Purdue Releases Details of Air Emissions Study

Purdue University data indicates pork producers may not have to regularly report or control air emissions.

Joe Vansickle, Senior Editor

June 19, 2012

8 Min Read
Purdue Releases Details of Air Emissions Study
<p> Compiling data and statistics for the national air emissions study of a sampling of U.S. livestock and poultry operations proved to be a massive undertaking for principal investigator Al Heber of Purdue University.</p>

Agricultural engineers ran testing equipment continuously during 2007 to 2009 in their quest to evaluate the level of air emissions emanating from 20 selected farms and 35 barns in eight states across the country.

The monitoring program took readings from the majority of these farms, which included five dairies, five pork production sites, three egg layer operations and one broiler ranch, according to Al Heber, professor in Purdue University’s Agricultural and Biological Engineering Department and principal investigator along with Richard Grant, professor of agronomy at Purdue.

Open-source emissions were monitored at 10 farms in manure storage facilities, which included five lagoons and one storage basin at pork production sites, three manure storage basins at dairies and one dairy corral. A hog lagoon and a dairy lagoon were monitored for 12 months continuously. All other area sources were monitored for 20 days each season for two years.

From those emissions results, Heber says it appears in the two years that it took to compile and analyze the massive amount of statistical data, pork producers stand an overall good chance of not having to implement pollution controls on their farms. They may need to report emissions of one or two pollutants.

That conclusion, of course, is pending final analysis of the data by the Environmental Protection Agency (EPA), which could take months to complete.

“The EPA will use the data to help them estimate the emissions from individual livestock operations using standardized methods and compare them with government regulatory thresholds,” he adds. “The data will also help the EPA to construct an agriculture strategy, which will outline steps for reducing farm pollution.”

Landmark Project

The project marked a historic and novel legal arrangement between the EPA and four major livestock and poultry groups called the U.S. EPA Air Consent Agreement.

For pork and poultry producers, the study offered a “one-time opportunity to participate in a legal agreement that provides protection against potential past federal air law violations” in exchange for an opportunity to determine emissions from farming operations, according to Heber’s final report to the National Pork Board. The Pork Board provided funding for the pork emissions work.

Under the legal aspects of the settlement agreement, participating industries were required to fund the National Air Emissions Monitoring Study (NAEMS) to measure farm level emissions of ammonia (NH3), hydrogen sulfide (H2S), particulate matter (PM) and volatile organic compounds (VOC).

Purdue University was designated the independent monitoring contractor to carry out the NAEMS. Purdue, in turn, contracted with Iowa State University, University of Minnesota, North Carolina State University, University of California at Davis, Cornell University, Texas AgriLife Research and Washington State University to operate the monitoring sites in those respective states.

The budget included $6 million from pork producers, $5 million from dairy, $2.8 million from eggs and $1 million from broilers for a total project cost of $14.8 million.

Painstaking Measurements

Heber says sample collection was a “painstaking process” with more than 100 persons involved in using about 80 standard operating procedures and a battery of probes and sensors, plus established and novel methods, including ultrasonic technology to measure the airflow through naturally ventilated barns, vibration sensors to monitor fan operation and flow direction sensors in the gas sampling system, among others. Micrometeorological techniques were used to estimate emissions of ammonia and hydrogen sulfide from the open-source manure basins and lagoons.

Three size classes of particulate matter were measured: TSP = total suspended particulate; PM10 = particles smaller than 10 microns in diameter; and PM2.5 = particulates less than 2.5 microns in diameter. PM10 and PM2.5 are regulated by the Clean Air Act.

“We also measured ammonia and hydrogen sulfide emissions, as Emergency Planning and Community Right-to-Know Act (EPCRA) regulations require that the release of either of these two compounds be reported if either is emitted at a rate of more than 100 lb./day for any 24-hour period,” Heber explains.

The final compound measured was the emissions of total non-methane volatile organic compounds (VOC), which is also regulated by the Clean Air Act.

Key Findings

Generally, the data indicates that some of the very largest hog operations might have to report emissions data for exceeding 100 lb./day of hydrogen sulfide release, Heber says. The gas contributes significantly to odor, even at very low concentrations, and is toxic to humans and animals at levels of about 5 to 10 ppm.

 Many medium to large operations could exceed the EPCRA’s reportable quantity thresholds for ammonia because more than 100 lb. of ammonia are released in any given 24-hour period from their facilities.

Field studies, however, have provided limited data that only covers a fraction of the overall picture of ammonia emissions.

