National Agroforestry Center
You may have heard it referred to as the
“smell of money,” but some people just think
it stinks. It’s part of any livestock operation,
sewage treatment plant, industrial sites like
paper mills, or landfills… odor. The good
news is that agroforestry practices like wind-
breaks can help—-these Working Trees real-
ly earn their keep! Plant species, density, and
placement are elements to consider when
designing a buffer for odor. Keep in mind
that a well-designed vegetative screen
is also pleasing to the eye and can
provide livestock benefits, too.
ODOR CAN TREES MAKE
Windbreaks 3 EMERGING TECHNOLOGIES
TO HELP CONTROL
between poultry farmers &
ODOR IS MORE
nearby community residents MEETS YOUR NOSE
rban expansion into rural areas commitment to being a good neighbor and an
where livestock are produced makes environmental steward.
maintaining good relationships a
challenge. Planting trees and shrubs as a
screen, however, can buffer odor, dust,
noise, and unpleasant views. Installing a veg-
Demonstrate Proactive Environmental
Dealing with ammonia emissions from
etative filter or windbreak is an opportunity poultry houses and its contribution to atmos- TRAPPING AIRBORNE
for poultry producers to not only increase pro- POLLUTANTS WITH FOREST EDGES
duction efficiency, but to demonstrate their see POULTRY on page 7
NAC Director’s Corner A commentary on the status of agroforestry
by Center Director, Dr. Greg Ruark
A New World Odor
he U.S. continues to grow by more than 3,000,000 people were done for other purposes that suggest windbreaks can be
each year. This population pressure is causing most of our designed to help alleviate some of the problem. For example,
cities to expand their boundaries. In addition, many fami- odor is attached to water and dust particles and is transported by
lies, in their search for open space, are constructing homes on wind . Windbreaks have been designed to modify wind move-
small tracts of rural land. As urban and residential dwellers ven- ment and trap dust for many decades. Tree species, especially
ture into areas that were previously rural in character, the differ- conifer types, have extensive leaf surface area that can interact
ences in lifestyles between farmers and city folks are becoming with water vapor and particulates that carry odor. Similarly,
painfully apparent. denser plantings will have a greater ability to detain or deflect
Farmers and ranchers view odors and dust that emanate from odors and agroforestry plantings that are properly located with
livestock, chemical sprays, and fertilizers as integral to the practice respect to the sources of odor will be more effective.
of agriculture and they have come to accept them as a part of life. It must be cautioned that there is still much to learn. For
In recent years the movement towards increasingly larger opera- example, what are the relative benefits of placing windbreaks on
tions for raising cattle, hogs, and poultry has resulted in situations the upwind and downwind sides of odor sources? What tree and
where large volumes of odor are generated at a given location. shrub species are best and what planting densities and intervals
What to do? This is a question that many are now asking. are needed? What are the maintenance requirements? Will it be
This issue of Inside Agroforestry attempts to identify and summa- necessary to periodically rinse the windbreaks so their foliage can
rize what is known about the potential of agroforestry technolo- retain its exchange capacity? However, one limitation we already
gies, particularly windbreaks, to attenuate odors. Although there know is that, as with most things, if a livestock operation
have not been a lot of research studies done specifically on odor or other odor generating activity gets very large not even
modification with trees and shrubs, there are numerous studies that Working Trees can offer much help.
It’s back!!! And it’s better!!!
he already-popular Working brochures are designed to help you
Trees for Communities inform and educate your clients
(WTC) brochure will make its including community members,
second, new-and-improved debut landowners, youth, and others. They
this summer. As agroforestry aware- are written for the landowner and
ness continues to grow so do NAC’s developed especially to aid you with
Working Tree publications. The publicity and technology transfer to
revised WTC brochure will address get Working Trees applied on the
many of the same issues as the first ground.
brochure including: the rural/urban Visit our website for a preview
interface, screening, dust and noise of any of NAC’s Working Trees
control, and enhancing the environ- brochures or coordinating displays:
ment for people, wildlife and recre- www.unl.edu/nac. You can also order
ation. But the new brochure will also publications from the website or, if
address storm water management, you prefer, contact Nancy Hammond
wastewater management, and green at: firstname.lastname@example.org or fax her
infrastructure. your request at 402-437-5712.
All of the Working Trees
2 Inside Agroforestry | Spring 2002
Windbreaks seem to offer bio-
logical, physical, and chemical
characteristics that can cleanse
the air of odor compounds.
