Mitigating Manure's Odor

Impact-Based Odor Control (IBOC) technology has been field tested for three years at a northern Iowa hog operation. The system has proven to be effective in mitigating odors and reducing related operational expenses.

Joe Vansickle, Senior Editor

September 20, 2011

7 Min Read
Mitigating Manure's Odor

An Iowa State University (ISU) agricultural engineer and his staff have devised new technology that monitors weather patterns and odor emissions, overseen by a control system that engages only when needed, and pacifies the environmental concerns of rural citizens residing near hog operations.

Impact-Based Odor Control (IBOC) technology has been field tested for three years at a northern Iowa hog operation. The system has proven to be effective in mitigating odors and reducing related operational expenses.

Control System

It’s often impractical and unnecessary to apply odor mitigation to all of the ventilation air in a hog barn, says ISU’s Steve Hoff, professor of agricultural engineering.

Instead, determine the critical time period when odor control is needed and apply it accordingly, conserving energy and maximizing odor mitigation. The ISU technology does just that, Hoff says.

The IBOC technology encompasses a weather station and an on-off control system linked to a biofilter with a bypass louver system (pictured), which enables the biofilter to be used to scrub ventilation air of hog odors only when needed, he explains.

That period of time is much smaller than you might think, based on weather station calculations and odor emissions, Hoff emphasizes. “You can have an odor control technology such as biofilters that are about 70% effective, but the time you need to operate that technology is very, very small because of weather patterns,” he says.

In the daytime, the atmosphere is unstable, the earth’s surface warms up, and a natural buoyancy lifts odorous emissions, eliminating the need to intervene.

“This weather station accounts for all of that, calculating atmospheric stability and evaluating wind direction to determine the potential impact on neighbors, depending on their location,” Hoff observes.

The weather station measures wind speed and direction, temperature, humidity and solar radiation. This information is fed into the overall control system, which then controls the on-off switch for odor mitigation using the biofilter.

Figure 1 illustrates the general principles behind the IBOC system, and pictures (at left) depict the use of the biofilter.

“This technology can be the control for an odor mitigation system that can be controlled on-off. It is not a mitigation technology, but it helps decide where and when not to use odor mitigation,” Hoff clarifies.

Research Trial

The farm research site is a 600-head, hybrid-ventilated (pit fans and curtains), deep-pit swine finisher comprised of two, 300-head rooms. The walls separating the rooms also separate the two manure pits, except for equalizing channels at the bottom of the separating wall. One 300-head room was designated as the control, while the other served as the treatment room.

“The treatment room is equipped with a biofilter capable of filtering 45% of the maximum required ventilation exhaust air, a technique we refer to as partial biofiltration,” Hoff explains.

To reduce barn energy costs for odor mitigation, researchers devised a motorized louver system that sent the exhaust air through the biofilter or bypassed the biofilter and exhausted the air directly into the atmosphere.

In the study, if the atmosphere was stable, indicating that odor plumes remained near the earth’s surface, and the wind direction suggested that a nearby neighbor would be impacted by odor, the louvers were set to direct the exhaust ventilation air through the biofilter.

When the atmosphere was unstable, indicating odor plumes would rise and mix vertically close to the odor emission source and neighbors would not be impacted, the bypass mechanism was activated to exhaust air (odor) into the atmosphere, Hoff explains.

For this project, six fictitious neighbors were plotted around the test site. Using these residents, wind-direction tracking alone reduced odor mitigation operation to no more than 17.9% of the time. “That is, if nothing else except wind direction tracking was conducted, and knowing the location of each of the six neighbors, odor mitigation was stopped 82.1% of the time, a significant savings in operational costs,” he says.

When atmospheric stability was added into the mix, odor mitigation was only required 7% of the time with the treatment vs. 100% of the time without the odor control technology, Hoff says. “That is, considering downwind potential neighbor impact, 92.9% of the time mitigation of odor was not required for the six neighbors modeled from this research site.

“In theory, the original $0.45/pig fan operational costs associated with the original biofiltration strategy has been reduced to $0.03/pig, while still maintaining significant odor impact control to the surrounding neighbors,” he says.

