CO2 Storage Options in Germany

Germany is the largest emitter of CO2 in the European Union. Many of the large point sources are inland, farther away from the coast, so that CO2 capture and storage can only become a widely applied option if suitable onshore storage sites can be found. Apart from storage capacity, storage safety and possible leakage rates are critical factors that influence the available storage potential. Although companies are willing to start storage projects in Germany soon, no legal or regulatory basis exists yet. Storage options that have been discussed for Germany include aquifers, natural gas and oil reservoirs, abandoned coal mines and unminable coal seams, abandoned potassium mines, mineralization, and injection into the sea. Pros and cons of the different options are described below. Aquifers and natural gas fields are considered to be the most realistic storage options for a near-term use. Oil fields will provide only local opportunities. Coal might be an option for the future. Potassium mines, the sea, and mineralization are not considered to be safe, economical, or acceptable options. Although the storage capacity of the gas fields can be estimated fairly accurately, the presumably larger capacity of deep saline aquifers is much more difficult to estimate. The problems of capacity estimates for single structures and Germany as a whole are discussed. To date, only a few regional assessments of storage options have been made. A consistent evaluation of underground structures and their potential suitability for CO2 storage is under way in a joint undertaking by the federal and state geological surveys and the hydrocarbon industry. An important task in this mapping project is the definition of criteria that can be used for site evaluation, comparison, ranking, and selection of sites. These criteria must be based on information generally available from standard underground information (well reports, logs, seismic profiles) and should include the selection and use of common default values for uncertainty estimates in cases when data are missing, e.g., sweep efficiencies or aquifers without information from drilling. The common methods for capacity estimation need to be applicable to different regions.