Evaporation Ponds: The Method That Still Dominates the Puna

An ancient method for a strategic mineral

Solar evaporation is by far the most widespread technology for extracting lithium from brines in the Lithium Triangle. In the Argentine Puna —where virtually all national production is concentrated— nearly every operating project relies on extensive pond systems that harness solar radiation and the dry high-altitude winds to concentrate the mineral.

The principle is simple and age-old: it follows the same logic coastal salt flats used to obtain common salt. Brine is pumped from the saline aquifer and left to evaporate in stages until the lithium reaches concentrations high enough for chemical processing. What changed is not the concept, but the scale and the engineering surrounding it today.

The brine's journey, pond by pond

The raw brine extracted from the salars contains just a few hundred parts per million of lithium, dissolved alongside sodium, potassium, magnesium, boron and other elements. The process begins by pumping that liquid into the first of a series of connected ponds. As water evaporates, the brine moves from one pond to the next, becoming increasingly concentrated.

At each stage, different salts precipitate —first sodium chloride, then potassium and magnesium salts— which are removed or left at the bottom. At the end of the circuit, a concentrate with several thousand ppm of lithium is sent to the chemical plant, where it is purified and transformed into battery-grade lithium carbonate or hydroxide. Each salar's magnesium-to-lithium ratio strongly conditions the efficiency of this entire route.

Time as a critical variable

The method's major limitation is its slowness. The full evaporation concentration cycle usually takes between twelve and eighteen months, depending on altitude, climate and brine chemistry. This means a project immobilizes a huge volume of liquid in the ponds for over a year before seeing the first gram of finished product.

That delay has financial consequences: it lengthens payback periods, ties up working capital in transit and makes production sensitive to rainy seasons or atypical years. A humid summer in the Puna can slow evaporation and disrupt an operation's annual planning.

Territorial footprint and water use

Evaporation ponds are visible even from space. A commercial-scale project can occupy hundreds, and in some cases thousands, of hectares of surface with its concentration ponds. That territorial footprint is one of the most scrutinized points among communities and regulators, along with water use.

Although the process does not require fresh water to evaporate the brine, it does demand industrial water for subsequent chemical processing, and it extracts large volumes of brine from the aquifer. In an arid high-altitude region, the water balance and the potential impact on nearby freshwater aquifers are central issues in every project's environmental assessments.

Why it still competes against DLE

Direct lithium extraction (DLE) promises to solve several of these limitations: it reduces times from months to hours or days, drastically shrinks the occupied surface and allows much of the brine to be reinjected. However, evaporation retains advantages that are hard to match in the short term.

The main one is cost. The Puna's brines rank among the lowest operating costs in the world, partly because the concentration energy —the sun— is free. The method is technologically mature, has decades of operating track record and low scaling risk. DLE, by contrast, often requires more energy, process water and reagents, and many of its variants are not yet proven at commercial scale for each type of brine. That is why, rather than an immediate replacement, they currently coexist, and several projects are exploring hybrid schemes.

The Puna, between tradition and transition

Argentina established itself as the world's fifth-largest lithium producer relying almost entirely on solar evaporation. The salars of the Jujuy, Salta and Catamarca Puna are the natural setting for this method, favored by altitude, low humidity and intense radiation that accelerate evaporation.

With the arrival of the RIGI in 2024 and the entry of new capital, the sector faces the dilemma of optimizing what already exists or betting on newer technologies. The Puna will likely follow a gradual path: ponds that keep operating for years, while DLE gains ground in specific projects. For now, the landscape of stepped ponds under the high-altitude sun remains the truest image of how Argentina produces lithium.