Point-source carbon capture methods are technologies designed to capture CO₂ emissions directly at their source, such as from power plants or industrial facilities, before they enter the atmosphere.
Pre-Combustion Capture
Pre-combustion capture is the process of capturing CO₂ before it is burned, and there are four basic stages of this process. First, a feedstock such as coal, natural gas, or biomass is gasified to produce a mixture of CO₂, hydrogen (H₂), and other gases. Then the CO₂ is separated from the other gases using a solvent or other separation process. Next, the H₂ and other gases are combusted to produce electricity or other forms of energy. Finally, the captured CO₂ is purified and compressed for storage or utilization.
This method can be more efficient than post-combustion capture because CO₂ is separated at a higher concentration, which decreases the amount of energy required to capture and purify it. The fact that it can be used with a variety of feedstocks — particularly coal, natural gas, and biomass — is another benefit. The approach can also be combined with other carbon capture technologies to further reduce emissions.
There are, however, several challenges associated with this technology, including high costs, technical complexity, and a requirement for large-scale infrastructure. The current cost of this technology is high compared to other forms of carbon capture, and the systems involved require a high level of technical expertise. Additionally, pre-combustion capture needs significant space for equipment and infrastructure, which can be a limiting factor in retrofitting existing facilities. Overall, it is a promising technology for reducing CO₂ emissions from industrial processes that use fossil fuels or biomass, but further research and development are needed to optimize its efficiency.
Post-Combustion Capture
The process of post-combustion capture (PCC) typically involves three stages. First, flue gas containing CO₂ is captured using a solvent or adsorbent material, which selectively binds to CO₂. Then, the solvent or adsorbent material is regenerated to release the captured CO₂. Finally, the released CO₂ is purified and compressed for storage or utilization.
The benefits of PCC are clear. It can be retrofitted to existing power plants and industrial facilities, making it a potential solution for reducing emissions from existing sources. Having been demonstrated in large-scale power plants, it is a proven technology that can be combined with other carbon capture technologies to further decrease emissions.
But PCC also faces challenges, particularly its high costs, energy requirements, and need for space. Retrofitting existing facilities can also be difficult because of PCC’s equipment and infrastructure requirements. So, while PCC offers a promising way to reduce CO₂ emissions from existing power plants and industrial processes, further research and development is required to improve its efficiency, reduce its costs, and increase its scalability. The porous structure of organic frameworks – such as MOFs and COFs – used in PCC systems provides an ideal matrix for CO₂ capture, as it offers a high surface area that allows for efficient adsorption of CO₂ molecules.
Oxyfuel Combustion Capture
Oxyfuel combustion capture (OFCC) is a three-stage process comprising the burning of fuel in pure oxygen to produce a high concentration of CO₂ and water vapor. The water vapor is then condensed and removed, leaving behind a stream of nearly pure CO₂. This captured CO₂ is then purified and compressed for storage or utilization.
This approach captures CO₂ efficiently because the concentration of CO₂ in combustion gases is much higher than that of conventional combustion. The technology can also be retrofitted into existing power plants and industrial facilities, reducing emissions from existing sources. And OFCC can be combined with other technologies to reduce emissions even further.
The drawbacks of OFCC, however, include high costs and energy requirements plus technical complexity. The technology is currently expensive, and a lot of energy is required to produce pure oxygen for combustion. Additionally, OFCC requires significant technical expertise to operate and maintain the system, which can be a limiting factor in retrofitting existing facilities. In fact, for OFCC systems, thermal stability of materials is essential, as the process requires high-temperature operations.
OFCC is a promising technology for reducing CO₂ emissions, but further development and research are required to maximize its economic and technical viability.
