In 2019, coal power accounted for 65% of China’s electricity and coal accounted for 71% of its 10.2 GTpa CO2 emissions. To meet its pledge of peak carbon by 2030 and carbon neutrality by 2060, China plans to shift away from coal. Fuel switching to natural gas for electrical generation is an interim solution that is in the portfolio of measures for meeting these goals. However, because of variability in emissions from coal and natural gas supply chains, the potential for benefiting from fuel switching also varies. Here, we use a high-resolution basin-to-power plant analysis for estimating methane and CO2 emissions in natural gas and coal supply chains. We illustrate how the variations in supply chains at the level of the sourcing of natural gas and coal from individual production regions can lead to differences in the effectiveness of fuel switching in reducing greenhouse gas emissions. The analyses are applied to four switching scenarios from domestic coal to imported natural gas at representative power plants in China. Life cycle emission factors for the natural gas supply chains evaluated in this study range from 650 to 1000 kg carbon dioxide/MWh of electricity generated and from 2.3 to 13 kg methane/MWh, depending on the allocation choice, power generation technology, and production region. For the coal supply chain, emissions range from 850 to 1100 kg carbon dioxide/MWh and from 0.4 to 4.0 kg methane/MWh, depending on the power generation technology and production region. We show that for these scenarios, in the short term fuel switching can increase radiative forcing by a factor of 3 or decrease it by 70%, depending on the supply chains, generation technology, and, in the case of natural gas, co-product allocation choices in the supply chain. We also quantify consumptive losses of natural gas over long supply chains and show that fuel switching results in differences in radiative forcing that evolve over time due to the influence of methane emissions.

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To achieve reductions in global warming, technology switching, such as converting to renewables or to lower carbon emitting fuels, must overcome the impact of infrastructure construction emissions. Current approaches for assessing construction emission impacts distribute emissions over the life of the infrastructure for the new technology or calculate a greenhouse gas payback time using a single global warming potential (e.g., GWP 20 or GWP 100 ) for greenhouse gases other than carbon dioxide. More realistic approaches account for the temporal evolution of the radiative forcing of short-lived climate forcing species, such as methane, and the timing of the construction emissions. These more realistic approaches lead to longer breakeven times than current approaches. For a case study of switching from coal-fired electricity generation to liquefied natural gas-fired electricity generation in China, an approach accounting for the timing of construction emissions and the temporal evolution of radiative forcing leads to payback times that are 4 times longer than estimated using current practices. The differences in the payback times will depend on factors that include the composition and duration of the construction emissions, but this case study demonstrates that the temporal features of construction emissions should be addressed in assessing the short-term climate benefits of technology switching.

Switching from coal to imported, low-emission liquefied natural gas (LNG) has the potential to be an effective interim measure for meeting short-term climate goals by reducing greenhouse gas (GHG) emissions from electricity generation. To make this switch on a large scale, the LNG supply chain will require significant new infrastructure. Radiative forcing from construction emissions will cause climate disbenefits until the time at which operational emission reductions due to switching fuels compensate for the construction emissions (the breakeven time). This work presents emission estimates for constructing LNG supply chains, including liquefaction facilities, transport ships, regasification facilities, pipelines, and power plants. Supply chain-and location-specific estimates of breakeven times for specific realistic fuel switching scenarios are estimated, taking the timing of construction emissions and the temporal variation of the GHG potency of methane relative to carbon dioxide into account. Breakeven times can range from 1 to 20 years or more, depending on a variety of factors, but particularly natural gas sourcing and land use changes associated with pipeline construction. Supply chains and infrastructure construction emissions both play a role in determining the short-term favorability of fuel switching.