Study: Minority of facilities produce most natural gas methane emissions


Leaky equipment at a small number of natural gas compressors, processors and pipeline facilities account for a big chunk of the methane escaping into the air, according to the latest reports from a national collaboration between energy companies and the Environmental Defense Fund. Two peer-reviewed studies published Tuesday in Environmental Science & Technology involved researchers from Carnegie Mellon and Colorado State universities taking field measurements at a combined 176 facilities in 13 states. They come as regulators look to crack down on emissions of the greenhouse gas and as companies tout an industry-wide reduction over the past three years. The study of gathering and processing facilities found 30 percent of them contributed to 80 percent of emissions, mostly caused by engine combustion or venting from liquid storage tanks. Of 45 compressor stations studied, two were identified as “super-emitters.” The studies did not identify individual sites. “At many, it was clear there was a broken valve or something malfunctioning,” said Allen Robinson, an author of both studies and head of the mechanical engineering department at Carnegie Mellon. “Under normal operation, they would probably not be super-emitters.” In some cases, employees of the facilities fixed those issues on the spot when researchers found them, one study stated. Methane is non-toxic and in no cases did the researchers find explosive levels of leaks, Robinson said. The pattern of isolated problems causing the most emissions “indicates a need to focus methane management measures on sites and equipment with the highest emissions profile,” said Don Santa, CEO of the Interstate Natural Gas Association of America. The Washington-based trade group last summer began developing industry guidelines to further cut leaks. Finding a subset of facilities or wells accounting for a large amount of leaks is consistent with other studies, said David Allen, a chemical engineering professor at the University of Texas at Austin who was not involved in this research. As the Obama administration considers plans to further reduce methane emissions from the growing oil and gas sector, the studies add to an effort by their environmental sponsor and companies to measure how great a problem it is and where it's coming from. The first of 16 studies planned by the collaborative, which was released in 2013, found lower amounts of methane leaking from wells than once predicted. Environmental Protection Agency estimates based on its inventory show emissions from hydraulic fracturing dropped 73 percent since 2011, and by 11 percent across industry activities, while production grew. “This new research, based on actual data, reflects the clear fact that methane emissions tied to shale development continue to drop significantly as advanced technologies are continuously and increasingly utilized across our operations aimed at protecting and enhancing our environment, especially air quality,” said Dave Spigelmyer, president of the North Fayette-based Marcellus Shale Coalition. The studies look at a part of the industry that is not well understood and highlight a need for tighter regulations, said Mark Brownstein, associate vice president for climate and energy at the Environmental Defense Fund. In 2013, the group said research was needed on emissions from facilities such as those in the latest studies before a better picture of the problem would emerge. “The only way that the public is going to have certainty that this part of the industry is taking the necessary steps to maintain and operate their equipment is through regulatory standards,” he said. Industry sponsors include Dominion, Columbia Pipeline Group and Williams, which are all building large pipelines to move natural gas from the Marcellus to new markets. Robinson noted the studies show gaps in reporting to the EPA's greenhouse gas inventory, as some facilities emitting gas into the air are not required to report figures to the government. The inventory relies on some outdated estimates for equipment, he said. “That's important, as people use that data to say emissions are going down or if using this for policy decisions,” he said. Researchers plan to use the data to create models that will better estimate total emissions and predict future levels. Robinson is involved in synthesizing findings from different studies coming out of the effort. “My hope is that in the next six months, some results of the synthesis will come out,” he said.



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