WASTE MANAGEMENT PIH-33
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Controlling Odors from Swine Buildings
Authors
J. Ronald Miner, Oregon State University
Clyde L. Barth, Clemson University
Reviewers
Russ and Mary Jeckel, Delavan, Illinois
Dale Purkhiser, Michigan State University
Odor control is a significant problem for pork producers
throughout the country. The problem most often consists of neigh-
bor complaints and occasional legal actions seeking either mone-
tary damages or court injunctions. To operate compatibly within
the community and to provide maximum self-protection, the pork
producer must be aware of some basic information and strategy
concerning odor control and practice those techniques appropriate
to the location.
Odors are primarily a subjective response; there are few
universally good or bad odors. People react to odors according to
their attitudes and previous experience. This factor is usable by
pork producers as they maintain an image of responsibility and
productivity. Operators of well-maintained and attractive facili-
ties who have maintained a cooperative public attitude are seldom
subjected to odor complaints. Odor frequently becomes an issue
along with complaints of water pollution, flies, noise, and other
issues when there is faulty site selection, improper facility
design, or inadequate management.
Compounds emanating from swine buildings have never exceeded
safe air standards and are not hazardous to humans. Under certain
situations, such as manure pit agitation, however, dangerous gas
concentrations can develop. Odors, therefore, are nuisance pollu-
tants and, like other nonhazardous assaults on the environment,
must be regarded accordingly. Important are intensity, duration,
and frequency of detection. Within an agricultural community, it
seems appropriate that livestock odors be occasionally noticed,
but nuisance complaints result when intensity or frequency
exceeds reasonable limits.
Sources of Odors
Odors from swine production facilities arise predominantly
from manure decomposition. Odor from fresh manure is generally
less offensive than odor released when manure undergoes anaerobic
or septic decomposition. The exact nature of this odor is a func-
tion of the ration fed to the animals, the animal's metabolism,
and the environmental conditions under which decomposition
occurs. Therefore, individual facilities can have differing
odors; anaerobic lagoons have odors easily distinguishable from
deep pit or scraped buildings.
Manure decomposition is not the only odor source. Rotting
feed materials may also contribute an objectionable odor. Some
food processing by-products fed to livestock are particularly
notorious. Ensiled cannery wastes, wet whey, cooked garbage, and
other decomposable materials deserve particular attention.
Recognize, however, that feeding of these by-products to live-
stock is frequently the best use for them thereby converting
them to nutritious feeds. The cost of solving the odor problem
must be balanced against the benefit of using what might other-
wise be a wasted resource with its inherent environmental cost.
Other odor sources include dead animals not quickly buried
or removed from the site, pesticide sprays, and manure handling
facilities. Each of these odor sources can be handled by
appropriate control procedures.
Odor Measurement and Analysis
Considerable effort has gone into identifying compounds
resulting from manure decomposition. These gasses, when released
into the air, are the odorous constituents. Ammonia, hydrogen
sulfide, skatole, indole, and the amines and mercaptans are the
most common. Although there is merit in identifying these com-
pounds as released, this help is limited in the design of an odor
control program.
More usable odor measurements include odor intensity more
often measured in the field with a Scentometer. This device con-
sists of a plexiglass box held in front of the nostrils so that
only air which has passed through an activated carbon filter is
inhaled. By standing on the site to be evaluated and breathing
through this device, it is possible to keep odorous compounds
from entering the nostrils. By selectively opening unfiltered air
ports, you can determine the ratio of odor-free air to dilute a
volume of odorous air to the barely detectable concentration.
This technique enables estimation of odor intensity. This esti-
mate can be used in documenting changes in odor intensity.
The measurement and estimation of odor detection frequency
has received widespread use for evaluating odor problems. This
approach attempts to determine the percentage of time that an
odor can be detected at the site where the receiver is located.
For example, if a home is near a pork production operation, it
might be important to estimate the percentage of time, (i.e., 5,
10, 20%), that odor would be detectable at that site. By consult-
ing available data on wind direction and velocity, temperature,
and relative humidity, it is possible to estimate odor distribu-
tion or frequency. This calculation is helpful in assessing the
severity of an odor problem.
Principles of Odor Control
Although odors seem mysterious and difficult to manage, the
principles of odor formation and control are relatively few and
straight-forward. For an odor to be detected downwind, odorous
compounds must be (a) formed, (b) released to the atmosphere, and
(c) transported to the receptor site. These three steps provide
the basis for most odor control. If any one of the steps is inhi-
bited, the odor will diminish.
Since odorous compound formation is generally the product of
biological decomposition, steps to stop odor formation generally
inhibit biological activity. Moisture reduction is the most com-
mon technique. By maintaining a manure-covered surface in a dry
condition (less than 40% moisture), anaerobic biological decompo-
sition is generally halted; odors are most prevalent immediately
following rainfall and when manure surfaces are allowed to remain
moist over an extended period. Other inhibiters of biological
activity of animal manure include chlorination, pH adjustment,
and in nature, temperature control.
