Storage potentials for carbon-rich products in Germany – a database and outlook on final storage of products derived from negative emission technologies

Abstract. Addressing the need to achieve the EU's net-zero emissions target by 2050, the inclusion of unconventional measures for CO₂ removal from the atmosphere into the technology portfolio appears necessary, meaning the implementation of carbon dioxide removal (CDR) or negative emissions technologies (NET). Various CDR approaches are explored for their potential in carbon dioxide removal but do not take into account the final disposal of by-products and end products as well as the potential of different areas for the required long-term storage. To complement existing methods, the NETPEC project (Negative Emission Technologies based on Photo-Electro-Chemical methods) proposes a novel approach utilizing (photo-)electrochemical methods to convert CO₂ into solid or fluid products for secure long-term storage. The aim of this work is to identify potentials for the final disposal of such carbon-rich products resulting from negative emission technologies and to develop a database of sites and areas in Germany, taking into account a broad regional distribution and sufficient storage capacities. Promising sites for storage are identified, highlighting the importance of comprehensive data collection and systematic evaluation. A database is established to catalog past, present and potential mining activity in Germany, providing essential information on storage potentials, regulatory considerations and potential estimations. Despite challenges in data availability and regulatory complexity, re-purposing old mining sites and mining related areas for storage offers significant potential in mitigating climate change by securely sequestering carbon-rich products. This study builds on the collection of data via the geological state offices towards the creation of a database on the determination of areas and estimations of potentials. The assessments suggest that even if only 1 % of these mining-related areas are considered suitable for storing carbon-rich products, a significant surface area of around 990 km² – larger than Berlin – would be available. Additionally, another 348 km² of subsurface space – surpassing the size of Frankfurt (Main) – could potentially be utilized. These figures highlight the immense storage potential of Germany's mining sites, making them key to the project's long-term carbon storage strategy. By utilizing existing infrastructure and geological formations, the project addresses the urgent demand for large-scale carbon storage while minimizing environmental impact and reducing costs. This database serves as a crucial foundation for informing, decision-making and ensuring effective implementation of carbon storage initiatives and shows possibilities for the subsequent use of such areas.