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

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.