Global demand for lithium is on the rise. Rechargeable batteries are driving growth, and with the highest electrochemical potential of all metals, lithium is an ideal power source. Lithium is extracted from minerals in igneous rocks, clay minerals, and from naturally-enriched continental brines hosted within salars. The latter is the preferred lithium source for investors as the prospecting, exploration, and development of a project are favorable on numerous fronts (cost, logistical, and environmental).

Roughly 60% of the global lithium resources are in South American continental brines. The paper, “The Characterization, Prediction and Recovery of Lithium from Continental brines in South American Salars: The importance of Hydrogeochemistry,” covers continental brines in South American salars from their formation and geological controls through mineralogy, chemistry, hydrogeology, resource estimation, grade prediction and the comparative economics of the deposits.

Mineral extraction from brines is distinct from hard-rock mining. Specifically, it requires the application of hydrogeological techniques and theories adapted for hyper-saline solutions. The most important tool for reserve definition and mine planning of lithium-rich brine deposits is a 3-D numerical model of variable-density groundwater flow and solute transport.

A brine is a solution containing a high amount of dissolved salts. Lithium brine is typically defined as hypersaline. The physical properties of the brine aquifer allow the geologist and the hydrogeologist to develop a three‐dimensional understanding of the brine deposit and to construct a “dynamic” numerical model to simulate a production schedule for the brine.

Currently, the lithium content of brines is too low to exploit economically. Major brines with elevated lithium are found in evaporated playas. Solar energy is used to pre-concentrate lithium. This has been the most economical method of achieving this concentration step. Lithium concentrations in producing salars range from a low (~200 ppm lithium) at the Silver Peak operation to a high of ~1,500 ppm lithium at the Salar de Atacama. Areas with high evaporation rates are preferred, and the paper mentions five existing brine production operations with advantageous conditions.

Before the lithium can be recovered, the maximum possible concentration must be achieved so it can then be separated from the brine or concentrated further. Project economics includes estimates of initial and sustaining capital, operating costs, and revenue estimates. The initial capital estimates for greenfield lithium brine projects (including solar evaporation technology) typically allocate from 30 to 50% of the initial capital cost to the construction of synthetically-lined ponds.

The sustaining capital consists of the capital investment required to keep the mine and plant operational, and the operating costs reflect the fixed and variable costs associated with a unit of production. Most greenfield project developers forecast operating costs between 2,000 and 3,500 USD/tonne LCE produced.