What is CCS?
What is Carbon Capture & Storage?
Carbon dioxide (CO₂) is all around us – it is part of the air we exhale and is essential to plant life and the Earth’s natural carbon cycle. Too much carbon dioxide, like that produced by industrial activities, however, can cause negative impacts on the Earth’s climate. Therefore, efforts are underway to reduce the amount of CO₂ in the atmosphere. Carbon capture and storage (CCS) is a method by which CO₂ emissions are removed from a point-source, such as a factory smokestack, before entering the atmosphere and are transferred to an appropriate site where they are pumped into specific rock formations under the Earth’s surface for permanent storage.
Today, CCS is currently deployed across 50 operational facilities and the industry continues to expand as interest and funding grows.
The Carbon Cycle – This diagram shows a simplified version of the processes involved in the carbon cycle. CO₂ is emitted naturally through root respiration and decaying organisms. CO₂ is also sequestered naturally through the natural breakdown of waste and organic matter. Humans play a part in the carbon cycle through the burning of fossil fuels which releases and causes an excess of CO₂ in the atmosphere.
Why Carbon Capture & Storage?
Carbon capture and storage (CCS) is an important technology that can be implemented on a scale large enough to reduce the overabundance of CO₂ in the atmosphere caused by industrial activities.
The above diagram depicts a potential secure energy future that utilizes carbon capture, transport, and offshore carbon storage infrastructure to produce low carbon energy. It is not to scale - and storage platforms, if any, will not be positioned in a manner that is visible from the shore. The diagram is for educational purposes only and does not depict activities involved in this project. Diagram designed by Battelle.
Science and industry agree that there are some processes in which managing CO₂ emissions are more difficult in the short-term, including electric power plants, cement factories, oil refineries, and steelworks, which need large amounts of heat that can only be produced using fossil fuels. By capturing CO₂ emissions from industry and storing them safely underground, CCS has the potential to usher the U.S. and the world into a new era of balanced energy abundance.
How Does Offshore CCS Work?
While there are many steps involved in the process of carbon capture and storage, there are three main components: capture, transport, and storage.
During the capture stage of CCS, CO₂ is collected at a source, such as a power plant or manufacturing facility, where it is sorted from other emissions. The primary industries that use CCS are ethanol plants, coal-fired power plants, landfills, and hydrogen energy facilities. Once the emissions are captured from the source, the CO₂ is sorted and transported.
During the transport stage of CCS, the captured CO₂ is transferred into a specialized compressor and put under pressures and temperatures bringing it to a stage that lies between a liquid and a gas, otherwise known as its “supercritical state.” This is done to decrease the amount of space the CO₂ takes up in pipelines and in the subsurface where it is stored. Once in a supercritical state, the CO₂ is then transported to a geologic storage facility, typically via pipeline, railcar, or tanker truck for onshore and via pipeline or barge for offshore. CCS has been done safely offshore in other countries such as Norway, where the CO₂ was transported offshore by pipeline or barge.
During the storage stage of CCS, CO₂ is injected to a depth of at least 2,600 feet for safe, permanent storage. For this project, the targeted depth for CO₂ storage is approximately 4,000-15,000 feet below sea level. The location beneath the surface where the captured CO₂ is stored is called a storage reservoir. These reservoirs are located under a confining layer, or cap rock, and are selected based on specific geologic requirements.
The above diagram demonstrates the potential steps involved in an offshore carbon capture and storage system. The process involves capturing CO₂ at a point-source (i.e., existing power plant, existing cement plant) and transporting the CO₂ via pipeline or barge to an injection well located offshore. It is not to scale - and storage platforms, if any, will not be positioned in a manner that is visible from the shore. The diagram is for educational purposes only and does not depict activities involved in this project. Diagram designed by Battelle.
Finding storage sites requires a detailed study of the underground subsurface and understanding the properties such as the porosity, which is the amount of empty spaces in a rock and permeability, which is how connected the empty spaces in a rock are and the ability of gas or liquids to flow through them. While underground sources of drinking water are not present underground offshore, careful consideration is given to the impact on marine environments and organisms.
The above images are thin sections of different types of rocks with varying degrees of porosity and permeability. The blue shows the pore space in each thin section. The pores in the thin section on the left are much larger and much more connected – indicating an ideal storage reservoir – and the thin section on the right show tightly packed pores with no connection – indicating an ideal cap rock.