renewablefuels: CO2 Supply: CO2 Capture from Air

CO2 Capture from Air

Technologies for extracting carbon dioxide directly from the atmosphere are known as “Direct Air Capture (DAC).” The process usually consists of three steps: air intake, e.g., via fans, CO₂ absorption (uptake of a gas or liquid into a material) or adsorption (accumulation of substances on the surface material), and separation of the absorbed or adsorbed CO₂ using thermal or electrical energy.

DAC systems differ in terms of the sorption material and the temperature requirements for separating CO₂ from the sorption material.

Absorption and Calcination Process System

The system developed by the Canadian company “Carbon Engineering” uses potassium hydroxide as the absorbent. Separating CO₂ from the sorption material requires high temperatures (850°C).

Adsorption and Desorption Process System

The system developed by the Swiss company “Climeworks” uses an amine-based porous granulate as the adsorbent. During desorption, the adsorbent is regenerated by heating to 70-95°C and applying moderate vacuum pressure. This process, compared to the high-temperature DAC process, can more easily utilize waste heat from other processes, thereby reducing energy demand.

For an overview of current capture technologies and their costs, see the following link:
Fasihi, M., Efimova, O., Breyer, C. (2019), Techno-economic assessment of CO2 direct air capture plants, Journal of Cleaner Production, Volume 224, S. 957-980.