CIS 1148

University of Idaho • College of Agricultural and Life Sciences

Odor Control Practicesfor Northwest Dairies

IntroductionOver the past several years, an increasing

number of large confined animal feeding opera-tions have been built in the Pacific Northwest.Large animal farms produce huge quantities ofodor-causing manure. The ever-increasing ruralpopulation results in conflicts, especially withdairy farmers. People living close to these feed-ing operations have the most problem withodors produced by the farms.

Little information is available on the impactof odor and airborne contaminants from live-stock operations on human health. Gases likeammonia (NH3) and hydrogen sulfide (H2S) athigh concentrations have negative effects onhumans. However, little data is available toshow definitive effects on health at low-levelexposure to these gases. Some states have evenput air quality standards into effect to controlthe amounts of ammonia and hydrogen sulfidereleased into the atmosphere.

There are various ways to prevent or eveneliminate odors produced from dairies and othersimilar operations. A livestock farm operatorwill need to consider the size of the farm, itsproximity to non-farming neighbors, the loca-tion of existing farm buildings, topography,weather conditions, and governmental regula-tions to draw an effective odor managementplan. General information on odors and howthey are perceived, the source of odors, theimportance of dairy farm site selection, andgood management practices are also itemsneeded to help with the odor problem.Understanding airborne contaminants’ move-ment and odor intensity is a must in evaluatingand minimizing the effects of odor emissions.

Contents

Sources of odor emissions . . . . . . . . . . . . . . . 2

Physical factors affecting odors . . . . . . . . . . 3

Open lot facilities . . . . . . . . . . . . . . . . . . . . . . . 3

Manure handling and storage systems . . . . 6

Composting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9

Anaerobic digesters . . . . . . . . . . . . . . . . . . . . . 9

Aerobic treatment . . . . . . . . . . . . . . . . . . . . . 10

Loading manure storage basins . . . . . . . . . 10

Manure additives . . . . . . . . . . . . . . . . . . . . . . 11

Land application . . . . . . . . . . . . . . . . . . . . . . . 12

Odor management plans. . . . . . . . . . . . . . . . 14

Facility odor sources . . . . . . . . . . . . . . . . . . . 14

Tiered odor control implementation. . . . . . 16

Public involvement . . . . . . . . . . . . . . . . . . . . . 16

Tables/Figures

Table 1: Mechanical separators . . . . . . . . . . 8

Table 2: Odor reduction & land application 12

Table 3: Typical odor management plan . . 14

Table 4: Information needed in OMPs. . 14-15

Table 5: Potential odor sources . . . . . . . . . 15

Table 6: Odor control management practices

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19-22

Figure 1: Manure placement by injectors 13

by Ron E. Sheffield, Pius Ndegwa, Mike Gamroth, Mario de Haro Marti

This publication will focus on four keyissues: understanding odors, selecting odor con-trol technologies and practices, developing odormanagement plans, and responding to com-plaints from neighbors. Methods of mitigatingodors will be discussed; for example, mechani-cal, chemical, and biological control of odors.Additionally, Table 6 is a comprehensive list ofodor practices and technologies that may beconsidered for control of odors on dairies in thePacific Northwest. The table is a list of sugges-tions for reference and should not be used as alist of required practices for any or all dairies.The selection of odor control practices should bemade along with production goals, inventory ofexisting infrastructure, regulatory requirements,the intensity of the odor problem, and the farm’snutrient management plan.

Sources of odor emissionsLivestock odors arise from many different

sources. More than 160 odorous compoundshave been identified coming from dairy, beef,swine, and poultry manure. Some of these gasesare said to contribute to global warming andacid rain production. There are four primarysources of odor from animal facilities: livestockbuildings and/or open lots, manure treat-ment/storage facilities, manure transport or con-veyance systems, and areas of land application.

Livestock stations—importance of dustreduction. Dust harbors gases, odors

Many variables cause odors that are almostimpossible to eliminate. A combination ofmanure solids, dander, hair, bedding, and feedare the cause of the majority of the dust prob-lems in animal feeding operations. Other factorsinclude animal activity, temperature, relativehumidity, ventilation rate, stocking density, andfeeding methods. Dust harbors gases and odorsand, therefore, dust reduction can significantlyreduce problem odors.

Tools can aid in the reduction of dust.Mechanical ventilation is very effective inremoving gases and dust from production barns,but it emits these compounds into narrow,highly concentrated plumes. Windbreak walls,biomass filters, and biofilters will help reduce theamount of dust that will travel downwind froma mechanically ventilated facility. Frequentcleaning and sprinkler installation are alsoeffective methods used in open lot production.

Sprinklers and cleaning are most helpful inevenings when animals become more active.However, there is some concern using thismethod because wet conditions may exacerbateodor release.

Manure treatment/storage facilities—sourceof most odors

Most of the odors from dairies come frommanure storage. There are two common types ofmanure treatment/storage facilities: liquidmanure storage and solid manure storage.Liquid waste is stored in storage basins whilesolid waste may be stockpiled or composted.

Liquid manure: Two common ways to storeliquid manure are storage ponds and formedtanks (settling basins). Formed tanks are con-structed of steel or concrete and located belowthe floor or possibly in another building above orbelow ground. Unlike in lagoons, liquid manurein these structures has no extra water added toenhance microbial activity. The surface area ofthese tanks is smaller than that of storage pondsor anaerobic treatment lagoons. These tanks pro-duce stronger odors than lagoons because themanure is more concentrated. Impermeable cov-ers can be placed over the top of tanks or basinsto prevent odor from escaping.

Solid waste: Odors from solid waste storageare usually considered to be less offensive thanthose from liquid storage. The solids removedfrom the liquid after a solid-liquid separationcan be either stockpiled or composted. Stackingis for storage only, while composting is for bothtreatment and storage. For the solid manure tobreak down (biodegrade), the appropriate ratioof carbon to nitrogen, porosity, and moisturelevel must be provided. Frequent mixing or turn-ing of non-composted material increases thetreatment efficiency, thus reducing the time inwhich the material is stabilized. Solid manurecan be stored indoors to prevent exposure towind, blown soil, and rain.

Land application of manure areas—biggestsource of complaints

Typically, more than 50 percent of all odorcomplaints filed nationwide occur duringmanure applications. When manure is appliedto land, its exposed surface increases allowing alarge odor plume to form. One way to solve thisdilemma is to directly rapidly incorporate orinject the manure into the soil. Odors can alsobe caused if concentrated liquid manure is

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pumped through the irrigation systems at highpressures or without dilution.

Other emission sources

Dead animals are potential sources of odor.Proper disposal of dead animals is a must.Animals should never be disposed of in manurebasins or storage pits. Truck and tractor activitycan cause large amounts of dust. Heavily trav-eled roads should be graveled or watered regu-larly to keep the dust down.

Physical factors affecting odorsThe physical environment affects emissions

of odors on or off the farm. Although little canbe done to change the weather, managementstrategies can be used to reduce odors beforethey escalate. Some factors that can be managedare oxygen, temperature, moisture content,time, dilution, air stability, and dust.

