The early years of the shale boom came with a widely held assumption that the vast quantities of natural gas liberated through high-volume hydraulic fracturing, or fracking, would help slow climate change by displacing coal-fired power plants and speeding the transition to a clean-energy future.
But that notion was seriously challenged as scientists began studying the life cycle of natural gas. Although natural-gas power plants emit fewer greenhouse gases than coal plants, the process of extracting, processing and transporting natural gas releases unknown amounts of methane into the air.
Because methane is a powerful greenhouse gas, the shale boom's net impact on climate change remains unclear. That uncertainty has widened the rift between fracking supporters and opponents, and was cited as one of the reasons behind New York's recent fracking ban.
It has also prompted a slew of scientific studies, many of which are scheduled for this year.
"It's pretty impressive how much work is being done here," said Drew Nelson, senior manager, natural gas at the Environmental Defense Fund. His organization, which supports fracking with stronger methane and other regulations, launched a series of 16 methane studies in 2012 in partnership with universities and industry. Six have already been published, and the remaining 10 could be released in peer-reviewed journals later this year.
"We by no means think we have a monopoly on doing oil-and-gas methane science," he said. The scope of studies being conducted around the country, and the caliber of the scientists involved "shows the importance of this issue," he added.
James Crawford, a research scientist at NASA's Langley Research Center, said scientists generally agree the natural gas boom could accelerate the transition to renewable fuels if the nation's average leak rates are kept to less than a few percent. But it's hard to find an average rate—the percentage of methane lost through leaks and other unintended releases—for the entire industry when emissions at each site vary based on factors like operator practices and state regulations, he said.
For example, a 2013 study in Utah's Uintah Basin found methane leak rates of up to 12 percent, while studies in other states have found much lower numbers down to 1 percent or less.
In an email, Nelson said the debate over methane shouldn't be about identifying a specific break-even point for methane leaks that would give natural gas the same net climate impact as other fossil fuels. "We know methane leakage is a big problem," and there are "lots of good, cheap, fast ways to reduce these leaks...the focus should be on fixing it," he wrote.
The U.S. Environmental Protection Agency is expected to propose regulations on methane emissions from industrial sources later this year. Other federal agencies including NASA and NOAA (the National Oceanic and Atmospheric Administration) have partnered with universities to track methane emissions from shale basins.
Here's a preview of some of the studies currently under way:
1. FRAPPÉ, short for Front Range Air Pollution and Photochemistry Éxperiment, is a collaborative effort among many research groups, including the National Center for Atmospheric Research, NASA, Colorado state regulators and various universities. The scientists, including NASA's Crawford, conducted aerial surveys over the Colorado Front Range last summer. Their plane-mounted instruments tracked emissions of methane and other gases from the region.
Crawford said their study was focused on overall air quality, but the data will show individual contributions from industries such as agriculture and oil-and-gas fields. For example, methane emissions from cattle feedlots are accompanied by emissions of ammonia, while oil-and-gas wells release methane along with heavier gases, including propane and ethane. Scientists can use these distinguishing characteristics to figure out what percentage of the methane comes from the energy industry.
The researchers are now analyzing the data and preparing the results for publication.
2. SONGNEX, or Shale Oil and Gas Nexus, is led by NOAA and involves many of the same research institutions from the FRAPPÉ project.
NOAA research scientist Thomas Ryerson said SONGNEX will provide follow-up data to FRAPPÉ by conducting aerial surveys over the Denver-Julesberg basin this spring. They also plan to take measurements in other basins including North Dakota's Bakken Shale, the Haynesville in Texas and the Marcellus Shale in Pennsylvania.
Ryerson hopes SONGNEX will shed light on the impacts of methane regulations. Colorado issued the nation's first state-based rules last year to reduce methane emissions from oil-and-gas fields. SONGNEX could show whether Colorado's regulations have simply kept pace with growing energy production, or if they're having a net impact on reducing methane, Ryerson said.
3. Environmental Defense Fund studies: Nelson, the EDF scientist, said six EDF methane studies have been submitted to scientific journals and could be released later this year after peer-review. The studies involve tracking methane from Boston's natural gas distribution pipelines; a transmission and storage study to trace how methane is lost as it's moved from place to place; and a coordinated campaign in the Barnett Shale where scientists used a variety of airplane and ground-based measurements to estimate local methane leaks.