A disturbing new study from researchers at Cornell University and the Environment Defense Fund has independently measured methane emissions from a number of ammonia fertilizer plants. The startling results suggest methane emissions are 100 times higher than industry estimates, and three times higher than the Environmental Protection Agency's estimate for all industry methane emissions in the United States.

Although the volume of methane emitted into the atmosphere by humans is much less than the amount of carbon dioxide released, it is a significantly more potent greenhouse gas – it is 84 times more potent than carbon dioxide and some suggest around 25 percent of manmade global warming is caused by methane emissions.

This new study set out to add some much needed objective measurements to an understudied sector of methane emissions: industrial users of natural gas. The majority of prior research has examined methane emissions at earlier points in the natural gas supply chain, including measurements at points of production and distribution. Methane emissions have also begun to be effectively tracked in residential and commercial areas.

To explore methane emissions from industrial users of natural gas the researchers used new methane-sensing equipment recently installed into some Google Street View cars. Fertilizer factories were identified as targets as they are a major user of natural gas, and six representative factories were selected, out of around two dozen in the United States. The sensor vehicles traveled on public roads near the factories to quantify downwind methane emissions escaping due to leaks, incomplete combustion, or inefficient chemical reactions during fertilizer production.

The results were incredible, with an average of 0.34 percent of all natural gas used in the factories found escaping into the atmosphere. The study then scaled this number up to all fertilizer manufacturing in the United States, calculating annual methane emissions to be 28 gigagrams. The industry reportedly only estimates its methane emissions to be 0.2 gigagrams per year. The EPA currently claims all industrial processes and product use in the United States produce a total of 8 gigagrams of methane emissions.

"We took one small industry that most people have never heard of and found that its methane emissions were three times higher than the EPA assumed was emitted by all industrial production in the United States," says John Albertson, co-author on the study. "It shows us that there's a huge gap between a priori estimates and real-world measurements."

This is not the first time in the last few years scientists have pinpointed errors in measuring real-world methane emissions. From underestimating methane emissions in the Arctic and discovering water reservoirs are releasing 25 percent more methane than predicted, to finding cattle emit 11 percent more methane than previously estimated, the bulk of these studies are revealing the scale of methane emissions is larger than anyone expected.

John Albertson suggests the recent growth in natural gas as a perceived environmentally-friendly alternative to more traditional "dirty fossil fuels" has made the tracking of methane emissions something of urgent importance.

"…natural gas is largely methane, which molecule-per-molecule has a stronger global warming potential than carbon dioxide," says Albertson. "The presence of substantial emissions or leaks anywhere along the supply chain could make natural gas a more significant contributor to climate change than previously thought."

The research was published in the journal Elementa.