Why is carbon dioxide more difficult to capture from flue gas than particulate matter?

Capturing carbon dioxide ($C{O}_2$) from flue gas is significantly more challenging than removing particulate matter due to fundamental differences in their physical properties and the concentration levels within emissions.

Differences in Capture Mechanisms

• Particulate Matter: Particulates are solid or liquid matter that can be removed through physical processes such as mechanical separation or electrostatic attraction. Devices like electrostatic precipitators and fabric filters effectively charge or trap these particles, allowing them to agglomerate and be easily collected for disposal.12
• Carbon Dioxide: As a gas, $C{O}_2$ cannot be captured by simple mechanical filtration. Post-combustion capture requires complex chemical processes, such as absorption using amine-based solvents, adsorption, or the use of specialized membranes to selectively separate the gas from the flue stream.3

Concentration and Cost

A major hurdle is that flue gas typically contains relatively low concentrations of $C{O}_2$—ranging from 4 percent in gas-fired plants to about 14 percent in coal-fired plants. Extracting these small amounts requires massive, energy-intensive infrastructure and expensive chemical solvents, making the process far more costly than the established, highly efficient methods used for particulate removal.32