Interesting science behind stinky Fort Collins days

Smell that?

It’s been characterized as “old man breath,” “the smell of death” and simply “rank” to those whose noses curl while on the back patio grilling a steak.

To those with cowboy hats, it's "the smell of money.''

It drifts into Fort Collins and Windsor from the southeast, often during the late morning and early afternoon, besieging innocent nostrils with the force of hundreds of thousands of farm animals.

And farm animals are exactly what you’re smelling. Although this olfactory adventure by some accounts has dissipated over the years, the stench of Weld County’s booming agricultural industry is still a familiar foe to Fort Collins and Windsor residents and visitors alike, especially when it rains or snows.

Here’s how it works.

More than 500,000 cattle and calves – roughly one-fifth of Colorado’s total – call Weld County home, sweet home, earning it the No. 1 ranking in the state and No. 3 in the country. Add 200,000 sheep and lambs to the mix, the most of any county in the nation, and Weld County’s four-legged friends outpace the population of Denver. As of 2014, one-fourth of the state’s 48 approved feedlots were in Weld County.

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And then there’s the JBS USA meatpacking plant, which processes thousands of cattle every day, dehydrates their blood and grinds up their bones and unused organs for use in commercial products.

So, yeah, the air can get a little stinky next door to Larimer County.

“You just have a lot of animals that are congregating in one space all at once,” said Shawn Archibeque, an associate professor at Colorado State University professor whose research includes the strange science of agricultural odors.

And along with a lot of animals comes a lot of … you know what.

But you don't need to be a professor of agricultural things to simplify the stench equation. You probably get the drift. Still ...

“Feces are going to smell,” Archibeque said. “As far as I know, everybody’s feces smells. And as you get more of it, it’s going to smell more.”

There's an interesting meteorological component to the stench stream.

For the smell to pack its bags and travel a couple dozen miles to Fort Collins, the wind has to be just right. Unfortunately, that happens a lot.

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A light breeze, about 10 mph, often meanders from the southeast into Fort Collins and Windsor from about 9 a.m. to 1 p.m. This breeze carries the aroma of Weld County’s many cows and sheep across Larimer County and up along the Poudre River Valley into the Front Range, setting off what’s called a diurnal wind pattern.

The Front Range generally takes on a diurnal wind pattern when there’s no large-scale weather system in the area, meteorologist and longtime Fort Collins resident Jim Wirshborn said. Warm air gets trapped in the mountains and sinks as it cools during the evening hours, sliding back down the mountains, rippling across the Poudre Valley again and blowing through Fort Collins and Windsor once more.

“It’s kind of like a tide, almost,” Wirshborn said. “It sloshes back and forth.”

The tide is a more pungent one when there’s moisture in the air because wet air carries smells better than dry air. Imagine the scent of wet pavement after a rain storm.

Odor is an exceptionally difficult thing to measure because it’s so personal, Archibeque said. What’s more, some chemicals travel farther than others, so what you’re smelling depends on how close you are to the source of the odor.

“To date, the best way to measure an odor is still probably the human nose,” Archibeque said.

And despite the wide array of tactics that can keep agricultural smells in check – from fiddling with the animals’ diets to sprinkling natural oils on the soil – one of the most effective ones is simply keeping facilities as clean and dry as possible.

That means frequent removal of manure and a good drainage system that prevents water from sitting around for too long, Archibeque said.

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The city of Greeley, home to the JBS meatpacking plant, has a bad reputation as the culprit of the smell, but it’s actually been somewhat of a champion in trying to get rid of it. Greeley encouraged JBS to install odor-reducing technology and banned feedlots from city limits about 15 years ago, city spokesman John Pantaleo said. Around the time of the ban, the city also bought and closed a big feedlot on its outskirts.

The stereotype of the stench has stuck around, but the “Greeley Unexpected” campaign launched a few years ago is helping to dissipate the bad smell that some people associate with the growing city.

The JBS technology includes a 180-foot chimney stack, which keeps a portion of the stink higher in the atmosphere where it won’t “offend our neighbors,” spokeswoman Misty Barnes wrote in an email. The plant also has scrubbing systems that pre-treat air before it heads to your back patio.

Agricultural producers don’t have to control their odors. The Environmental Protection Agency doesn’t categorize odor as a pollutant, and Colorado has few regulations on animal methane emissions.

Mostly, people try to minimize the funk because they want to be good neighbors, Archibeque said.

It would appear, then, that the smell isn’t as bad as it once was.

“I’m probably a bad person to ask about that,” said Archibeque, who has lived in Fort Collins off and on for 20 years. “I’m pretty used to it.”

Reporter Jacy Marmaduke covers environment and breaking news for the Coloradoan. Follow her on Twitter at @jacymarmaduke.