Flexible operation and fugitive methane emissions limit the potential of power plant carbon capture and storage

To fully decarbonize electricity generation, there is a need to meet electricity demand at times of low solar and wind availability. Natural gas combined cycle (NGCC) generation with carbon capture and storage (CCS) that reduces power plant CO₂ emissions is one technology proposed for this purpose. However, CCS does not capture all power plant CO₂ emissions and does not address methane emissions that occur upstream of NGCC power plants. Furthermore, the cost of CCS is often not evaluated at capacity factors that represent likely use cases of NGCC power plants in low-carbon grids. Therefore, we evaluate the effect of uncaptured fugitive methane emissions on the climate benefits of CCS and the role of NGCC capacity factors on the economics of CCS. Accounting for time- and region-dependent methane leakage, we find that CCS reduces system-level greenhouse gas emissions between 21 % and 88 %, with remaining climate impacts being primarily due to uncaptured methane emissions. At average United States methane leakage rates of 2.95 %, CCS reduces system-level greenhouse gas emissions by 47–71 %. In addition, we estimate that CCS-related capital and operating expenditures only make CCS cost-effective at high capacity factors and in the presence of financial supports such as the California cap-and-trade program and United States 45Q tax credits. These findings highlight significant technical and economic challenges of using NGCC with CCS to achieve full grid decarbonization.