Fuel prices, security of supply and dependence on raw materials pose new challenges for energy suppliers. Researchers at Fraunhofer IEG are investigating how heat and strategic raw materials can be extracted from the underground at the same time. The idea: Hot deep water provides heat for grids and industry – and at the same time lithium for batteries. This reduces costs, strengthens regional value creation and makes the heat supply future-proof.
“We want to make geothermal energy doubly valuable: it can provide clean heat and at the same time provide strategic raw materials such as lithium,” says Dr. Katharina Alms from Fraunhofer IEG. Water from a depth of several kilometers contains not only energy, but also dissolved metals. The study uses the example of the North German Basin to show how these resources can be developed together. For operators of geothermal plants, a second mainstay would be created in the long term through additional revenues from existing infrastructure through the production of lithium or copper. There are currently three research and five commercial sites that use hydrothermal energy from deep reservoirs in the North German Basin. More than 50 other locations are in the planning phase.
High potential in the underground
Hot, saline waters with relevant lithium metal contents circulate in the subsoil of northern Germany. In deep sandstones, concentrations of up to 600 milligrams per litre can occur. The estimated total potential in the North German Basin is up to 26.5 million tonnes of lithium metal (equivalent to 141 million tonnes of tradable lithium carbonate). Lithium is the key to batteries and energy storage. Demand is rising sharply. Domestic production reduces import dependencies and strengthens security of supply. Energy suppliers could become heat generators and at the same time raw material suppliers for lithium through geothermal energy.
How Combined Use Works
The basic idea of geothermal energy is simple. A borehole pumps hot water from a depth of several thousand meters. On the surface, it releases the heat to a district heating network or industrial processes. The water then flows through a system that filters out lithium in a targeted manner. The deep water is then returned to the underground. The researchers combined geological data, laboratory analyses and technical models, such as pumping rates, concentrations and efficiencies. This makes it possible to provide location-specific forecasts of how much lithium can be expected. As a rough rule of thumb, several tons of lithium carbonate per year and plant should be possible for a typical geothermal plant.
Economic lever for the heating transition
The combined use significantly improves the economic efficiency of geothermal energy. Additional revenue from lithium helps to recoup high initial investments for drilling. This makes projects more attractive for geothermal plant operators, energy suppliers and industry. At the same time, new value chains are being created locally. This strengthens the resilience and independence of energy systems.
Challenges in implementation
The technology for lithium extraction has already been tested, but is still in the transition to industrial application. The first pilot projects worldwide show the feasibility, but large-scale plants are still under construction. For economically viable domestic lithium production, five factors must interact:
Is there enough lithium dissolved in the deep water underground and available in the long term?
Can deep water be brought to the surface at a sufficient pumping rate?
Do heat and raw material generation complement each other in a technically efficient way?
Can tools and materials withstand the demanding conditions underground?
Are environmental compatibility, approvability and social acceptance right?
“Domestic lithium production only works if geology, technology, operation and acceptance fit together,” emphasizes Katharina Alms. “For energy suppliers and industry, this means that success lies not only in the raw material itself, but also in the system understanding of the entire subsurface and plant integration.” Geothermal energy can do more than heat. In combination with the extraction of strategic raw materials, it becomes a central building block for a sustainable, resilient and economically viable energy supply.
About the study:
The team of authors comes from the partners GFZ Helmholtz Centre for Georesearch, Karlsruhe Institute of Technology, Fraunhofer IEG, Federal Institute for Materials Research and Testing BAM, BWG Geochemische Beratung GmbH, GEOMAR Helmholtz Centre for Ocean Research, University of Kiel, University of Potsdam and Federal Institute for Geosciences and Natural Resources BGR. The results were published in the journal Geothermics: “Perspectives of co-extraction of geothermal heat with the critical raw materials lithium and copper from sedimentary basin fluids on the example of the North German Basin”, DOI: 10.1016/j.geothermics.2026.103726 This work was carried out under the umbrella of the Helmholtz Forum Earth and Environment in the CuLiWell project. It was partially funded by the European Union’s Horizon Europe research and innovation programme under the project ‘CRM-geothermal – Raw materials from geothermal fluids: occurrence, enrichment, extraction’ under grant agreement number 101058163. Further funding was provided by the “Li-Fluids” project of the German Federal Ministry for Economic Affairs and Energy (BMWE), funding codes: 03EE4034A (BGR) and 03EE4034B (Fraunhofer).
