Amid significant environmental concern about the impact of more widespread lithium mining, various methods of extracting the battery material from brine could offer a cleaner solution – and reignite a historic Cornish industry.

August 31, 2024 Mark Hutchins

Cleantech Lithium has begun preliminary drilling and feasibility studies for a direct extraction plant in Laguna Verde, Chile.

Photo: Cleantech Lithium

Lithium demand is rising and pricing agency Benchmark Mineral Intelligence (BMI) expects a million-ton lithium materials market in 2024 and a compound annual growth rate of 15% to 2033.

Analysts including BMI anticipate the onset of a lithium shortage around 2029 amid environmental and political concerns about the required expansion of lithium mining and processing and their concentration in a small number of countries.

Lithium is largely produced via open-air evaporation of brine – in South America’s “lithium triangle” – or from hard rock mining, mostly in Australia. China, which processes that Australian material, has domestic hard rock and brine-based mining capacity. BMI estimates 34% of lithium is mined in Australia, 28% in South America, and 20% in China.

Energy intensive hard rock mining relies on diesel-powered mining equipment and high-temperature processing. Brine concentration and processing via evaporation, while having lower CO₂ emissions, is water-intensive in arid regions, prompting concerns about the overuse of aquifers. The resulting opposition to projects ensures that the lithium mining industry is slow to react to demand fluctuation.

Direct lithium extraction

Direct lithium extraction (DLE) approaches offer an alternative by extracting lithium from brine using thermal or chemical processes. BMI estimates the method accounts for 4% of today’s lithium and will reach 12% by 2030.

“Some commercial projects have been up and running for years,” said Federico Gaston Gay, principal analyst for lithium at BMI. “Now there is renewed interest. Mining and oil and gas companies are looking at DLE and they have the money and the expertise to develop it.”

Water used during DLE can be returned to aquifers. DLE processes are typically powered by electricity and in some cases, the same brines could also be used for geothermal power generation.

“Our approach to DLE means there is minimal water depletion from the sub-surface aquifer and, if used with renewable power as we intend, there are minimal emissions associated with the operations,” said Steve Kesler, executive chairman and interim CEO at Cleantech Lithium (CTL). The company is ramping up DLE projects in Chile and operates a pilot processing plant producing eluate which is processed by a third party into battery-grade lithium carbonate, ready for testing by battery suppliers.

Gaston Gay noted that while there is potential, industry claims about reduced environmental impact still need to be proven. “In most cases brines are reinjected so in theory the balance of the aquifer is not changed,” he said. “DLE operations also take a fraction of the land required by evaporation ponds. These differentiations could make a big difference to environmental credentials but there’s not enough information available to definitively say it is cleaner.”

The largest of CTL’s planned extraction sites, Laguna Verde, is estimated to hold around 1.8 million tons of lithium carbonate equivalent. Initial drilling and a pre-feasibility study are underway, after which CTL will seek investors, offtake partners, and debt funding to cover the estimated $450 million build cost for a full-scale DLE plant at the site.

DLE production costs can vary greatly depending on brine composition, temperature, and depth, as well as other conditions at a project site and the specific technology used. CTL’s Kesler said that he expects the company’s projects to be “relatively low cost” compared to other lithium mining operations. Gaston Gay, meanwhile, noted that DLE costs should compare favorably with hard rock mining. Against conventional brine extraction, however, DLE replaces natural evaporation in the sun with a more energy intensive process. Further treatments may be required pre- or post-extraction, also leading to potentially higher cost.

New tricks

While DLE processes are commercially proven and already in operation, scaling up to a more significant market share will require new technology and applications. Gaston Gay noted that operational projects located in Argentina and China are more an enhancement of conventional evaporation than a completely new process and that a dramatic scale-up of any process is likely to come with complications.

In a 2023 paper published in Nature Reviews Earth & Environment, scientists led by Argentina’s National University of Jujuy divided DLE technology into seven broad categories at varying levels of commercial development. “Some proposed DLE approaches, such as ion pumping or Li+ [lithium]-selective membranes, are completely new and will require more ample engineering efforts to reach industrial scale,” wrote lead author Maria L. Vera. “Conversely, other proposals, such as ion exchange, solvent extraction, or electromembrane processes, have been ­studied for decades … the challenge here is to adapt these methodologies to the complexity of lithium-rich brines.”

