Global consumption of the alkali metal lithium is growing rapidly. During the past decade annual production of lithium has risen to 85,000 tons. This is mainly due to its use in batteries of electric vehicles as well as laptop batteries and smartphones. Several million tons of lithium are mined in countries such as Australia, Argentina and Chili every year, which account for more than 80% of global production. Chile has the world’s largest known lithium reserves (8 million tons). In Europe, Portugal has small reserves of the raw material. In Germany, lithium can be obtained from brine which is pumped through geothermal stations during energy production; but until now there have been no processes available that could extract this resource in a cost-effective and environmentally-friendly manner.
Now (2020), German scientists at the Karlsruhe Institute of Technology (KIT) have designed a method that could enable lithium mining in Germany through a minimally invasive process using the deep waters in geothermal plants of the Upper Rhine Trench. During this process the lithium ions are filtered out of the thermal water, and in a second step they are further concentrated until lithium can be precipitated as a salt. Currently, the scientists, together with industry partners, are building a special test facility for producing lithium from brine, which will be integrated into an existing geothermal energy plant. With the help of this facility, the scientists hope to produce several kilograms of lithium carbonate. If their endeavour is successful large-scale production of the metal would come into reach. This would require large production facilities to be built next to the geothermal plants and allow several hundred tons of lithium to be produced. The scientists expect that the lithium produced would, first and foremost, be used in battery devices for electric cars, which is an important step towards advancing the climate protection program of the German government.
Until now (2020), lithium has been produced either from salar brine sources (mostly in South American countries) or extracted from rock formations, containing spodumene, lepidolite, petalite, amblygonite, and eucryptite(Australia), which requires a wide range of processes. Because of the amount of energy consumption and materials required lithium production from mining is a more costly process than brine extraction. However, the minerals gained from mining have a higher lithium content than those from saltwater lakes. Of the five minerals, spodumene is most frequently used for lithium production. After mining, spodumene is heated to 1100°C and then cooled to 65 degrees. It is then crushed and roasted again with concentrated sulphuric acid. Finally, sodium carbonateis added, and the resulting lithium carbonate is crystallized, heated, filtered, and dried.
Extraction of lithium from brines is an equally elaborate process.The saltwater must first be pumped to the surface into several large evaporation ponds to undergo solar evaporation over a number of months. Potassium is often extracted first from early ponds, while later ponds have increasingly high concentrations of lithium. When the lithium chloride in the evaporation ponds reaches the required concentration, the solution is pumped to a recovery plant where extraction and filtering remove any unwanted substances (boron or magnesium). It is then treated with sodium carbonate to extract lithium carbonate. The lithium carbonate is then filtered and dried. Excess residual brines are pumped back into the pond.
The new production method has several advantages over conventional processes: as the scientists plan to use infrastructure of already existing geothermal plants, through which every year about 2bn litres of brine water is pumped, no new wells will have to be drilled. Also, the method does not produce a lot of overburden and has only minimal land consumption. The lithium ions will be continuously extracted within only a few hours in the thermal water cycle of the geothermal plant. The thermal water is returned underground after use, thus, no toxic substances can harm the environment and the production process does not impair energy or heat production. In the South American salt lakes the enrichment process takes several months and heavy rainfall can set back production by weeks or even months. In addition, the process offers the possibility of extracting other rare and valuable elements such as rubidium or caesium. These are used in laser and vacuum technology, for example.
The extraction of lithium combined with geothermal energy production has great potential. Some experts believe that the Upper Rhine Trench might even hold one of the greatest lithium reserves in the world. However, there would have to be more than one lithium-production site installed to satisfy European lithium demand. Also, it is far cheaper to produce lithium in South America than in Germany. In the end, it all depends on how far battery producers are willing to accept higher prices to get an environmentally-friendly product.