Oxygen: The presence or absence of oxygenin a material can affect the odor it emits.Situations where oxygen is limited or not presentcreate anaerobic environments and producemore odors than situations with plenty of oxy-gen (aerobic environments).

Temperature: The greater the temperaturethe faster biological reactions occur. Every 20°Fincrease in ambient temperature doubles thespeed of biological reactions. Anaerobic condi-tions speed the production of odors but shortenthe duration of odor production. Aerobic condi-tions speed bio-stabilization of the waste result-ing in reduced odor production.

Moisture content (MC): Moisture contentaffects reactions that occur in decomposingmaterial. The higher the water content, the lessoxygen is present, again causing more intenseodors. Water in decomposing material can alsobecome volatile and produce odors that mixwith the air. Lower levels of moisture can slowbiological reactions that produce odors.

Time: The longer a substance is allowed todecompose, the more the odors produced willbecome more offensive. However, the majority ofodors are produced in the first three to five daysof decomposition. Odor production or releasedecreases with time because organic materialbreakdown rates also decrease with time.

Dilution: The intensity of an odor is reducedas the dilution ratio is increased. High concen-trations of organic material and poor ventilation

are a perfect foundation to produce highly con-centrated odors.

Air stability: Air stability can be affected bywind speed, air temperature, and topography.These factors are very hard to manipulate orchange; however, management tools can be usedto reduce the spread of odors by these factors.

Dust: Odor compounds can easily attachthemselves to dust particles. Dust reductionaround an animal operation is, therefore, aneffective method of reducing odor dispersionfrom the source.

Open lot facilities—importance of water management

Environment and short-term weather pat-terns are the primary cause of dust and odoremissions from confined animal facilities.During low moisture conditions, dust is the pri-mary problem in open lots. Under high moistureconditions, odor is the primary problem. Watermanagement is very important to controllingodors produced by open lot facilities. Keepingboth dust and odor at their minimum levels bymoisture management is impossible, but whenthe moisture content of an open-lot surface is 25to 40 percent, both dust and odor are at man-ageable levels. When optimal moisture contentis reached, other manure properties such asdepth, bulk density, and texture become moreimportant factors in controlling dust and odor.

Managing open lot odor

The three most important ways to controlodor are avoiding anaerobic conditions by keep-ing (a) manure and other organic materials asdry as is practicable, (b) manure storages andsurfaces exposed to oxygen, and (c) corral sur-faces hard, smooth, and free of uncompactedmanure.

Open lot design—eight suggestions

New facilities and expanding operationshave the best opportunity to implement odorreduction designs. Existing lots can also be mod-ified to use new designs to help reduce theamount of odor produced. Here are eight sugges-tions.

1. Slopes: Open lot surfaces should have aslope of 3 to 5 percent down and awayfrom the feed apron to move rainwateraway and reduce the likelihood of pro-

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ducing puddles that can turn anaerobic.Mounds can be used to enhance drainageof the lots. In some situations, moundsmay not be practical because of impairedlivestock performance.

2. Runoff: Slopes should also minimizepen-to-pen runoff. This will help preventwater from puddling behind manureridges that develop under fence linesbetween corrals.

3. Corral access: Provide convenient accessto corrals. Frequent removal of manurewill ensure proper drainage.

4. Firm soils: Use corral soils that are firm,stable, and not easily eroded into rills andgullies. Eroded corrals are prone to detainwater.

5. Fill soil: A supply of fill soil may be help-ful in maintaining lots. Use the soil to fillareas where erosion and gouging occurs.This will help fill areas where puddlesmay form.

6. Design: Design pens to have an edge-to-edge manure removal. Odd-shaped pensare harder to maintain. They make itmore difficult to remove the manureproperly. Hard, smooth, rectangular-shaped pens are the most effective formanure removal.

7. Drain channels: Minimize the potentialfor backwater from major drainage chan-nels. Temporary flooding in the bottomend of corrals can be a source of strongodors. Maintain drain channels to ensurethere will be no backwater in the corrals.

8. Divert rainfall: Divert clean rainfallrunoff around corrals and manure stor-ages to relieve pressure on the holdingpond and reduce the amount of waterthat is potentially detained on the corralsurface or around the base of manurestockpiles.

Mounds: 3 reasons for them

Manure mounds are constructed in flat,open lots for three reasons:

1. Temporary storage for excess manure. 2. Cattle refuge from muddy, wet, and cold

conditions. 3. Means to enhance the water-shedding

efficiency of corrals with little or no slope.

Mounds should be placed parallel to theslope of the lot. This will prevent the moundfrom blocking water flow. Round mound topspromote good drainage and avoid creating holesfor puddling. A shallow “W” lot cross-sectionalshape is preferred to reduce slope lengths,increase drainage, and reduce manure accumu-lation along fences. Manure mounds requiremaintenance to work properly.

Stabilize the mound by mixing the upperhalf of the mound surface with chopping bed-ding, a soil mix, or by disking in lime. Barn limeor hydrated lime reacts more quickly than agri-cultural limestone. Start by adding one pound oflimestone per square foot of mound; add morelime until the mound surface is stable. Fly ashproduced by power plants can also stabilize thesoil, but may be very heavy in toxic cadmiumand lead. If the quality of the ash is low, the sta-bilizing capacity will be low. Some states mayalso regulate the use of fly ash, so be sure tocheck state regulations.

Lot maintenance helps limit odor emissions

Open lots will always need some type ofmaintenance to keep odor emissions low.Again, the key is to keep the corral surface hard,smooth, and as dry as possible, maintaining afirm 1- to 2-inch base of compacted manureabove the mineral soil.

Frequent and proper removal of manure willhelp maintain open lots. Removal of manuredaily when cows are in the milking parlor willkeep the corral surface in excellent shape.Manure removal equipment needs to beadjusted to ensure the 1- to 2-inch layer of com-pacted manure above the mineralized soil.Weekly removal may be a more economicaloption and a better management tool to use inyour operation. If manure is not removed daily,lots should be harrowed to break up manuredroppings and to help dry urine spots.

The type of blade used to scrape the corralcan affect the efficiency of water removal.Scraper blades that are pushed make it more dif-ficult to obtain optimum manure depth andsmooth surfaces. Push blades often gouge or scarthe surface and reduce the ability for the corralto shed runoff water. Blades that are pulledleave a smoother surface. Training of machineryoperators in the proper techniques and methodsis important.

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Frequent inspection of corrals for damagelike pits, holes, and wallows is important to asound management program. This could be assimple as having the feed truck driver, nightwatchman, or pen riders scout for problems inpen maintenance. The sooner the damage isfixed, the fewer problems will result. Holes andwallows near watering troughs and feedingareas should be a high priority.

Water supply maintenance is essential toprevent puddling of overflow water. Leaky watersystems like overflow waterers, misters, and lotsprinklers can make a significant contribution toodors produced. Feedlot employees should betrained to watch for malfunctions in wateringsystems.

