A study released earlier this week in the peer-reviewed Proceedings of the National Academy of Sciences that reported government calculations on U.S. methane emissions could be grossly underestimated is drawing a bevy of media attention and creating groundswells of both support and criticism.
The study, conducted by researchers at the Carnegie Institution for Science and others at Harvard University, used modeling tools to trace variations in atmospheric methane measurements. Based on that analysis, the study found that human activity created methane emissions that were about 1.5 times greater than the government -- in particular the U.S. Environmental Protection Agency (EPA) -- had estimated.
Furthermore, the study suggests that U.S. onshore oil and gas drilling "could account for 50%" of the measured emissions in the South Central part of the country, where researchers found "large discrepancies" with government estimates. Methane emissions in the region were found to be 2.7 times greater than those reported in most methane inventories, according to the study.
Thus far, the study has gone a long way in stirring up the ongoing debate about horizontal hydraulic fracturing (fracking) and its role in greenhouse gas (GHG) emissions.
Earlier this year, the EPA revised its own estimates and said emissions produced by the oil and gas industry had declined significantly as a result of tighter pollution controls.
The study also comes just days after Colorado proposed a set of rules, crafted in conjunction with some of the state’s leading exploration and production companies, that would help reduce methane emissions during production and transport by requiring operators to perform frequent leak checks with up-to-date technologies (see Daily GPI, Nov. 18).
It's widely held that when methane is combusted it has an environmental benefit that other fossil fuels do not, but when it's released during production, methane is a leading GHG source, behind carbon dioxide. It remains a concern for environmentalists.
The study took atmospheric methane observations from across North America between 2007 and 2008 by analyzing nearly 5,000 air samples researchers collected from communications towers. The study also utilized more than 7,000 samples taken during that time from an aircraft monitoring program.
Emissions from livestock were found to be nearly twice as high as previously estimated, while emissions from oil and gas operations in places such as Oklahoma and Texas were 2.7 times greater than previous estimates.
The Environmental Defense Fund hailed the study and said it aligned with one conducted by the National Oceanic and Atmospheric Administration and the University of Colorado at Boulder in August (see Shale Daily, Aug. 6). That study found significant methane emissions in and around Utah.
Steve Everley, a national spokesman for the industry outreach group Energy In Depth, though, wrote in a blog post that the Carnegie study was conducted at a time before onshore drilling spiked. He added that researchers also could not adequately say what sources were producing the additional methane.
In a statement provided to NGI's Shale Daily, the EPA said it was reviewing the study and encouraged by the fact that there are now more methane emission measurements available.
"EPA is committed to using the best available data for our inventory and continually seeks opportunities to update and improve our estimates," the agency said in the statement. "Research studies like these will add to our knowledge base of [GHG] emissions and will help us refine our estimates."