The $2.2 million, six-state project funded by the Agriculture Department (USDA) to provide baseline rates for emissions of gases, odor and dust particulates in hog and poultry barns will be finished by the end of this year.

It took a year to select and calibrate instruments and set testing protocols; about a year and a half to collect data; and another year and counting to analyze the data.

But the end is growing near for completion of the groundbreaking USDA-funded study on aerial emissions from animal confinement barns, says project coordinator Larry Jacobson, University of Minnesota agricultural engineer.

He suggests the air-sampling project provides agriculture with its first comprehensive monitoring of gas and odor emissions from actual animal production farms.

The following types of animal housing systems were studied:

  • Swine farrowing with pull-plug gutters in Illinois;

  • Sow gestation with pull-plug gutters in Minnesota;

  • Swine finishing with deep pits in Iowa;

  • Swine finishing with pull-plug gutters in Texas;

  • Conventional high-rise laying hen houses in Indiana; and

  • Broiler houses on floor litter in North Carolina.

Air sampling from two adjacent, identical buildings was conducted for each type of housing from the winter of 2003 through the spring of 2004.

Sample Collection

Baseline emission data was collected for ammonia, hydrogen sulfide, carbon dioxide, odor and particulate matter under 10 microns in size, says Jacobson.

Sampling was conducted using a mobile trailer located between two barns. Gas measurements were taken sequentially every 10 minutes at 12 locations (six in each barn). Odor samples were collected in 10-liter Tedlar bags every two weeks, and submitted to an olfactometry lab for analysis by a trained sniffing panel. Gas and odor samples were collected at the air inlets and outlets. Dust measurements were collected continuously at the exhaust air location for each barn.

Ventilation rate, static pressure, temperature, humidity and wind speed and direction were also calculated or recorded continuously during the study.

Concentrations of the various parameters were taken, and emission rates for these parameters were then calculated. Jacobson explains that the various instruments simply recorded the concentration level of a compound at the various locations inside and outside of the buildings. Emission rates are concentration levels multiplied by the barn's airflow rates. To be accurate, gas, odor or dust emission rates are calculated by subtracting out the difference in concentration rates between the outlets and the inlets.

“One needs to account for the level of gases or odors entering the barn to accurately calculate rates,” says Jacobson. “The assumption that there is no ammonia, hydrogen sulfide or odor coming into the barn may result in the overestimation of the building emissions.”

Overall Results

In general, the magnitude of gas and dust emissions measured in this study didn't vary much over the course of the year, comments Jacobson.

Aerosol concentrations, on the other hand, were quite seasonal, with high levels in the winter, during times of low air exchange, and low levels in the summer, when high rates of ventilation were provided, he says.

“Odor emissions did not follow this flat trend of other emissions, and showed a very seasonal variation, with higher rates in the summer when there were warmer temperatures, and lower rates in the winter when outside temperatures were cooler,” observes Jacobson.

Concentrations, Emissions By Housing Type

Summary data for the four swine sites in the study show these trends:

  • For the two sow units, ammonia and hydrogen sulfide concentrations inside the barn averaged 14 ppm and 0.5 ppm for gestation, and 6 ppm and 0.3 ppm for farrowing, respectively.

  • Ammonia emissions were 15-20 and 11-12 g./day/animal unit (AU) for gestating and farrowing sows, respectively. (One AU equals 1,100 lb; one lb. equals 454 g.) Hydrogen sulfide emissions were consistently 1.4 to 1.6 g./day/AU for both types of sows.

  • Ammonia concentrations in the finishing barns were about twice as high in the deep-pit barns compared to the pull-plug barns (20 ppm vs. 9 ppm). Hydrogen sulfide levels were similar in both types of finishing manure handling facilities, ranging from 0.4 to 0.6 ppm.

  • Ammonia emissions from deep-pit finishing barns were also higher (50 to 60 g./day/AU) than from the pull-plug barns (35 to 40 g./day/AU). Hydrogen sulfide emissions were quite similar for both types of finisher manure containment, ranging from 3 to 4.5 g./day/AU.

  • Gestation barns consistently recorded higher concentrations and emissions of dust and odor than farrowing barns.

  • Pull-plug finishers had much higher concentrations and emissions of dust than deep-pit finishers. But deep-pit finishers had twice the odor concentrations and emission levels as their pull-plug counterparts.

