The latest in a string of studies gauging the volume and impact of methane leaks from shale gas development supports the validity of current estimates by the federal government to direct policy.
The peer review study released Monday afternoon by the Proceedings of the National Academies of Science reports direct measurements of methane emissions at 190 onshore natural gas sites in the United States. The report found:
Total emissions estimated based on measurements in this work (2,300 Gg) are comparable with the most recent EPA national GHG inventory (2,545 Gg) in the 2011 inventory, released in April 2013.
The PNAS study represents a collaboration between the industry, the Environmental Defense Fund, and academic teams from the University of Texas, Arizona State, Temple, Berkley and other institutions. It found that lower-than-expected leaks at specific shale gas well sites were largely offset by greater-than-expected leaks elsewhere in the gas processing and transmission system:
The measurements indicate that well completion emissions are lower than previously estimated; the data also show emissions from pneumatic controllers and equipment leaks are higher than Environmental Protection Agency (EPA) national emission Q:8 projections. Estimates of total emissions are similar to the most recent EPA national inventory of methane emissions from natural gas production.
The report will surely stimulate controversy on the critical issue of whether natural gas is an effective means to transition away from energy sources that exacerbate climate change, and whether the federal government is armed with enough information to oversee the industry. Natural gas burns cleaner than coal, with less carbon and virtually no particulate matter and other toxic pollutants, such as mercury. But methane is a potent greenhouse gas, especially over the short term. (Oil and natural gas production also releases hazardous air pollutants -- HAPs -- and volatile organic compounds -- VOCs -- which are not the focus of the study.)
To help inform policy, scientists are making new efforts to gauge how much unaccounted methane leaks into the air at wells, pipelines and processing stations, and what the impact is. According the PNAS study:
These measurements will help inform policymakers, researchers, and industry, providing information about some of the sources of methane emissions from the production of natural gas, and will better inform and advance national and international scientific and policy discussions with respect to natural gas development and use.
(Questions related to the industry’s impact on air are distinct from policy issues related to water pollution. The natural gas industry is exempt from federal laws that govern chemicals injected into the ground, and how the waste that flows back from wells is handled and disposed of.)
The PNAS study is one of several that have emerged in the last two years in the wake of a paper by Robert Howarth and Anthony Ingraffea that found natural gas is not as clean-burning as advertised. Howarth, a climate scientist at Cornell University, has been involved in the discussion of methane’s impact on air since it became a pressing national issue with the advent of the domestic shale gas boom enabled by horizontal drilling and high volume fracking. Howarth and his Cornell colleague Tony Ingraffea essentially kick-started the debate in 2010 when they published a controversial paper challenging conventional wisdom that natural gas production was less of a warming threat than coal.
The topic was again in the news earlier this year when a study by the National Oceanic and Atmospheric Administration in the Uinta Basin in Utah suggested that benefits of natural gas production were offset by excessive methane leaks in the system. Climate change reporter and author Andrew Revkin offers an excellent history of the discussion – along with comments and reaction from academic stakeholders on both sides of the debate -- in his recent post for New York Times Dot Earth.
Howarth characterized the findings in the PNAS paper as representing a “best case scenario” of methane leakage because the measurements were taken only at places where industry allowed access for researchers. By comparison, the Utah study was derived from observations and measurements collected by equipment on planes that flew over broad areas, rather than relying on access to individual sites granted by industry.
The PNAS paper “is not representative of what industry is actually doing, but what it wants to be,” Howarth said. Still, he added, the study is an important addition to the small but growing body of knowledge on the extent and impact of methane leaks. “It’s a new science, and I’m impressed with what they have been able to do in this short time frame,” he said.
Lawrence Cathles, a colleague of Howarth at Cornell who argues the climate gains from natural gas development outweigh the losses, said it was not feasible that industry could hide or disguise the volume of methane emissions. “Actually, we will know immediately, and in plenty of time to do something about it, if industry is deceiving us,” he said in a statement that can be viewed here. “In order for methane to contribute to greenhouse warming it must increase dramatically in its atmospheric concentration, and this will be easy to notice.
As expected, industry's ties and involvement with the study were immediately challenged by critics upon its release. The Public Accountability Initiative, a watchdog group, issued this statement:
The failure to disclose the significant conflict of interest of one of the authors, Jennifer Miskimins, appears to constitute a violation of PNAS's conflict of interest policy. Miskimins is listed as a professor at Colorado School of Mines in the article, but has been an employee of Barree Consulting, an oil and gas consultancy offering fracking services, since 2012 -- prior to the submission of the study to PNAS.
The disclosure failure may warrant an erratum or possible sanctions on the authors of the study, according to PNAS rules. PNAS's conflict of interest policy is here: http://www.pnas.org/site/authors/coi.xhtmlA day after this assessment, Steve Horn, writing for DeSmog Blog, reported that nine members of the 11-person steering committee overseeing the study have direct ties to industry interests. You can find the list and the rest of Horn's post here.