Fertilizer is bad, apparently. Photo : Getty

People tend to equate methane with cow farts (though their burps are worse), but we may be pointing our fingers in all the wrong places, according to a new study. The production of ammonia for fertilizer may result in up to 100 times more emissions than has been previously estimated for this sector . And that alone is more than what the Environmental Protection Agency estimates all industries emit across the U.S.


The stu dy, published May 28 in the journal Elementa, zooms into the ammonia fertilizer industry because it relies heavily on natural gas to run its production plants. Ammonia is a compound made of nitrogen, which is used across the agriculture sector to fuel the growth of crops. While the ammonia fertilizer industry’s emissions of carbon dioxide are better understood, emissions of methane—which has 25 times the global warming potential of carbon dioxide over a century—were a huge question mark. Until now.

The team of authors from Cornell University and the Environmental Defense Fund had two sampling adventures in June 2015 and September 2016 that took them to six ammonia fertilizer plants in the Midwest, including Oklahoma, Kansas, and Iowa. They used their findings to estimate industry-wide emissions throughout the U.S. The team found that the fertilizer industry results in 29 gigagrams of methane emissions a year. The EPA, however, reports this industry emitted only 0.2 gigagrams of methane a year between 2015 and 2016. As for all industries (like waste, chemical, and metals production ), the EPA estimates 8 gigagrams, which is still much smaller than this single industry’s.


A worst case scenario—where other plants are consuming more natural gas than the ones analyzed—resulted in methane emissions that reached 139 gigagrams a year. For context, that’s equivalent to the carbon emissions from 669,314 passenger vehicles driven in a year. Or more than the carbon emitted from 3 billion pounds of coal burned. Best case scenario, the emissions are just 2 gigagrams of methane a year, which is still a lot more than what the EPA currently estimates for this industry.

That is pretty wild, but this is an estimate based only on six plants. They make up more than 25 percent of the 23 plants operating in 2016 and are also of varying sizes to represent the different facilities throughout the U.S., so the six are a pretty good sample. But the authors would like to examine more plants to be sure.

The researchers drove downwind from the facilities in a Google Street View car decked out with a killer methane analyzer that recorded the methane levels in the air. That way, the team was able to capture the methane emissions near the facility in the areas where wind was likely to push it. This poses some limitations, though, because not every plant had the best road access. The authors recommend looking at airborne measurements next time, too. The team looked at samples over just a few days in a single month over these two years. Capturing a longer timeline of data could further verify (or disprove!) their analysis.

Methane emissions feel especially relevant these days. The Trump administration has been attempting to roll back methane regulations since President Awful took office. (The Department of Energy actually called natural gas “freedom gas” the other day.) A coalition of states and environmental groups like the Sierra Club pressed a judge Friday to stop Trump from rolling back these protections, reports E&E News.


Methane isn’t just dangerous for our planet because it’s worsening climate change; its emissions are often coupled with particulate matter and other air pollutants that pose threats to the health of communities closest to the facilities where it’s being emitted.

This study is a reminder that things could be much worse than we think.