The mining legacy mine water is to become a lithium supplier

Coal mining has left a lot of contaminated sites. However, the water that has to be pumped out of the mines could be useful for electromobility.

Day after day, thousands of cubic meters of water are pumped from the long-disused mines in the Ruhr area and on the Saar and channeled into rivers. It is an expensive “eternal task” because the pumps must not be switched off so that the drinking water in the former mining regions does not mix with the polluted water from the coal mines. The mining group RAG spent around 290 million euros last year to keep the water in check.

A virtue out of necessity?

Volker Presser, professor at the Leibniz Institute for New Materials in Saarbrücken, wants to turn the costly problematic mine water into a raw material supplier. Because on its way through the rock layers into the old mining tunnels, the rainwater is enriched with many minerals, especially sodium and potassium. In very small quantities, however, there is also valuable material in mine water – including lithium. And that is what Presser wants to get out of the mining legacy.

Lithium plays a decisive role in electromobility because the element is a core component of battery cells. And the more electric vehicles roll on the streets, the more lithium is needed. And so far that has been completely imported, mainly from Australia and South America. “The German economy is currently completely dependent on imports, since lithium is not extracted in the country,” emphasizes Michael Schmidt from the German Raw Materials Agency (DERA).

Battery cell production in Germany

Only a few battery cells are still being manufactured in Germany. The production capacity is currently far less than 10 gigawatt hours, says Schmidt. The demand will increase by leaps and bounds. The Chinese automotive supplier Svolt Energy Technology wants to set up its European production in Saarland. Tesla plans to start mass production of battery cells on the site of its future plant near Berlin .

Based on previous announcements from the industry, raw materials expert Schmidt expects a production capacity in Germany of 70 to 240 gigawatt hours by 2025. Then, according to his information, the lithium demand in Germany could rise to up to 30,500 tons per year.

The mass does it

Presser wants to cover a small part of this requirement with its development. “Our approach is to understand mine water as an eternity opportunity and to make it usable as valuable water through innovative technology,” he explains. One liter of mine water only contains around 20 milligrams of lithium. But in this case: the mass does it. The scientist calculates that an estimated 1900 tons of lithium would be washed away with the mine water every year.

His test project with water from two former mines on the Saar is funded by the RAG Foundation, among others, which has to pay for the permanent follow-up costs of hard coal mining.

Energy efficient process

Presser and his team run the mine water through a cell that contains two electrodes with different polarities. Lithium and chlorine ions remain in the cell, while all other dissolved substances run off again with the pit water. Fresh water then flows into the cell and collects lithium and chlorine in the form of lithium chloride. This process is repeated several times so that the concentration of lithium chloride in the water continues to increase. After the water has evaporated, it is finally in solid form. The lithium chloride has to be processed further in order to obtain elemental lithium.

And what does it cost to extract lithium from mine water? Presser cannot say that yet: “The project has just started – in two years we will be able to say more about optimal electrode materials and process parameters.” In any case, the energy requirement should not be of great importance in terms of cost. Since the electrical charge introduced is almost completely recovered, the process is largely energy-efficient, says Presser.

Mining in the Ore Mountains

Lithium from mine water is not the only project to extract the raw material in Germany. Deutsche Lithium plans to mine the light metal in the Ore Mountains soon. The company suspects around 125,000 tons in the deposit near Zinnwald.

Managing director Armin Müller is following an ambitious schedule. All approval procedures should be completed by 2022. The construction of the mine and the attached factories could then be completed in the course of 2024, he reports. Total investments of 159 million euros are required for the project.

No geologically scarce raw material

Is it worth the effort to extract lithium in Germany? Michael Schmidt is careful: Lithium is not a geologically scarce raw material. “We do not expect major deficits until 2023 or 2024. However, these can occur from 2025, globally and in Europe.” If the production in Germany were economical compared to the global supply, “something like that can make sense”.

But the price development for lithium is difficult to predict. There have been violent rashes in recent years. At its peak, a ton of lithium carbonate cost around 19,000 dollars (around 15,600 euros) in 2018, and at the beginning of 2021 only 6700 dollars (around 5,500 euros), reports Schmidt. From 2025, however, prices are expected to rise sharply. There could be a chance for lithium, mined or dried in Germany.