(209e) Cost Analysis Model for Air Capture Sorbents

Air capture is the technology of capturing carbon dioxide (CO₂) from ambient air to mitigate climate change impacts. For air capture, a sorbent is used to bind carbon dioxide either chemically or physically. Being in its early development stages, air capture sorbent costs are difficult to estimate. The sorbent is the most significant part of an air capture system and can contribute as much as half of the total weight. If we allocate a fraction of the revenue of CO₂ collection to sorbent cost, then we can estimate the value of a kilogram of sorbent by setting the net present value of the allocated CO₂ revenue minus the sorbent cost to zero. Using this assumption, we developed a model to estimate the maximum allowed budget for an air capture sorbent with known characteristics. For every sorbent with a known capacity (𝐶 [kg CO₂/kg sorbent]), cycle duration (𝑇 [min]) and degradation rate (𝑑𝑟), we can calculate the maximum allowed budget for the sorbent (𝐵 [$/kg sorbent]) in a market with a known price of carbon dioxide (𝑃_CO2 [$/ ton CO₂]) and a given discount rate (𝑟).

To date, the authors have not been able to find a comprehensive cost analysis for any of air capture sorbents. There are lab-scale sorbents with exceptional capacity and kinetic characteristics, but these features do not guarantee an affordable large-scale sorbent and a cost-effective air capture process as a result of that. When an air capture sorbent has a high degradation rate (resulting in a short lifetime), the model shows that the sorbent’s economy cannot be significantly improved even with substantial improvements in capacity and cycle duration.

Although approximate, our model provides a baseline estimation for commercial cost limits of air capture sorbents produced and tested on lab-scales. The analysis points to the importance of the lifetime of the sorbent. Additionally, the model provides a useful insight in comparison between air capture and flue gas scrubbing and even predicts a budget for new post-combustion sorbent, since the analysis readily carries over to other separation problems.