Myth: Carbon capture and storage is not a feasible way to reduce human CO2 emissions
Reality: With the right technologies and know-how, successful CCS will allow a viable industry that will reduce the human contribution to atmospheric CO2 levels.

Carbon capture and storage (CCS) is the separation and capture of carbon dioxide (CO2) from the emissions of industrial processes and storing it in deep underground geologic formations. CCS enables industries to continue to operate while emitting fewer greenhouse gases (CHGs), making it a powerful tool for addressing mitigation of anthropogenic CO2 in the atmosphere.

However, storage must be safe, environmentally sustainable, and cost-effective. Suitable storage formations can occur in both onshore and offshore settings, and each type of geologic formation presents different opportunities and challenges. Geologic storage is defined as the placement of CO2 into a subsurface formation so that it will remain safely and permanently stored. There are five types of underground formations for geologic carbon storage:

  1. Saline formations
  2. Oil and natural gas reservoirs
  3. Unmineable coal seams
  4. Organic-rich shales
  5. Basalt formations
Myth: The CO2 gas behaves the same in the atmosphere as it does when injected deep underground.
Reality: The elevated temperatures and pressures that exist at the depths where CO2 is injected changes its characteristics, allowing for storage of much greater volumes of CO2 than at the surface.

CO2 can be stored underground as a supercritical fluid. Supercritical CO2 means that the CO2 is at a temperature in excess of 31.1°C (88ºF) and a pressure in excess of 72.9 atm (about 1,057 psi); this temperature and pressure defines the critical point for CO2. At such high temperatures and pressures, the CO2 has some properties like a gas and some properties like a liquid. In particular, it is dense like a liquid but has viscosity like a gas. The main advantage of storing CO2 in the supercritical condition is that the required storage volume is substantially less than if the CO2 were at “standard” (room)-pressure conditions.

Temperature naturally increases with depth in the Earth’s crust, as does the pressure of the fluids (brine, oil, or gas) in the formations. At depths below about 800 meters (about 2,600 feet), the natural temperature and fluid pressures are in excess of the critical point of CO2 for most places on Earth. This means that CO2 injected at this depth or deeper will remain in the supercritical condition given the temperatures and pressures present.

Myth: There is nothing preventing injected CO2 from migrating to the Earth’s surface through the overlying rock, making CO2 leakage inevitable.
Reality: There are four main mechanisms that help trap CO2 in the subsurface and prevent it from migrating to the surface.

Each of these mechanisms plays a role in how the CO2 remains trapped in the subsurface: Structural, Residual, Solubility, and Mineral. Read more about these trapping mechanisms here. When properly injected and stored, CO2 will remain underground. If the process is faulty, leakage can occur. However, most CCS projects implement alert systems to monitor this unlikely occurrence.

Myth: Any location that has an injection well can be used to inject and store carbon.
Reality: A specific set of characteristics are needed to make a setting appropriate to act as a storage complex. These characteristics are determined through a rigorous characterization process that includes assessing potential storage risks and meeting the regulations under the U.S. Environmental Protection Agency’s (EPA) permitting process that grants permission to inject COfor carbon storage purposes.

The term “subsurface storage complex” refers to the geologic storage site that is targeted to safely and permanently store injected CO2 underground. When assessing a storage site, some of the reservoir characteristics that are studied for long-term CO2 storage include storage resource, injectivity, integrity, and depth. It also includes a storage formation with at least one, or usually multiple, regionally continuous sealing formations called caprocks or seals. All of these characteristics must examined by subsurface experts in order to determine if a potential storage complex has adequate conditions for CO2 storage.

Myth: Little to no work has been done to actively validate the concept of long-term carbon storage. 
Reality: There are many projects within the United States and around the world where geologic storage of CO2 is being successfully performed.

Carbon dioxide (CO2) storage is currently happening across the United States and around the world. Large, commercial-scale projects, such as the Sleipner CO2 Storage Site in Norway and the Weyburn-Midale CO2 Project Project in Canada, have been injecting CO2 for many years. Each of these projects stores more than 1 million metric tons (MMT) of CO2 per year. Large-scale efforts are also currently underway in China, Australia, and Europe. These commercial-scale projects are demonstrating that large volumes of CO2 can be safely and permanently stored.

Additionally, a multitude of other carbon capture and storage (CCS) efforts are underway in different parts of the world to demonstrate the capability of geologic storage and technologies for future long-term CO2 storage. To date, more than 200 CO2 capture and/or storage operations (including in-development and completed) have been carried out worldwide.

Read the origin and history of carbon capturing here.