that geothermal power plants pump out of the ground to generate energy. And the technology is not limited to extracting lithium — it can also recover a variety of other rare earth elements and valuable metals out of what is now being treated as wastewater.

In the parlance of geothermal engineering, this is called “solution mining by nature,” and the potential profits to be made from it are immense — so much so that it has gained the attention of two Hawaii County Council members, Margaret Wille and Daniel K. Paleka Jr., who are convening a hearing on the subject next month.

“To my knowledge, none of our facilities are doing anything to get minerals from brines.” — Mike Kaleikini, Ormat Technologies

Wille, who chairs the council’s Committee on Agriculture, Water and Energy Sustainability, says the hearing will center around one question: Does Ormat Technologies Inc. — the owner of Puna Geothermal Venture, which operates Hawaii’s only geothermal power plant — have plans in the works to adopt the technology?

It’s a salient question, with millions of dollars in royalties at stake. That’s because, by , the rich reservoir of valuable minerals sitting underneath the PGV plant belongs to the state. So, the thinking goes, the state — as well as Hawaii County — could see a windfall from any profits that Ormat, or any other company, makes out of it.

Currently, the PGV plant supplies up to 38 megawatts of power to the Big Island’s electric utility, the Hawaii Electric Light Co., and Ormat sends about $2 million to $3 million a year — totaling about 10 percent of its profit from the operation — to the state as royalties.

If Ormat were to dabble in the mineral-extraction business, Wille says an additional royalty arrangement could be hammered out on top of it. “If there are rich minerals, the community should benefit from that,” she said.

Mike Kaleikini, senior director for Hawaiian Affairs at Ormat, says such discussion is premature.

“They know they are sitting on such valuable minerals — why wouldn’t they be interested?” — Roxanne “RJ” Hampton

“To my knowledge, none of our facilities are doing anything to get minerals from brines,” Kaleikini said. “All we do here is to concentrate on generating electricity. That’s our focus.”

But Roxanne “RJ” Hampton, who has been researching Ormat’s operations, finds it hard to believe that the company isn’t interested. After all, she says, the company has known for years that the ground underneath the PGV plant is rich in lithium and other , such as high-quality silica, copper, zinc and even gold.

Hampton, who will be presenting her research findings at the council hearing, says the rewards of mineral extraction are simply too great for the company to ignore. “They know they are sitting on such valuable minerals — why wouldn’t they be interested?” she said.

Mineral-Extraction Technology

The idea of extracting minerals from geothermal brine has been around for years — at least since the 1960s — but most efforts at commercializing it have failed so far.

Simbol Materials, a 7-year-old company based in California, is trying to change that. In 2010, it received a $3 million grant from the U.S. Energy Department and pumped $6.7 million of its own money into a pilot project aimed at showing the financial feasibility of extracting high-quality lithium from geothermal brine.

Since 2011, it’s been taking the mineral-extraction developed at Lawrence Livermore National Laboratory and applying it at its demonstration plant that uses brine from the 49.9-megawatt Featherstone geothermal power plant in the Imperial Valley of California.

The process works like this: After the Featherstone plant pumps up the hot brine and uses its heat to make steam to spin a turbine and generate electricity, Simbol borrows the still-warm fluid for roughly 90 minutes and passes it through a series of membranes, filters and adsorption materials to extract lithium. Once that’s done, Simbol sends it back to the Featherstone plant for re-injection underground.

“If there are rich minerals, the community should benefit from that.” — Hawaii County Council member Margaret Wille

If the process can be efficiently scaled up, it’ll have major advantages over current lithium mining processes. Today, most of the world’s lithium production is in South America, where the brine containing lithium is extracted from underground and slowly concentrated in the hot sun. The process is slow, and the cost of building a set of underground pipes to extract the brine and deal with leftover waste is substantial.

Simbol is now planning the construction of a full-scale production plant. When it’s up and running, the company expects it to be able to produce 16,000 tons of lithium a year from a 50-megawatt geothermal power plant.

The financial reward would be considerable: The price of lithium in 2014 was estimated by the to be $6,600 a ton — an increase of more than 27 percent since 2010.

On paper, at least, the PGV plant on the Big Island seems well situated for a similar mineral-extraction project. Still, it’s unclear whether Ormat has an interest — let alone the technological know-how and financial muscle to absorb the upfront costs — in taking on such an effort.

But Wille says it’s important that she and fellow county officials investigate the matter with due diligence in case Ormat does decide to capitalize on the minerals.

Hampton, who once worked as a legislative aide to former Hawaii County Council member Emily Naeole, concurs: “If they can take that waste and turn it into wealth, then we have to make sure that they share that with us — with the state,” she said.