The data for emissions also indicates that exceeding PM10 thresholds in the Clean Air Act are extremely unlikely. “Particulate matter is a complex mixture of extremely small particles that in swine barns originates mainly from feed, litter, fecal material and animals,” Heber says. Emissions from swine facilities can result in health and nuisance concerns, but can vary significantly in swine barns.

Volatile organic compounds (VOC) are defined as “any volatile compound of carbon,” and are regulated by the EPA to prevent the formation of ozone. VOCs emitted from swine manure can affect health at concentrations above certain thresholds, but the risks associated with exposure to indoor and outdoor concentrations at livestock farms still need to be assessed, he comments.

Heber formulated 33 key findings for emissions from the pork sites in the NAEMS, condensed by emissions category.

Researchers measured air emissions from five pork production sites.

Hydrogen Sulfide

•  The study indicated, conservatively, that single-site swine farms would need 200,000 gestation sows, 15,000 farrowing sows and 250,000 finishers to generate 100 lb./day of hydrogen sulfide.

•  Based on only open-source emissions, the NAEMS indicated to reach the 100 lb./day EPCRA hydrogen sulfide threshold during a typical day during the period of maximum emissions would require about 150,000 sows or 230,000 finishers in climates like North Carolina. It would require about 13,500 sows or 18,000 finishers in climates like Iowa and Oklahoma.

•  Hydrogen sulfide emissions from pull-plug barns were most influenced by the amount of manure in the pits, increasing as manure accumulated and spiking during flushing.

•  Hydrogen sulfide emissions from deep-pit finishing and farrowing barns increased as hogs and pigs grew.

•  Manure depth in deep-pit gestation barns was the most important factor influencing hydrogen sulfide emissions.

•  Hydrogen sulfide emissions at all lagoon sites seemed to show a single peak during the year, although the timing of that peak was different at each site.

•  Sulfur content in the farm’s water supply was a major determinant of hydrogen sulfide emissions. For each 100 mg/liter increase in water sulfur content, there was an average 2,150 mg/day/sow increase in hydrogen sulfide emissions.

•  Hydrogen sulfide emissions from the open sources were much lower at the farms in North Carolina than at the farms in Iowa and Oklahoma.


•  The study indicated, conservatively, that it would take 5,000 sows or finishers to generate the threshold level of concern of 100 lb./day of ammonia.

•  Based on only open-source emissions, the NAEMS indicated, conservatively, it would take 1,500 sows or 10,000 finishers to reach the EPCRA ammonia threshold on an annual average basis.

•  Lagoon emissions ranged from 20-70% of total ammonia emissions for a 7,000-head, pull-plug/lagoon finishing farm with nine barns.

•  On pull-plug sow farms with fewer barns, lagoon emissions accounted for up to 90% or more of the farm’s total ammonia emissions.

•  Lagoon ammonia emissions at all sites were a clear function of temperature.

•  Ammonia emissions from finishing barns were directly related to animal density and activity, whereas in sow gestation barns it was directly related to activity and sometimes temperature and airflow.

•  Open-source ammonia emissions were clearly cyclical, with maximum emissions during the summer and minimum emissions during the winter; they were a function of temperature at all testing sites.


•  The study indicated, conservatively, that it would take 2.5 million gestation sows and 200,000 finishers on a single site to emit the threshold level of concern of 250 tons of PM10 per year.

•  PM10 was generally 50% of the TSP emissions (totally suspended particulate or dust), although it was about 25% at one finishing farm. PM2.5 emission was consistently 10-20% of the PM10 emission.

•  PM10 emissions from finishing barns was correlated to animal density and activity.

•  PM10 emissions from sow gestation barns was correlated to animal activity. From farrowing barns,  it was related to piglet weight and activity.

Volatile Organic Compounds

•  Isopropanol, acetaldehyde, 2-butanone, 4-methylphenol, acetic acid and propanoic acid were the main VOCs observed at swine farms. Emissions were mostly dependent on season.

Heber says the cost to report ammonia and hydrogen sulfide data to the EPA is “insignificant.” The costs to reduce dust and VOC, if necessary, though very unlikely, can’t be determined until the abatement requirements are determined.

“If ammonia becomes regulated under the Clean Air Act to control PM2.5, then the costs to control its emissions could be significant,” Heber warns.

Many methods exist for controlling air pollutants and livestock odors, the most affordable and manageable being biocovers on outside storage and indoor deep pits that eliminate outside storage.

To learn more about emissions levels for other species and how pork compares, go to http://engineering.purdue.edu~odor/index.htm .  

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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