Anthropogenic Methane Emissions in California’s San Joaquin Valley: Characterizing Large Point Source Emitters

Monday, 14 December 2015: 17:33
3012 (Moscone West)
Francesca Mia Hopkins1, Riley M Duren1, Charles E Miller1, Andrew D Aubrey2, Matthias Falk3, Lacey Holland4, Simon J Hook5, Glynn C Hulley5, William R Johnson5, Le Kuai6, Toshihiro Kuwayama7, John C Lin4, Andrew K Thorpe8, John R Worden1 and Thomas Lauvaux9, (1)NASA Jet Propulsion Laboratory, Pasadena, CA, United States, (2)Jet Propulsion Laboratory, Pasadena, CA, United States, (3)California Air Resources Board, Research Division, Sacramento, CA, United States, (4)University of Utah, Salt Lake City, UT, United States, (5)NASA Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, United States, (6)University of California Los Angeles, Los Angeles, CA, United States, (7)California Environmental Protection Agency Air Resources Board, Sacramento, CA, United States, (8)JPL/NASA/Caltech, Pasadena, CA, United States, (9)Pennsylvania State University Main Campus, University Park, PA, United States
Methane is an important atmospheric pollutant that contributes to global warming and tropospheric ozone production. Methane mitigation could reduce near term climate change and improve air quality, but is hindered by a lack of knowledge of anthropogenic methane sources. Recent work has shown that methane emissions are not evenly distributed in space, or across emission sources, suggesting that a large fraction of anthropogenic methane comes from a few “super-emitters.” We studied the distribution of super-emitters in California’s southern San Joaquin Valley, where elevated levels of atmospheric CH4 have also been observed from space. Here, we define super-emitters as methane plumes that could be reliably detected (i.e., plume observed more than once in the same location) under varying wind conditions by airborne thermal infrared remote sensing. The detection limit for this technique was determined to be 4.5 kg CH4 h-1 by a controlled release experiment, corresponding to column methane enhancement at the point of emissions greater than 20% above local background levels. We surveyed a major oil production field, and an area with a high concentration of large dairies using a variety of airborne and ground-based measurements. Repeated airborne surveys (n=4) with the Hyperspectral Thermal Emission Spectrometer revealed 28 persistent methane plumes emanating from oil field infrastructure, including tanks, wells, and processing facilities. The likelihood that a given source type was a super-emitter varied from roughly 1/3 for processing facilities to 1/3000 for oil wells. 11 persistent plumes were detected in the dairy area, and all were associated with wet manure management. The majority (11/14) of manure lagoons in the study area were super-emitters. Comparing to a California methane emissions inventory for the surveyed areas, we estimate that super-emitters comprise a minimum of 9% of inventoried dairy emissions, and 13% of inventoried oil emissions in this region.