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In recent months a debate has been going on between experts about the extent of the world’s reserves of lithium.
Some seek to show that the world has limited reserves of lithium - insufficient to justify the conversion of the world’s automobile fleet to electric vehicles powered by lithium batteries and run them sustainably.
The reserves of lithium in the Salar de Uyuni have become a key factor in this debate.
The consultancy firm Meridian International Research states that the Salar de Uyuni only has 300,000 tonnes of lithium (metal) that is realistically recoverable, and this at a high cost to the environment.
Year after year, the USGS (United States Geological Survey) continues to publish that Uyuni has a reserve of 5.5 million tonnes of lithium.
In 1989, ORSTOM (Office de la Recherche Scientifique et Technique d'Outre-Mer, today IRD, French Scientific Research Institute) drilled a borehole to a depth of 120 metres at the centre of the Salar without reaching its base. This showed that layers of highly porous salt crust, saturated with brine, alternate with layers of highly impermeable clay, also saturated with brine. The study counted 11 layers of salt crust (more than 80 m) and 10 layers of clay (almost 40 m). It was also found that nearly all the samples contain the same quantity of dissolved salts, and that the lithium content tends to fall slightly at greater depths.
In 2004, DUKE UNIVERSITY drilled another deep borehole, also in the centre of the Salar, as part of a paleoclimatological study of South America, for which the Salar de Uyuni provides unique scientific evidence. This borehole was drilled to a depth of 214 metres, without reaching the base of the Salar. The Duke researchers confirmed the same formation of layers of salt crust alternating with layers of clay. They found a total of approximately 170 metres of salt crust and 44 metres of clay, with the height of the layer of salt tending to increase at greater depths. The presence of lithium in the deep brine was also proven.
Only by drilling more boreholes all over the Salar will we be able to determine the true depth of the brine, its salts content, and the real reserves of lithium.
Nevertheless, we can make a new estimate, based on the information available today and assuming the following hypotheses:
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The Salar is an inverted cone, with an area of 10,000 km2 at its base and a depth of 220 m.
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The pattern of lithium concentrations is the one found by ORSTOM at the centre of the Salar.
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The layers of salt and layers of clay alternate in the manner found by Dukes University at the centre of the Salar.
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Lithium can only be extracted from the brine in the layers of salt, and these, according to ORSTOM, have an average porosity of 40% over the Salar as a whole.
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According to the data collected and based on the above hypotheses, we can state that there are more than 350 million tonnes of metallic lithium in the Salar.
Even using the most modern extraction technologies, however, no more than 40% of the lithium in the brine can be physically recovered. This means that the reserves of lithium that are realistically available and could be supplied by Uyuni to the world are 140 million tonnes of lithium.
Given the probable reserves in Uyuni, there is sufficient lithium in the world to develop lithium batteries on a massive scale and enable motor vehicles with combustion engines to be replaced by electric vehicles.
Learn more about the debate:
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Image litografica of salting
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