Safe Solutions
for Permanent CO2 Storage
Capturing CO2 can only make an effective, sustained contribution to climate protection if the CO2 can be stored safely and permanently. Finding viable storage solutions is a must for the success of CCS.
Saline aquifers are suitable for permanent underground carbon storage. Typically more than 800 meters below the earth's surface, these rock formations consist of microscopic cavities filled with saltwater. CO2 would be injected into an aquifer under high pressure, where it would displace and partially dissolve in the saltwater in a process similar to the carbonation of mineral water. This is an attractive solution because aquifers have the capacity to store the quantities of CO2 that would be captured at power plants.
Depleted natural gas reservoirs represent another option for permanent carbon storage. Gas accumulated and was conserved in such formations for millions of years, providing a naturally created storage facility for CO2. Pressurized CO2 is already injected into oil reservoirs around the world in order to boost their production and extend their operating lives. Now, we can benefit from this experience for carbon storage.
Depleted oil and gas reservoirs in Germany could store a lot of carbon although not enough on their own to store the amount of carbon that would be captured in power plants.
Depleted natural gas reservoirs represent another option for permanent carbon storage. Gas accumulated and was conserved in such formations for millions of years, providing a naturally created storage facility for CO2. Pressurized CO2 is already injected into oil reservoirs around the world in order to boost their production and extend their operating lives. Now, we can benefit from this experience for carbon storage.
Depleted oil and gas reservoirs in Germany could store a lot of carbon although not enough on their own to store the amount of carbon that would be captured in power plants.
Safe and permanent underground carbon storage would help prevent the CO2 concentration in the earth's atmosphere from increasing. The nature of the geological structures suitable for storage and their depth below the earth's surface render impossible the sudden release of quantities of CO2 large enough to impair breathing. Saline aquifers, for example, are several thousand meters below ground and have been insulated from surrounding formations for very long periods of geological time.
A viable geological storage facility needs to consist of a porous rock formation for CO2 storage and at least one impermeable stratum (known as cap rock) above it to prevent the CO2 from escaping. The quality of the cap rock is decisive for a storage facility's integrity and thus a key criterion for site selection.
What would happen to the CO2 stored in such a facility over the next several millennia? Most, and perhaps all, of the CO2 would dissolve in the water contained in the rock formation in a process similar to the carbonation of mineral water. Because it's denser, this CO2-infused water would sink to the formation's floor. Mineral processes would the crystallize then CO2 and bind it to the rock formation. Thus, with the aid of nature and time, CO2 can be permanently sequestered far below ground.
Earthquakes pose no serious threat to underground storage facilities. No storage facilities are planned for seismically active regions along the borders of the continental plates. And in seismically stable regions, effects are imperceptible or so small that they would not damage the integrity of the cap rock.
Storage facilities must offer sufficient natural safeguards against the escape of CO2. Their integrity would also be monitored continuously. The utility industry has decades of operational and institutional experience storing natural gas underground, experience that would help ensure safe and reliable carbon storage. Moreover, all facilities would be subject to regulatory consent and oversight.
A viable geological storage facility needs to consist of a porous rock formation for CO2 storage and at least one impermeable stratum (known as cap rock) above it to prevent the CO2 from escaping. The quality of the cap rock is decisive for a storage facility's integrity and thus a key criterion for site selection.
What would happen to the CO2 stored in such a facility over the next several millennia? Most, and perhaps all, of the CO2 would dissolve in the water contained in the rock formation in a process similar to the carbonation of mineral water. Because it's denser, this CO2-infused water would sink to the formation's floor. Mineral processes would the crystallize then CO2 and bind it to the rock formation. Thus, with the aid of nature and time, CO2 can be permanently sequestered far below ground.
Earthquakes pose no serious threat to underground storage facilities. No storage facilities are planned for seismically active regions along the borders of the continental plates. And in seismically stable regions, effects are imperceptible or so small that they would not damage the integrity of the cap rock.
Storage facilities must offer sufficient natural safeguards against the escape of CO2. Their integrity would also be monitored continuously. The utility industry has decades of operational and institutional experience storing natural gas underground, experience that would help ensure safe and reliable carbon storage. Moreover, all facilities would be subject to regulatory consent and oversight.
Research into the technology for underground carbon storage is under way around the world. Such technology is already in use on a commercial scale in a number of projects. But there's still a lot of research ahead to determine the storage potential of individual sites, to study the long-term stability of geochemical processes during storage, and to calculate the costs of underground storage. We also need to assess the options for monitoring storage facilities once they become operational and to work with policymakers to address regulatory and consents issues.
We're partnering with 18 companies from nine countries in a project called CO2SINK, the first EU-funded carbon storage research project. Its purpose is to do further research into storage processes and to help move this technology to an industrial scale. Under the close supervision of the agency responsible for mining and geology in the German state of Brandenburg, up to 60,000 metric tons of CO2 will be stored more than 600 meters underground in saline aquifers near Ketzin, about 20 miles west of Berlin. Sensors monitor how the CO2 reacts in the porous rock formations which draw it in like a sponge. This experiment is being coordinated by the German Geo-Research Center (GFZ) in Potsdam. CO2SINK, which involves relatively small quantities of CO2, is an important milestone that will help us realize our medium-term plans to conduct our own storage tests on a larger scale. E.ON Gas Storage, a subsidiary of E.ON Ruhrgas, is responsible for developing carbon storage facilities for the E.ON Group. It develops and operates underground natural gas storage facilities, giving it valuable expertise and experience with storage technology and the consents process for storage facilities.
We're partnering with 18 companies from nine countries in a project called CO2SINK, the first EU-funded carbon storage research project. Its purpose is to do further research into storage processes and to help move this technology to an industrial scale. Under the close supervision of the agency responsible for mining and geology in the German state of Brandenburg, up to 60,000 metric tons of CO2 will be stored more than 600 meters underground in saline aquifers near Ketzin, about 20 miles west of Berlin. Sensors monitor how the CO2 reacts in the porous rock formations which draw it in like a sponge. This experiment is being coordinated by the German Geo-Research Center (GFZ) in Potsdam. CO2SINK, which involves relatively small quantities of CO2, is an important milestone that will help us realize our medium-term plans to conduct our own storage tests on a larger scale. E.ON Gas Storage, a subsidiary of E.ON Ruhrgas, is responsible for developing carbon storage facilities for the E.ON Group. It develops and operates underground natural gas storage facilities, giving it valuable expertise and experience with storage technology and the consents process for storage facilities.
