Copied from nature - locked up for eternity - storage of carbon dioxide and nuclear waste at depth

It is societal consensus that adequate and reliable supplies of affordable resources need to be obtained in environmentally sustainable ways [1]. The prevailing view in the scientific community is that large amounts of carbon dioxide (CO₂) from the atmosphere and highly radioactive waste must be disposed of safely - kept away from human habitat for a very long time. In that regard, studies on natural processes that extend over very long periods help to understand the long-term behaviour of deep geological repositories. You can't carry out experiments over thousands of years. However, processes similar to those that occur at depth can also be found in nature. In combination with short-term laboratory experiments and field tests, it is possible to provide a comprehensive and reliable picture of the situation and to give a prognosis on the long-term.

In the context of climate policy, the storage of CO₂ in deep geological formations is seen as a potential means to reduce anthropogenic greenhouse gas emissions and mitigate respective global warming effects. However, questions arise: is it feasible to store CO₂ safely without endangering humans or the environment? Science and technology did provide answers to this question. In this context the GFZ driven experimental pilot site at Ketzin demonstrated the safe and reliable injection of CO₂ into a saline aquifer on the research scale [1].

The search for a site for the disposal of highly radioactive waste is an intergenerational social and political task with a geoscientific core. The first challenge is to narrow down suitable areas. The second is to analyse the subsurface using geoscientific knowledge, methods and data to determine its suitability in detail. It is the famous search for needles in the haystack. In order to identify the site with the best possible safety the search has to be carried out systematic and specific [2].

The question to be answered is: how accurate, reliable and robust must be our knowledge for a decision where and how to dispose CO₂ or nuclear waste in the subsurface? Ultimately, it is necessary to clarify which data is needed in order to reduce the uncertainties of our conceptual thinking and ensure the development of repositories in practice.

[1] Kühn, M., Bruckman, V. J., Martens, S., Miocic, J., Stasi, G. (2024): Preface to the special issue of the Division Energy, Resources and the Environment at the EGU General Assembly 2023. - Advances in Geosciences, 62, 67-69. https://doi.org/10.5194/adgeo-62-67-2024

[2] Kühn, M., Kempka, T., Liebscher, A., Lüth, S., Martens, S., Schmidt-Hattenberger, C. (2011): Geologische CO₂-Speicherung am Pilotstandort in Ketzin - sicher und verlässlich. - System Erde, 1, 2, 44-51. https://doi.org/10.2312/GFZ.syserde.01.02.4

[3] Kühn, M., Heidbach, O., Heumann, A., Zens, J. (2021): Nadeln im Heuhaufen. - System Erde, 11, 2, 6-11. https://doi.org/10.48440/GFZ.syserde.11.02.1