Researchers from the University of Cincinnati recently studied the sources of methane at three sites across the nation in order to better understand this greenhouse gas, which is much more potent at trapping heat in the atmosphere than is carbon dioxide.
The UC team, led by Amy Townsend-Small, assistant professor of geology, identified sources for methane in Carroll County, Ohio, Denver, Colorado, and Dallas-Fort Worth, Texas, by means of an analysis technique that consists of measuring carbon and hydrogen stable isotopes (isotopic composition). This approach provides a signature indicating whether methane is coming from natural gas extraction (fracking), organic/biologic decay, or the natural digestive processes of cattle.
With isotopic composition analysis, it is possible to tell whether the source is from fracking or from biogenic processes (like bacterial decomposition in landfills or algae-filled water). It is a laborious technique to implement, but its use makes it possible to trace and attribute the source of methane production.
Results from this study, where 23 water wells were sampled and tested three to four times each year and a total of 191 samples examined in the lab, found that methane levels in samples from these water wells came from decay of organic matter (decomposition of plants) biological processes occurring in subsurface coal formations.
In the Denver region, the isotopic composition signatures of the samples collected demonstrated that up to 50% of methane emissions in the region were from agricultural practices (cattle) and/or landfill sources, with the other half (about 50%) coming from fracking for natural gas.
Similar testing in the Barnett Shale region of Dallas/Fort Worth, involving the collection and analysis of 120 samples in 2013, found that 64% of the methane emissions came from fracking while 36% came from landfills and cattle.
sampling methods need to be examined in detail in this study by an independent group.
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