Fence lines need to be inspected to removeany ridges of manure that form under them.The ridges will form dams that will back up theflow of water in the corral and produce odors.The water that puddles because of this is also theprime breeding ground for insects.

Open lot runoff control structures

• Corrals: Design corrals, settling basins,and open channels to avoid clogging,backwater, and poor drainage.

• Settling channels: Where settling chan-nels are used to reduce solids loading inholding ponds, make sure machineryaccess for solids removal is convenientunder all weather conditions.

• Lagoons: Improve lagoon performanceand reduce odor potential by monitoringsludge consistently and removing sludgein a timely manner.

• Holding ponds: Use natural topographyto make shallow holding ponds. Thisoption is less prone to anaerobic condi-tions but is probably not feasible in highrainfall areas.

• Holding ponds: Pump down holdingponds as soon after storm events asweather permits.

Dust management plan for open lots

There are many things in common betweendust control and odor control. Dust is producedwhen dry manure is crushed into smaller parti-cles from the activity of livestock. When the ani-mals move around the corral, manure dust issuspended in the air. The peak times of day for

dust accumulation in the air are late afternoon,evening, and early morning hours because after-noon heat, wind, and solar radiation removemuch of the moisture leaving it dryer than anyother times of the day. As the temperatures coolin the evening, cattle become more active. Theywill move to the feed bunk and start social activ-ities. The atmosphere becomes more stablebetween dusk and midnight than during theafternoon so more manure particles suspendedin the air by cattle activity tend to remain nearthe ground.

The three general approaches to dust con-trol include:

• Remove dry, loose manure from the corralsurface;

• Maintain moisture regime at the corralsurface to within 25 to 40 percent moisturecontent; and

• Attempt to reduce peak cattle activity dur-ing the critical late afternoon hours.

Lot design: avoid dust, moisture accumulation

The most effective way to manage odor anddust in an open lot is to make sure there is noaccumulation of moisture in small, localizedareas. In semi-arid and arid regions, applyingsupplemental moisture to maintain optimummoisture content in the corral surface often off-sets daily evaporation. Water trucks should haveeasy access to a water supply throughout theyard. Deadheading or rolling empty should beavoided over long distances.

It has been proven that reduced stock densitywill reduce the amount of dust in the air by 29percent. This works best in areas of moderateannual rainfall. Stocking densities can have aneffect on the behavior of the animals. In cases ofhigh density, there is a greater chance of stressand reduced performance. Managers shouldexperiment carefully with stocking density on asmall scale to avoid disaster. Research is notclear on what the limit is. This relationship hasyet to be fully understood.

Other emission reduction options

In high-risk areas close to larger populationsand more traffic, additional steps may need tobe taken to reduce emissions. Solid-set sprinklers,vegetative barriers, and improved manureremoval equipment may increase the effective-ness of the management scheme.

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Solid-set sprinkler systems

Solid-set sprinkler systems work very well indryer climates, but they are expensive. Sprinklersystems require a great deal of site-specificdesign based on seasonal water balance calcula-tions, but in general terms, systems should havethe following characteristics:

• Sufficient capacity to deliver 0.25 inches ormore of water per day evenly across theentire yard

• Sprinkler patterns that overlap by 50 per-cent of the diameter of throw

• Sprinklers located so that their throw doesnot extend all the way to the feed apron

• Water that is drawn from a holding tankto avoid creating a demand peak on themain water system that may reduce drink-ing water delivery during hot afternoons

The use of holding pond water is an experi-mental technique. Using this method couldamplify the possibility of increased disease trans-mission among livestock.

Vegetative or artificial barriers

For odor control around open lots, vegeta-tive, and artificial barriers may be used toincrease dispersion around open feedlots by ele-vating dust-laden air from the ground surfaceand mixing it with cleaner air above. Fast-grow-ing trees also provide a visual barrier that mayreduce nuisance complaints and improve rela-tions with neighbors and passers-by.

Manure removal equipment

All equipment should be operated by skilledemployees to ensure a firm, smooth, and evenlygraded corral surface. Box scrapers do an excel-lent job because it is easy to adjust the bladeheight.

Manure handling and storage systems

Noxious odors can be generated whenmanure is stored for as little as three days.Application of stored manure on land can bedetrimental to the air quality in the surroundingarea. Storing manure makes it possible to applywhen the nutrients in the manure will benefitthe plants the most, reducing water pollutionand complying with state and federal regula-

tions. However, long-term storage may producestrong odors. A thoughtful review of how yourfarm manages its manure is the first step in pre-venting offsite odors.

The location of the manure storage facilityneeds to be carefully considered. Anything thatcan be done to create a larger area of separationbetween the storage facility and the closestneighbors will be an advantage to the farm. Itmay benefit the farm to have the storage sitenear the fields where the manure is to be spread.This will reduce labor costs at spreading timeand also reduce the concentration of vehicletraffic between the barn and fields.

Open storage systems can cause seasonalproblems with odor. Day-by-day changes in theweather can affect odors produced. Manure stor-age is usually the main focus of the sources thatcause odors. However, collection pits, separationbasins, and flushing of recycled pond effluentcan also be major sources of odor on the farm.Even though these may be much smaller in sur-face area, these structures may comprise themajority of a farm’s odor emission. The follow-ing methods may be implemented to provideadditional odor control:

• Covers• Liquid-solid separation• Composting• Anaerobic digestion• Liquid aerobic treatment• Manure additives

Covers

Odors from open manure storage facilitiescan be significantly reduced by properly cover-ing the stored liquid. Covers reduce the amountof odor, hydrogen sulfide, ammonia, andvolatile organic compounds that are emittedfrom stored liquid manure. Such reductions aremade possible by: 1) minimizing the amount ofsurface turbulence in the liquid, 2) providing amedia for beneficial bacteria to grow and trans-form these compounds as they move throughthe cover, and 3) containing odorous gases untilthey are treated via a biofilter. The main disad-vantages of covers are their initial cost and/ormaintenance. When selecting the appropriatetype of cover, consider:

• Type and size of manure storage system.• Type of manure treatment system (if any).

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• Frequency of pumping.• Amount and quality of labor available.• Cost of the cover material.The surface area of the cover is typically how

the price is determined. The larger the surfacearea that needs to be covered the higher the cov-ering cost. Impermeable covers have been con-structed and maintained over storage ponds of25-acres or larger for more than 15 years.

Rigid and flexible covers

Rigid covers are commonly made of con-crete, wood, and PVC and are used on small andmedium sized pits and settling basins. They canreduce odors from a pit as long as the manure isnot agitated. Lightweight roofs made of fiber-glass, aluminum, and flexible plastic mem-branes, can be used to contain odorous gases.These types of covers are usually more expensivebut last much longer than other types of covers.On average, the typical rigid cover lasts 10 to 15years. Non-corroding materials can extend thelife of covers. Without non-corroding materials,covers will only last a few years.

