This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: Natural gas leaks are a significant source of methane emissions in cities, but it can be hard to pinpoint exactly where and why they happen. And methane, a potent greenhouse gas that is the main chemical component of natural gas, has been historically undercounted or omitted in emissions estimates, according to a team of atmospheric and climate science researchers in the Penn State College of Earth and Mineral Sciences.
To help address this, the team analyzed methane emissions readings from seven measuring towers in and around Baltimore and compared them to aggregated 2022 neighborhood gas usage data provided by a local gas distribution company. They found a daily cycle of methane emissions in urban and suburban neighborhoods, while urban sites also showed a seasonal trend in emissions. To explain this, the researchers found evidence that Baltimore's daily emissions trends could be correlated with consumer use of natural gas, while seasonal leaks could be caused by legacy cast-iron pipes and urban repair schedules.
They published their results in Environmental Science & Technology. "This study shows progress toward a process-based understanding of methane leakage from urban natural gas distribution systems," said Ken Davis, professor of atmospheric and climate science and co-author of the paper. "Our method also provides a conceptual foundation for inferring patterns in local-scale methane emissions in Baltimore, which could be applied to existing atmospheric methane measurements in other cities." When measuring methane emissions using atmospheric observations, emissions are usually estimated for the whole city but not parsed out spatially by neighborhoods, explained corresponding author Helen Kenion, a postdoctoral researcher at the University of Cincinnati who led this study as part of her doctoral dissertation in meteorology and atmospheric science from Penn State, completed in 2025 under Davis.
"By analyzing natural gas usage data in combination with these localized, high-resolution emissions monitoring data, we were able to make some interesting connections and find new clues about where methane emissions come from," Kenion said. Seven measuring stations, which were then overseen by the U.S. Department of Commerce's National Institute of Standards and Technology, took a reading of the amount of methane in the air 328 feet (100 meters) above the ground every two seconds.
Kenion then used a method she developed in 2024 to estimate methane emissions from the neighborhoods surrounding the towers based on the readings. At the two measuring stations where both methane measurements and gas usage data were available, researchers found that daily gas usage rates showed a daily cycle that was very similar to daily methane emissions rates, and that both usage rates and emissions were lowest at night and highest during the day. Since gas lines in cities and neighborhoods are pressurized 24 hours a day, the daily usage and emissions cycle could not be attributed to gas pipeline leaks due to their clear pattern of daily fluctuations, Kenion explained.
"Since these daily fluctuations were not tied to seasonal trends, but rather a daily cycle present in both summer and winter, it's unlikely that postmeter leaks—leaks that occur after the pipeline has offloaded gas into smaller consumer lines and gas usage readings are noted—are entirely due to leaking heat furnaces," Kenion said. "It would have to be leaks originating from something used year-round, like water heaters or kitchen appliances." Discover the latest in science, tech, and space with over 100,000 subscribers who rely on Phys.org for daily insights. d research that matter—daily or weekly. Though the gas companies routinely monitor leaks in the main pipelines, the small lines into homes and buildings and hookups to appliances are not checked frequently and could leak small amounts when appliances are in use.
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