Solving the Case of California’s Extra Methane, A new paper details the culprits behind excess emissions of the potent greenhouse gas in the Los Angeles basin

Solving the Case of California’s Extra Methane, A new paper details the culprits behind excess emissions of the potent greenhouse gas in the Los Angeles basin by Stephanie Paige Ogburn and ClimateWire, May 15, 2013, Scientific American
In Southern California, scientists knew the missing methane had to be coming from somewhere. Was it dairies? Landfills? Natural seeps? Oil and gas operations? Emissions of methane from the Los Angeles basin had been estimated in the mid-2000s as part of the state’s landmark cap-and-trade bill, known as A.B. 32, which regulates emissions of the powerful greenhouse gas. But later measurements of the air in the region showed there was a lot more methane being emitted than was accounted for, more than a third as much. Where was this “missing” methane coming from? … Now, Jeff Peischl, an associate scientist at the National Oceanic and Atmospheric Administration’s Cooperative Institute for Research in Environmental Sciences, has solved this puzzle, outlining the sources of the missing methane in a paper published yesterday in the Journal of Geophysical Research.

In his analysis, Peischl found that the methane leak rate from Los Angeles-area oil and gas operations was 17 percent. This is high; leakage rates of “fugitive emissions” from oil and gas drilling operations are currently estimated at 4 percent by U.S. EPA (ClimateWire, April 4). The California Air Resources Board has been working toward pinning down this leakage percentage in its own way, too. Peischl’s paper cites a survey it did of oil and gas producers in which it queried them about the equipment they use. Based on those results, CARB’s revised estimate for fugitive emissions from the Los Angeles basin is 12 percent. While this new figure is not yet incorporated into the state’s greenhouse gas inventory, Peischl was encouraged that his calculated emissions and the board’s were in the same ballpark, even though they used an entirely different methodology.

Paul Wennberg, a scientist at the California Institute of Technology who did two of the previous studies in the region that showed methane emissions were much higher than the earlier inventory, was encouraged by Peischl’s results. He pointed out that if the missing methane was from fossil fuel extraction, this could be a “win-win” situation. Methane, or natural gas, is valuable. Oil and gas producers would certainly benefit from reducing their leakage. “This is an important finding that we need to follow further,” Wennberg wrote in an email. CARB is doing just that. According to Bart Croes, chief of the agency’s research division, Peischl had presented his work to the agency at an earlier date, and it is continuing research in this vein. Peischl’s results were surprising, Croes said, because many people thought dairies and landfills were likely sources for the mystery methane. “There was this suspicion that they could be a major contributor, but they don’t seem to be,” he said. Now that it knows the sources, the board is working to determine where exactly that methane is coming from. Staff members are driving electric vehicles equipped with sensors to measure methane leaks around Southern California and implementing a network of stationary methane monitors. … “Once we understand what the methane emissions are, then we’ll explore, through our research, options to control these emissions or reduce them somehow,” he added. [Emphasis added]

Methane Emissions Higher Than Thought Across Much of U.S. by Science Daily, May 15, 2013.

Mystery solved: “Extra” methane in LA’s air traced to fossil-fuel sources Press Release May 14, 2013. National Oceanic and Atmospheric Administration, United States Department of Commerce. [More at press release below]

Mystery Solved: Previously Unexplained Higher Levels of Greenhouse Gas in L.A. from Fossil-Fuel Sources Press Release by Cooperative Institute for Research in Environmental Sciences, May 14, 2013
The missing link—exactly where the extra methane, a powerful greenhouse gas, is coming from in Los Angeles—has finally been identified, according to a study led by a scientist at NOAA’s Cooperative Institute for Research in Environmental Sciences (CIRES). The research explains why the estimates of methane given off by various sources are 35 percent lower than the levels that have actually been measured in the atmosphere by scientists. “We identified methane sources based on their unique chemical signatures in the atmosphere much like you’d identify a person from their fingerprints,” said lead author Jeff Peischl, a CIRES scientist who works at NOAA’s Earth System Research Laboratory in Boulder, Colo. Using an innovative experimental technique, the scientists were able to find out that methane quantities coming from activities related to fossil fuels contributed to the discrepancy. Leaks from natural gas (methane) delivery systems in the urban area, geologic seeps such as from the La Brea tar pits, and leaks from local oil and gas exploration activities account for the “missing methane sources” in Los Angeles. …  In addition, they were able to identify that 8 percent of the methane emissions in the L.A. basin is due to leaks from the local oil and gas industry, which corresponds to a 17 percent leak rate for the Los Angeles–area oil and gas operations. This leak rate for the operations was similar to the findings of an independent study carried out by CARB. [Emphasis added]

Quantifying sources of methane using light alkanes in the Los Angeles basin, California by J. Peischl, T. B. Ryerson, J. Brioude, K. C. Aikin, A. E. Andrews, E. Atlas, D. Blake, B. C. Daube, J. A. de Gouw, E. Dlugokencky, G. J. Frost, D. R. Gentner, J. B. Gilman, A. H. Goldstein, R. A. Harley, J. S. Holloway, J. Kofler, W. C. Kuster, P. M. Lang, P. C. Novelli, G. W. Santoni, M. Trainer, S. C. Wofsy,and D. D. Parrish. May 14, 2013. Online April 17, 2013. Journal of Geophysical Research: Atmospheres
doi: 10.1002/jgrd.50413

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