Flexible covers can be used to contain odorsfrom an outdoor system. The tarp is attached tothe systems perimeter as tightly as possible.There is a center support column with radiationstraps that supports the outer shell. Air is forcedin under the cover with a low-pressure blower.This blower will maintain a constant operatingpressure. During agitation the cover is deflatedallowing it to lie on the support straps.

Permanent roofs constructed of wood, con-crete, or an inflated cover can reduce odors asmuch as 80 percent. Rigid roofs prevent the lossof ammonia gas by 80 percent. In one study,hydrogen sulfide and ammonia emissions werereduced by 95 percent when an inflated coverwas used.

Floating covers

Floating covers can be made from naturaland artificial floating materials. Natural coversare usually formed from fibrous materials in themanure and appear as floating crusts. Artificialfloating organic covers, called bio-covers, arecommonly made of straw, chopped cornstalks,sawdust, wood shavings, rice hulls, and manyother similar materials. Polystyrene foam, plas-tic mats, and geotextile fabric are also used ascovers.

Covering the surface of liquid manuregreatly reduces gases that are emitted into theatmosphere. Permeable covers, like straw, reduceodors by as much as 60 to 85 percent. When anaerobic layer is established on the surface of theliquid, odorous compounds that escape are bro-ken down aerobically before they are releasedinto the atmosphere. Barley, wheat, andchopped cornstalks are used to form an organicfloating cover. Straw is applied to the manurestorage systems with a chopping/blowingmachine. The cost, labor involved, and the lifeof the cover may vary considerably for organiccovers.

Researchers in Germany have estimated theuseful life of a straw cover to be six months.Other studies indicated that a 2- or 3-inch layerof straw would only last for several weeks.Studies conducted in Canada indicated that alayer of straw 6 inches in depth could last threeto five months only requiring applications ofnew straw in small areas. Overall, 8-inch thick-nesses may work for odor control, but 12 inchesare needed for extended life. Straw may vary incost considerably. Special equipment is alsorequired to apply the straw on the manurebasin.

Other floating permeable covers, such asgeotextile fabric, provide a more permanentlong-term solution than straw covers. There hasbeen a significant reduction in the levels ofhydrogen sulfide, ammonia, and odor whengeotextile covers are used. Because of the diffi-culty in lifting the covers, geotextile covers areespecially suited to facilities where manure isnot frequently agitated and/or completelypumped out. After the removal of the manure inthe fall, the geotextile may sink to the bottom ofthe pit and become partially submerged whennew manure is added. In colder winter months,this is not a problem because biological activityis reduced. When spring comes, it may take sev-eral months for the geotextile to dry out andfloat again. Supports may need to be placedunder the geotextile to keep the cover frombecoming submerged. The average lifeexpectancy of a geotextile cover is five to sevenyears. It costs approximately $0.25 to $0.32 persquare foot.

Floating plastic cover sheets are also used toreduce odor emissions. A plastic cover developedin Canada is an inexpensive and lightweightsystem. Air pressure under the plastic is created

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with fans and a perforated pipe system to holdthe plastic cover up. Fans are used to produceuniform air pressure. Perimeter sealing may be aproblem if the manure needs to be agitated orpumped frequently.

Liquid-solid separation

One way to reduce energy costs for an aero-bic system or to reduce the loading on an anaer-obic lagoon is to remove solids from the manurestream ahead of the storage. By separatingsolids, biochemical oxygen demand (BOD) andnutrient loading are reduced on liquid systemsdownstream. Two methods to remove solids frommanure include mechanical separation andgravity settling.

Mechanical separators

Mechanical separators of animal wasteinclude: inclined screens, vibrating-screens, beltpresses, and screw presses. Manure is collected ina pit sized to store all the flush water to be useduntil separation is done. A submersible or sta-tionary bottom-impeller lift pump mixes themanure and liquids into a slurry and pumps itacross the separator where the liquid drains offto storage as the solids accumulate below the

separator. These devices are modestly effective inremoving solids producing a product with amoisture content of between 60 and 70 percent(Table 1).

Separators with few moving parts, such asinclined screens and vibrating-screens, are moreeffective when large amounts of water aremoved through the devices, such as in flushingsystems. Most mechanical separators requiredaily cleaning and flow adjustments. Screenswill need to be replaced periodically when thesolids removal rate decreases.

Gravity separation

A gravity settling basin is cheaper and canremove 50 percent or more of the solids from liq-uid manure. Solids can be settled and filtered bya shallow basin (2- to 3-feet deep) with concretefloors and walls and a porous dam or perforatedpipe outlet. Basins should allow access by afront-end loader to remove solids when neces-sary.

An alternative is an earthen settling basinfor 6- to 12-months storage of solids. The basintop width should be no more than 100 feet witha length-to-width ratio near 3:1 and a liquiddepth of 8 to 10 feet. Basin contents should be

Table 1. Performance of mechanical separators (Source: Zhang, R.H. and P.W. Westerman, 1997)

Total Solids Separation Efficiency (%)Separator Animal Screen Size in Raw Manure Total Total Kjedhal Total

(mm) (%) Solids COD Nitrogen Phosphorus

Stationary screen

Swine 1.5 0.2 – 0.7 9 24 – –1.0 0.2 – 0.7 35 69 – –1.0 1.0 – 4.5 6 – 31 0 – 32 3 – 6 2 – 12

Dairy 1.68 4.6 49 – –Vibrating screen

Swine 1.7 1.5 3 6 – –0.841 1.5 – 2.9 10 1 – 14 – –0.516 1.8 27 24 – –0.516 3.6 21 – 52 17 – 49 5 – 32 17 – 34

0.39 0.2 – 0.7 22 16 – –0.44 1 – 4.5 15 – 25 13 – 26 2 – 5 1 – 150.104 3.6 50 – 67 48 – 59 33 – 51 34 – 59

Dairy 1.7 0.9 – 1.9 8 – 12 – – –0.841 1 – 1.8 12 – 13 – – –0.6 1 – 1.7 10 – 16 – – –

Rotating screen

Swine 0.75 2.5 – 4.12 4 – 8 4 – –0.8 1 – 4.5 5 – 24 2 – 19 5 – 11 3 – 9

Belt press

Swine 0.1 3 – 8 47 – 59 39 – 40 32 – 35 18 – 21Centrifuge

Swine – 1 – 7.5 15 – 61 7.8 – 44 3.4 – 32 58 – 68

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thoroughly agitated and removed for landspreading either by liquid manure spreader orslurry irrigation. If an earthen basin is used, pro-ducers may be required to make regular inspec-tions as required by their permit. The damstructure and waste level must be constantlymonitored, and the dam structure maintained toallow visual inspection for structural deteriora-tion.

