WASTE MANAGEMENT                                  PIH-33


           Controlling Odors from Swine Buildings

J. Ronald Miner, Oregon State University
Clyde L. Barth, Clemson University

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-

     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

     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

     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
PIH-105   Scraper Systems for Removing Manure from
          Swine Facilities

REV 6/88 (5M)


Cooperative Extension Work in  Agriculture  and  Home  Economics,
State  of Indiana, Purdue University and U.S. Department of Agri-
culture Cooperating. H.A. Wadsworth,  Director,  West  Lafayette,
IN. Issued in furtherance of the Acts of May 8 and June 30, 1914.
It is the policy of the Cooperative Extension Service  of  Purdue
University  that  all  persons  shall  have equal opportunity and
             access to our programs and facilities.