New Technology

“The beauty of this is that while biofilters are a good control technology for now, we are working on some more sophisticated odor mitigation techniques, including some work with ultraviolet destruction of odors (photo catalysis), which may be more expensive to operate. But with our control technology, you are minimizing the amount of time that you actually have to operate it, meaning operational costs are very low. You just use it when you absolutely have to,” Hoff says.

As the next step in the process, Hoff, with the assistance of research associate Lun Tong, is finishing work on a portable weather station that could be transported to different sites. The portable unit would be applicable to any site that needs to mitigate odor and has an on-off odor control system.

One day, producers may be able to simply buy the weather station in a box and install it on their farm, he says. Iowa State is seeking a commercial partner to meet that goal.

Assessment Model

The Community Assessment Model (CAM) was developed by Hoff in 2005 to assist in evaluating hog facilities for siting, taking into account potential odor problems. Hoff estimates he has used the model to facilitate siting more than 100 hog units in Iowa.

Hoff and fellow ISU agricultural engineer Jay Harmon work on CAM with the Iowa Pork Industry Center and the Coalition to Support Iowa’s Farmers to project the viability of a site. Data on the location and proximity of neighbors and odor concerns are collected and then analyzed using a CAM computer program at Iowa State.

“It gives the producer a scientific basis for evaluating his or her prospective site, summarizing hours of exposure (to odors) for each individual neighbor and for various levels of odor from each source,” Hoff states.

CAM was developed because Hoff is not in favor of using simple distance requirements as odor requirements for siting animal operations.

“You put a circle around a point (for the proposed building site) and say if there are no neighbors within this circle, you can build there, no problem,” he states. But that process doesn’t take into account predominant weather patterns. “A neighbor to the north (of Iowa State at Ames) can be much more affected by hog odors than a neighbor to the south because of our predominant weather patterns in Iowa in the summertime.”

CAM takes into account predominant weather patterns between March and October, proposed size of the hog facilities and the management system.

“It is a preplanning tool for siting that very conservatively estimates odor exposure to a neighbor and provides ‘what if’ scenarios before producers actually build,” he explains.

Uniquely, CAM also accounts for existing odor sources that affect neighbors near a proposed site, Hoff says. For example, two 2,400-head facilities in an area may not trigger an odor issue. However, a third 2,400-head unit may collectively trigger odor levels above a certain threshold that may be offensive in a community.

Hoff is currently working with a pork producer who wants to build a facility in a community, even though the model says the odor load would be too high. It’s a case where investing in odor mitigation strategies such as installing a biofilter may prove to be the best solution to avoiding neighborhood complaints, he says.

CAM is effective for new construction, remodeling and expansion projects, and can evaluate the impact of hog odors for up to 100 neighbors and analyze up to 20 odor sources in a community, Hoff says.

For CAM, localized weather data relies on the 12-13 weather stations located throughout Iowa.

As most odor mitigation strategies are fairly costly, and do not provide direct payback in terms of animal performance, Hoff doesn’t fault pork producers for not installing odor mitigation systems.

“We feel the best odor mitigation technique is proper siting in the first place. If you properly site your facility, you should never have any need for odor mitigation,” he says.

A number of Iowa pork producers have used CAM, and several have decided not to build on sites because the model suggested there could be potential problems, Hoff says.

For more information on CAM or siting issues in Iowa, contact Hoff at [email protected] or (515) 294-6180, or Harmon at [email protected] or (515) 294-0554.

About the Author(s)

Joe Vansickle

Senior Editor

Joe, a native of Indiana, is a graduate of the University of St. Thomas in St. Paul, MN, with a bachelor’s degree in journalism. He worked on daily newspapers in Albert Lea, MN and Fairmont, MN, before joining the staff of National Hog Farmer in 1977. Joe specializes in animal health issues, federal regulations, environmental concerns, food safety and writing about the swine veterinary community. Joe has won several writing awards from the Livestock Publications Council. In 2002, he earned the Master Writer Program Award from the American Agricultural Editors’ Association.

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