Shelterbelts: an answer
Joe Colletti and John Tyndall
Forestry Department, Iowa State University
In a March 24, 2002 editorial the Des
Moines Register asserts that “ . . . a clean
environment is essential to the progress and
prosperity in Iowa.” They also indicate that
Iowa could lead the nation in both hogs pro-
duced and clean air. The potential of shelterbelts is related
Because odor is very difficult to mea- to livestock odor characteristics, such as: research suggests that reduced wind speeds
sure and human perception is variable, the odor sources are at ground level, odor cause drift pesticide to drop (70 percent to 90
odor issue is complex and requires numer- travels as aerosols and dust, and the odor percent) from the air stream. Simulation of tall
ous approaches to provide desired outcomes. plume at times hugs the land. Because of barriers around manure lagoons show reduc-
The livestock industry uses a suite of tech- these characteristics, shelterbelts of even tions of 26 percent to 92 percent.
nologies and management practices to deal modest heights (i.e. 20 to 30 feet) seem •By physical interception of dust and other
with air quality issues. About 95 percent of ideal for plume interception and disrup- aerosols - A forest cleans the air of micro-parti-
livestock odor is controlled by standard tion. Shelterbelts are also adaptable to cles twenty-fold better than barren land. Leaves
manure management. Yet livestock odor most production and odor situations. with complex shapes and large circumference to
control and clean air concerns continue to be area ratios collect particles most efficiently.
hotly debated. So, what new technologies There are several ways that shelterbelts can
ameliorate livestock odors: •By acting as a sink for the chemical con-
could be blended with standard livestock stituents of odor - Volatile Organic Compounds
practices to enhance odor control? •By facilitating dilution of odor into the lower (VOC’s) have an affinity to the cuticle of plant
An emerging technology is shelterbelts. atmosphere - Shelterbelts create surface turbu- leaves. They are adsorbed and absorbed. Micro-
Field-level shelterbelt and livestock odor lence that intercepts and disrupts odor plumes. organisms on plant surfaces can metabolize and
control research is limited, so initial esti- They lower wind speeds over manure storage breakdown VOC’s.
mates of shelterbelt efficacy are based on units allowing for slower release of odor.
•By providing a visual & aesthetic screen - A
allied research. Based on a large body of •By encouraging dust and other aerosol deposi- well-landscaped livestock operation is much
knowledge, shelterbelts have the potential to tion by reducing wind speeds - Wind tunnel more accepting to the public than one that is
be an effective and inexpensive odor control modeling of a three-row shelterbelt quantified not. Out of sight may be out of mind.
device particularly when combined with reductions of 35 percent to 56 percent in the
other control methods. downwind transport of dust. Pesticide drift see SHELTERBELTS on page 7
Spring 2002 | Inside Agroforestry 3
The science of
odor control is
ODOR IS MORE
closing T H A N W H AT
nose. MEETS THE NOSE
L reasons: odor is becoming an increas-
ingly contentious issue, primarily for
animal waste need to be processed. The
United States annually produces about 130
times more animal waste than human waste.
1) Livestock operations are continuing to Livestock odors occur as gases that are
grow in size, and released from microbial decomposition of
manure and other organic matter. These
2) More people are moving into rural
gases can include from 80 to 200 different
areas, thus closing in on many livestock
compounds that can cause odor. Some odors
can be detected at extremely low concentra-
These two changes over the past couple tions. Ammonia and hydrogen sulfide (rot-
of decades have set-up a collision course ten egg smell) are two particularly trouble-
between farmers and non-farmers as well as some odors. With so many possible odorous
neighbor against neighbor. Concerns about compounds, the interactions among the dif-
odors from large facilities goes beyond non- ferent combinations can cause either more
farm residents who may move toward the or less odor than a direct sum of the individ-
facilities, but also include many farm neigh- ual gases. Odors can also be absorbed and
bors when a large confinement facility transmitted by dust particles.
moves in next door. People do not like There are a variety of livestock odor
unpleasant smells especially from sources sources including livestock buildings,
that do not provide them direct benefit. manure storage facilities, and during land
To illustrate this dramatic change in application of the waste material. These
livestock operations, the Environmental sources can cause odor continuously or only
Protection Agency reports that the total during certain times or conditions. For
number of animal units increased about 4.5 example, the odor from a livestock building
million (about a three percent increase) from is generally constant, but odor from land
1987 to 1992. However, the number of live- application of livestock waste will occur
stock operations has decreased during the periodically and vary due to the weather
same period. conditions at the time.
