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Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Pp. 505-528 in Animal Agriculture and the Environment: National Center for Manure and Animal Waste Management White Papers. J. M. Rice, D. F. Caldwell, F. J. Humenik, eds. 2006. St. Joseph, Michigan: ASABE.  .(doi:10.13031/2013.20264)
Authors:   Larry D. Jacobson, Susan L. Wood, David R. Schmidt, Albert J. Heber, José R. Bicudo, Roger D. Moon

The siting of new animal production facilities and expansion of existing facilities in the United States has become increasingly difficult due to the air quality concerns of residents surrounding livestock and poultry operations. Such concerns often include the effects of nuisance odors on quality of life and the effects of odors and manure gases on both human health and the environment. This white paper primarily addresses the development of setback distances with regard to nuisance odor issues, although some general discussion on human health issues related to emissions from animal production sites is included. Environmental concerns such as water quality impacts and recreational land use issues stemming from livestock and poultry facility emissions are only mentioned and not fully discussed.

Most livestock and poultry in the United States are now raised in specialized production buildings or feedlots, which in order to provide a healthy environment for the animals inherently release odors and gases into the atmosphere. Because of these airborne emissions, the animal industry has an impact on the air quality near these farms and subsequently affects the siting of animal production operations and nearby neighbors and/or businesses.

The establishment of setback distances based on airborne emissions from animal production units requires knowledge of federal, state, and local concentration or emission standards. The regulation of air emissions requires enabling legislation, rules and regulations, and an enforcement process (Lesikar et al., 1996). Congress passed the original Clean Air Act in 1955 and subsequent amendments to regulate air pollution at the federal level. The Environmental Protection Agency (EPA) is directed to interpret the intent of congressional legislation related to environmental matters and to formulate the rules and regulations that implement legislation such as the Clean Air Act. This act established ambient air quality standards for six compounds: nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), lead (Pb), and particulate matter (PM). The PM category was initially for only PM10 (particles less than 10 m in aerodynamic diameter). However, recent concerns about human health effects caused by fine PM (Lippmann et al., 2000) have led the EPA to propose new standards for PM2.5 (particles less than 2.5 m in aerodynamic diameter).

In addition to formulating environmental quality standards, the EPA delegates authority to the states and provides oversight of State Air Pollution Regulatory Agencies (SAPRAs). These agencies must first obtain regulatory authority from their respective state legislatures then formulate rules and regulations in regard to air quality for that state. State air quality standards are often more stringent than the National Ambient Air Quality Standards (NAAQS) set by the EPA and can also include constituents such as odor and gases that are not regulated at the federal level. In reviewing existing state standards for hydrogen sulfide (H2S), ammonia (NH3), and odors, a total of 42 of 50 states have standards for one or more of these particular airborne contaminants.

The use of setback distances between livestock and poultry farms and neighboring residences and businesses is the most common technology used to reduce the impact of odorous air emissions from animal production sites. Determination of setback distances are difficult and usually involve compromises; large setback distances often restrict the development of new or the expansion of existing animal production sites, while small setback distances are insufficient to mitigate the frequency and severity of nuisance events. The determination of appropriate setback distances is imperative to the viability of the livestock production industry and the quality of life of neighbors. However, many setback distances are determined on the basis of anecdotal and subjective information rather than objective and scientific relationships.

The airborne emissions from animal production sites that should be considered when determining setback distances include odor, gases, dust, insects and microorganisms. The quantity and proportions of these emitted materials are primarily a function of animal species, facility design, and management. Odor emissions from animal production sites are probably the most important factor to consider when determining setback or buffer distances from neighbors and communities. Other airborne emissions may have a greater environmental impact but odor is typically used as an indicator for these other pollutants and everyone has a sensor for odor.

The establishment or determination of setback distances from animal production facilities can be accomplished using guideline approaches or by the use of dispersion models. Guidelines are used to determine setback distances based on criteria such as empirical formulas based on animal units, animal housing system, physical size of operation, or similar parameters. The dispersion model method is a more robust tool that inputs specific airborne emissions, such as odor, ammonia, or pathogens, from the animal production site as well as weather conditions then estimates a concentration of the pollutant (odor, ammonia, etc.) downstream which can be used to establish a setback distance.

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