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Siting Animal Production Operations
Establishing sites for new and expanded animal production facilities
in Minnesota, Wisconsin, and other parts of the Upper Midwest has become
increasingly difficult due to the air quality concerns of residents
living near these 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. “Site Selection
of Animal Operations using Air Quality Criteria,” a white paper
that primarily addresses the development of setback distances with regard
to nuisance odor issues, has recently been prepared for the National
Center for Manure and Animal Waste Management (see Resources
for their web site address). Some general discussion on human health
issues related to emissions from animal production sites is also included.
Environmental concerns such as water quality impacts and recreational
land use issues stemming from livestock and poultry facility emissions
are only mentioned.
The predominant approach to address the release of agricultural air
emissions is the use of setback distances between animal production
sites and neighboring residences and businesses. Determination of setback
distances is difficult and usually involves compromises—large setback
distances restrict the development of new or the expansion of existing
animal production sites and small setback distances are insufficient
to mitigate the frequency and severity of nuisance odor events. But,
the determination of appropriate setback distances is imperative to
the viability of the livestock production industry. 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. Odors 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 a guideline approach
or by the use of dispersion models. Guidelines are used to determine
setback distances based on criteria such as zoning or land use or 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 takes as 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.
In Minnesota, the OFFSET method is a step by step process that systematically
uses empirical field odor emissions as well as weather data for the
state to predict the setback distance required for several odor annoyance
free frequencies levels. The first step is to identify all of the odor
sources at an animal production site. The next step is to select the
odor emission number on a per square foot basis for buildings or manure
storage units from tabulated values. Finally, determine the total surface
area of the barns and/or storage units, credit any odor control technology,
and then calculate the total odor emission factors for each source.
A new extension publication that describes OFFSET in more detail, OFFSET-Odor
From Feedlots Setback Estimation Tool (FO-07680-C), is available
from the University of Minnesota Extension Service. The Biosystems and
Agricultural Engineering Department has also created an online OFFSET
calculator that will calculate the Total Odor Emission Factor (TOEF)
and determine the setback distance at the various odor annoyance frequencies
for up to five odor sources using the concepts found in the publication.
For information on both, see Resources.
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