A third alternative consists of a large rectan-gular metallic or concrete settling tank with a3:1 length-to-width ratio with an 8-foot depth.Tank volume depends on a peak-flow waste-water detention time of 10 to 30 minutes. Mostsolids in livestock manure settle in about 10minutes although some additional settlingoccurs for hours. Tank inlets and outlets are baf-fled and solids are removed by automated skim-mers and scrapers. Unless substantial solidsstorage is added to the settling tank volume,tank cleaning will need to occur frequently.

Flocculants and polymers

Chemical treatment of wastewater involvesthe addition of chemical flocculants and poly-mers to alter the physical state of dissolved andsuspended manure solids. This increases the per-cent of suspended manure solids removed bysolid separation equipment. Chemicals can beadded to wastewater to coagulate dissolved par-ticles into larger clumps called “flocs.” Theselarger particles can be separated more readily.Decisions about whether to use a chemicallyenhanced separator system should consider thecost of the chemicals and additional equipmentrequirements, such as mixing devices and meter-ing pumps that may be needed for chemicaladdition.

Bench-scale separation evaluations offlushed swine manure over an inclined screenseparator indicate that a 1/32” screen is a moreefficient choice than a 1/16” screen, with orwithout polymer additions. Some questions thatproducers may want to consider include: Why ispolymer use being considered? Will solids sepa-ration alone suffice? Do the costs of the polymerand the additional equipment outweigh theanticipated benefit?

In summary a solid/liquid separator mayaccomplish the following:

• Reduce the volume of manure storageneeded

• Improve anaerobic digestion

• Reduce concentrations of phosphorus, copper, and zinc in sludge and effluents

• Reduce pipe clogging problems• Produce value-added by-products• Allow the use of irrigation or direct soil

injection equipment• Reduce pumping horsepower needed and

increase pumping distances• Allow a greater hauling distance for the

solids versus liquid slurry

CompostingComposting is a biological process where

microorganisms convert organic material into asoil-like material called compost. The process ofcomposting can be accelerated when managedas a treatment rather than allowing nature totake its course. This is an aerobic process used tobio-stabilized solid waste. During the process,the volume of material can be reduced by asmuch as 50 percent. Composting will also kill allweed seeds and pathogens that are in themanure.

Composting is not typically recommended asan odor control method for solid manure; how-ever, if managed properly, odors should not be aproblem. On the other hand, if poorly managed,composting can produce odors. To efficientlycompost, the following are required for propermicrobial growth: An efficient supply of oxygen(5 to 15 percent), a moisture content of 50 to 60percent, pH between 6.5 and 8.0, and a blend ofmaterial that meets a desired ratio of carbon tonitrogen, ideally between 20:1 and 30:1.(Optimal C:N ratio is 25)

Details on the proper method for compostingcan be found in NRAES 54, On Farm CompostingHandbook. See www.nraes.org/. Management isthe key factor to producing a quality productwith minimal odor emissions.

Anaerobic digesters can generate income from methane

Anaerobic digesters are designed and man-aged to optimize the bacterial decomposition oforganic matter under controlled conditions con-verting carbon material into methane (CH4).The process time for treating animal waste toreduce the odor potential and stabilize theorganic material varies depending on the system

page 9

design. The end products of this process are pri-marily odorless methane and carbon dioxide.

Anaerobic digesters are very expensive($400/cow) and are only effective if properlymanaged. The conversion of methane to electri-cal power via a generator or producing hotwater via a boiler allows the digester to be one ofthe few manure systems that can generateincome. Economics and management require-ments typically limit these systems to operationslarger than 500-head and areas where eithersubsidized programs offset construction or oper-ational costs or where energy costs are greaterthan $0.05/kW, a unit of power equal to 1,000watts.

In the 1970s, many digesters were installedfollowing government grant programs focusingon reducing our nation’s reliance on foreignenergy sources. Many of these digesters failed,resulting in a poor “track record” for these sys-tems. These failures relate to issues of low gasyield, low quality gas; poor and inexperienceddesign and installation; high managementrequirements; and poor quality equipment andmaterials selection. A lot of research has beendone and is still on-going on anaerobic diges-tion, and the systems are now better understood.The designs and control of today’s anaerobicdigesters are much better, and the technology ismore promising in controlling odor from animalfacilities.

Aerobic treatmentAerobic treatment of manure adds dissolved

oxygen to the manure, converting carbon to car-bon dioxide and microbial biomass. Aeration ofthe manure can be accomplished by rigorousagitation (surface aeration), blowing air intopumped liquid manure (saturation), or by bub-bling air up from the bottom of a tank or pond(micro-bubble aeration). The amount of oxygenrequired is directly related to the goal of treat-ment. If BOD reduction is the goal then the aer-ation system must supply 100 percent of theoxygen requirement of the microorganisms tostabilize the material. For the conversion ofnitrogen and ammonia to nitrate, nearly twicethe BOD demand will be required.

Aeration systems have been very well studiedfor treatment of low strength industrial andmunicipal wastes. Livestock wastes and manurecontain much more organic material and non-

biologically available material than most indus-trial and municipal waste systems. Therefore,proper sizing of lagoon and equipment selectionare very important aspects in the design andoperation of a livestock aerobic lagoon. Systemproviders should be able to demonstrate howthese issues have been addressed in their design.

Loading of manure storage basinsExcessive odors and hydrogen sulfide have

been observed in several storage basins in theNorthwest. The exact “cause and effect” of theseodors is not known, however several factors havebeen identified that would increase the likeli-hood of excessive odors being produced inmanure basins where both parlor wastewaterand manure is stored:

• Large amounts of water being used in milkparlor, either for flushing or chiller waste-water

• Construction of a basin greater than 180-day storage requirement, and the pondlevel is maintained near capacity

• Solids accumulation exceeding 15 percentof the pond storage volume.

Lagoon loading is the amount of volatilesolids allowed to be introduced into the lagoonliquid volume each day for treatment. Excessiveloading hinders proper treatment of the wasteand results in unacceptable odors. Ponds loadedat correct rates provide adequate treatment andhave fewer odor problems.

Pink-, red-, or purple-colored ponds are fromnaturally occurring sulfur-reducing bacteria andare associated with fewer odor problems. Themicrobe also reduces chemical oxygen demand,ammonium, nitrogen, and soluble phosphorusin the pond liquid. Effluent from a purplelagoon can be used to seed a non-purple pondas long as conditions in the non-colored pondwill support growth of this microbe.

High concentrations of several factors canlimit the growth of sulfur reducing bacteria:

• Arsenic• Copper• AntibioticsChecking the acidity (pH), the electrical con-

ductivity (EC), and oxidation-reduction potential(ORP) can be used to monitor the potential toproduce odors. If the pH is too low, hydrated

page 10

lime or caustic soda can be added. Fresh watercan be added if the electrical conductivity isabove 2000mV (millivolt). ORP levels should bebetween -50mV and 0mV.

Manure additivesMany manure additives on the market today

are used in pits, ponds, animal feed, and in theair to reduce odors. Additives work only underappropriate management and favorable envi-ronmental conditions. Research has shown littleeffectiveness of additives as a single cure to afarm’s odor problem. Field tests show that someworked well on one farm while being completelyineffective on other farms.

