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Post-Combustion Capture or Direct Air Capture in Decarbonizing US Natural Gas Power?

revised on 24.01.2020, 22:14 and posted on 27.01.2020, 07:36 by Habib Azarabadi, Klaus S. Lackner

This analysis investigates the cost of carbon capture from the US natural gas-fired electricity generating fleet comparing two technologies: Post-Combustion Capture and Direct Air Capture (DAC). Many Natural Gas Combined Cycle (NGCC) units are suitable for post-combustion capture. We estimated the cost of post-combustion retrofits and investigated the most important unit characteristics contributing to this cost. Units larger than 350 MW, younger than 15 years, more efficient than 42% and with a utilization (capacity factor) higher than 0.5 are economically retrofittable. Counterintuitively, DAC (which is usually not considered for point-source capture) may be cheaper in addressing emissions from non-retrofittable NGCCs. DAC can also address the residual emissions from retrofitted plants. Moreover, economic challenges of post-combustion capture for small natural gas-fired units with low utilization, such as gas turbines, make DAC look favorable for these units. Considering the cost of post-combustion capture for the entire natural gas-related emissions after incorporating the impact of learning-by-doing for both carbon capture technologies, DAC is the cheaper capture solution for at least 1/3 of all emissions.


This project was supported by Shell’s New Energy Research and Technology (NERT) Program for this work. We would like to acknowledge the invaluable input of NERT’s Dense Energy Carriers team (DEC) during the course of this work.


Email Address of Submitting Author


Arizona State University


United States

ORCID For Submitting Author


Declaration of Conflict of Interest

One of the authors declares his interest as a technical advisor in a startup company that licensed specific technology for direct air capture from Arizona State University.