TitleMethane still belches from USA's old oil and gas wells
BodyTwo studies out this week focus on unintentional emissions of methane — a potent greenhouse gas — into the air. One study found that millions of abandoned oil and gas wells across the USA could release a significant quantity of methane into the atmosphere but are not included in total emission counts. A second study found that only a few active natural gas wells produce the majority of known methane emissions. Methane is a greenhouse gas 30 times more potent than carbon dioxide at trapping atmospheric heat and thus is a prime contributor to global warming. Methane accounts for nearly 9% of all greenhouse gases emitted as a result of human activity in the USA. The Environmental Protection Agency said the oil and gas industry is the largest source of methane in the atmosphere in the USA, followed by livestock emissions and landfills. The first study, published Monday, appeared in the Proceedings of the National Academy of Sciences. The second study, published Tuesday in the Environmental Science & Technology journal, was supported by several natural gas companies and the Environmental Defense Fund. In the first study, Mary Kang and colleagues from the Woodrow Wilson School of Public and International Affairs and Princeton University measured methane from and near 19 abandoned oil and gas wells in Pennsylvania. The authors found that all of the wells emitted some level of methane. Three wells were "high emitters," releasing the gas at a rate much higher than the others. "These measurements show that methane emissions from abandoned oil and gas wells can be significant," Kang and her co-authors wrote in the first study ever to measure methane from old wells. Kang said wells are pathways for gases and other fluids that would otherwise remain trapped deep underground to migrate upward. The authors estimate that abandoned wells in Pennsylvania could account for 4%-7% of all human-sourced methane emissions in the state. The researchers say the wells in Pennsylvania could be representative of all the wells across the country. "There is no regulatory requirement to monitor or account for methane emissions from abandoned wells in the United States," Kang wrote. In the second study, researchers from the University of Texas found that leaks at a small group of wells — about 20% — cause most of the known methane emissions. The wells extract natural gas through hydraulic fracturing, known as fracking. "To put this in perspective, over the past several decades, 10% of the cars on the road have been responsible for the majority of automotive exhaust pollution," said David Allen, a chemical engineering professor at the University of Texas and the study's lead author. The release of methane from the wells was highest along the Gulf Coast, the study found, but lowest in the Rockies. Overall, methane pollution in the USA has declined 11% since 1990, even as the federal government has pushed for a greater reliance on natural gas. Unlike carbon dioxide, which accumulates and lingers in the atmosphere for hundreds of years, methane tends to degrade in a decade or so, according to David Archer, a climate scientist at the University of Chicago.
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