Confined animal feeding operations are However, predicting odor impacts can
major contributors in meeting the produc- be a difficult process. Because the odorous
tion demands of consumers for meat, milk, gases and dust are transported by the wind,
poultry, and eggs. For this economical flow the impact area and magnitude can change
of food to continue, producers must have frequently depending on the wind direction
access to the best cost-effective technology and speed. Some of the gases are heavy and
to produce the commodities while protecting travel more closely to the surface while the
natural resources including air quality. lighter ones will disperse higher into the
atmosphere. The roughness of the surround-
Odor Sources & Transmission ing ground surfaces can vary through the
With a larger number of livestock in year and will impact how much of the odor-
greater concentrations, larger quantities of ous dust can be trapped.
4 Inside Agroforestry | Spring 2002
Epithelium. Epithelium. The flow of air through the nose
during normal breathing and
sniffing. Used by permission of
St. Croix Sensory, Inc. (1997).
Odor Effects The measurements of odor are further com- completely disappear. However, the science
People respond to odor differently. plicated by the variables that can occur at a and technology of managing odors is contin-
Although the human olfactory organ is quite site during sampling such as different weath- uing to develop. For example, the University
sensitive, the response to odor is related er conditions. Because of these variables, the of Minnesota has developed the Odor from
more to past memories or cultural experi- odor intensity at the time of sampling can Feedlots Setback Estimation Tool to aid
ences. There is not very much information easily be more or less than one hour earlier. Minnesota livestock producers in siting new
about the impact of odors on human health. livestock facilities. This tool is the result of
Most of the existing information refers to
Managing Odor four years of data collection and field testing
the adverse health effects individual gases, Odor management is a result of the with a variety of livestock facilities in
e.g. ammonia, or dust, but no specific infor- overall management of the farm operation. Minnesota.
mation about odors. One study did show General maintenance of the buildings and Windbreaks fall into this developing
that odors from a swine facility had a nega- the nutrition of the feed ration are normal category. Preliminary information suggests
tive effect on the moods of neighbors such farm management needs that can influence that windbreaks may be able to provide
as anger and frustration. These psychologi- odor emissions. Waste management plans some odor mitigation. For more informa-
cal impacts can be as significant as a per- have become a standard part of livestock tion about windbreaks and odor, see
son’s physical health. Due to these con- operations in recent years. Livestock odor Shelterbelts Answer to Growing Odor
cerns, effort is warranted to minimize odors management techniques fall into three areas: Concerns on page 3.
thus benefiting the community and the live- • Preventing the generation of odor - including
stock producers alike. Adapted from Understanding Livestock
feed additives, aeration, manure additives, etc. Odors by Ronald Sheffield, Animal Waste
• Capturing and destroying the odor - including Specialist and Robert Bottcher, Professor
Assessing Odor biofilters, waste storage covers, organic mats, and Ventilation Extension Specialist,
Measuring odor is a complex process. etc.
Biological and Agricultural Engineering
Although work is underway to develop an • Dispersing or disguising the odors - including Publication AG-589, North Carolina State
effective measuring device, the most com- vegetative or structural windbreaks, setback
distances, site selection, etc.
University and Offset: Odor From Feedlots
mon assessment approach, to date, involves
Setback Estimation Tool by Larry Jacobson,
the use of panels of people who sniff odors
The cost of several of the above tech- David Schmidt and Susan Wood, Dept. of
captured by an instrument from a particular
niques currently presents significant eco- Biosystems and Ag. Eng. University of
site. The panel will define the smell based
nomic barriers to implementing them. There Minnesota Extension Service. Publication
on several different parameters including:
are also some unanswered questions about FO-07680-GO, 2001.
• Concentration or threshold - what is the mini the effectiveness of some of the techniques. www.extension.umn.edu/distribution/live-
mum detectable concentration level Additional research is needed to refine the stocksystems/DI7680.
• Intensity - the strength of the odor above a different approaches and find the most tech-
certain threshold nically and economically effective methods.
• Persistence - the rate of change of the intensity What does the future hold
of the odor for the co-existence of livestock
• Character - what the odor smells like such as feeding facilities and the sur-
earthy, fruity, rotten, chemical, etc. rounding communities? The gen-
• Hedonic tone - the degree of acceptability or eration of livestock odor is a fact
offensiveness of the odor of life and will probably never
Spring 2002 | Inside Agroforestry 5
orest edges are a lot like windbreaks in that they represent a ical processes.” This research also indicates that the active filter-
sudden and dramatic change in vegetation and surface ing processes occur close to the forest or windbreak edge and that
structure that effect wind speed and direction. Researchers windbreaks may not need to be extremely wide, greater than 90
at the Institute of Ecosystem Studies investigated the effects of feet, to have an influence on trapping airborne pollutants.
