Geothermal Brine: How a Single Resource Can Serve Two Energy Goals?
The energy transition presents a dual challenge: producing more clean energy while securing the supply of critical minerals essential to low-carbon technologies. Lithium for batteries, manganese and rare earths for wind turbines and electric motors — these materials have become as strategically important as energy sources themselves.
In certain geological contexts, a single underground resource can address both imperatives simultaneously. Geothermal brines, hot fluids circulating at depth that can contain up to 30% dissolved solids [1], offer the possibility of producing electricity while extracting critical minerals within the same drilling circuit.
Geothermal brine thus constitutes an integrated model. A single resource can support both an energy value chain and a mineral value chain.
Geothermal Energy: A Multi-Faceted Resource from the Subsurface
Geothermal energy involves harnessing the natural heat contained in the Earth's subsurface to produce electricity, heat, or a combination of both. According to the IEA report highlighted by the EGEC (European Geothermal Energy Council), this resource holds an extensive potential that goes well beyond electricity production alone. It also contributes to building heating and cooling, thermal storage, and, in certain contexts, the recovery of raw materials such as lithium. It is this capacity to valorise geothermal fluids not only for their heat but also for their mineral content that forms the central focus of this article.
To go further:
What Is Geothermal Brine?
Drilling at depth in zones with a high thermal gradient frequently reveals a particular fluid: geothermal brine. Far more than simply hot, salty water, this solution results from millions of years of interactions between water and deep rock formations.
Definition and Geological Origin
A brine is defined as a highly mineralised water whose concentration of dissolved salts far exceeds that of seawater. In a geothermal context, it refers to groundwater that has remained in close contact with deep rocks over long periods, under conditions of high temperature and significant pressure.
It is precisely this geological process of prolonged water-rock interaction — at great depth and high temperature — that gives geothermal brine its particularly rich chemical composition [5]. Research conducted notably by Idaho National Laboratory and Stanford University indicates that these brines, resulting from long-term, high-temperature water-rock interactions, contain chemical components including critical and strategic raw materials such as lithium, manganese, and silica, at concentrations and flow rates that may allow for economically viable recovery [5].
Physical and Chemical Characteristics
Several parameters characterise these fluids. TDS (Total Dissolved Solids) corresponds to the total quantity of minerals and dissolved substances present in a liquid. For reference, seawater has a TDS of approximately 3.5%. Certain geothermal brines can reach values close to 30% [1], representing a concentration of dissolved substances nearly nine times greater than that of seawater.
Among the notable characteristics of these fluids:
A post-turbine temperature typically ranging between 80°C and 95°C [1], which still represents an exploitable thermal energy source after electricity production.
The presence of numerous dissolved chemical elements: lithium (Li), manganese (Mn), silica (SiO₂), zinc (Zn), lead (Pb), strontium (Sr), rare earths, and many others [5].
Concentrations generally expressed in ppm (parts per million), a unit corresponding to 1 mg of substance per kilogram of fluid. These concentrations may appear low, but the high production flow rates of geothermal plants make extraction potentially viable on an economic basis [1].
The Link Between Brine and Geothermal Energy: Two Goals, One Circuit
Geothermal brine is not merely a thermal vector. It lies at the heart of geothermal plant operations and can, depending on the chosen configuration, become a simultaneous energy and mineral resource. This articulation between energy production and raw material recovery represents the central concept analysed here.
The Classic Scheme: Heat In, Fluid Reinjected
In a conventional geothermal plant, the process follows a closed-loop logic. The hot brine is first pumped from the subsurface; its heat is then extracted to drive a turbine and produce electricity; then the cooled fluid is reinjected into the geological reservoir [7]. This closed-loop system aims to limit surface discharges and maintain pressure equilibrium in the underground reservoir [3]. In this classic configuration, the chemical elements dissolved in the brine return to the subsurface without being valorised.
The Expanded Scheme: Adding a Mineral Extraction Step
An evolution of the model involves integrating a mineral recovery unit between the electricity production step and reinjection. The U.S. Department of Energy indicates that operators are developing processes to extract critical materials from geothermal brines with a significantly lower environmental footprint than traditional mining, prior to reinjecting the fluid into the reservoir [3].
In practice, the brine thus serves three successive purposes within the same circuit: electricity production → mineral extraction → reinjection. The added extraction unit may use techniques such as DLE (Direct Lithium Extraction). DLE refers to a set of processes — adsorption, ion exchange, among others — that allow lithium dissolved in a fluid to be isolated directly without requiring prolonged evaporation, as is the case for salar operations in South America. The California Energy Commission validated this approach at pilot scale, with direct production of lithium carbonate from synthetic brine [8].
