Massive potential lithium source found in Pennsylvania

The rolling green hills of western Pennsylvania have been stripped for coal for over 2 centuries and drilled for unconventional natural gas from shale rocks since the turn of the 21st century. As it turns out, the hills also sit on a lithium trove. A recent study shows that wastewater from Pennsylvania shale gas wells contain enough lithium to supply 40% of U.S. demand for the critical battery metal (Sci. Rep. 2024, DOI: 10.1038/s41598-024-58887-x).

Some speculate that this discovery could spark a lithium rush. The answer is complicated, and it’s marred by technoeconomical, health, and environmental concerns.

Hydraulic fracturing—or fracking—uses pressurized water to crack shale rocks and release trapped natural gas. This generates large volumes of brackish wastewater containing dissolved salts and harmful chemicals, which have been linked to environmental contamination and health impacts such as asthma and lymphoma in children. The fracking industry is attempting to deal with the challenge of disposing of the produced water.

Justin Mackey, a geochemist at the National Energy Technology Laboratory and colleagues estimate that wastewater from Pennsylvania’s Marcellus Shale fracking wells could provide roughly 1160 metric tons of lithium per year. The lithium comes from ancient volcanic eruptions that occurred when the shale rock was being deposited. The researchers analyzed thousands of gas well production records and used computer simulations for their lithium concentration estimates.

Wells in northeastern Pennsylvania have a median lithium concentration of 205 mg/L, while those in the southwest had a median of 127 mg/L. Lithium today is extracted from brines containing 200 mg/L, but higher concentrations of over 500 mg/L improve the economics for traditional evaporation-based techniques.

The low lithium concentrations in the Marcellus Shale make it an unlikely source to tap purely for the metal, says Daniel Bain, a geologist and environmental scientist at the University of Pittsburgh and a coauthor of the paper. “This would not be cost-effective. Extraction processes to get lithium out of these brines are pretty resource intensive.”

But fracking is expected to increase over the next decade even without lithium in the equation. Many oil field brines also contain lithium. “Some might argue if we are producing oil and gas anyway, we might as well grab lithium from produced water,” says Seth B. C. Shonkoff, an environmental and public health scientist at Physicians, Scientists, and Engineers for Healthy Energy. Even if it is technically possible to recover that lithium, though, it might not make economical sense for companies.

Exxon and other fossil fuel firms are planning to tap into using newer direct extraction techniques, but the economics are still unclear. Even if it is cost-effective to extract lithium from fracking wastewater, disposal of the remaining contaminant-laced wastewater will remain an issue. For lithium extraction, just as for fracking, there needs to be careful assessment of the climate, health, water quality, and other environmental tradeoffs, Shonkoff says.

Nicole Deziel, an epidemiologist at the Yale School of Public Health questions the wisdom of continuing fracking even if the side benefit is electrification-friendly lithium. Overall, moving away from fossil fuel extraction and expanding renewable energy sources makes sense for the long run. “We need to embrace new technologies responsibly so we don’t create a new environmental health hazard,” she says.

Bain agrees on the need for caution—especially since the lithium estimates have a degree of uncertainty and several factors influence the amount of lithium that can be extracted from the wastewater. “It’s here, but does that mean it’s accessible? That’s really the question to explore,” he says.