Methane leaks from ammonia fertilizer plants are 100 times higher than self-reported industry estimates, alone exceeding Environmental Protection Agency (EPA) estimates for total industrial processes every year, according to new research out of Cornell.

The production of fertilizer utilizes natural gas, which in recent years has been touted as a “bridge fuel” towards clean energy due to its potential to have lower greenhouse gas emissions when compared to traditional fossil fuels (ahem, “freedom gas”). But unintentional methane leakage can occur anywhere along the product line, from incomplete chemical reactions and fuel combustion to transportation pipeline leaks, resulting in emissions that may go unaccounted for.

“But natural gas is largely methane, which molecule-per-molecule has a stronger global warming potential than carbon dioxide,” said John Albertson in a statement. “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.”

To reconfigure such miscalculations, researchers outfitted a Google Street View (GSV) car with a methane sensor and assessed a variety of sources over the course of a three-day campaign in June 2015 and 16 days in September 2016. The team drove around on public roads to extraction areas, power plants, and municipal pipelines until their sensors caught a whiff of a downwind methane plume, at which point they would circle the facility several times.

In total, their measurements calculated that 0.34 percent of the gas used in plants analyzed is emitted into the atmosphere. When scaled to industry standards, that number reaches 28 gigagrams, or 100 times higher than the self-reported estimate of 0.2 gigagrams by fertilizer plants annually.

“Even though a small percentage is being leaked, the fact that methane is such a powerful greenhouse gas makes the small leaks very important,” said co-author Joseph Rudek. "In a 20-year timeframe, methane’s global warming potential is 84 times that of carbon dioxide.”

Writing in the journal Elementa, the authors are quick to note a handful of limitations in their work. First of all, it is a relatively small sample size; just six plants were monitored over the course of a short chunk of time, constraining how variable losses might be. Accessibility also played a major role as some facilities were located nearby better maintained public roads. Regardless, the study “fills an important knowledge gap in quantifying 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,” said Albertson. “It shows us that there’s a huge gap between a priori estimates and real-world measurements.”