Although odorous compounds may have formed in manure or
manure storage systems, few complaints will be registered unless
these compounds are allowed to escape into the atmosphere. The
most common means of inhibiting the escape of odorous compounds
is covered manure storage tanks. Covering inhibits the inter-
change of odorous compounds between the liquid surface and over-
lying atmosphere. This interchange may also be reduced by alter-
ing the chemical state of the compound of greatest concern. For
example, in regions where hydrogen sulfide is a major problem,
the addition of lime or other alkaline material will reduce
hydrogen sulfide volatility. This procedure should be tried on a
small scale, however, to make certain the chemical adjustment
will improve rather than worsen the odor problem.
Another means of preventing odor is inhibiting transport of
manure odor from the production and release site to the area
where odor control is necessary. Odor transport has been inhi-
bited in certain locations by the installation of sprays that
scrub the odorous materials from the air, and of barriers that
cause more complete mixing of the odorous materials with odor-
free air to achieve sufficient dilution. This approach has
received only limited application with livestock production odors
but is widely used in industry.
Odor Control Techniques
Perhaps the most critical and effective means of reducing
odor complaints occurs in the initial site selection. Although it
is difficult to set definitive perimeters beyond which odor will
not be a problem, a pork producer must seriously consider odor
control as he selects a site. Sites near residential develop-
ments, commercial enterprises, and recreational areas are partic-
ularly prone to problems. A site may be ideally suited for live-
stock production in terms of transportation, feed supply, and
zoning regulations, but may be inappropriate because of existing
or proposed development in the area.
There is a general relationship between the perception of
odor nuisance, separation distance, and size of a swine produc-
tion facility. For facilities of 1,000 or fewer animals the
incidence of odor complaints is noticeably reduced beyond one-
quarter mile. For larger units, separation distances of approxi-
mately a half mile are necessary for adequate protection.
Terrain is another factor to consider in site selection.
Facilities in a confined valley are particularly prone to have
odors drift down the slope with relatively little dilution. Such
sites should be avoided if residences or other odor sensitive
sites are downslope.
Although wind direction is important in evaluating an odor
control site, most locations have winds from several directions
during the year. The simple location downwind of development is
not sufficient. By referring to published data, one can estimate
the percentage of time the wind will blow from the odor source to
the point in question and thereby make a more rational decision
concerning site suitability. Where distance alone is used as the
criterion, it must be expected that odors can be transported in
excess of a mile downwind under appropriate climatic conditions.
If these conditions are sufficiently rare and the damage is
slight, this might not be an inhibiting factor toward develop-
ment.
The second opportunity for reducing odor problems occurs
during the design and construction of a facility. By application
of odor control principles, the probability of odor can be minim-
ized. Designing outdoor lots that are well drained, watering sys-
tems that do not flow onto the lot surface, and runoff control
facilities that are remotely located from areas of odor sensi-
tivity will achieve some odor reduction. In modern, roofed hous-
ing units the methods of manure removal from the pens, manure
transport, and handling are most important for odor control.
Also, animals must be kept clean and dry. Among approaches for
accomplishing this are slotted floors, flushing gutters, and fre-
quent pen scraping. Covered storage tanks control odor release
from stored manure. Where treatment is required and odor control
is important, aerobic systems such as oxidation ditches and
floating surface aerators, although more expensive, are effective
to curtail odor emissions.
The operation and management of a livestock production
facility also offer considerable opportunity for odor control.
Maintaining the operating systems is probably most important.
Overflowing manure storage tanks, broken scrapers, leaking water-
ers, and ruptured retention ponds and dikes are among the most
common causes of odor complaints.
Anaerobic swine manure treatment lagoons are of special con-
cern in odor control. Properly designed and managed lagoons are
not free of odors but seldom cause an odor problem. However,
overloaded or shock-loaded lagoons are more likely to have objec-
tionable odors. Where multiple-celled lagoons are used, it is
important that the cell or cells receiving fresh manure not be
loaded in excess of the recommendations for your particular area.
Anaerobic lagoon odors are most common in the spring and early
summer when the water temperature warms and manure accumulated
during the winter undergoes rapid decomposition. Another alterna-
tive is to add surface aeration sufficient to maintain the lagoon
surface in an aerobic condition.
Where practical, locate lagoons as far as possible from
neighboring residences, roads, and other odor-sensitive areas.
Separation distances are particularly important when anaerobic
lagoons are used. One helpful approach is to double the normal
separation distances. This may make the selection of anaerobic
lagoons inappropriate for larger (more than 1,000 head) facili-
ties in other than the most remote sites. Shielding lagoons from
view is also helpful.
Disposal techniques and timing are also important for odor
control. When manure is applied to cropland, a field downwind of
neighboring residences on that day is important. Morning applica-
tion is more desirable than late afternoons, which limits drying
time. Neighbors are generally most sensitive to odor problems in
early evening when utilizing outdoor recreational facilities.
