Mining the Future: Lithium Extraction and Renewable Energy
It took a long time, but something is finally being done about fossil fuels and their impact on the planet. One of the key resources in this effort is lithium, a lightweight metal that is a vital component in EV batteries. Lithium extraction, like any resource extraction, has several negative impacts on the environment, but does it balance out to a more sustainable future for all?
In the following article, we’ll take a look at that question as well as some of the basic facts about lithium and its use in vehicles. Let’s get started.
What Is Lithium?
Lithium is a silvery metal with the symbol Li on the periodic table. It’s also the lightest metal on the table, even lighter than oxygen and half as dense as water. If you’ve heard of it before, it’s almost certainly because it’s the defining ingredient in rechargeable Li-ion batteries.
Batteries consist of an anode, a cathode, a separator, an electrolyte, and positive and negative current collectors. In Li-ion batteries, lithium acts as the electrolyte, shuttling charge-carrying ions from the anode to the cathode through the separator and back again. As they move, the lithium ions create free electrons in the anode, in turn generating a charge in the positive current collector, from which it flows into the device being powered, such as an electric motor.
There are several reasons why lithium makes an ideal electrolyte. For one, it’s cleaner than lead-acid batteries like the ones used in conventional cars. Li-ion batteries also charge up more quickly than lead-acid batteries, hold their charge for longer, and can withstand more recharging cycles, making them a great source of power for cars.
The Lithium Mining Process
Another factor in lithium’s favor is availability. Lithium is mined from deposits in the earth, with the largest deposits found in Chile totaling 9.3 million metric tons. Australia, Argentina, China, and the United States follow, with sizable reserves also found in Bolivia. There are two basic methods of lithium extraction: hard rock mining and brine extraction.
Brine extraction is the process by which most of the world’s lithium is produced. It involves extracting the metal from underground brine reservoirs, or “salars.” Most of these are found either in an area between Argentina, Chile, and Bolivia known as the “Lithium Triangle,” or dotted around China.
The process begins with pumping salty water to the surface, where it’s slowly allowed to evaporate in open pools. A slurry of hydrated lime (Ca(OH)2) is added to the pools to precipitate out unwanted salts like boron and magnesium. When the lithium in the brine is concentrated enough, the brine is pumped to a facility for further cleaning and purification, filtration, and finally, treatment with soda ash (Na2CO3) to precipitate out lithium carbonate (Li2CO3). This lithium carbonate is then washed and ready for further processing into batteries.
Hard Rock Mining
Hard rock mining involves digging metal-bearing ore out of the ground. While lithium can be found in over 100 minerals, extractors typically focus on just five: spodumene, lepidolite, petalite, amblygonite, and eucryptite, of which spodumene is the richest source.
The extracted ore is crushed and roasted at about 2,000 °F, cooled to 140 °F, milled, and subjected to acid leaching, which involves mixing it with sulfuric acid and reheating it at around 500 °F. The resulting soluble substance is called lithium sulfate, which can then be processed into usable lithium.
Lithium Extraction and Sustainability
Lithium is a critical component in clean energy, but that doesn’t mean the extraction process isn’t without its environmental drawbacks. Specifically, both the brine extraction process, which yields the most usable lithium, and mining can lead to air and water pollution, possible groundwater contamination, and land degradation.
This is because the extraction process disrupts local environments and consumes huge amounts of water — as much as 2.2 million liters are needed to extract a single ton of the metal. The resulting wastewater is laden with chemicals, both from the refining process and leftover from the ores or water containing the metal. Fortunately, several advances have been made or are currently under study, which could make the industry far more sustainable and less damaging to the environment.
One is direct lithium extraction. This involves extracting only lithium from either an underground brine source or mining byproducts using resins, or absorbent materials. The resin attracts lithium to the water’s surface, where it’s collected, and the water is reintroduced to the original aquifer. Compared to other methods, direct lithium extraction results in less pollution, lower water consumption, and a much faster processing time.
Other methods include harvesting lithium from the steam produced in geothermal power plants or using reusable porous ion-exchange beads to extract metal from subsurface brines. Currently, all of these technologies are still under development or have only recently been put to industrial use. But as electric vehicles gain ground among drivers, they could be the key to the cleaner transportation of the future.
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