Study: Natural gas may not be 'bridge fuel' to fight climate change

The U.S. natural gas infrastructure has far more leaks than federal authorities previously reported, according to new findings.

A study released Thursday by Stanford University and Massachusetts Institute of Technology (MIT) revealed that, while natural gas emits less carbon dioxide during combustion than other fossil fuels, the potential for leaks — which emit the more potent greenhouse gas methane — put a damper on its "climate benefits." 

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President Obama, however, credited natural gas as a top factor in bringing the U.S. closer to energy independence during his State of the Union address.

"One of the reasons why is natural gas, if extracted safely, it’s the bridge fuel that can power our economy with less of the carbon pollution that causes climate change," he said in his address.

But the study's team of authors who reviewed more than 200 reports found emissions of methane are significantly higher than official estimates, with leaks from the natural gas system being one significant contributor.

"However, because of the high global warming potential of methane, climate benefits from natural gas use depend on system leakage rates," the study states. "Some recent estimates of leakage have challenged the benefits of switching from coal to natural gas, a large near-term greenhouse gas reduction opportunity."

Right now the Environmental Protection Agency's best estimate is the country's natural gas system leaks about 1.5 percent of gross production — or 28 million tons of methane per year. The new study says there's a gap between that estimate and the actual measurements by roughly 14 trillion grams of methane. 

"This new technology is critical because, if our policy is going to continue to focus on using gas as a “bridge fuel,” we need to double down our efforts to mitigate the leaks," said co-author Francis O'Sullivan of MIT.

While the gas system is leakier than thought, in the long run, electricity generation through the burning of gas opposed to coal makes a greater dent in total greenhouse gas emissions over 100 years, according to the study. 

When it comes to powering trucks and buses with natural gas in place of diesel fuel, however, gas will likely add to effects that compound global warming.

"Fueling trucks and buses with natural gas may help local air quality and reduce oil imports, but it is not likely to reduce greenhouse gas emissions," said lead author of the report Adam Brandt, an assistant professor at Stanford said in a statement. 

"Even running passenger cars on natural gas instead of gasoline is probably on the borderline in terms of climate," Brandt added.

Why the disconnect in calculations from researchers and the EPA? 

The study's authors say the EPA conducts atmospheric tracking of emissions, which misses possible contributing elements. 

For instance, emission rates for wells and processing plants are left to operators on a voluntary basis, meaning leaks might go unrecorded since the EPA is not allowed on site more than half of the time. 

"It's impossible to take direct measurements of emissions from sources without site access," said Garvin Heath, a senior scientist with the National Renewable Energy Laboratory and a co-author of the new analysis. 

Methane emission levels in general, including all factors are about 50 percent higher than what the national accounts report, the report states. 

The EPA also doesn't regulate natural emissions from wetlands and geologic seeps, and puts added weight on human activity.

And the study's authors are concerned because methane is roughly 30 times more potent than carbon dioxide on a 100-year basis, and more so in short term. 

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