CTL says it has opted for one of the better-known processes as a measure of risk reduction. “The purification technology has been around for many years, across multiple industries including uranium and treatment of water, so there is relatively little technology risk in the process,” said Kesler. “We’ve also aimed to mitigate that risk by working with some of the most respected names in the industry.”

The availability of technology options should also make DLE more adaptable to different site conditions. “At Laguna Verde, for example, we’ve been testing various adsorbents to understand which works best with our brine in terms of selectivity of lithium molecules and rejection of other minerals,” Kesler added. “Not all brines are the same, it’s a case of working through and optimizing the process and technology rather than having to reinvent anything.”

Diversified supply

Another reason for recent buzz around DLE is its potential to greatly increase the amount of lithium available for extraction. At existing brine projects, BMI estimates better process efficiency with DLE could increase yields by up to 670,000 tons per year. The process could also bring lithium mining to several new regions.

Vera et al. estimated that 50% to 85% of lithium-rich continental brines are in the lithium triangle region, with China the second largest source. Geothermal brines and oilfield brines, with lower lithium concentration, are found in many more regions but have not been considered viable because evaporation to the required concentration would take too long, or the deposits are in regions without sufficient land or a suitable climate for open air evaporation.

Several DLE testing projects are underway in Europe, with Vulcan Energy Resources sites, in Germany among the most advanced. “Phase one” of Vulcan’s project is expected to produce 24,000 tons of lithium hydroxide per year and the company has signed supply agreements from 2025 with a number of battery industry offtakers.

Vulcan’s project, located in Germany’s Upper Rhine Valley, combines DLE with a geothermal energy plant. Brines from various drilling sites are piped to the plant. The heat from the brines is used to generate electricity and the brines are then treated to produce a pre-product – lithium chloride suspended in water. This will then be trucked to a site close to Frankfurt where it will be further processed, via electrolysis, to produce battery-grade lithium hydroxide.

Horst Kreuter, Vulcan Energy Resources’ co-founder and chief representative, said that the first geothermal cluster has begun producing the lithium chloride, which is being kept in storage awaiting completion of the electrolysis plant.

Vulcan has exploration licenses for further drilling sites around the Upper Rhine Valley and says the electrolysis plant could also be used to process brines shipped from further afield. “The electrolysis plant has cost of about $30 million to build so you can’t place one at every site,” said Kreuter. “The plant is highly flexible, we can add different pre- and post treatments and can work at different temperatures and pressures. We are planning ahead and starting to look at other areas of Europe as well.”

There are plenty of other areas in Europe that are worth exploring for brines which could be suitable for DLE. In the southwest of the United Kingdom, Cornish Lithium is working on several projects and targeting 15,000 tons of DLE production across multiple small sites by 2030.

Compared to the project in Germany, Cornish Lithium expects to find brines at lower temperatures and lower lithium concentrations. A temperature of around 80 C is too low for geothermal power but may be enough to provide district heating to the local area. The lower concentration in the brine may also enable the project to make use of cheaper extraction processes and thus scale up faster.

“The brine in Cornwall is very clean –it’s actually less salty than the seawater,” said Neil Elliot, corporate development manager at Cornish Lithium. “Our most recent exploration found lithium concentrations of over 100 parts per million. That means we can look at membrane technologies and several other concentration techniques.” Working with membrane technology, such as the reverse osmosis that’s commonly used in water desalination, means that DLE could potentially yield clean water for local communities as well.

Hard rock alternative

Alongside its DLE project, Cornish Lithium is developing hard rock lithium mining at another site in Cornwall which is expected to produce another 10,000 tons per year of lithium hydroxide by 2030.

The company plans to redevelop a disused china clay pit and to build a processing plant within a kilometer of the site. The materials mined at the site could be processed quite differently to the spodumene mineral typically mined in Australia. Cornish Lithium has worked with Australian company Lepidico to develop a suitable process. Life cycle assessments performed on Lepidico’s project estimate a 40% reduction in carbon emissions compared to typical hard rock lithium mining. “Normally, with a hard rock project, you have to roast the ore at temperatures above 1,000 C,” said Elliot. “Instead, we use a chemical process developed by Lepidico, utilizing sulfuric acid to produce lithium.”

That route should also enable the company to produce battery-grade lithium hydroxide at the same site without further shipping or processing. “The idea is we get to a final product in Cornwall that we can ship direct to users in the battery industry,” added Elliot.