Studies find shale-gas wells leak less methane than expected, but wells aren't the whole story

A study by the University of Texas "found that leaks from shale-gas fracking appear to be quite low — which implies that swapping out coal for shale gas is indeed beneficial from a climate perspective," as long as gas producers are careful, Brad Plumer writes for The Washington Post. "As natural gas gets extracted from the ground and processed and transported, some of it can leak out into the atmosphere as methane. And methane is a powerful greenhouse gas in its own right, trapping more than 20 times as much heat as carbon-dioxide over a 100-year period,"  (World Resources Institute graphic)

"On the one hand, burning natural gas for electricity emits just half the carbon dioxide that you get from burning coal. But if the methane 'leakage rate' from all that natural-gas infrastructure gets above 3.2 percent, one recent study found, then natural gas starts to lose its climate advantage," Plumer writes. The Environmental Protection Agency estimated the leakage rate at around 1.5 percent in 2013, but other studies have estimated the rates to be higher. (EPA graph of greenhouse gas emissions in the U.S.)

But now, a peer-reviewed study by the University of Texas, which took direct measurements of 489 shale-gas wells recently drilled in the U.S., found that "the methane leakage rates from these wells were fairly low — lower, in fact, than the EPA's estimates," Plumer writes. "The EPA had estimated that about 1.2 million tons of methane were probably seeping out of these wells. But the researchers found that only around 957,000 tons of methane were coming out." While that seems like good news for natural gas, the study only looked at natural gas production, which accounts for about half the methane leaks from natural gas in 2011. The study was financed by the Environmental Defense Fund and nine oil and gas firms. (EPA chart: Sources of greenhouse gas emissions in U.S.)

"There's also a lot of methane that seeps out when that natural gas gets processed and moved across the country in pipelines. That's why the Environmental Defense Fund is financing 16 different studies to get a complete look at America's natural-gas infrastructure. Natural gas is still a fossil fuel in its own right. It may lead to fewer global-warming emissions than coal, but it still produces emissions." (Read more)