Yangtze Cities Underestimate Methane Emissions from Natural Gas Use

Natural gas has long been touted as a cleaner alternative to coal and oil in China's rapidly expanding cities. However, a recent study suggests that its climate benefits may have been seriously overstated due to significant methane emissions from the supply chain.

Researchers studying the Yangtze River Delta metropolitan cluster found that methane leakage from natural gas consumption is far higher than previously thought. The study, published in Nature Cities, used a decade of atmospheric observations between 2012 and 2021 to reconstruct methane emissions associated with fossil fuel use.

The researchers focused on ethane, a hydrocarbon commonly found alongside methane in natural gas, as a companion tracer for emissions from fossil fuel systems. By examining ethane variability over time and comparing it with atmospheric transport simulations, the scientists were able to separate the signal linked to natural gas consumption from other methane sources.

The study's findings indicate that natural gas leakage rates are significantly higher than the 0.2 percent commonly assumed in China's inventories. The estimated leakage rate of 3.5 percent means that roughly one molecule of natural gas out of every thirty is lost somewhere between the supply system and final use.

The researchers calculated that natural gas consumption in the Yangtze River Delta produced average methane emissions of approximately 0.68 teragrams per year between 2012 and 2021, with an uncertainty range extending from 0.48 to 0.83 teragrams annually. The study highlights the importance of reassessing methane budgets at the sector and regional levels, particularly in rapidly urbanizing areas where gas demand is rising quickly.