Real-World Examples
In California, the California Energy Commission demonstrated that expanding geothermal production will benefit considerably from the creation of an additional value stream through the recovery of useful metals, such as lithium, from geothermal fluids [7]. The process described by the Commission clearly illustrates the dual-use logic: the lithium-rich fluid is pumped to the surface, its heat is removed to drive a turbine, then the lithium is extracted before the spent brine is reinjected underground [7].
In Canada, at the Mont Meager site, a study published in Scientific Reports concludes that this dual use can generate additional revenue favouring the development of geothermal fields, even those that are not viable for energy production alone, thereby supporting Canada's transition to a low-carbon economy [4].
In the Dakotas, researchers from the University of North Dakota successfully generated geothermal electricity from hot water naturally produced by oil wells in the Williston Basin. This type of low-temperature geothermal co-production from existing wells represents a potential estimated at more than 30 gigawatt-hours of electricity at the national scale [9]. This example is particularly telling: it demonstrates that already-in-place drilling infrastructure can be valorised to produce geothermal energy without requiring entirely new, dedicated boreholes.
Conclusion
Geothermal brine offers a concrete example of what a natural resource can achieve when considered from an integrated perspective. In a closed-loop circuit, this same underground fluid can produce renewable energy and enable the extraction of critical minerals, with a surface footprint representing approximately 1 to 2% of that of conventional salars and an estimated reduction of approximately 85% in carbon emissions compared to traditional methods [2]. The Mont Meager example in British Columbia illustrates this well: green energy and critical minerals from the same borehole, with the capacity to make viable projects that would not have been profitable on the basis of energy production alone [4].
This model illustrates how geological resources can be conceived in an integrated manner to address two major priorities of the energy transition: clean energy production and security of supply for critical minerals. Beyond the environmental benefits, the economic complementarity between energy and minerals also improves the viability of drilling projects, opening new prospects for the mining and energy sector as a whole.
The development of projects that valorise subsurface resources in a responsible and diversified way is part of the vision of a mining and energy industry oriented toward the future. Geothermal brine is one example among others of how natural resources can be reimagined in light of current climate and strategic challenges.
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References
[1] "Critical Minerals Extraction from Geothermal Brines." Joule / ScienceDirect, 2025. Elsevier, https://www.sciencedirect.com/science/article/abs/pii/S2542435125003526.
[2] "Critical Minerals Extraction from Geothermal Brines." Pure Penn State Research, 2025. Pennsylvania State University, https://pure.psu.edu/en/publications/critical-minerals-extraction-from-geothermal-brines/.
[3] U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy. "Geothermal Energy: Mining a Secure Future." DOE/EERE Presentation, 2023. U.S. Department of Energy, https://www.energy.gov/sites/default/files/2023-03/SME_Presentation_Geothermal_Energy_Mining_A_Secure_Future.pdf.
[4] Authors not specified in the provided excerpts. "Assessment of Critical Mineral Extraction from Brines at Mount Meager." Scientific Reports, 2025. PMC/National Institutes of Health, https://pmc.ncbi.nlm.nih.gov/articles/PMC12500984/.
[5] Neupane, G. "Assessment of Mineral Resources in Geothermal Brines in the United States." Proceedings of the 42nd Stanford Geothermal Workshop, 2017. Stanford University / INL, https://pangea.stanford.edu/ERE/pdf/IGAstandard/SGW/2017/Neupane2.pdf.
[6] International Energy Agency. The Role of Critical Minerals in Clean Energy Transitions. IEA, 2021. https://iea.blob.core.windows.net/assets/ffd2a83b-8c30-4e9d-980a-52b6d9a86fdc/TheRoleofCriticalMineralsinCleanEnergyTransitions.pdf.
[7] California Energy Commission. "Pilot Scale Recovery of Lithium from Geothermal Brines." CEC Publications, 2024. California Energy Commission, https://www.energy.ca.gov/publications/2024/pilot-scale-recovery-lithium-geothermal-brines.
[8] California Energy Commission. "Pilot Scale Recovery of Lithium from Geothermal Brines." Report CEC-500-2024-020, 2024. California Energy Commission, https://www.energy.ca.gov/sites/default/files/2024-03/CEC-500-2024-020.pdf.
[9] U.S. Department of Energy, EERE. "EERE Success Story — DOE-Funded Project: First Permanent Facility to Co-Produce Electricity from Geothermal Resources at an Oil and Gas Well." Energy.gov, 2016. U.S. Department of Energy, https://www.energy.gov/eere/success-stories/articles/eere-success-story-doe-funded-project-first-permanent-facility-co.
