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Direct and indirect measurements and modeling of methane emissions in Indianapolis, IN



Kuldeep R. Prasad


Abstract Based on recent EPA Greenhouse Gas Inventories, releases of methane (CH4) from the natural gas supply chain in the United States account for approximately 23% of the total US CH4 emissions. However, there continue to be questions regarding the accuracy of current CH4 emission inventories for emissions from natural gas production, transmission, distribution, and usage. In this paper, we describe results from bottom-up direct measurements of methane emissions from selected sources in the large isolated city of Indianapolis, IN. The bottom-up results are based on direct component sampling at metering and regulating stations, surface enclosure measurements of surveyed pipeline leaks, and tracer/modeling methods for other urban sources. These bottom-up measurements are used to inform the compilation of a methane emission inventory for the city equal to 28 Gg/yr with an upper bound estimate of 50 Gg/yr. We also describe top-down emission estimates for the whole city based on an aircraft mass balance method (68 Gg/yr with a lower bound estimate of 34 Gg/yr) and inverse modeling of tower observations of ambient methane levels (58 ±33 Gg/yr) which clearly show good agreement between these independent methods. The aircraft results further show that a large landfill accounts for approximately 33% of the top-down whole city estimate. With the landfill and other biogenic methane emissions omitted, the top-down estimate is 6.8 times the corresponding non-biogenic bottom-up
Elementa: Science of the Anthropocene


Greenhouse Gas Emissions


Prasad, K. (2014), Direct and indirect measurements and modeling of methane emissions in Indianapolis, IN, Elementa: Science of the Anthropocene, [online], (Accessed May 25, 2024)


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Created October 13, 2014, Updated June 11, 2020