Impact of Monitoring Study

Steve Hoff, professor of agricultural engineering at Iowa State University, was in charge of the Iowa portion of the air emissions project, and had some surprising observations on the two, 1,000-head, deep-pit finishers he monitored.

“One of the things that surprised us was the highest ammonia levels did not occur when the manure pits were being agitated in preparation for land application,” he points out. “That was the time when hydrogen sulfide levels were at the highest, but they still did not exceed the ammonia emission levels.”

Declares Hoff: “What I am telling producers is that based on our results, hydrogen sulfide is not the gas that is a reportable quantity as defined by the Environmental Protection Agency (EPA), or in a swine finishing system.”

Rather, ammonia is the gas of concern. “I have been telling producers that based on our studies, if they have a deep-pit site that is at or above 2,000-pig capacity, the chances are very good that at least once a year they will exceed 100 lb. of ammonia that will trigger a reportable quantity for that gas,” he states. A reportable quantity is 100 lb./day in any one day during the year.

If ammonia or hydrogen sulfide is triggered as a reportable quantity, producers are required to report that event to the EPA to comply with the following two rules: First, the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA) establishes guidelines and procedures to respond to releases of hazardous substances. Second, the Emergency Planning and Community Right-To-Know Act (EPCRA) is designed to help local communities protect public health, safety and the environment. Filing a report does not mean that producers will be penalized, stresses Hoff.

EPA's Clean Air Act is another concern for producers, but threshold levels for violations are based on an annual basis, with limits depending on several factors, including whether or not an area is classified as an attainment area.

“And the results are showing that most of our swine production operations are nowhere close to violating the Clean Air Act,” he says.

Establishing Proper Protocols

In Hoff's mind, the six-state monitoring study will provide EPA with solid protocols to follow when it comes to regulating air emissions from the animal-feeding industry, as well as guiding producers' future housing and manure management decisions.

“We cannot, as an industry, operate without having good, solid research data describing the emissions from our facilities, because the perception will be much worse than reality,” he emphasizes.

Home Is Where The Gases Are

For rural homeowners concerned about levels of toxic gases, the biggest threat may come from inside their homes, rather than any nearby hog operations, says Iowa State University agricultural engineer Steve Hoff.

In a one-year study funded by the National Pork Board, Hoff compiled results from what he believes may be the first direct comparison of outdoor rural air to ambient air inside homes in the area — and found in every case higher levels of gases inside homes.

Testing Protocol

Hoff tested for ammonia and hydrogen sulfide gas levels at four, 2,000- to 4,000-head swine finishing operations in Iowa, some with deep pit manure storage systems and some with outside storage basins (but no lagoons). These results were compared with test results from four nearby rural residences and one home in the suburbs of Des Moines.

“The idea is that we are trying to put together health-based standards at the same time that our state Department of Natural Resources is currently evaluating gas concentrations located near 10 of the largest pig and poultry facilities in the state of Iowa,” he explains.

The four residences were located from 251 ft. to 3,300 ft. away from the nearest hog farm, and the fifth home, near Des Moines, was five miles from the nearest hog farm.

Simultaneously, air quality inside the homes and outside the homes was monitored for ammonia and hydrogen sulfide gas levels.

Testing Results

In all five cases, the concentrations of ammonia and hydrogen sulfide gases inside the homes registered “significantly higher” levels than the gas levels in the ambient air surrounding the homes, says Hoff.

The highest ammonia levels were detected in the fourth home tested, in which the occupants were heavy smokers, he adds.

Interestingly, the ammonia levels in the fifth home tested, the residence near Des Moines, were higher than all test results taken near the hog units, even though the city home was very clean and there were no smokers or cats living there, states Hoff.

The highest hydrogen sulfide levels recorded were found inside the fourth home, situated just 251 ft. from the hog production site. The highest outside air levels of hydrogen sulfide were detected at this same site. The managers of the hog operation lived in this home.

Weather stations were erected at all test sites. Each site was monitored for about three weeks. At no time was there a downward plume of air observed during the monitoring period that would influence gas levels around the residences, stresses Hoff.

The ISU ag engineer says there are two lessons to be learned from this exercise: Don't overlook some important air quality issues for the protection of human health, and “don't blindly blame animal agriculture for air quality situations that have nothing to do with animal agriculture.”
Joe Vansickle