Method for Estimating Global Methane Emissions from Oil and Natural Gas Production
Ariana Tribby is a fourth-year graduate student in Prof. Wennberg's laboratory at Caltech, where she has been tracking and modeling methane emissions. Methane is a greenhouse gas with a relatively short lifetime and a global warming potential that is significantly higher than that of carbon dioxide. Methane originates from both natural (i.e., biogenic) and man-made (i.e., anthropogenic) sources and activities. The levels of atmospheric methane have been increasing dramatically over the past decades and now stand at approximately 3 times the preindustrial levels. "Mitigation of methane emissions," says Ariana, "poses an attractive avenue by which we can reduce global warming." In her work, Ariana is focusing on anthropogenic methane emissions, specifically the ones produced from the oil and gas sectors ofthe economy. In the U. S., the fossil fuels industry is one of the large contributors to anthropogenic methane emissions.
To separate the man-made methane emissions from the natural ones, anthropogenic methane is better tracked using chemical tracers that do not have biogenic origins and are only emitted as the result of various human activities. For example, in hydraulic fracking, a widely used industrial process to produce natural gas, non-biogenic hydrocarbons, such as ethane and propane, are extracted together with methane, and can then be used as chemical tracers to model methane emissions. Several studies attempted to use the ratio of methane to ethane to model emissions. However, the economics of ethane utilization makes such analysis difficult andprone to error. Given the challenge, Ariana is using an additional chemical tracer - propane, in her work. With RSI support, Ariana is now combining analysis of various in situmeasurements, global simulations (e.g., Harvard's GEOS-Chem), and economic trends to produce models that will provide a more accurate estimate of methane emissions due to losses that occur during the production of natural gas and oil. Doing this exciting and complex research has been a rewarding part of Ariana's graduate experience at Caltech, but it also helped her develop a keen sense on purpose and the ability to see how her research work can have direct and beneficial outcomes:
"The research I've been doing with diagnosing methane emissions has escalated my concern of our current greenhouse gas emission trajectory, and I want to continue to be a part of critical studies that can help us reduce global warming."
Ariana is a native of California, "born and raised in Blythe - a rural town in the middle of the desert." Her interest in Earth Sciences was first piqued when she was an undergraduate at Pomona College, where as an intern in NASA's Airborne Science Research Program, she had an opportunity to make real-time measurements of air pollution flying over Los Angeles and the San Joaquin Valley. Ariana says that "besides feeling ill on the airplane, that was very turbulent from taking measurements at low altitudes, I had a lot of fun, and I thought, I should continue studying Earth Science and Atmospheric Chemistry." Although Ariana no longer needs to get on a plane to collect data, in her work she continues to employ results from global aircraft campaigns, such as High-performance Instrumented Airborne Platform for Environmental Research (HIAPER) Pole-to-Pole Observations program, known as HIPPO, and NASA's Atmospheric Tomography Mission (ATom).
In the next two years, Ariana will start planning on wrapping up her graduate work. When asked about her plans after completing her doctorate thesis, she says:
"My dream right now is to be involved in bridging the gap between scientists and policy makers, to facilitate their communication, and to figure out ways we can work together in bringing down man-made emissions of greenhouse gases."
Ariana's work is part of the 2020 RSI research grant titled "Constraining Oil and Natural Gas Methane Emissions using Ethane and Propane" and supports research efforts in the RSI Climate Science Initiative. To learn more about greenhouse emissions, please visit Prof. Wennberg's laboratory webpage and read recent publications on tracking methane within Californian South Coast Basin:
Wunch, Debra, Toon, Geoffrey C., et al. Quantifying the loss of processed natural gas within California's South Coast Air Basin using long-term measurements of ethane and methane. Atmos. Chem. Phys., 16, 14091–14105
Wennberg, P., Mui, Wilton, et al. On the Sources of Methane to the Los Angeles Atmosphere. Environ. Sci. Tech-nol. 2012, 46, 17, 9282–9289