Microbiological additives

Microbiological additives, or digestivedeodorants, generally contain mixed cultures ofenzymes or microorganisms designed toenhance the degradation of solids and reducethe volatilization of ammonia and/or hydrogensulfide. The microorganisms metabolize and sta-bilize manure. Digestive deodorants need to beadded frequently to select for certain bacteria.

Many different studies and research concludethere is a wide variability in the results fromdigestive deodorants. The supplemental organ-isms may not be suited for the environmentalconditions in manure storages. Manure alreadyhas many different species of organisms so it isquestionable whether adding a small amount ofspecific microbes will be helpful.

Masking agents

Masking agents only cover one smell withanother. Masking agents are a mixture of com-pounds that have a strong odor of their own. Intheory, the desirable odor will mask the undesir-able odor. This is usually only a short-term solu-tion to an odor problem.

Masking agents are made from vaporizedmaterial usually consisting of aromatic organiccompounds. Vaporized agents are sprayeddirectly over the manure. Non-vaporized agentsare added directly to the manure. The effects ofmasking are difficult to predict because ofchanging environmental conditions. The mainadvantages to masking agents are their lowcosts, and they are generally non-hazardous tothe environment.

Counteractant

Counteractants neutralize odors and do notreact chemically with the odors but reduce theperceived odor level. Counteractants are usuallyneutral and are very safe to handle.Counteractants are more expensive than mask-ing agents, but they usually lower or maintainodor levels. Their effectiveness is also not alwayspredictable.

Adsorbents and absorbents

Adsorbents and absorbents are biological orchemical materials that can collect odorouscompounds in their surfaces (adsorb) or interiors(absorb). Examples of materials include sphag-num peat moss, sawdust, rice straw, sodium ben-tonite, charcoal, and certain natural zeolites.

Chemical additives

Chemical additives chemically alter odorouscompounds or enzymes. Chemical additives canbe used to kill bacteria that produce volatileorganic compounds. Long-term use of chemicaladditives can be time consuming, costly, andrequire specialized product delivery systems.

When dosing chemicals into manure, sidereactions will occur in addition to the desiredreactions. When calculating dosing rates, makesure to account for safety and consider all sidereactions that may occur. Testing before addinga chemical additive to the whole lagoon or pit isrecommended.

Chemical additives are classified by theirmode of action:

• Oxidizing agents: Chlorine (as gas orsodium hypochlorite), potassium perman-ganate, and hydrogen peroxide will oxi-dize sulfides and inhibit sulfideproduction. Ozone also has been used asan oxidizing agent.

• Precipitants: Iron and zinc salts willreact with sulfides to form insoluble com-pounds. Ferrous and ferric chloride havebeen used for that purpose.

• pH control: Sodium hydroxide or limecan be added to manure to raise the pH,inhibiting sulfide production.

• Electron acceptors: Electron acceptorsare taken up preferentially to the sulfateion, and thus prevent sulfide formation.Sodium nitrate can be used for this pur-pose.

page 11

Land application odors can last hours to days

Land application of manure can be a majorsource of odor. The odors from applied manurecan last from a few hours up to several days.There are several factors that can affect theintensity and duration the odor is present.Surface area is one of the major contributors tothe odor. If manure is spread over a large area, agreater amount of manure is exposed to the air.This allows more odor molecules to enter theatmosphere. Solid and liquid manures also havevery different odors. Liquid manure odors aremuch stronger than solid manure odors. Theconditions the manure was stored in and themethod of application can also have a greataffect on the intensity of the odors emitted whenthe manure is applied to the land.

Manure characteristics

Fresh manure has a different odor than doesstored manure. In most cases, manure that isstored for long periods of time under anaerobicconditions will have a more intense odor thanmanure that has been treated in an aerobiclagoon, and it will cause more odor problemswhen being spread on the land. Solid manure isless odorous than liquid manure or slurry.Manure that is stored in piles or stacks generallycontains fewer odor-causing substances.However, the moisture content of the materialwill have a great impact on the amount of odorthat is being emitted when piles are stirred dur-ing land application.

Large amounts of odors can be producedwhen liquid manure is being pumped fromponds or tanks. Agitation when pumping liquidmanure causes odors to be released. The methodused to apply liquid manure will determine theodor generated during and after application.Typically, the finer the droplet of liquid manureproduced during application, the greater theamount of odor emitted. Smaller droplets willalso be carried further by the wind, and odorsmay spread for more than a mile downwind,even under low-wind conditions.

Land characteristics

Applicators should take into considerationthe location and distance of the application siterelative to the nearest residence. This informa-tion will help determine the method of applica-

tion. For example, direct injection may be con-sidered close to residences, while sprinkler irriga-tion may be used in areas far downwind ofneighbors.

Injection and incorporation

Untreated liquid manure can be directlyinjected into the soil. This method greatlyreduces the amount of odor produced from landapplications of manure (Table 2). Another com-mon way to apply liquid manure is simplyspread it on the soil surface. To reduce odor, theliquid manure should be incorporated into thesoil as soon as possible. Incorporation of manurereduces odors, but not as much as direct injec-tion into the soil. Speedy incorporation or directinjection also helps the soil retain nitrogen. Thiscan triple the amount of nitrogen available inthe soil from the manure

Many different types of equipment can beused with the injectors. Narrow tines, sweeps,disk injectors, and covers (Figure 1), and eventhe conventional chisel plows can be used wheninjecting manure into the soil. Choosing thetype of equipment used with the injectors is animportant decision. You will need crop residueleft on the soil surface to prevent erosion in wetweather. Concentrated manure or separatedmanure solids placed on the soil surface shouldbe incorporated with conventional tillage equip-ment immediately following application to pre-vent odors.

Drag hose injectors—up to 1 million gal. a day

Drag hoses are used for direct injection of liq-uid manure into the soil from a storage tank. A4- to 6-inch diameter hose is drug across a fieldbehind the tractor. This hose delivers themanure to the injector or a low-mounted distri-bution manifold. If the low-mounted distribu-tion manifold is used, some type of tillage must

page 12

Table 2. Odor reduction using various land applicationmethods

Application Method Odor Threshold

Broadcast 2818Plow 200

Harrow 131Inject 32

Unmanured 50

be performed to incorporate the manure into thesoil. Drag-hose injector systems are capable ofapplying nearly 1 million gallons in a day whiledramatically reducing the cost and time ofapplication compared to applying the materialusing a slurry tank.

