- Post-combustion carbon capture is a widely studied and increasingly implemented method for reducing carbon dioxide (CO₂) emissions from fossil fuel-based power generation and industrial processes. It refers to the capture of CO₂ from flue gases after the fuel—typically coal, natural gas, or oil—has been combusted. This approach is particularly attractive because it can be retrofitted to existing power plants and industrial facilities with minimal disruption to their core operations.
- The primary goal of post-combustion capture is to prevent the release of large quantities of CO₂ into the atmosphere, thereby mitigating the environmental impacts of climate change.
- The flue gas produced during combustion typically contains a dilute stream of CO₂ (around 10–15% for coal and 3–6% for natural gas), along with nitrogen, water vapor, oxygen, and trace pollutants. This low concentration of CO₂, combined with the large volume of gas, presents a challenge for efficient and cost-effective separation. The most mature and commonly used method for post-combustion capture is chemical absorption using amine-based solvents such as monoethanolamine (MEA). In this process, flue gas is passed through an absorber column where the CO₂ chemically reacts with the amine solution to form a weakly bonded compound. The CO₂-rich solvent is then sent to a stripper (regenerator), where it is heated to release pure CO₂ and regenerate the solvent for reuse.
- Alternative technologies to amine scrubbing are also under development, including solid sorbents (e.g., metal-organic frameworks, zeolites), membrane separation, and cryogenic distillation. While many of these methods offer potential energy or cost advantages, amine-based systems remain dominant in commercial applications due to their technical maturity and reliability. However, the energy required to regenerate the solvent—known as the “energy penalty”—can be significant, often reducing the net efficiency of a power plant by 20–30%. Innovations in solvent chemistry, process integration, and heat recovery are actively being pursued to reduce this energy burden.
- Post-combustion carbon capture has the critical advantage of flexibility. Since it treats the exhaust gases directly, it does not interfere with the combustion process, allowing it to be applied to a wide range of existing facilities, including power plants, cement kilns, steel mills, and waste incinerators. This adaptability makes it a vital component of near-term carbon mitigation strategies, particularly for hard-to-abate sectors where alternatives like electrification or hydrogen are not yet feasible.
- Once captured, the CO₂ can be compressed, transported, and either stored in deep geological formations (carbon capture and storage, CCS) or utilized in various industrial processes (carbon capture and utilization, CCU), such as enhanced oil recovery, mineralization, or synthetic fuel production. Long-term storage in saline aquifers or depleted oil and gas fields offers a promising solution for permanent CO₂ removal from the atmosphere.
