Climate Benefits of Carbon Capture Implementation Depend on Timing and Methane Emissions Uncertainty

Electricity produced at new natural gas power plants results in lower direct emissions of CO2 than from new coal power plants, but methane emissions from production and delivery of the natural gas offsets some of the climate... [ view full abstract ]

Electricity produced at new natural gas power plants results in lower direct emissions of CO₂ than from new coal power plants, but methane emissions from production and delivery of the natural gas offsets some of the climate benefits. Furthermore, the contribution of methane to the life cycle climate impacts of natural gas relative to coal will change as carbon capture and sequestration (CCS) reduces CO₂ emissions at the power plants.

This work compares the life cycle radiative forcing (RF) and cumulative radiative forcing (CRF) over time from electricity generated at new coal and natural gas power plants. We include a range of capture rates for each plant type and model the effect of delaying CCS deployment by 20 years. Finally, we also examine a wide range of methane leakage rates (1-10%) that either stay constant or decrease over time.

We find that coal CCS rates of 90% are necessary for coal power to result in lower radiative forcing under likely leakage rates. Most scenarios that show a climate benefit from coal power with CCS also require that the natural gas plant does not employ CCS. Lower initial leakage rates (below 3%), reducing the leakage rate over time, or delaying the start of CCS operations at both plants lead to lower forcing from the natural gas plant in most cases. We also find that natural gas plants without CCS are likely to have lower climate impacts than coal plants that capture the minimum amount of emissions to comply with new U.S. EPA rules. These results highlight the importance of early deployment of CCS, and the narrow set of circumstances under which new coal power plants lead to lower radiative forcing than new natural gas power plants.