Methane mitigation in cities: how new measurements and partnerships can contribute to emissions reduction strategies

Friday, 19 December 2014
Francesca Mia Hopkins1, Susan E. Bush2, James R Ehleringer3, Chun-Ta Lai4, Joshua P Rambo4, Elizabeth Brooke Wiggins5, Joshua Miu4, Valerie Carranza6 and James Tremper Randerson7, (1)University California Irvine, Irvine, CA, United States, (2)University of Utah, Salt Lake City, UT, United States, (3)Univ Utah, Salt Lake City, UT, United States, (4)San Diego State University, San Diego, CA, United States, (5)University California Irvine, Tifton, GA, United States, (6)Los Angeles Valley College, North Hollywood, CA, United States, (7)University of California Irvine, Irvine, CA, United States
Cities generate a large fraction of anthropogenic methane emissions that are increasing with urbanization and greater reliance on natural gas as fuel. New measurements of methane in cities suggest an as-yet unrealized potential for city-scale methane mitigation. We present high-resolution methane observations from four cities in North America to demonstrate the utility of methane surveys for identifying urban methane sources. We used portable, continuous on-road measurements to determine the spatial distribution of methane in Fairbanks, Los Angeles, Salt Lake City, and San Diego. Across cities, methane tended to be highly concentrated in space, suggesting discrete, point emission sources. Elevated methane levels were found near known emission sources, such as landfills, wastewater treatment facilities, and natural gas-fueled power plants, and revealed the location of fugitive leaks in natural gas infrastructure. The mix of sources and sizes of methane leaks varied among cities, highlighting a need for locally adaptive emissions regulation. Urban methane observations can inform anthropogenic processes in development of methane mitigation strategies. We discuss specific examples of how continuous atmospheric measurements can enhance the design of mitigation strategies in these cities, and potential contributions of these approaches to cross-sectoral efforts to reduce methane emissions at the city level.