The movement of lithium through Earth’s systems comprises two distinct cycles. One is a natural, geological process that unfolds over millions of years, slowly distributing the element through the planet’s crust and oceans. The other is a rapid, human-driven cycle that extracts, processes, and utilizes lithium on a vastly accelerated timeline. These two pathways are now intersecting, as industrial activities are mobilizing lithium at a scale that perturbs its natural balance.
The Natural Lithium Cycle
Lithium is one of the few elements created in the Big Bang, and it was subsequently incorporated into the Earth’s crust. Its concentration in most terrestrial rocks is relatively low, ranging from 20 to 70 parts per million by weight. The natural lithium cycle begins with the slow weathering of silicate rocks, particularly granites and pegmatites, which releases the element into surface water and groundwater.
Once liberated from its mineral source, lithium travels through river systems, eventually reaching the oceans. In marine environments, it can be incorporated into clay minerals forming on the seafloor or become part of sedimentary deposits. Lithium ions can substitute for other elements like magnesium and iron within the crystal structure of these clays.
The Industrial Lithium Cycle
Commercial extraction primarily relies on two methods: hard-rock mining and brine evaporation. Hard-rock mining targets lithium-bearing minerals like spodumene, which are found in coarse-grained igneous rocks known as pegmatites. This process involves mining the ore, crushing it, and subjecting it to high temperatures and chemical treatments to isolate the lithium. Spodumene ore is roasted at temperatures exceeding 1000°C to alter its crystal structure, making the lithium more accessible for chemical leaching.
The second major source is lithium-rich brine found in underground reservoirs beneath salt flats, or salars, most notably in South America’s “Lithium Triangle.” This method involves pumping the brine to the surface into vast evaporation ponds. Over a period of many months, solar evaporation concentrates the lithium salts as the water disappears. Both methods yield material refined into compounds like lithium carbonate or hydroxide, which are used to manufacture products such as lithium-ion batteries.
Environmental Consequences of Extraction
Lithium extraction has significant environmental consequences that differ by method. Brine evaporation, prevalent in arid regions like Chile’s Salar de Atacama, is exceptionally water-intensive. Extracting a single tonne of lithium can require evaporating approximately 2 million liters of water, placing immense strain on local water tables and freshwater reserves. This level of water consumption can lead to the salinization of remaining freshwater sources, disrupting fragile desert ecosystems and impacting the indigenous communities that depend on these limited resources.
Hard-rock mining presents a different set of environmental challenges. It involves the physical disruption of landscapes through open-pit mining, which can permanently alter the local topography. The process is also energy-intensive, particularly the roasting stage, which accounts for a substantial portion of the total energy consumption. Furthermore, the use of chemicals like sulfuric acid for leaching poses risks of soil and water contamination if not managed with strict environmental controls.
Lithium Recycling and Waste Management
The end-of-life stage for lithium-containing products, especially batteries, introduces another set of challenges. Recycling lithium-ion batteries is complex due to the wide variety of battery chemistries, designs, and the use of strong adhesives that make disassembly difficult. Mishandling during this process also carries safety risks, as damaged batteries can be flammable. These factors contribute to low global recycling rates.
The two dominant industrial recycling methods are pyrometallurgy and hydrometallurgy. Pyrometallurgy involves shredding and melting battery components at high temperatures, an energy-intensive process. Hydrometallurgy uses acids to dissolve the metals from the shredded battery material. Improper disposal of these batteries in landfills allows for the potential leaching of hazardous materials into the soil and groundwater. This poses an environmental risk and wastes a resource that required significant energy and water to produce.