Methane emissions data has improved materially in recent years,but the numerous studies have also revealed gaps in understanding and technology,ICF International said in a guide to the literature.
The report, issued April 26, compared and synthesized 75 studieson methane emissions from the gas industry, along with the U.S. EPA's greenhousegas inventory. It concluded that, by and large, emissions from the industry havedeclined since 1990, especially relative to the volume of gas produced.
However, the gas system is much more challenging to evaluatethan, say, a power plant, where the stack is the main emissions source and thereis a relatively accurate understanding of how many are operating, Joel Bluestein,a senior vice president at ICF, said at an April 26 roundtable discussion.
"There's still a lot of uncertainty," he said, underscoringthe importance of continued research into the sources of methane emissions. "Scienceis never done."
The EPA in April released a version of its greenhouse gas inventorywith updated activity and emissions factor data for much of the oil and gas equipment.The agency had been using what most industry participants and observers consideredoutdated information to calculate the amount of methane escaping from the sector,and many of the studies included in the ICF report informed the EPA's .
The new data had mixed implications for the different segments of the industry.The transmission and storage segment and the distribution segment both have apparentlyhad lower emissions than the EPA had been assuming. The production segment, by contrast, has been releasing significantlymore methane than was previously understood,the EPA found.
There is consensus that a significant proportion of the emissionscomes from a small fraction of the equipment, according to the ICF report, whichwas commissioned by the Natural Gas Supply Association, Interstate Natural Gas Associationof America, American Petroleum Institute, American Gas Association and Gas ProcessorsAssociation.
But how to best find and fix these so-called super-emitters isa matter of some debate, industry representatives said. Pam Lacey, the AmericanGas Association's chief regulatory counsel, said that even more detailed data wouldhelp the industry determine where to deploy its resources. She underscored the importanceof private and government research to advance inexpensive, high-accuracy technologiesto monitor gas systems for methane releases and alert operators to leaks.
Kyle Isakower, the American Petroleum Institute's vice presidentof regulatory and economic policy, agreed, noting that operators face limitationswhen it comes to reducing methane emissions in a cost-effective way. "The technologyexists," Isakower said. "It's a relative cost issue."
Lacey added that "there's not that much low-hanging fruitleft" when it comes to tackling oil and gas methane emissions, necessitatinghigher-tech approaches.
The EPA has already begun to step up its regulations on methaneemissions from the oil and gas sector, and Donald Santa, INGAA's president and CEO,expressed concerns about the cost-effectiveness of the proposals.
Federal regulators have proposed unreasonably frequent leak surveysand impractically low thresholds for leaks that must be repaired in short order,he said. Further, some repair work may require evacuating all the gas from a pipeline,conceivably resulting in greater methane emissions than the leak was producing inthe first place, he noted. As a practical matter, setting rigid timelines for leakrepairs could also result in service disruptions during periods of peak gas use,he added.
Santa stressed that he and INGAA's members, pipeline operators,are not opposed to regulating methane output. Rather, their concerns lie in whetherregulations "get the most bang for your buck" by letting companies focuson the most significant methane sources.