The US natural gas system leaks far more methane than had been estimated previously, according to a new report that synthesizes the results of more than 200 different studies across a number of different fields of research.
This work comprises the first thorough comparison of evidence on natural gas system leaks in the US, and shows, unequivocally, that major organizations (such as the EPA) have greatly underestimated total US methane emissions.
Given the great effect that methane has on the climate (30 times more potent than CO2 as a greenhouse gas), the findings are certainly notable — to put it lightly….
“People who go out and actually measure methane pretty consistently find more emissions than we expect,” stated the lead author of the new analysis, Adam Brandt, an assistant professor of energy resources engineering at Stanford University. “Atmospheric tests covering the entire country indicate emissions around 50% more than EPA estimates. And that’s a moderate estimate.”
The press release provides more:
The new analysis, which is authored by researchers from seven universities, several national laboratories and federal government bodies, and other organizations, found these atmospheric studies covering very large areas consistently indicate total US methane emissions of about 25% to 75% higher than the EPA estimate.
Some of the difference is accounted for by the EPA’s focus on emissions caused by human activity. The EPA excludes natural methane sources like geologic seeps and wetlands, which atmospheric samples unavoidably include. The EPA likewise does not include some emissions caused by human activity, such as abandoned oil and gas wells, because the amounts of associated methane are unknown.
However, the analysis also finds that some recent studies showing very high methane emissions in regions with considerable natural gas infrastructure are not representative of the entire gas system.
“If these studies were representative of even 25% of the natural gas industry, then that would account for almost all the excess methane noted in continental-scale studies,” explained researcher Eric Kort, an atmospheric science professor at the University of Michigan. “Observations have shown this to be unlikely.”
Overall, the analysis makes it clear that the natural gas industry would really have to clean itself up a great deal (with regard to leaks) in order to deliver on its promise of being a “greener” alternative to coal and/or oil.
“Reducing easily avoidable methane leaks from the natural gas system is important for domestic energy security,” stated Robert Harriss, a methane researcher at the Environmental Defense Fund and a co-author of the analysis. “As Americans, none of us should be content to stand idly by and let this important resource be wasted through fugitive emissions and unnecessary venting.”
Speaking on the topic of why the gas industry has underestimated the emission rates for its wells and processing plants, researcher Garvin Heath, a senior scientist with the National Renewable Energy Laboratory, stated: “Self-selection bias may be contributing to why inventories suggest emission levels that are systematically lower than what we sense in the atmosphere.”
No surprise there. On that note, the analysis mentions a study where the EPA asked 30 gas companies to cooperate and allow site access to researchers — only six of the 30 companies that were asked ended up allowing the EPA on site.
The new findings were just published in the journal Science.
Image: Natural gas production facility via Shuttersock
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