- Carbon Capture and Storage (CCS) is a critical technology in the global effort to reduce greenhouse gas emissions and mitigate climate change. It involves capturing carbon dioxide (CO₂) emissions from industrial processes or power generation, transporting the captured CO₂ to a storage site, and injecting it deep underground into geological formations for long-term isolation from the atmosphere.
- CCS is designed to prevent CO₂ from entering the atmosphere, where it would contribute to global warming, and instead sequester it safely and permanently.
- The carbon capture stage typically occurs at large point sources such as coal or natural gas power plants, cement factories, steel mills, and chemical processing facilities. Capture technologies fall into three main categories: pre-combustion capture, where CO₂ is removed before fuel is burned; post-combustion capture, where CO₂ is extracted from flue gases after combustion; and oxy-fuel combustion, where fuel is burned in pure oxygen, resulting in a flue gas that is mostly CO₂ and easier to purify. Among these, post-combustion capture is the most widely deployed due to its compatibility with existing infrastructure. Solvents like amines are commonly used to chemically absorb CO₂ from exhaust gases, although other methods, such as solid sorbents and membrane separation, are also being developed.
- Once captured, the CO₂ is compressed into a supercritical fluid—a dense form that behaves like both a gas and a liquid—and transported, typically via pipelines, to a suitable storage site. The choice of transport method depends on factors such as volume, distance, and terrain. CO₂ pipelines are already in widespread use, especially in the United States, where they have been used for decades in the oil industry for enhanced oil recovery (EOR).
- The final stage, carbon storage, involves injecting the CO₂ into deep underground rock formations, such as saline aquifers, depleted oil and gas reservoirs, or unmineable coal seams. These geological formations are located thousands of meters below the Earth’s surface and are sealed by impermeable rock layers that prevent the gas from escaping. Over time, the CO₂ becomes trapped through a combination of physical, chemical, and mineral processes—such as structural trapping, solubility trapping (dissolving into groundwater), and mineral trapping (reacting with minerals to form stable carbonates).
- One of the primary advantages of CCS is that it allows for the continued use of fossil fuels in energy production while significantly reducing associated CO₂ emissions. This makes it especially important for hard-to-decarbonize sectors like cement, steel, and chemical production, where process-related emissions are difficult to eliminate through renewable energy alone. CCS is also viewed as a key enabler of negative emissions technologies, such as Bioenergy with Carbon Capture and Storage (BECCS) and Direct Air Capture (DAC), which can actively remove CO₂ from the atmosphere.
- However, CCS faces a number of technical, economic, and societal challenges. The technology is expensive, with high capital and operational costs, especially in the capture phase. Additionally, public concerns about the long-term safety of CO₂ storage—such as the risk of leakage or induced seismicity—must be addressed through rigorous monitoring, regulation, and transparent communication. Despite its challenges, large-scale demonstration projects around the world, such as the Sleipner and Snøhvit projects in Norway and the Petra Nova project in the U.S., have proven the feasibility and safety of CCS under controlled conditions.
