idw – Informationsdienst Wissenschaft
Nachrichten, Termine, Experten
Nachrichten, Termine, Experten
29 April 2025/Kiel. Increasing the natural uptake of carbon dioxide by the ocean or storing captured CO₂ under the seabed are currently being discussed in Germany as potential ways to offset unavoidable residual emissions and achieve the country’s goal of greenhouse gas neutrality by 2045. However, which carbon dioxide removal (CDR) and storage methods could actually be used depends heavily on local conditions. In Germany’s North Sea and Baltic Sea waters, the options are limited to just a few approaches. This is the conclusion of a first feasibility assessment carried out by researchers involved in the CDRmare research mission. The study was recently published in the journal Earth’s Future.
Avoiding emissions is the primary goal on the path to climate neutrality. However, with the need to offset hard-to-avoid CO2 emissions in the future by removing CO2 from the atmosphere, ocean-based carbon dioxide removal (CDR) and storage methods are attracting increasing attention. But what opportunities does Germany have to utilise its marine areas for this purpose? This question has been addressed in a new study, in which researchers have for the first time attempted to assess the feasibility of ocean-based CDR and storage in German waters, taking into account local marine conditions as well as where the required materials, infrastructure and energy for such large-scale operations would have to come from.
“Site-specific factors play a crucial role in determining which ocean-based CDR and storage methods could realistically be considered. Our analysis helps us to understand what scale we are talking about when discussing the deployment of these methods in German waters — and where along the process chains foreseeable bottlenecks or limitations to feasibility might arise,” says co-lead author Dr Wanxuan Yao, who was a climate modeller at GEOMAR Helmholtz Centre for Ocean Research Kiel at the time of the study.
Comprehensive Assessment of CO₂ Removal Methods and Their Impacts
For their analysis, the team reviewed current scientific literature and incorporated findings from their own research as part of the CDRmare DAM research mission. For each method, they assessed factors such as the amount of water, materials, energy, land or sea area required, possible by-products and waste streams, necessary infrastructure and transport routes required, operating costs and what is currently known about potential environmental and societal impacts.
“In addition, we looked at whether there are already established processes for measuring and monitoring CO2 removal rates and potential environmental impacts for each method. Without such monitoring frameworks, none of the proposed approaches has a realistic chance of ever being deployed on a large scale,” explains co-lead author Dr Teresa Morganti, a marine biologist at the Leibniz Institute for Baltic Sea Research Warnemünde at the time of the study.
Ten marine CDR methods shortlisted
At the end of the multi-year selection process, five methods of CO2 removal remained that could potentially be implemented in German North Sea and Baltic waters. A further five approaches would require deployment in international waters or cooperation with other coastal states.
“The options we’ve outlined are intended to raise specific, practical questions and challenges that would need to be addressed in the event of any large-scale application, and to provide a basis for further discussion. It’s important to emphasise, however, that these outlines do not take into account the legal, political or economic frameworks, nor do they address whether the potential environmental impacts of targeted marine carbon removal are consistent with our societal values and ethical principles. These are essential questions that need to be addressed in follow-up studies,” says Dr Nadine Mengis of GEOMAR Helmholtz Centre for Ocean Research Kiel, co-author of the study and CDRmare co-chair.
Expectations for marine CDR often too high
The research team is therefore working systematically to develop methods and processes that provide a realistic picture of how feasible marine CDR techniques actually are, and what their consequences might be for both people and ecosystems. “Once you scale up marine CDR methods for a particular region, making the true scale of interventions tangible, it becomes clear that earlier expectations were often too high because such practical considerations had not been taken into account. We need many more of these context-specific feasibility studies if we are to arrive at robust estimates of the potential for marine CDR,” says Nadine Mengis.
There is also a risk that high expectations might encourage countries like Germany to place too much hope in future technological solutions, while scaling back existing and proven measures to reduce greenhouse gas emissions in the meantime. “This must not be the outcome of our research,” stresses Nadine Mengis.
The marine CDR and storage methods described in the study include:
Methods to increase the CO₂ buffering capacity (alkalinity) of the ocean:
1. Production of a silicate-based alkaline solution and its distribution in shallow coastal waters along Germany’s North Sea coast
2. Production of a lime-based alkaline solution and its distribution along shipping routes in the German North Sea
3. Spreading of ground basalt of volcanic origin along the German coastline
4. Discharge of sodium hydroxide produced via electrolysis in desalination plants (there are currently no desalination plants in the North Sea or Baltic Sea)
Methods to restore and expand vegetated coastal ecosystems:
5. Establishing and expanding kelp forests around the German North Sea island of Heligoland
6. Restoration and expansion of mangrove forests in Indonesia
7. Artificial upwelling of nutrient-rich deep water to enhance plankton production in the North Atlantic (strengthening the ocean’s biological carbon pump)
8. Offshore Sargassum (algae) farming in the South Atlantic subtropical gyre, followed by biomass sinking
Methods for storing captured biogenic CO2:
9. Cultivation of large macroalgae, with subsequent conversion of the biomass into biomethane; the CO2 released during combustion would be captured and stored in saline aquifers in the German North Sea
10. Direct air capture of CO2 with subsequent storage in subsea basalt crust off the coast of Norway
Yao, W., Morganti, T. M., Wu, J., Borchers, M., Anschütz, A., Bednarz, L.-K., et al. (2025). Exploring site-specific carbon dioxide removal options with storage or sequestration in the marine environment – the 10 Mt CO₂ yr⁻¹ removal challenge for Germany. Earth’s Future, 13, e2024EF004902.
https://doi.org/10.1029/2024EF004902
http://www.geomar.de/n9864 Download image material
https://cdrmare.de/factsheets/ Factsheets on marine carbon removal and storage methods
https://cdrmare.de/ CDRmare website
https://storymaps.arcgis.com/stories/d5d72d29f18944ae87e2297928d7fad0 Science Story on the 10-million-tonne challenge
Merkmale dieser Pressemitteilung:
Journalisten, Wissenschaftler
Biologie, Chemie, Meer / Klima, Umwelt / Ökologie
überregional
Forschungsergebnisse, Wissenschaftliche Publikationen
Englisch
Sie können Suchbegriffe mit und, oder und / oder nicht verknüpfen, z. B. Philo nicht logie.
Verknüpfungen können Sie mit Klammern voneinander trennen, z. B. (Philo nicht logie) oder (Psycho und logie).
Zusammenhängende Worte werden als Wortgruppe gesucht, wenn Sie sie in Anführungsstriche setzen, z. B. „Bundesrepublik Deutschland“.
Die Erweiterte Suche können Sie auch nutzen, ohne Suchbegriffe einzugeben. Sie orientiert sich dann an den Kriterien, die Sie ausgewählt haben (z. B. nach dem Land oder dem Sachgebiet).
Haben Sie in einer Kategorie kein Kriterium ausgewählt, wird die gesamte Kategorie durchsucht (z.B. alle Sachgebiete oder alle Länder).
