East Coast cities emit twice as much methane as EPA estimates: study
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E-mail Xinhua, July 25, 2019
CHICAGO, July 24 (Xinhua) -- Using an instrumented airplane, a team of researchers led by the University of Michigan (UM) has found unexpectedly that emissions over five major cities along the East Coast are twice the Environmental Protection Agency (EPA)'s estimate for methane and almost 10 times the estimate for natural gas.
The airborne measurements covered Washington, D.C., Baltimore, Philadelphia, New York, Providence and Boston during 20 research flights that took place over a month in spring 2018. National Oceanic and Atmospheric Administration (NOAA) Twin Otter aircraft measured levels of methane, carbon dioxide, carbon monoxide and ethane upwind and downwind of urban areas.
"We found that methane emissions in the five largest cities that we sampled are significant-about double what the EPA estimates for the total emissions," said Genevieve Plant, a postdoctoral researcher in the UM Department of Climate and Space Sciences and Engineering and lead author of the study.
The study, posted on UM's website on Tuesday, directly measured downwind plumes of emissions coming from these five cities, which included leaks from pipes and appliances. Researchers analyzed the ratio of ethane to methane to calculate how much methane was due to natural gas leakage.
"There's a real lack of data on urban emissions, including end-use losses," said NOAA scientist Colm Sweeney. "In our study, we found leaks and end-use losses in just five cities were larger than what EPA estimates for leaks in the entire country... The problem is we still do not know exactly where it is coming from. Is it the pipes? Is it the appliances?"
"What we do know is that this provides a huge opportunity for emissions reduction if we can determine the source of these leaks."
Methane is a primary component of natural gas. Atmospheric methane is a powerful greenhouse gas that also contributes to ground-level ozone pollution. Quantifying methane emissions is important for assessing its current and future impact on climate and air quality.
The study has been published in Geophysical Research Letters. Enditem
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