New study elevates concerns about climate impact of natural gas
20 July 2023
A new study published in Environmental Research Letters finds that even small amounts of methane losses (‘leakage’) from natural gas extraction and supply chain can drive up natural gas CO2-equivalent GHG emissions to equal or exceed the effects of coal.
Global gas systems that leak over 4.7% of their methane (when considering a 20-year timeframe) or 7.6% (when considering a 100 year timeframe) are on par with life-cycle coal emissions from methane-leaking coal mines, according to the study. The study assumed the global warming potential (GWP) of methane relative to CO2 to be 82.5 and 30 over a 20/100 year timeframe, respectively.
The study also considered the climate effect of SO2 emissions from coal combustion. SO2 has a negative radiative forcing (i.e., a climate cooling effect) on its own (GWP20 = -156 and GWP100 = -40) and even more negative GWP values when interactions between sulfate aerosol and clouds are included (GWP20 = -367 and GWP100 = -94).
The SO2 co-emitted with CO2 alters the emissions parity between gas and coal. Assuming 1.5% sulfur coal that is scrubbed at a 90% efficiency (with no coal mine methane), a gas system leakage rate as low as 0.2% is on par with coal when considering climate effects over a 20 year timeframe, the study found.
Recent aerial measurement surveys of US oil and gas production basins find wide-ranging natural gas leakage rates 0.65% to 66.2%, with similar leakage rates detected worldwide. According to recent literature data analyzed in the study, several aerial surveys of US oil and gas systems show methane leakage rates between approximately 1% and 10%, with one survey in offshore Gulf of Mexico showing methane leakage rates of 23.8% - 66.2%.
Numerous scenarios run in the study indicate that even at relatively low methane leakage rates, the benefits of natural gas do not outweigh coal. Several natural gas production systems evaluated by aerial surveys demonstrate gas leakage rates that can far surpass the GHG emission intensity of coal.
Source: Evaluating net life-cycle greenhouse gas emissions...