Direct Air Capture (DAC) is a technology that aims to remove carbon dioxide (CO2) directly from the atmosphere. It involves deploying large-scale facilities that can extract CO2 from ambient air, concentrating it, and storing or utilizing it for various purposes. DAC is considered a potential tool in the fight against climate change because it can help reduce the concentration of greenhouse gases in the atmosphere.
The process of Direct Air Capture typically involves several steps:
Air Intake: Large fans or blowers draw in air from the surroundings and pass it through filters to remove particulate matter and other impurities. The filtered air then enters the DAC system.
CO2 Adsorption: The captured air is directed through a sorbent material, typically an amine-based chemical, which has a high affinity for CO2. As the air passes over the sorbent, the CO2 molecules chemically bond with the material, while the remaining air components continue through the system.
CO2 Desorption: Once the sorbent material becomes saturated with CO2, it needs to be regenerated for reuse. This is done by applying heat or changing pressure conditions, which releases the CO2 from the sorbent. The resulting concentrated CO2 stream can be collected.
CO2 Purification: The captured CO2 may still contain traces of impurities. It goes through a purification process to remove any remaining contaminants, ensuring a high-quality CO2 stream suitable for various applications.
Storage or Utilisation: The captured CO2 can be stored underground in geological formations such as depleted oil and gas reservoirs or deep saline aquifers. This is known as carbon capture and storage (CCS). Alternatively, the CO2 can be utilized for different purposes, such as producing synthetic fuels, chemicals, or building materials. This approach is referred to as carbon capture and utilization (CCU).
It’s important to note that DAC is an energy-intensive process, requiring significant amounts of electricity to operate the fans, pumps, and heating elements. The source of this energy can greatly impact the overall carbon footprint of DAC facilities. To minimise emissions, renewable energy sources such as solar or wind power can be used to power DAC systems.
While Direct Air Capture has the potential to remove CO2 from the atmosphere, its current deployment is limited and relatively expensive compared to other climate change mitigation strategies. However, ongoing research and technological advancements may help reduce costs and improve the efficiency of DAC in the future, making it a more viable tool for addressing the challenges of global carbon dioxide levels and climate change.