The USGS has developed tools to help companies and researchers find them all.

United States Global Survey (USGS) reports have long demonstrated that while there is technically plenty of lithium found in the Earth's crust to meet demand, extracting this battery metal in the usual fashion (hard rock mining and brine evaporation) hasn't been very sustainable or cost-effective, requiring large amounts of energy, water, or infrastructure.

The highest concentrations of lithium are often in pegmatites formed underground. Mining these hard rock pockets of lithium-rich minerals is expensive as well as energy- and water-intensive. The remaining lithium produced in the world today comes from arid salt flats. This process slowly evaporates concentrated lithium from naturally occurring brine pools. While producing lithium from brines is an improvement in budget and energy usage compared to mining hard rock, this process still requires a vast footprint and months to complete.

Wastewater from oil and gas production offers an increasingly important source of lithium in the United States, and USGS has set out to quantify how much of the battery metal is available in this petroleum industry byproduct.

Each year, billions of gallons of saline water are pumped from deep underground to the surface during oil and gas production. These brines, known as "produced waters," can be 10 times saltier than seawater and are often contaminated with oils, greases, and heavy metals that are either pumped back into the ground or intensively treated. These briny wastewaters often contain lithium and other critical minerals in high demand.

"Treating waste as a potential resource is a crucial shift for the energy and mineral fields," said USGS Associate Director for Energy and Minerals Sarah Ryker. "Every state, and every country, has legacy waste from extractive industries. A key question is how much of that waste could be put to use to strengthen energy and mineral supply chains."

Recovering critical minerals during oil and gas production could provide an eco-friendly use of these produced waters, reducing the carbon footprint of the petroleum industry as it winds its way down and transitions to greener energy production. To establish the feasibility of potential resources, USGS researchers are working to develop foolproof methods, search tools, and resources indicating where lithium-rich waters might be and how much lithium they could contain.

USGS

The USGS National Produced Waters Geochemical Database is an evolving tool for exploring the potential for recovering commodities such as lithium from the byproducts of oil and gas production. This map shows the locations of more than 6500 measurements of lithium concentration in oil and gas wastewater.

Investigating unusual sources

To aid in this circular approach, researchers from the USGS Oil and Gas Waters Project have drawn from an unassuming tool in the hunt for areas with high lithium concentrations. The U.S. Produced Waters Database is an online compilation of geochemical information from roughly 113,000 samples analyzed by academia, private industry, and several federal and state agencies.

"This database lets us look across the nation to identify national and regional trends in lithium concentration, as well as understand resource availability at the local scale," said Madalyn Blondes, who has worked on the database for over a decade. She also notes that many of the samples were taken before lithium was considered critical.

The datasets can now be processed through machine learning algorithms to predict how much lithium is in locations that haven't yet been sampled.

The objective of the USGS Oil and Gas Waters Project is to provide information on the volume, quality, impacts, and possible uses of water produced during the generation and development of hydrocarbons and the like, as well as related fluids injected into reservoirs for energy development and associated waste disposal.

The USGS Brine Research Instrumentation and Experimental (BRInE) Laboratory has focused on measuring concentrations of critical minerals in samples taken at oil and gas wells, as well as running experiments heating up rocks collected from deep underground to mimic and study the geologic conditions, rock chemistry, and pressure interact to create valuable brines.

"At the USGS, we have both the technical knowledge of how to analyze the samples and an understanding of the geologic context from our research," said Blondes. "I think lithium recovery from energy wastewaters has real potential. The data are showing that there are high concentrations of lithium in places across the country where it could be a really important resource. And the infrastructure to produce it is already there."

Real-world labs

"We're at a really exciting time where we have both the computing power and the incoming data to run these models and predict where energy and mineral commodities may occur at significant concentrations," said Katherine Knierim, a USGS research hydrologist working on lithium estimates in the Smackover formation in southern Arkansas, a hotspot of petroleum production with promising concentrations.

Knierim used the USGS database to train a machine-learning model that generates spatially continuous prediction maps of sedimentary basin brine lithium from regional geology, geochemistry, and temperature data. The Oil and Gas Water Project is now using this model to lead an expanded assessment of lithium resources for the entire Smackover Formation throughout the Gulf Coast, as well as other target formations throughout the United States.

Several companies have already launched pilot recovery programs to recover commodity metals from legacy sites or their own produced waters.

In 2021, the Department of Energy partnered with USGS and sent low-flying aircraft across California's lithium-rich Salton Sea area to gather magnetic, radiometric and elevation characteristics of rocks above and below ground, analyzing the data to understand how the area's geothermal heat and fluids are generated and transported through the earth, and what similar locations could be both geothermal and lithium hotspots.

Research is also being done extensively in the Appalachian (Marcellus and Utica), Gulf, Permian, Williston, and Denver-Julesburg Basins.

Ryker explains this research presents more than just meeting demands for lithium and low-carbon energy, but more importantly, demonstrates new thinking of wastes as feeding back into production, redefining the untapped potential of geologic resources and waste at historic and modern-day mines as part of a wider circular economy.

"Our science is identifying ways to turn waste into an opportunity, not only a liability," said Ryker. "Our goal is to bring this science to bear on both clean-up at legacy waste sites and waste management at present-day sites."