A GEOTHERMAL power plant in California will soon be producing more than just electricity. The valuable metal lithium could be extracted from its hot waste water.
The technique, developed by California-based , could bolster lithium supplies at a time when they are being squeezed by our growing reliance on high-density batteries. Global lithium consumption is projected to increase threefold by 2020 as electric cars and energy storage in the electrical grid become more common.
Lithium is usually extracted from soil, in a process that consumes a lot of water, or from brine dried in large salt ponds. The geothermal waters at the Salton Sea, about 250 kilometres inland and on top of the active San Andreas fault, are just as lithium-rich as the most productive brine lakes in Bolivia and Chile. Simbol says Salton鈥檚 waters can be exploited with a much smaller environmental footprint.
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鈥淭he geothermal waters are just as lithium-rich as the most productive brine lakes in Bolivia and Chile鈥�
Geothermal plants draw on underground water as hot as 360 掳C to make steam and drive turbines. Previous attempts to pull lithium from this mineral-rich water were scuppered because it contains high levels of silicates, which clog equipment. Looking to capitalise on growing demand for lithium, Simbol uses a technique licensed from Lawrence Livermore National Laboratory in California to precipitate out the silicates, so they can be filtered out of the water.
The remaining water flows over a chemical resin that pulls lithium ions from the salty solution and into a compound of lithium chloride, before the lithium-depleted water is returned to the ground. The water鈥檚 heat partially drives the extraction process.
The lithium chloride can be mixed with sodium carbonate to form lithium carbonate suitable for shipping. Having successfully tested the process, Simbol is now building its first demonstration plant, projected to produce about 1 tonne of lithium metal a month. Should that plant deliver, larger facilities will follow.
鈥淭he environmental impacts of this kind of mining are comparatively minimal,鈥� says Michael McKibben, a geologist studying the Salton Sea at the University of California, Riverside.
Simbol鈥檚 CEO, Luka Erceg, says the method may also yield other valuable metals such as zinc and manganese. 鈥淭he Salton Sea鈥檚 got half the periodic table in it.鈥�
