Ammonia emissions attracting significant attention

By G. Tom Tabler, Center of Excellence for Poultry Science at the University of Arkansas's Avian Advice - Farmers in all segments of animal agriculture of United States are under pressure to minimize the impact of their farming operations on the environment.
calendar icon 8 January 2007
clock icon 9 minute read


Even though most environmental concerns during the past two decades have focused on water quality issues, air quality has recently attracted significant attention, especially ammonia emissions from poultry housing. While agricultural emissions have historically been ignored by United States regulations, recent regulations may signal a change.

Understanding Particulate Matter

We all know about particulate matter in the air, except that we call it dust, smoke, smog or haze. Since dust particles tend to settle out on calm days, while smoke, smog or haze particles remain suspended, it should also be apparent that air contains particles of different sizes. Particles (also called particulate matter or PM) are classified by the approximate diameter of the particles present. There are over 25,000 micrometers in an inch and the diameter of a human hair is usually 50 to 75 micrometers. The size of the particles in air is abbreviated using the particle size (in micrometers) as a subscript. For instance, PM2.5 shows that particles of 2.5 micrometers or smaller are involved.

Particles between 2.5 and 10 micrometers (called “coarse particles”) are generated from the soil, factories, roads, row-crop farming operations or rock crushing operations. Smaller particles (PM2.5 or smaller) arise from automobile exhaust, power plants, wood burning, industrial processes, diesel powered vehicles, organic compounds, ammonia emissions, brush fires or volcanic eruptions. Coarse particles may stay suspended in air for a few minutes or hours and travel up to 30 miles, while fine particles can stay in the air for days or weeks and may travel several hundred miles. When animals or humans breathe air containing particulate matter, fine particles penetrate deeper into the lungs than coarser particles and can cause coughing, wheezing, shortness of breath and lung damage (EPA, 2006).

New Air Quality Standards

The National Ambient Air Quality Standards (NAAQS) were issued by the EPA in 1997. The NAAQS were developed for six pollutants that the EPA considered common throughout the United States:

  1. Carbon monoxide (CO)
  2. Lead (Pb)
  3. Nitrogen dioxide (NO2)
  4. Ozone (O3)
  5. Particulate matter (PM)
  6. Sulfur dioxide (SO2)

These pollutants were chosen based on two criteria: the protection of public health; and the protection of public welfare, such as damage to animals, crops, vegetation and buildings or decreased visibility (Mukhtar and Auvermann, 2006).

Since only small amounts of these pollutants are generally emitted directly, these standards would initially appear to have little to do with poultry houses. However, research has shown that ammonia can combine in the air with nitrogen or sulfur oxides to form very small particles (PM2.5’s) of ammonium nitrate or ammonium sulfate.

The reaction of ammonia in the atmosphere to form PM2.5’s means that the NAAQS regulations aimed at reducing PM2.5 emissions will likely require reductions in ammonia emissions from animal agriculture operations (Gay and Knowlton, 2005).

Ammonia Emissions

Ammonia can travel as far as air can go in 5 or 6 days (Knowlton, 2000). Particle (PM2.5) formation can prolong existence of emissions in the atmosphere and therefore influences the geographic distribution of acidic depositions (Sommer and Hutchings, 2001). This means that ammonia lost from Arkansas poultry farms may be affecting air and water quality in the Midwest or East. Midwestern agricultural practices have, for years, been blamed for eutrophication in the Gulf of Mexico. Problems in the Chesapeake Bay are likely associated, in part, with ammonia deposition from upwind agricultural areas such as Ohio and North Carolina (Gay and Knowlton, 2005).

Dramatic increases in air concentration of ammonia in areas of intensive agriculture have been reported, and estimates indicate that animal agriculture accounts for 50 to 85% of total ammonia volatilization. The loss of gaseous ammonia has direct implications on the nitrogen content and the fertilizer value of animal manure. In addition, a recent study by the National Research Council (NRC, 2003) identified ammonia emissions as a major air quality concern at regional, national, and global levels. It is, therefore, important and in producers’ own best interest that animal agriculture takes the ammonia emissions issue seriously. Figure 1 lists estimates of ammonia emissions from man-made sources in the U.S. during 1994. Note that poultry was responsible for almost 27% of total ammonia emissions estimates.

Figure 1. Estimates of ammonia emissions from man-made sources in the U.S. in 1994 (Battye et al., 1994).

Producers are aware from their own experience and estimates confirm that ammonia emissions will change with the seasons, the geographic region, production techniques, manure management practices, the number of animals present and type of animals produced (EPA, 2004). In general, however, the greatest ammonia losses are associated with land application of manure (35%-45%) and housing (30%-35%; Gay and Knowlton, 2005).

Ammonia Source

Poultry producers deal with ammonia on a daily basis and some may wonder about the source of ammonia. The ammonia is not directly produced or excreted by the birds, but is a common by-product of poultry wastes. Birds excrete waste containing unused feed nitrogen in the form of uric acid. Ammonia is formed through the microbial breakdown of uric acid. Conditions that favor microbial growth will result in increased ammonia production. These conditions include warm temperatures, moisture, pH in the neutral range or slightly higher (7.0 – 8.5) and the presence of organic matter – factors normally present in abundance in poultry waste handling systems (Carey, ND).

What to Do

The frequent and total removal of litter and manure from poultry houses would reduce the ammonia emissions concern. Yet, in most cases, due to the cost of cleanout and replacement bedding, this is not a viable option for most producers that may only clean out once a year or less.

The most appropriate strategy to control ammonia is to reduce ammonia volatilization. A number of compounds are available for use by poultry producers to reduce the pH of poultry litter to promote formation of NH4+ ions that will bind to other compounds and thus reduce the amount of volatile ammonia (Carey, ND). However, since manure, which neutralizes these acidifying agents, is constantly produced, these compounds provide pH control for only a short time.

Perhaps the simplest thing most poultry producers can do to minimize ammonia emissions is to control litter moisture. The more moisture there is in the litter, the more potential for ammonia emissions from that litter. Ferguson et al. (1998) confirmed the relationship between higher litter moisture and increased litter ammonia. Increases in litter moisture from approximately 56% to 60% resulted in an increase in litter ammonia release. Keeping the litter dry depends, in part, on how well drinker management is maintained. Closely monitor the drinker height and regulator pressure. Promptly address leaking nipples or lines. Remove wet litter from the house if a major leak or spill occurs.

Also, know what is in the water the birds are drinking. If you don’t know, have the water tested to determine its quality. While often overlooked, water quality has a major impact on flock health and performance as well as litter conditions. Ventilation is also critical to maintaining proper litter moisture. Humidity levels must be maintained below 70% to prevent caking. If you do not currently do so, consider using litter amendments to lower the pH early in the life of the flock. This will decrease ammonia emissions and allow you to ventilate for moisture removal instead of ammonia removal which should allow a decrease in fan run time, thereby saving fuel. It will take an integrated approach to reduce ammonia emissions from animal agriculture. Keep in mind there is no one product or management practice that will solve all the problems.


Meeting new air quality standards and complying with future regulations has the potential to affect practically every farm in America and perhaps put some out of business. Controlling ammonia emissions from poultry and livestock facilities will be a daunting task in the future for livestock producers. Producers will have to use an integrated approach that attacks the problem from several different angles.

There are products available to help control litter pH early in a flock. Excellent house management will be required to keep litter moisture at optimum levels. Producers, not politicians, will ultimately have to solve the air quality concerns associated with livestock production. Increased producer involvement is needed at all levels – local, county, state and national if we are to have workable programs that keep farms viable while benefiting the environment, instead of unrealistic expectations that cannot be met.


Battye, R., W. Battye, C. Overcash, and S. Fudge. 1994. Development and selection of ammonia emission factors. EPA/600/R-94/190. Final report prepared for U.S. EPA, Office of Research and Development. USEPA Contract No. 68-D3-0034, Work Assignment 0-3.
Carey, J. B. No Date. Mitigation strategies for ammonia management. Available at: Accessed October 12, 2006.
EPA. 2004. National emission inventory – Ammonia emissions from animal husbandry. Available at: October 12, 2006.
EPA. 2006. Laboratory and field operations – PM2.5. Available at: region4/sesd/pm25/p2.htm#2 11/16/06
Ferguson, N. S., R. S. Gates, J. L. Taraba, A. H. Cantor, A. J. Pescatore, M. L. Straw, M. J. Ford, and D. J. Burnham. 1998. The effect of dietary protein and phosphorus on ammonia concentration and litter composition in broilers, Poult. Sci. 77:1085-1093.
Gay, S. W., and K. F. Knowlton. 2005. Ammonia emissions and animal agriculture. Virginia Cooperative Extension, Biological Systems Engineering, Publ. No. 442-110. Virginia Polytechnic Institute and State University, Blacksburg, Virginia. Knowlton, K. 2000. Ammonia emissions: the next regulatory hurdle. The Jersey Journal, October 2000, 47:56-57.
Mukhtar, S., and B. W. Auvermann. 2006. Air quality standards and nuisance issues for animal agriculture. Texas Cooperative Extension Service, Publ. No. E-401. Texas A&M University System, College Station, TX.
NRC. 2003. Air Emissions from Animal Feeding Operations. The National Academies Press. Washington, DC.
Sommer, S. G., and N. J. Hutchings. 2001. Ammonia emission from field applied manure and its reduction – invited paper. European Journal of Agronomy 15:1-15.

Source: Avian Advice - Winter 2006 - Volume 8, Number 2

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