Odor and emissions: Hot topic at Midwest Manure Summit

By Kayla Jentz

University of Nebraska-Lincoln ag engineer Rick Stowell discussed management practices for reducing odor and emissions to kick off the Midwest Manure Summit, held Feb. 26-27 in Green Bay, Wis. It was reoccurring topic throughout the two-day conference. 

Air quality issues for dairy

Stowell discussed air quality issues related to dairies, including odor, ammonia, greenhouse and other gas emissions, and dust, and why those issues should be managed. Every dairy produces odor, he noted. However, what the smell is, how often it occurs and how negative the impact affects others differently.

“A lot of farmers are too close the farm or are too used to the smell to realize the farm produces an odor,” said Stowell. But, odors evoke complaints that can be bad for business and that can affect farm sustainability.”

Stowell called ammonia a real and growing environmental concern, especially in areas like the Chesapeake Bay. Those concerns are increasingly being addressed with regulations. 

Many argue about what level animal agriculture plays in ammonia emissions, but dairy and other livestock are big contributors, Stowell said. “Dairy is at 20% for all ammonia emissions in the U.S., behind poultry (23%) and beef (25%),” he explained. Those numbers are the estimated contributions of various U.S. ammonia sources based on the National Emissions Inventory (EPA, 2008).

A lot of misperception and uncertainty surrounds greenhouse gases, Stowell said. While he’s heard concerns about U.S. Environmental Protection Agency (EPA) regulations, state policies and a “cow tax,” in reality the only EPA reporting rule on the books is for greater than 3,200 cows, and most policies dealing with greenhouse gases lack legislative support, he explained.

“Animal ag is only about 3% of the greenhouse gas emissions – most from beef, then dairy, which is mostly from the animal itself via rumination and belching – despite media overreaction to the topic,” said Stowell.

Stowell has also heard about “green consumers” who want products with a “low carbon footprint,” but said there’s a lag in willingness to pay premiums for those products by retailers and consumers.

Where to start?

Stowell recommended thinking about what others think in regards to your farm, or any farm. Farmers tend to hide what they do behind walls or curtains, he said, but one thing neighbors might get to see – and smell – are manure applications. The strong eye-nose-brain connection, occasional acute/intense emissions, proximity and perceived lack of control should be concerns for dairy producers as they are for their neighbors.

To address some of those issues, Stowell suggested starting with land application.

“Get it below, and keep it low” is his strategy for managing emissions and odors. He recommended getting manure below the soil surface via injection, or incorporating it less than 24 hours after application. He also suggested maximizing droplet size and controlling spray distance for application.

During application, Stowell recommended thinking about “how the wind will blow” and “how your neighbors know.”  Communicating with neighbors ahead of time, conveying appreciation of their interests, as well as describing your efforts to minimize impact, are crucial. You also want to limit the sensory effects with things like property line windbreaks, limiting use and tracking on public roads, and turning off or removing end-guns on pivots.

Outside of land application, Stowell suggested looking at your facilities as a potential chronic source of odor complaints, a place where regulatory control is most likely. But, he cautioned, finding a way to limit cattle area odor emissions will likely just shift the issue to an odor concern for manure storage and handling.

Ration and feed management to avoid overfeeding protein are ways to reduce ammonia emissions. Using multiple rations, testing feeds regularly, balancing for metabolizable protein and managing byproduct use are all ways to avoid overfeeding protein. 

Finally, Stowell recommended taking a look at manure collection procedures and consider the effects of cleaning frequency. With a scrape system, cleaning more often is better for odor, but less often may be better for ammonia emissions, he said. With flush systems, more often is generally better, depending on quality of flush water (which could provide a burst of emissions itself). 

Transferring manure below the soil surface into storage using a closed pipe or conduit is best. For liquid manure, Stowell recommended maintaining and enhancing solids removal. And for solid manure, limiting the moisture addition will help control odor, ammonia loss and flies.

• Rick Stowell is a University of Nebraska-Lincoln ag engineer. He can be reached by email at rstowell2@unl.edu, or via phone at 402.472.3912.

• For more information visit http://www.extension.org/pages/15538/air-quality-in-animal-agriculture.