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Researchers have discovered massive amounts of lithium in hydraulic fracturing wastewater from gas wells in Pennsylvania, USA. Using an innovative technique to extract the element with a yield greater than 90%, the source could meet up to 40% of the country’s demand. This would go a long way towards achieving the goal of meeting all lithium needs from local sources by 2030.
Lithium is one of a group of elements essential for making today’s technologies, such as smartphones and laptops. It is also used in energy transition technologies such as electric vehicles and photovoltaic panels. With the increase in demand, its price has increased by approx 550% in just one year. On the other hand, carbon neutrality goals could increase global demand by 400%.
Paradoxically, its exploitation causes controversy due to the large environmental impacts, not only of its extraction, but also of the supply chain. It is estimated at 8 billion dollars, and 90% of the world’s lithium reserves come from Australia, Chile and China. Much of it is extracted in Chile and then processed in China before being sent to its final destination. This includes significant carbon emissions, not to mention the unethical practices and geopolitical issues in which China is involved.
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To reduce impacts and ease supply, the United States plans to “manufacture” the lithium it needs locally. Recent studies have shown that the by-products of hydraulic fracturing of hydrocarbons (oil and gas) could be important sources of lithium. However, these wastewaters are currently poorly treated and reused, which represents an additional environmental problem for the country.
Researchers from the University of Pittsburgh (in Pennsylvania, United States of America) propose the exploitation of lithium from these sources, thus enabling their valorization while improving the availability of the element at the national level. Specifically, they found that wastewater produced from gas operations in the Marcellus Formation region of the central Appalachians could contain economically viable concentrations of lithium.
Note that the United States already has an operating lithium extraction mine in Nevada. However, “it’s different,” says Justin Mackey, lead author of the new study, ua blog post from the University of Pittsburgh. ” This is a waste stream and we consider the beneficial use of this waste “, he explains, talking about the wastewater from hydraulic fracturing of hydrocarbons. Exploitation of this new source therefore does not require additional mining operations. The research results are available in the journal
Scientific reports.
Map of the study area, showing the extent of the Marcellus Shale, gas well locations. © Justin Mackey et al.
A reservoir that can meet 40% of the country’s demand
The Marcellus Formation is a geological basin consisting of natural gas deposits from the Upper Paleozoic. In order to extract it, numerous drilling operations are carried out in the region. To do this, operators use huge amounts of water for hydraulic fracturing. This technique consists of drilling a well approximately 1,500 meters deep, then injecting water under very high pressure to extract the gas from the rocks and sediments.
Approximately 95% of wastewater from Marcellus operations is reused for ongoing hydraulic fracturing operations. However, these liquids contain significant amounts of dissolved solids (more than 100,000 mg/l) and therefore require a rigorous treatment process before they can be reused. As a result, the amount of water reused is still small compared to the injected water.
According to reports from area operators (required by Pennsylvania Environmental Protection Authorities), this wastewater contains large amounts of lithium. However, until now no precise measurements have been carried out to quantify it. ”
The discovery of lithium in Marcellus Shale wastewater was not a surprise, but there were insufficient measurements to quantify the source “, explains Mackey.
Indeed, the Marcellus is a geological shale formation deposited during the period of Devonian volcanism (between 416 and 359 million years BC). There are alternating layers of limestone that are formed from volcanic ash, which separated lithium from other minerals through diagenesis (transformation of sediments into sedimentary rocks). This makes it an ideal and accessible target for element extraction.
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Histogram showing distribution of estimated annual lithium (Li) mass yield from shale gas operations in Pennsylvania. A probability density function (PDF) fitted by Monte Carlo simulations (n ​​= 25,000) shows that the highest likely estimate of Lija’s annual mass yield is 1160 (95% CI 1140-1180) t/yr. © Justin Mackey et al.
According to the new study team’s analysis, the region could provide massive lithium yields of up to 1,160 metric tons per year. This could meet between 30 and 40% of national demand, bringing the country closer to its goal of being completely self-sufficient by 2030. Laboratory experiments by researchers have shown that it is possible to extract lithium from aqueous hydraulic fracturing waste with a yield of over 90%.
However, “concentrations, production volumes, and extraction efficiencies vary between operational areas,” the researchers state in their report. This could affect recovery performance. However, the country has other sources of lithium-rich wastewater that could also be tapped, including West Virginia.
As a next step, the researchers plan to assess the long-term environmental impacts of this new lithium mining technique. Pilot installations will then be started to explore different possible extraction techniques.