Methane Emissions in Large Cities Studied

Methane Emissions in Large Cities Studied


Methane is a potent greenhouse gas and can be released by both human-made and natural sources. Large cities emit significant amounts of methane, but in many cases the exact emission sources are unknown. Major sources of methane emissions in cities can include heating systems, landfills, wastewater, and road transport. Precisely mapping and quantifying these sources for a specific city can help with reducing methane emissions.

Sara M. Defratyka, Université Paris Saclay, Gif-sur-Yvette, France, and colleagues have conducted mobile measurements of methane and its sources throughout Paris. The researchers conducted street-level surveys over 17 days throughout Paris from September 2018 to March 2019. The team used car-mounted instruments based on cavity ring-down spectroscopy (CRDS), with air inlets situated on the roof of the car, and portable instruments for walking measurements to detect methane and its probable sources based on the isotopic composition of methane. The team covered 30 % of the entire Paris road network.

A total of 90 potential methane leaks were detected in Paris. 63 % of those leaks came from natural gas distribution networks, 33 % from sewage networks, and 4 % from heating furnaces of buildings. Based on their findings, the researchers estimate that the total methane emission rate of Paris is at least 190 t per year. The actual number is likely higher because the method does not report mobile methane sources from road transport, such as buses that use natural gas or biogas as fuel. The team’s findings suggest that the natural gas distribution network, the sewage system, and furnaces could be promising targets for methane reduction efforts.



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