When manure disposal is necessary and odor control is critical,
immediate incorporation of the manure can effectively minimize
odor complaints. Where soil is suitable and neighbors are par-
ticularly close, direct soil injection is a valuable technique.
The ``Extra Mile''
The above approaches generally provide great assistance to
the livestock producer in coping with complaints of neighbors.
When these techniques are not suitable, further steps must be
taken. Although some are experimental and have not received
widespread acceptance, they are worthy of consideration. There
are alternate waste treatment schemes that can be employed to
reduce odor emission. These are generally more expensive but may
be justified for larger enterprises or where site conditions or
separation distances are such that conventional treatment systems
release unacceptable levels of odor. These systems generally
require more sophisticated design.
Aerobic manure treatment systems are helpful. Most common
among these are oxidation ditches, aerated storage tanks, and
aerated lagoons. By maintaining manure in an aerobic condition,
odorous gas production is markedly reduced. For each of these
systems it is important that adequate aeration capacity be pro-
vided and that management is sufficient to keep the equipment in
top operating condition. Manure solids separation may be prac-
ticed ahead of each of these systems to minimize aeration
demands.
Anaerobic digesters similar to those used in municipal
wastewater treatment plants may be used for swine waste treat-
ment. Anaerobic digesters represent a significant initial invest-
ment and an ongoing operational demand; however, they provide
nearly complete control of the odorous gasses being released.
Some cost recovery can be effected where it is feasible to use
the biogas being produced to an economic advantage. Digesters do
not provide complete waste treatment, thus are most commonly cou-
pled with some means of effluent storage, either with or without
aeration.
Flexible covers have been applied to anaerobic lagoons in
situations where odor control is essential. These covers prevent
uncontrolled escape of odorous gasses. The collected gasses may
be burned or subjected to subsurface soil absorption. Lagoon cov-
ers require careful design to avoid premature weather damage and
allow convenient gas removal.
Air scrubbing equipment to reduce odor levels within swine
buildings has been studied and has been adopted in some European
buildings. It is not currently manufactured in the U.S.A. Most
building designers have been able to control odors within their
units by other means.
Odor control chemicals are widely available. Little data
exist concerning the effectiveness of most of these materials.
Some have been effective under specialized conditions; others
have been disappointing. The cost of using odor control chemicals
is highly variable, but generally they are an expensive alterna-
tive. Liquid products are quoted at $10-20 per gallon and solid
forms at $1-15 per pound. It is important that a trial be con-
ducted with the control chemical to make certain it operates to
your satisfaction before you buy large quantities.
Odor control chemicals are generally one of four types.
Masking agents have an odor stronger and, it is hoped, more
pleasant than the odor being masked. These chemicals may be
applied by aerial spray or directly to the odor source. They are
best used intermittently and only when anticipating severe prob-
lems. After prolonged use, neighbors may find the masking agents
more offensive than the original odorous compounds. Odor-masking
agents are perhaps the most predictable and generally the most
effective of the odor control compounds.
Odor counteractants, are materials that interact with odors
and result in less odor intensity. Owing to the great variability
in odorous gasses these compounds have had limited success.
Laboratory and limited field trials with odor absorption
chemicals provide some encouragement. These materials are most
successful when the absorbent powder or granule can be applied to
a solid surface to prevent the escape of target gasses.
Enzymatic products, designed to alter the biological path-
ways involved in manure decomposition, are available for odor
control. Again, only limited data are available on these materi-
als, and their success has been erratic.
Other techniques include perimeter spray systems and wind-
breaks to disperse the odors and shield the livestock enterprise
from direct sight. These and other approaches may be tried where
odor control is especially critical and the additional cost can
be justified.
An important ``extra mile'' effort involves being a good
neighbor and trying to influence your neighbor's attitude in a
positive way. Practice good public relations by sharing some of
the good things from your farm with neighbors. As an example, one
pork producer treats neighbors to some whole hog ground pork at
Christmas, plants extra sweet corn, has a neighborhood whole hog
barbecue, and contributes to worthwhile community projects.
Additional information can be found in the following PIH
fact sheets:
PIH-21 Systems of Runoff Control
PIH-35 Legal Guidelines for Swine Waste Treatment
PIH-62 Lagoon Systems for Swine Waste Treatment
PIH-63 Flushing Systems for Swine Buildings
PIH-67 Swine Waste Management Alternatives
PIH-76 Methane Gas from Swine Manure
PIH-91 Pumping Liquid Manure from Swine Lagoons
and Holding Ponds
PIH-95 Gravity Drain Gutters for Swine Manure
Systems
PIH-105 Scraper Systems for Removing Manure from
Swine Facilities
REV 6/88 (5M)
______________________________________________
Cooperative Extension Work in Agriculture and Home Economics,
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culture Cooperating. H.A. Wadsworth, Director, West Lafayette,
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