Methane Leaking From Natural Gas Operations Underestimated
Environment: New estimates of leaked methane point to reduced climate change benefits of natural gas over coal
By Jeff Johnson
GATHERING LOSSES
Natural gas gathering operations leak enough methane to power 3.2 million households.
Credit: Environ. Sci. Technol.
A new study finds methane is leaking at surprisingly high rates from a mostly unaccounted for part of natural gas operations—facilities that collect, compress, and process natural gas for pipeline distribution after drilling and hydraulic fracturing (Environ. Sci. Technol. 2015, DOI: 10.1021/acs.est.5b02275).
The study found that gathering and processing had methane losses twice that of earlier estimates by the Environmental Protection Agency. “This was the first-ever national study on methane emissions from natural gas gathering facilities,” notes Anthony J. Marchese, a Colorado State University mechanical engineering professor, who led the new study.
FIELD COLLECTIONS
Researchers used ambient measurements of methane and tracer gases to derive methane loss from natural gas gathering and processing operations.
Credit: Colorado State University
U.S. natural gas production has shot up by more than 26% over the past 10 years, largely owing to new hydraulic fracturing and horizontal drilling technologies. Natural gas burns cleaner and emits about half the carbon dioxide of coal when used to generate electricity. But methane, the primary component in natural gas, is a potent greenhouse gas when leaked to the atmosphere. The climate change impact of methane is 80 times that of CO2 over the first 20 years after leakage and 20 times as potent over a 100-year span. Methane leakage from oil and gas operations is responsible for nearly one-third of all U.S. methane emissions, and EPA estimates that if methane leakage exceeds about 3% of production, the natural gas climate benefit over coal is lost.
Currently, EPA assumes about 1.3% of all methane generated through oil and gas production is lost to the environment and has estimated that about 20% of that comes from gathering and processing operations. “There is not a high level of confidence in EPA’s number,” Marchese says. “The data are old and mostly estimates, coupled with a handful of recent measurements and industry-supplied data.”
In the new work, Marchese and his team sampled ambient methane concentrations at 114 gathering facilities and 16 processing plants in 13 states. The team measured methane and tracer gases near the facilities to determine methane emissions from a given site and used computer methods to extrapolate their measurements to the national scale.
Marchese’s team found methane loss to be nearly twice EPA’s estimate for this sector. The new figures would raise the total methane loss to more than 1.5% of production, Marchese says.
Although the percentage seems small, the amount of gas lost from gathering facilities is valued at $390 million a year, Marchese says, and could provide enough gas to fuel 3.2 million households. “It may be a bitter pill for industry to swallow,” he says, but notes that his study was partially funded by gas companies that want to know about leaks.
Marchese’s study is one of 16 funded and organized by a small group of gas producers and the Environmental Defense Fund, an advocacy group, that are trying to lock down methane loss from all aspects of natural gas production—from exploration to burning in natural gas vehicles. The final report will combine all these data and is expected by year’s end. When completed, Marchese says, the new total loss number “may be north of 2%.” How far north that number goes will determine whether methane retains its perceived greenhouse gas advantage over coal.
Katie Brown, a spokeswoman with Energy In Depth, a petroleum-industry-funded research, education, and outreach organization, stresses that even with the new leakage emissions, the total lost to the environment from the oil and gas system production still makes natural gas a cleaner fuel than coal.