Follow The Lithium - Part 3
Updated: Jan 3
Lithium Mining and Extraction, Traditional Methods
Why do so many existential-environmental debates hang on determining which environmental effects will kill us first? Lithium mining and extraction is certainly in that category:
Using current technology, lithium is a key element in the renewable energy transition. The transition is necessary to mitigate global climate change.
Current lithium mining techniques use a lot of groundwater, take up large swaths of land, leave that land severely damaged, and have large carbon footprints.
Long story short: Lithium mining and extraction are dirty businesses, but, for now, we have to do it.
Lithium is relatively abundant (25th most abundant element in earth’s crust). It occurs in two primary forms:
Minerals (spodumene, pegmatite, petalite), and clays or sedimentary rocks (hectorite)
Salt lakes and brines (including salars, salt water, underground lakes, and geothermal brines)
Minerals and Clays: Open Pit Mining
Lithium minerals and clays are mined using typical open pit mining techniques: Overburden removal, Ore Removal, Crushing, Digestion or Calcining, Precipitation. The largest currently known Lithium mineral deposits are located in Australia at Greenbushes, near Bridgetown, about 250 Km south of Perth. Production at Greenbushes is predominantly spodumene (Li2O.Al2O3.4SiO2). Greenbushes’ three existing pits will ultimately merge and expand into a single open-pit approximately 2.8 km (1 ¾ miles) long, 1 km (0.6 miles) wide, and up to 450 m (1,395 ft) deep. Two additional pits will be opened to satisfy rising Lithium demand.
Tianqi Lithium partners with Albemarle in the Greenbushes Australian mine. Tianqi is the majority partner with fifty one percent, 51%, of the venture. Albemarle owns forty nine percent, 49%. Chinese private citizens Wei Ping Jiang (28.2) and Jing Zhang (4.65%), in turn, own the largest interests in Tianqi.
Lithium mining is subject to many of the same objections that other open pit mining operations encounter:
Overburden removal often has dire consequences for local ecosystems and, if not done consciously, damages cultural artifacts and historically significant sites. Removing and preserving the overburden for subsequent site remediation alters watercourses and wildlife patterns. Commercially useful Li ores are often found near the surface, thus moderating the amount of overburden that must be removed.
Like many pit mined ores, Lithium is usually not present in high concentrations. With one exception, *1 Lithium minerals contain 1.5%-4% Lithium. Sedimentary rocks and clays typically contain less than 2%. Thus, the initial mining operation must remove 20 to 40 times as much material as the amount of lithium it contains. Once processed, the waste rock and fill (tailings) must be moved or stored somewhere – causing changes in surface hydrology, groundwater levels, and flow paths, among other objectionable effects.
Lithium ore processing, extraction, and concentration procedures use highly concentrated and potentially toxic acidic or alkaline agents. *2 The agents themselves require caution, and the leachate or residue that remains after their use presents water quality issues.
At the end of the pit mines usefulness, a large and generally unsightly hole is left in the ground. While remediation is mandatory (at least for newer mines), mining companies have not fully embraced the concept – often leaving behind indelible evidence of their activities.
Brine: Evaporative Extraction
Brines are “mined” using salt brine extraction. In a typical application, a deep well is drilled to reach subsurface underground lakes. The lake’s brine is then pumped to the surface and diverted to settling-evaporation ponds. During the typical one- to one and a half-year evaporation process, sodium, calcium, and potassium chlorides crystalize from the brine, leaving a more concentrated solution of lithium salts (typically, LiCl). Calcium carbonate is used to precipitate the Li salts (as Lithium Carbonate, Li2CO3) and remove magnesium [as Magnesium Hydroxide, Mg(OH)2]. *3
Around 40 percent of the world’s lithium carbonate production and over 25% of known Lithium reserves originate in underground brine lakes and aquafers near the Salar de Atacama, a Chilean salt flat covering approximately 3,000 square kilometers (~ 1,200 square miles). Sociedad Química y Minera de Chile (SQM), by virtue of its operation at Salar de Atacama, has become the second most highly capitalized Lithium extraction firm.
For all practical purposes, the salar consists of an overburden of dried salts underpinned by concentrated salt brine solutions. The salar sits in a basin surrounded by mountains (Andes to the east, Cordillera de Domeyko to the west). The basin has only tenuous, mostly seasonal-ephemeral, connections to surrounding drainages. Hence runoff from the surrounding mountains accumulates in the basin and is not diluted by either rainfall or the influx of riverine waters.
The salar’s geography-geology conspires to make it one of the driest places on earth, receiving less than 30 mm (1 1/4 inch) of annual rainfall. Its elevation (2,300 meters, ~7,100 ft) contributes to the Lithium industry’s highest evaporation rate (3,500 mm/year, 138 inches per year).
Like many volcanic regions, the surrounding mountains contain elevated levels of lithium and other mineral salts. These factors combine to produce a brine that contains up to 2,700 parts per million Lithium – nearly five times the concentration observed in other commercially viable brine lakes.
In common with Open-pit mining, brine extraction is acreage intensive, and often contributes to land destruction, contamination, and high-water consumption. Notably for the Atacama, the water consumption, estimated to be 500,000 gallons per ton of Li2CO3 occurs in areas already subject to drought and desertification.
These conditions place extreme pressure on local populations, leading one observer to the conclusion: “Communities are suffering a slow violence that’s creating conditions of ecological exhaustion.” *4
In 2018, SQM (negotiating with the Chilean government) agreed to spend up to $15 million annually to promote “sustainable development” in local communities. Several key indigenous associations, including the Atacama Indigenous Council (CPA) rejected the payments. In CPA’s view, the payments are merely a distraction from ensuring that the Atacama environment is protected. CPA calls for the deal to be annulled because the government and mining interests did not consult with the indigenous peoples first.
In June of 2021, SQM attempted an “end-run” around CPA. Rather than continuing to negotiate with CPA, SQM made direct compensation offers to each of the eighteen affected communities. Only three of those communities accepted SQM’s terms, and four others are still negotiating.
For the rest, the conflict remains unresolved at this time. A may also serve as a cautionary tale for companies and agencies that attempt to expand U.S. production.
*1 Crystalline Zabuyelite, found near Lake Zabuye in Tibet, contains 17% to 18.8% Lithium. Deposits of this mineral have also been identified in Zimbabwe and the Piedmont area of North Carolina. *2 Two primary methods are in use: The acidic method calcine the ore at ~1,100 C followed by treatment with concentrated sulfuric acid to derive Lithium Sulfate and Aluminum Silicate from the ore. The alkaline process calcines the ore in the presence of Calcium Carbonate to yield Lithium Oxide and Calcium Aluminum Silicate. A third method, Chlorination Roasting, is less prevalent. *3 A more detailed flowchart for this process and its variations is in P. Meshram et al. / Hydrometallurgy 150 (2014) 192–208 *4 James J.A. Blair, assistant professor at California State Polytechnic University, Pomona, coauthor of NRDC report on lithium mining in South America. C.f. also https://www.nrdc.org/stories/lithium-mining-leaving-chiles-indigenous-communities-high-and-dry-literally
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