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CEIC-05-05

"CO2 capture from ambient air: An example system"

Joshuah K. Stolaroff, Greg V. Lowry & David W. Keith

Abstract:
In order to mitigate climate change, deep reductions in CO2 emissions will be required in the coming decades. Carbon capture and storage will likely play a large role in these reductions. As a compliment to capturing CO2 from point sources, CO2 can be captured from ambient air, offsetting emissions from distributed sources. In this paper, we show that CO2 capture from air is physically and thermodynamically feasible, discuss the various routes available, and explain why NaOH solution is a viable sorbant for largescale capture. An example system using NaOH spray is presented. With experimental data and a variety of numerical techniques, the mass transfer of CO2 to falling drops of NaOH solution is calculated, and an example contacting system developed. The cost and energy requirements of the contacting system are estimated and combined with estimates from industry and other research to estimate the cost of the complete system. We find that the cost of capturing CO2 with the complete system would fall between 240 and 550 $/t-C, and improvements are suggested which could reduce the cost by about 100 $/t-C from the upper bound. Policy implications of this result are discussed.

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