Odor Eaters

1/15/2011 2:00 PM


Indigenous Plants a Practical Solution for Poultry Pollution


Janice F. Booth
Maryland Correspondent

CENTREVILLE, Md. — The problem: the acrid smell of nitrogen, ammonia and particulate matter billowing from poultry house exhaust fans. In addition to the pervasive and unmistakable odor, what is exhausted from poultry houses carries minute particles of feathers and dander that clog lungs and kill vegetation.

The solution: tough, resilient, cheap plants that love to gobble up nitrogen, ignore drying wind sweeping across them night and day, and know how to slough off dust that settles so thickly on their foliage you could write your name on their leaves.

Once again, common sense and practicality prevail. Problem to solve? Tackle that problem with solutions that are at hand. In this case, warm season grasses and street trees.

Seven years ago, horticulturalist Shawn Belt was working at the National Arboretum in Washington, D.C. His colleague, Denny Townsend, was researching “urban street trees,” those ubiquitous, tough shrubs and trees that grow down alleys and out of rubble piles. Belt and Townsend put their heads together and decided there might be useful applications for these street fighters of the botanical world.

The good news about urban, indigenous plants: They grow fast, cost next-to-nothing to propagate, withstand the sometimes harsh, regional climate and absorb nitrogen like sponges. Switch grass, osage orange trees and American elm had a champion!

Belt was familiar with the work of Paul Patterson and Bud Malone — using trees as windbreaks for the odorous emissions from livestock, swine and dairy barns. Applying the same idea to chicken houses, Belt began some test plots at poultry farms in Pennsylvania, Maryland and Delaware.

Kim and Tim Austin of Serenity Farm in Centreville, Md., were among the first adapters of Belt’s project.

“The Austins raise broilers, the NASCAR of chickens,” Belt observes. “I wondered, Could my plants mitigate the odor and emissions from the Austins’ fast-growing, quick-turnover poultry houses?’ “

The Austins are among the top 10 broiler producers in the region; they’ve been at poultry farming for more than four years, and they’re proud of their farm and the chickens they produce.

“This farm was Tim’s mid-life crisis,” Kim notes with a smile. “Some guys buy sports cars; my husband bought 30 acres and thousands of chickens. We work at this 365 days a year.”

Serenity Farm’s tidy 30 acres houses over 100,000 chickens, winter and summer. It takes 17 days to sanitize the houses, and another batch of broilers is under way. But, no matter how clean, from those tidy chicken houses can emit fumes that can cause coughing and watery eyes. The 9-foot, side-wall exhaust fans move out the old air from among the chickens’ cages, and that stale air is laden with ammonia and nitrogen. In addition, suspended in the fowls’ foul air are particles of chicken dander and feathers.

Belt knew the Austin farm would be a tough test for his plants. He also knew that if these street-fighter plants were to succeed they would have to resist wind, heat, ammonia and a heavy coating of toxic dust. They would also have to grow quickly, ignoring not only the chickens’ toxic winds but the summer droughts and winter cold.

And they did.

The first buffers of spindly, foot-high coastal switch grass and Chinese silver grass took hold in a blink. Within the first 12 months, the scrawny clumps grew from 12 inches to 8 or 9 feet high. The twigs of Austree willows Belt and the Austins planted behind the grasses as back-up took off, too. The willows are tall, with trunks the size of a man’s arm.

These grasses and trees are doing a great job absorbing nitrogen and ammonia from the air and taking the pollutants down into their roots. The particulate matter, instead of flying into the eyes and lungs of the farmers, is being captured by the leaves and eventually sloughed off into the soil — where the dander and dust are absorbed. And, these tough guys love their work. They are beautiful, waving rows of grass and trees, against the gray shoulders of the chicken houses.

The plants are so hardy that Belt has been able to move them closer to the fans, thus cutting down the amount of land required for the buffers. Instead of 50 feet, the plants are growing and filtering the air as close as 20 feet from the giant fans.

“This has been a great quick-fix for our fan exhaust problem,” says Kim Austin.

The switch grasses and Aussie willows are cheap to propagate, grow fast and need very little land.

“Just because we’re a chicken farm doesn’t mean we don’t want to help the environment,” she says.

She has agreed to plant some American elm trees to see how they’ll fare, so far from the mean streets of the city.

“Tim and I are planting crape myrtle and forsythia, too. Maybe they’ll help with the buffer zone, and they are pretty, too.”

The experiment has been so successful that Belt has begun another, larger buffer project at Hillandale Farm in Gettysburg, Pa. Hillandale is an egg-laying facility which includes six chicken houses with a total of 1.2 million birds. For this huge setting, Belt has planted a large and varied collection of potentially useful buffer plants, including bayberry, American elm, hackberry, alders, oaks, red maple, black locust and osage orange. Patterson is involved with the fact-finding at this site.

In a recent progress report, Belt notes the statistics gathered by Patterson: “ a tree/shrub windbreak planted opposite tunnel fans reduced dust (particulate matter) by 67 percent at a distance of 20 feet downwind from a five row windbreak, and odor by 50 percent.”

Those are impressive reductions in emissions.

If you’re thinking of planting an emissions barrier and checking for yourself how these street trees and grasses work, Belt’s research suggests the following design plan for planting grasses around your chicken house exhaust fans:

Two rows of grasses, minimum, should be planted.

Plant the rows as close as possible to the fans, probably about 20 feet away.

Space the grasses two feet apart.

Stagger the plants if you’re using several varieties, with the tallest grasses at the ends of the break.

Extend the rows 20 feet beyond the ends of the fans, preferably arcing in toward the building.

A more detailed explanation can be downloaded from the USDA-NRCS website:



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