Wastewater irrigation—efficient but potentially odorous

The use of irrigation equipment is an effi-cient way to apply liquid manure when a crop isgrowing. However, this method may produceextreme amounts of odor. If managed properly,the odor released from this method can bereduced. Reducing irrigation system odors can bedone by:

1. Using nozzles and pressures that producelarge-sized droplets.

2. Installing drop nozzles rather than spraynozzles on center pivot systems.

3. Adding dilution water to the liquidmanure before applying.

Small droplets have a higher potential to becarried by the wind. This will cause the area ofdrift to be much larger than if a large dropletsize was produced. Droplet sizes are determinedby the nozzle size and the pressure the systemuses. The larger the nozzle and the less pressurea systems uses, the larger the droplet size andthe less likely the drops will drift in the wind.Aerosol drift from irrigation systems is also apublic relations issue when the droplets cover a

windshield or a drying set of clothes in yourneighbor’s backyard.

Drop lines can extend the nozzles 2 to 8 feetfrom the pipe closer to the ground. This willreduce evaporation from the liquid manurebefore it hits the ground and reduce the lengthof time the droplets fall through the air. Consultwith your irrigation dealer to ensure that yoursystem is properly designed to prevent erosion orexcessive ponding.

Solid manure

Fresh or stockpiled solid manure appliedonto the fields should be incorporated into thesoil immediately following application. Loadingsolid manure also creates odors. If the solidwaste needs to be stored, consider covering itwith fresh straw or a finished compost to reducethe amount of odor released into the atmos-phere.

Timing and location of applications:Communicate with neighbors

Apply on days when the wind is not blowingtowards homes of neighbors. Try to spread onweekdays because people are more likely to beaway from their homes. Avoid weekends andholidays. Talk with neighbors to make sure theydo not have a social event planned during theday of application. Letting your neighbor knowwhen you are going to spread large quantities ofmanure can also be an effective tool. People usu-ally object less if they know you’re concerned.

page 13

Figure 1. Manure placement injectors

Manure and odor managementplans can improve PR

Manure Management Plans (MMP) havebecome a common practice for dairies. Theseplans document the proper handling and appli-cation of manure and wastewater onto croplandto protect water quality. Similarly, OdorManagement Plans (OMP) are emerging to doc-ument proper handling of manure and waste-water to protect air quality. Similar to MMP, anOMP systematically identifies potential odorsources, determines odor control practices toreduce these odors, and establishes criteria forimplementing these strategies (Table 3). A suc-cessful OMP can lead to better public relations.

Five steps for developing an OdorManagement Plan (OMP)

1. Fully describe the farm and the manurehandling, storage, and application sys-tems (Table 4).

2. Create a list of potential odor sources onthe farm.

3. Determine which of the odor sources aremost likely to bring about odor com-plaints and/or rank them in their order ofodor generation potential.

4. List one or two odor control practices foreach of the significant odor sources.

5. Develop a protocol to respond to odorcomplaints.

Facility odor sourcesNuisance odors can be the result of a single

odor event, odor source, or a combination of sev-eral sources and events. Therefore, it is impor-tant to inventory all odor sources on the farm(Table 5). This inventory should be systemati-cally conducted on-site to ensure that all odorsources are included. Be specific; include all col-lection basins and manure storages and stock-piles.

Odors from dairies originate from three pri-mary sources: manure storage structures (includ-ing collection and mixing pits, settling basinsand stockpiled solids); barns and open lots; and,land application of manure. Feed storage, mor-tality disposal and collection sites, and silagebunkers may also be sources of odor.

page 14

Table 3. Typical contents of an odor management plan

1. Cover sheet

2. Facility information

3. Facility description & vicinity map

4. Description of manure management system & site map

5. Description of Land Application System

6. Climatic data

7. Facility odor sources and rankings

8. Tiered implementation of odor control practice

9. Public involvement

10. OMP review process

Table 4. Farm and manure systems information neededin odor management plans (OMPs)

1. Cover sheet• The facility for which the plan was prepared• Who prepared the plan• Preparer’s association or affiliation (i.e. consulting firm, engi-

neering firm, university, etc.)• Primary contact phone number• Signature line for reviewer to sign and date

2. Facility information• Facility name• Physical address of the facility• County• Owner and operator• Other contacts associated with implementation of OMP• Phone numbers—facility and primary numbers for listed con-

tacts

3. General• Type of facility• Number of animals present and future plans, include: age

ranges, breeds (feedlots note the majority breed)• Type of housing used related to age groups• General description of nearby residential and public

amenities, etc.• Scaled vicinity map• Potential areas for odor movement• All residences• Public use areas (parks, recreational areas, schools, etc.)• Roads general topography, etc.• Other CAFO facilities within a 2-mile radius of the facility

4. Climate dataList typical climate conditions for the area as well as conditionswhen odor is most prevalent. Requires minimum of two years data (recommend five years).Obtain weather information from local area weather stations and onseveral Web sites. Also list:

• Odorous conditions – decomposition of organics• Amount of gas released and where it travels• Wind speed and direction(s)• Temperature ranges during seasons• Relative humidity• Precipitation

Continued on p.15

Develop a bulleted list of odor sources on thefacility. Provide a brief description of each odorsource, including the size of the odor source(physical area) and its distance from the road-ways, neighbors, property boundaries, etc.

The OMP must also identify the many on-farm odor sources likely to have the highestpotential to cause nuisance odors. Rank eachodor source as low, moderate, or high. Alsoinclude an explanation of the ranking and whyit is listed as an odor source. Any sources withlow odor production should also be listed with anexplanation of how current, positive manage-ment practices are affecting them. Several factorsshould be evaluated when ranking odor sources:

• Surface area—more surface area, moreodor emission

• Odor frequency • Odor duration• Odor intensity • Organic loading biochemical oxygen

demand or BOD—high BOD, high micro-bial activity, more gas production

• Moisture content—high moisture, moreanaerobic

• Nutrient levels—high N, more ammoniarelease

• Chemical compounds hydrogen sulfide(H2S), ammonia (NH3), volatile fatty acids(VFAs), volatile organic compounds VOCs)

page 15

Table 4. Farm and manure systems information neededin odor management plans (OMP) (continued)

5. Manure management systemVery detailed description of current manure handling system:

• Cleaning systems and management• Transfer systems and management• Separation systems and management• Include descriptions of:• Timing• Frequency• Duration• Volumes• Dimensions• Flow rates• Location of bypasses, etc.• Scaled site plan (if not on file with the ISDA)• Visual for manure management system• Detail: housing, transfer mechanisms (direction of movement),

separation systems, storage areas.

6. Land application systemsPresent management practices used to land-apply both solid andliquid manure:

• Type of equipment used• Delivery systems• Timing, frequency, and duration of practices• Proximity of residential and public use areas to land application

sites• Land Application Site Plan (optional)- Idaho State Department

of Agriculture may already have one on file in a nutrient man-agement plan

Table 5. Potential sources of odor on a dairy

Process Location Information needed in an odor management plan (OMP)

Manure storage & processing Liquid storage ponds Size, depth, storage period

Separation systems Type, screen size, removal frequency, size & depth of gravity basins

Solids storage areas Size, removal frequency, runoff collection

Pumping stations Size, operation cycles

Manure removal Scraping Removal frequency

Flushing Removal frequency, flush volume

Feed management Feed storage areas Feed description, runoff collection

Feed alleys Feeding and cleaning frequency

Animal housing Barns Size

Open lots Size, lot maintenance, runoff collection

Animal mortalities Collection areas Size, fly and vector control, removal frequency

Disposal area Size, fly and vector control, removal frequency

Land application Liquid manure Method, locations, frequency, pressure, incorporation method

Solid manure Method, locations, frequency, incorporation method

Usually the human nose will work to deter-mine odor problem areas, but everyone’s senseof smell varies in the ability to detect differentcompounds. Several methods are currently beingused to determine odors, although many havenot been sufficiently researched yet. Include anytest results in your explanation for ranking ofsources.