forest edges, as a result of forest fragmentation, on wind-borne “In fact , the forest edges have been shown to act as
nutrients and pollutants. “hotspots” of deposition, showing up to a four-fold increase in
This study examined the concentrations of sulfur, nitrogen, the rate of atmospheric delivery compared with nearby areas
calcium and water at the forest edge, in the adjacent field and in without edges. Much of this enhanced deposition is thought to
the forest interior. All of the edge measurements were taken with- result from the dry deposition of particles and gases from the
in 10 feet of forest edge and the interior measurements were deposition of horizontally driven fog or cloud droplets. In these
taken between 75-90 feet of the forest edge. During the study cases, it is the abrupt structure of the forest edge that creates a
period the concentration of water was not discernably different in trap for horizontally driven materials.”
the study zones. However, there was a marked increase in total This research and similar research efforts indicate that wind-
sulfur, dissolved inorganic nitrogen and calcium at the forest breaks may be an effective tool in managing odors in urban and
edge over the amounts found in either the adjacent field or forest rural landscapes.
interior. These researchers “…demonstrate that forest edges
adjoining agricultural or urban landscapes are effective at scav- Adapted from “Forest Edges as Nutrient and Pollutant
enging and concentrating airborne nutrients and pollutants and Concentrators: Potential Synergisms between Fragmentation,
that the intensity of this effect is partly determined by the struc- Forest Canopies, and the Atmosphere,” Weathers, Cadenasso,
ture of the forest edge. These filtering and concentrating func- Pickett: Conservation Biology, vol. 15, No. 6, December 2001,
tions may have important ramifications for below canopy ecolog- pages 1506-1514.
Should you be receiving and
reading Inside Agroforestry?
Inside Agroforestry covers the latest agroforestry news
and information, and reaches an average of 9,500 natural
resource professionals across the country and internation-
ally three times per year. We’ve covered topics like:
Green Infrastructure & Communities, Specialty
Forest Products, Wildlife, Carbon, Marketing
Agroforestry, Small Farms, Water Quality,
Wildlife, and of course, Riparian Forest Buffers,
Windbreaks, Living Snowfences, Silvopasture,
and Alley Cropping.
If you or someone you know would like to be added to our
database or have updates to your address, please
contact Nancy Hammond at email@example.com
or fax information to her at 402-437-5712.
6 Inside Agroforestry | Spring 2002
Poultry Although trees around the perimeter of poultry houses offer
many potential advantages, there are some negative aspects to con-
continued from page 1 sider. These include: some land will be taken out of production,
cost of the trees, labor for planting and maintenance, restricted view
pheric nitrogen and fine particulates is representative of challenges of poultry houses, limited farm access to designated roadways, and
that all animal-related agriculture may face in the future. Trees strate- a potential habitat for wild birds.
gically planted on poultry farms may help reduce ammonia emissions Of course, success depends on individual farm situations,
by physically capturing both ammonia gas and the ammonia-laden house orientation, type of ventilation system, available tree species
dust particles. and width of the windbreak. Service roads, loadout areas and antic-
The roots of trees are effective in absorbing nutrients. More than ipated width of the tree spread at maturity are all factors when con-
80 percent of nitrogen and phosphorus can be kept from entering sidering tree spacing. Allow for property lines, dwellings, traffic
adjacent water courses through root absorption or reduction in over- visibility, surface and subsurface drainage rights-of-way, and over-
land flow. Trees also have the ability to clean the air by capturing head and below-ground utilities when placing trees.
carbon dioxide. Desirable features of trees for use with poultry farms include
maximum vegetative density with complex leaf shapes, waxy or
Increasing Production Efficiency “hairy” leaves for efficient filtering ability, tap or deep roots, wind
Properly established windbreaks are an energy-efficient, natur- tolerance, low maintenance and care, medium to fast growth and
al system that can reduce heating costs as much as 10 to 40 percent tolerance to nutrients found around houses. Shrubs and trees that
and reduce cooling costs by 20 percent for poultry houses. attract wild birds due to seeds or nesting site and those with a wide
Windbreaks can also serve as a living snowfence. A tree wind- crown that obstruct traffic may be undesirable for some operations.
break can capture up to 12 times more snow per foot of height than Extracted from “The Benefits of Planting Trees Around
a picket fence, and it is 90 percent less expensive. Poultry Farms.” By George Malone, Extension Poultry Specialist
Another potential benefit may be improved biosecurity. By and Dorothy Abbott-Donnelly, Extension Agent-Renewable
restricting airborne particulates, trees may aid in blocking airborne Resources. University of Delaware Extension Bulletin 159.
