Neptune Energy reports a lithium resource estimate of 43 million tonnes of lithium carbonate equivalent (LCE) for its Altmark project in Saxony-Anhalt. That is not 43 million tonnes of elemental lithium, a proven economically recoverable reserve, or lithium already being produced. The resource is associated with lithium-bearing brine beneath the Altmark natural-gas field, and the project remains in pilot development.
What does the 43-million-tonne figure measure?
Neptune Energy says specialist firm Sproule ERCE assessed the resource in August 2025 under the CIM/NI 43-101 standard. The company announced the result on 24 September 2025. The figure is stated as lithium carbonate equivalent (LCE), a standard way to express the amount of a lithium compound represented by a resource; it is not the mass of elemental lithium in the ground. Neptune’s announcement does not, by itself, provide enough detail to independently evaluate the resource categories, assumptions, or economic viability.
A separate 2025 presentation by the German Geological Society (DGGV) described an estimated 40–50 million tonnes LCE in place. That range is the presentation’s characterization and should not be treated as a replacement for the underlying technical assessment. The presentation also reported average brine lithium concentrations above 400 mg/L, with peaks up to 600 mg/L.
Resource, reserve, and production are different
- Resource: an estimate of lithium present in a geological setting. It does not establish that all of it can be extracted profitably.
- Reserve: the economically recoverable portion established through technical and economic evaluation. The available company announcement does not establish that the 43 million tonnes LCE is a reserve.
- Production: material actually extracted and processed. The project is still testing its extraction process, so the resource figure is not current output.
Where is the lithium, and how would it be extracted?
The project lies in the Altmark area of Saxony-Anhalt, associated with the Altmark natural-gas field. Neptune says the lithium is dissolved in geothermal brine held in fine rock pore spaces at depths of roughly 3,000–4,000 metres. A 2025 DGGV presentation identifies the brine-bearing geology as Permian Rotliegend rock.
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Neptune proposes to bring brine to the surface through wells and use direct lithium extraction (DLE) to separate lithium, then pump the remaining water back into the reservoir. DLE covers multiple methods; Neptune has tested ion exchange and adsorption and says adsorption is the more promising approach for Altmark conditions. In the process it describes, an adsorbent captures lithium ions from the brine. The lithium is then released into a lithium-chloride solution for further processing into lithium carbonate or lithium hydroxide monohydrate. Neptune’s project page describes the project and its proposed process.
What stage is the project at?
Neptune says Saxony-Anhalt’s mining authority granted the Jeetze-L production licence in April 2024. The company also says further approvals are needed before development can proceed. A production licence is therefore not evidence that a commercial plant is operating or that all project permits are in place.
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Neptune reported testing ion-exchange and adsorption methods during 2024–25, including producing lithium carbonate from Altmark brine. As of its 13 August 2026 update, the company was conducting Pilot Phase II with Fraunhofer IEG, evaluating adsorbent materials and optimizing adsorption. The pilot unit is described as handling up to 1,000 litres of thermal water per day; that is pilot capacity, not commercial lithium output. Neptune’s update provides the current pilot details.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When could Altmark produce lithium?
Neptune targets a gradual start to commercial production from 2030 and says output could reach up to 25,000 tonnes LCE annually in the 2030s. Those are company targets, not achieved production or guaranteed forecasts. The company’s September 2025 release had described a demonstration phase after pilot work, subject to further mining permits.
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The available material does not establish the project’s commercial-scale recovery rate, production costs, environmental performance, or whether the target schedule will be met. Nor does it provide enough information to independently assess the economic recoverability of the stated resource. Neptune says DLE can reduce land requirements and avoid open pits and evaporation ponds, but that is a company claim about its proposed approach, not an independently established outcome for Altmark or a universal result for DLE projects.
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