Natural gas: Not all that clean (but we can fix it!)

Nature reveals that natural gas is quite a bit more polluting than we thought – with less-than-airtight facilities leaking 60% more methane than estimated, or about $2 billion in lost natural gas:

The analysis, published on 21 June in Science, is one of the most comprehensive looks yet at methane output from US oil and gas production, and reinforces previous studies that suggested emissions outpaced government estimates. That research prompted the US government to develop regulations that would restrict methane emissions from oil and gas production — rules that US President Donald Trump is now attempting to roll back.

The latest study shows that the US oil and gas supply chain emits about 13 million metric tons of methane, the main component of natural gas, every year. That’s much higher than the US Environmental Protection Agency’s (EPA’s) estimate of about 8 million metric tons.

If left unchecked, [says study leader Ramón Alvarez, an atmospheric chemist at the Environmental Defense Fund, a non-profit group in Austin, Texas], methane emissions from the oil and gas industry could erode the potential climate benefits of using natural gas, which releases far less carbon dioxide and other toxic pollutants than coal when it is burned.

Before 2012, published estimates of the US methane leakage rate ranged from 1% to about 8%, Alvarez says, and the lack of consensus pushed scientists to better characterize those rates in subsequent years. Alvarez and his team pooled data from some of these studies — many of which quantified emissions at individual facilities — and validated the measurements using aircraft surveys. The scientists covered regions that accounted for about 30% of US gas production.

They then extrapolated the figures to estimate methane leaks at the national level. The team concluded that methane emissions in 2015 were about 60% greater than estimates from the EPA’s greenhouse gas inventory: a 2.3% leakage rate compared to the 1.4% estimate from the EPA. “Instead of coming from the well to the pipeline, the gas is escaping through vents or other openings in the system, and it adds up to a lot of emissions,” says Alvarez.

“This is important work,” says Shane Murphy, an atmospheric scientist at the University of Wyoming in Laramie. “They took all these isolated measurements and combined them into something that’s more quantitative.”

The findings reduce the uncertainty around the magnitude of US methane emissions, says Daniel Zimmerle, an energy researcher at Colorado State University in Fort Collins. “I think now it’s in the right ballpark,” he says. “But I would be surprised if this would be the final word on the topic.”