poultry diseases from entering, as well as exiting, your farm. www.rec.udel.edu/Poultry/tree_buffer.pdf
Figure 1. A shelterbelt system
3,4,1,2 design for a hypothetical swine
production facility. The numbers
Hog confinement refer to the functional interac-
tion and means by which the
shelterbelt will mitigate livestock
1,3,2,4 odor. The number 1 refers to
Ventilation creation of air mixing turbu-
lence, the number 2 refers to
dust deposition, the number 3
1,2 refers to particulate interception,
and the number 4 refers to sites
Field for land of air pollution sinks. Other
Storage lagoon application important design considerations
Waste storage include: livestock type, odor
sources, air/wind patterns, the
1,2 species of trees/shrubs used,
Shelterbelts teristics that can cleanse the air of odor
compounds. Also, they are flexible in
pelling evidence exists that they will help
to further reduce odor.
continued from page 3 design. Further, they are relatively low
cost adding only pennies (<$0.20) per ani- For more information, contact Joe Colletti,
A generalized windbreak is shown in mal and seem to provide psychological- Associate Professor of Forest Economics or
Figure 1. This design provides “buffering” aesthetic values as well. Researchers agree John Tyndall, Research Assistant, Forestry
around the sources of odor and is adaptable that multiple control strategies increase Department, Iowa State University, (515)
for most types of livestock systems. the effectiveness of odor reduction. 294-4912 or visit our website at
Based on some direct and mostly Clearly much work needs to be done to http://www.forestry.iastate.edu/res/
indirect analysis, shelterbelts seem to offer quantify the efficacy of specific shelter- odor_mitigation.html
biological, physical, and chemical charac- belts and livestock operations, but com-
Spring 2002| Inside Agroforestry 7
June 27, 2002 July 20, 2002 October 5-9, 2002
Pacific Northwest Special Forest Association for Temperate Society of American Foresters
Products Council Workshop. Agroforestry Annual Meeting. National Convention.
Springfield, OR. Contact: John Hegg, Lanesboro, MN. Contact: Dean Winston-Salem, NC. www.safnet.org/
541-683-6644, firstname.lastname@example.org Current, 612-624-4299, calendar/presentations.
July 13-17, 2002 email@example.com. October 25-26, 2002
Soil and Water Conservation Society August 23-24, 2002 Special Forest Products Production
2002 Annual Conference. Special Forest Products Production and Marketing Conference. Cape
Indianapolis, IN. Contact: Nikki and Marketing Conference. Girardeau, MO. Contact: Julie
McClain, 765-747-5531, www.hoosier Sinsinawa, WI. Contact Mike Bolin, Rhoads, 573-882-3234,
chapterswcs.org/activities/settingpace 217-333-2778, firstname.lastname@example.org. RhoadsJ@missouri.edu.
Inside Agroforestry is published quarterly by the USDA
National Agroforestry Center. Mission
Phone: 402-437-5178; Fax: 402-437-5712.
The USDA National Agroforestry Center (NAC) is a partnership of the Forest Service, Research &
Greg Ruark, Center Director ext. 27 Development (Rocky Mountain Research Station) and State & Private Forestry and the Natural Resources
Michele Schoeneberger, FS Research Lead ext. 21 Conservation Service. The Center’s purpose is to accelerate the development and application of agroforestry
Rich Straight, FS Lead Agroforester ext. 24
technologies to attain more economically, environmentally, and socially sustainable land-use systems. To
Bruce Wight, NRCS Lead Agroforester ext. 36
Kimberly Stuhr, TT Specialist/IA Editor ext. 13 accomplish its mission, the Center interacts with a national network of partners and cooperators to conduct
Ryan Dee, TT Assistant ext. 14 research, develop technologies and tools, establish demonstrations, and provide useful information to natural
Mike Majeski, FS Agroforester resource professionals.
St. Paul, MN phone: 651-649-5240
Jim Robinson, NRCS Agroforester
Fort Worth, TX phone: 817-509-3215 USDA policy prohibits discrimination because of race, color, national origin, sex, age, religion, or handicapping condition.
Gary Kuhn, NRCS Agroforester Any person who believes he or she has been discriminated against in any USDA-related activity should immediately con-
Spokane, WA phone: 509-358-7946 tact the Secretary of Agriculture, Washington, DC 20250.
www.unl.edu/nac Opinions expressed in Inside Agroforestry are those of the author and do not necessarily represent the policy of the USDA
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Inside Agroforestry | Spring 2002