Researchers delve into the science of why things smell

By STEVE BROWN

Capital Press

McKENNA, Wash. -- To some farmers and ranchers, it's the smell of money, but for neighbors and others, it's the unmistakable smell of livestock and poultry manure.

For poultry and livestock producers, managing manure can be a challenge. The odor and quantity can be daunting, but advances in technology and nutrition can provide help.

Being a good neighbor is a priority at Wilcox Farms, a major egg operation in Western Washington with 700,000 chickens.

"My whole family lives here, with neighbors all around," farming operations director Chris Wilcox said. "Most of these neighbors we grew up with."

The farm has been in operation since 1909, and Wilcox described how things have changed.

"Initially the practice was to apply manure to the land, and there were lots of odor complaints," he said. "Then they found that plowing it under sealed off the flies and the odors."

In 1990, the state Department of Ecology challenged the family farm to balance soil nutrition needs with the effluent from the chickens and the dairy, which had 3,000 cows. Selling off all but 200 of the cows was a step in the right direction.

Since then, the farm has taken to composting all the manure on site, then shipping the compost to grain growers in Eastern Washington, marketing director Wendy Shaw said. Buying organic grain from them for the farm completes a cycle that benefits both parties.

"We're in transition to 100 percent organic," Shaw said. "We're about 35 to 40 percent right now. We're cage-free and free-range. The organic requirement is 2 square feet per bird; ours get 4 or 5 square feet."

Giving the birds plenty of room, with housing units dispersed across the farm's 1,700 acres, was initially intended to minimize disease, she said, but it also helps minimize odors.

Wilcox said as the area's population grows, "Smells will become an issue, so we're taking further steps. ... Managing the moisture is the biggest part."

Just like in municipal sewage treatment, aeration of liquid waste feeds microbes that eat odor-causing bacteria. That practice, running massive stir pumps 12 hours on and 12 hours off in the farm's 33-million-gallon fertigation pond, was costing $50,000 a year in electricity.

"This year we're dripping in hydrogen peroxide, which adds a lot of oxygen," Wilcox said. "We turn the aerators on one hour at a time twice a day. The stuff is expensive, but it's cheaper than electricity."

That pond collects runoff from parking lots and the processing facilities -- "gray water" -- which is applied to 500 acres of organic wheat and beans.

"When we export the crops, we export the nutrients," Wilcox said. "Ecology likes that."

He said the farm still has smells "once in a while," but not every day.

"We have weddings here on the farm, and no one wants farm smells in the middle of that," Shaw said. "We also have harvest events, Easter egg events, tractor pulls and farm tours. It's got to be a nice place to visit."

Wendy Powers, professor of animal agriculture at Michigan State University, said in addition to manure handling, researchers are looking at the diets of cows, pigs, chickens and horses. More than 200 compounds have been identified, she said. The compounds themselves may have pleasant, unpleasant, strong or faint odors. What gives manure its odor is how these compounds interact.

"While we can't predict how or which are the most influential odorants that interact and create manure odor, we do know that many of the odorants are the result of the breakdown of proteins that are excreted in urine and feces," Powers said. "Much of the research to control odors through diet has focused on reducing diet protein."

The other area of research is feeding of fiber, she said. "Cows eat quite a bit of fiber, and some people think that cow manure smells better than pig manure."

A University of Idaho Extension study found little value in manure additives.

"Field tests show that some worked well on one farm while being completely ineffective on other farms," according to the report.

The 2008 report, "Odor Control Practices for Northwest Dairies," studied microbiological additives, masking agents, adsorbents and absorbents, and chemical additives.

The report suggested developing good relations with neighbors: "Give advance notice when you are planning to spread manure. Let your neighbors know that you are willing to talk about odor problems and you care. Ask your neighbors if they would like some compost or separated solids for their garden."

Tips for managing odor

Jay Harmon, of the agricultural and bioengineering department at Iowa State University, offered several steps to managing odor:

* Siting decisions: Consider historical prevailing winds, size of the facility and distance to nearby dwellings.

* Manure handling: Injecting manure can reduce odor by 50 to 75 percent compared to broadcasting.

* Dietary manipulation: Cutting crude protein levels and bumping crystalline amino acids can reduce odors 20 percent.

* Cover manure storage: Both permeable (straw, cornstalks, geotextiles) and impermeable (high-density polyethylene) covers help prevent gases from escaping. Snow and rain accumulation on the impermeable covers must be managed.

* Visual barriers and eye appeal: Well-kept sites get fewer complaints, and people complain less when the livestock operation is out of sight.

* Biofilters: Drawing exhaust air through a biofilter bed can reduce odor, ammonia, hydrogen sulfide and dust.

* Vegetative environmental buffers: A properly designed filter helps lift and mix odorous gases. A wedge-shaped design, with shorter shrubs/trees planted in the outside rows and progressively taller trees in the rows closer to the buildings, will help with this lifting and mixing action.

Harmon suggested focusing on the simple solutions first. "Consider management as well as cost. If you are building new facilities, spend time focused on proper siting. Consider covering or protecting outside manure storage. And be careful with manure application. Remember, you are hauling odor to your neighbor's doorstep."

-- Steve Brown

Online tool

A free online air quality assessment tool is available at http://naqsat.tamu.edu/ that addresses different points within a farm, including manure storage, housing and land application.