Natural gas is growing as a part of the world's grid mix, because its carbon per kilowatt-hour is much lower. But methane leaks that emit large volumes of climate-change gas into the air may offset that advantage.
Now, a Google Street View car has allowed researchers to pinpoint and quantify the severity of natural-gas leaks in five different cities.
A 2016 leak at one of the country’s largest natural-gas storage facilities drew substantial attention to the detrimental effects of methane leaks on the atmosphere.
While large-scale leaks can be detected and measured, an unknown amount of methane continues to leak from more than 1 million miles of low-pressure pipes that are used to transfer gas from production facilities to homes and businesses.
In cities, these emissions are usually measured "top down" via sensors in airplanes. But that approach isn't granular enough to pinpoint individual leaks in natural-gas pipes, nor to measure how severe those leaks are.
Now a collaborative team, led by scientists at Colorado State University, the Environmental Defense Fund, and Google Earth Outreach, has devised a method for quantifying methane-emission levels and associating them with much more granular locations in a number of metropolitan areas, as described by The Washington Post.
The method was described in a paper published by Environmental Science & Technology.
The scientists slightly modified a 2012 Subaru Impreza hatchback run by Google Earth to gather local mapping data. They routed an intake tube through the front bumper, added a real-time onboard analyzer in the load bay, and installed locating and environmental sensing equipment on the roof.
That let the cars gather and process data on the estimated level of methane emissions in any given area the car passed through—a bottom-up measurement approach that was critical for accurately locating methane leaks.
The results aren't terribly surprising: cities that have accelerated programs to replace aging natural-gas pipelines fared best, including Burlington, Vermont, and Indianapolis, Indiana.
Older cities or locations didn't fare as well: Boston and Staten Island proved to be releasing an estimated 1,300 and 1,000 tons of methane a year respectively. Most of the leaks measured were categorized as low, but they added up.
One of the team's main goals was to generate reliable data that could be used to prioritize pipe-replacement projects, letting cities quickly replace the leakiest and highest-emission sections. Consider it a win-win for the industry and the environment.
Map of methane leaks in Greater Boston area, published in Environmental Science & Technology.
Natural-gas production has risen substantially over the last decade, due to a combination of falling costs, lower carbon emissions per kilowatt-hour generated, and significant new supplies made possible by improvements in fracturing techniques.
At the same time, the scientific community has begun to focus on learning more about its overall risks to, and impacts on, the environment.
Researchers now estimate that methane released at production facilities has been grossly underestimated—and that the greenhouse-gas impact of methane is 84 times higher by weight than that of carbon dioxide.
So while natural gas does have its inherent advantages, the methods in which it is produced and transferred are receiving more scrutiny.
New and better data-collection methods, including the modified Google Street View cars, can provide a much needed objective viewpoint on exactly how dire the problem of leaky infrastructure really is.
— Matthew Pilgrim