(625d) How Do Variations in Ambient Carbon Dioxide Concentration Affect Direct Air Capture Performance?

Direct air capture (DAC) relies on ambient air as the inlet stream to contactors, where CO2 is removed. For a typical DAC process, large swings in ambient concentration on a daily basis are not unusual. While the average ambient concentration of CO₂ in air is typically around 419 ppm⁽¹⁾, regional variations exist and local conditions can oscillate around this average.^(2,3) These swings have a non-trivial impact on DAC process performance, especially when using a fixed cycle time. Since most studies focus only on an average ambient CO₂ concentration, it is not well understood how fluctuations around the average affect DAC performance and operation.

This talk will discuss the experience Climeworks has with inlet CO₂ concentration variability and the effect on our DAC technology. First, breakthrough data at different inlet CO₂ concentrations will demonstrate the impact at a small scale. Next, we will use pilot plant data to demonstrate the influence of inlet CO₂ concentration fluctuations at a larger scale. We will then use modelling to help provide the fundamental reason why DAC performance is strongly dependent on inlet CO₂ concentration. Finally, the implications of what this means for process and cycle design will be discussed.

References

[1] Lyndsay, Rebecca. “Climate Change: Atmospheric Carbon Dioxide” NOAA. April, 9, 2024. https://www.climate.gov/news-features/understanding-climate/climate-cha….

[2] Cai, Xuqing, et al. "Assessing Impacts of Atmospheric Conditions on Efficiency and Siting of Large-Scale Direct Air Capture Facilities." JACS Au 4.5 (2024): 1883-1891.

[3] Jamdade, Shubham, et al. "Incorporating Diurnal and Meter-Scale Variations of Ambient CO2 Concentrations in Development of Direct Air Capture Technologies." ACS Sustainable Chemistry & Engineering (2024).