Devices used: These are a few of the devicesused.

• Measuring reduction in BOD—indi-cates the system is becoming more aerobic

• Olfactometry—collecting air samplesand presenting them before a panel oftrained individuals to measure intensity.Typically done by specific laboratories

• Nasal Ranger, Mask Olfactometer orScentometer—devices used in the field toevaluate odor intensity

• N-butanol scale—different dilutions ofN-butanol used to compare odor intensity

When ranking the sources, consider the dis-tance of the sources to public areas or neighbors.Dilution of odors is caused through the mixingof odor with ambient air. The dilution is a func-tion of distance, topography, and meteorologicalconditions.

Farther distances will result in fewer odorcomplaints. Wind breaks or tree lines willencourage mixing of odorous air with clean air,whereas valleys, draws or low areas may con-centrate odors.

Maximum dilution occurs when the cool airnear the ground is heating and rising, especiallyduring the mid-day in full sun. Conversely, dur-ing the late evening, the odorous air is trappednear the ground, and it will flow downhill in aconcentrated plume. Of these three factors—dis-tance, topography and meteorology—inade-quate separation distance is typically the majorfactor leading to nuisance complaints.

Tiered implementation of odorcontrol practices

Three steps or tiers are typically taken whenevaluating solutions to an odor problem.During each tier, the level of odor controlbecomes increasingly more stringent and poten-tially the cost of control practice becomes moreexpensive. The tiered process allows facilities totarget odors sources with effective control efforts

while minimizing cost. An economic and techni-cal evaluation should be included with each tier.

Tier #1—low cost

This involves little management changesand low-cost odor control practices (OCP). Itshould include a bulleted list of primary OCPs tobe implemented. Each bulleted item shouldaddress the following points:

• How and when it will be implemented• Estimate of cost to implement and benefits• Sources it will impact (reduce odor emis-

sion)• How it will be monitored to demonstrate

reduction• General quantitative and/or qualitative

reduction goals

Tier #2—moderate cost

This involves moderate managementchanges and moderate-cost OCPs. This bulletedlist will include secondary OCPs to be imple-mented. The bullets should contain the informa-tion from tier #1.

Tier #3—mid to high cost

This involves most management changesand mid-to-high cost OCPs and should containsthe same information as the previous tiers.

Public involvement: Responding to complaints

One of the most important pieces of an odormanagement plan is how the farm will respondto complaints. First, it is difficult to separate seri-ous odor complaints resulting from excessiveodor emissions from complaints registered bydisgruntled neighbors. Second, it is difficult todetermine how many valid complaints areneeded to trigger the implementation of an odorcontrol technology or a major review of yourOMP. And third, there must be some method formonitoring the effectiveness of an odor controltechnology.

The complaint response protocol will set upan OMP and set guidelines for an acceptablenumber of odor events and some method toevaluate the effectiveness of odor control prac-tices. For this, it is critical to foster and maintaina good relationship with neighbors and othercommunity members.

page 16

page 17

Avoid odor complaints

Avoid odor complaints by making an effortto control odor emissions, including peak odorevents such as manure agitation or land appli-cation of concentrated manure. These effortsand their perceived effect on odors should bedocumented.

Establish a relationship with neighbors andcommunity leaders

An effective complaint response planrequires the input of neighboring residents andcommunity leaders, such as environmental serv-ice specialists, regulatory agencies, and countycommissioners. These individuals provide anhonest evaluation of farm odor impacts. Theycould be listed on the OMP and help in thedevelopment of the complaint response plan. Ateam approach fosters communication and aflow of information, which is critical to respond-ing to complaints.

Monitor odor events

Monitoring odor events will help verify odorcomplaints and identify odor sources.Monitoring might include scheduled drivesaround the farm perimeter with a notebookrecording the date, time, and location of moni-toring and recording the relative strength ofodors detected. Other monitoring might includerecord keeping of odor events by neighbors. Thestrength of odors can be recorded on a threepoint intensity scale, where 1 = detectable odors,2 = recognizable odors, and 3 = very distinct andannoying odors.

Set acceptable intensity and frequency limits

Since odors are a part of all dairy, livestock,and poultry operations, it is impossible to expect100 percent odor-free air around the farm.However, frequent odor events of high intensityare unacceptable. Therefore, some reasonablefrequency of odor events should be established.This frequency could include a given number ofodor events per month or per year that areacceptable. Above this frequency, odor controlpractices would be implemented. Establishingthe acceptable frequency and intensity (howoften and how strong) of odor events should bedone with input from your neighbors and com-munity leaders so everyone is familiar with thegoals of the farm.

Evaluate odor control practices

After an odor control practice has beenimplemented, an honest evaluation of its effec-tiveness is needed. A complaint response planshould outline the evaluation methods and tech-niques. This evaluation should consist of a mix-ture of laboratory analysis, field odorassessments, and relative odor evaluations asdescribed above.

Your OMP should describe how the publicwill be involved in the process. Dairies shouldkeep the public aware of actions underway andhow the process is going either through phonecontact, small public meetings, newsletters, ornewspaper interviews. These actions are at thediscretion of the producer.

Odor management plan (OMP) review

Periodically the OMP will need to beassessed. It should be clearly be stated who isgoing to assess it and when. Special provisionsshould also be made if significant changes aremade to the manure handling system, nutrientmanagement plan, or if there is a dramaticincrease in odor complaints. Remember, theOMP is a working document that should be flex-ible and allow for modifications if needed.

Good neighbor relations

Being friendly and courteous to people whoneighbor the facility can go a long way to helpimprove the image of the operation. The appear-ance of the farming operation also helps. Aclean farmstead is much more pleasing to lookat than an unclean one. The way a managerhandles complaints and concerns is also a vitalpart in keeping good relations with neighbors.

Be caring to neighbors

Give advanced notice when you are plan-ning to spread manure that may cause offensiveodors. Talk with your neighbors to avoid spread-ing manure around outdoor events that maypotentially be ruined. Let your neighbors knowthat you are willing to talk about odor problemsand you care. Ask your neighbors if they wouldlike some compost or separated solids for theirgarden.

Set up a communications system

This will help solve any problems before theyget out of hand. Some people feel more comfort-able talking to someone other than the person

with the problem. Give concerned members ofthe community a contact person to talk to.Lastly, work with community leaders and regu-latory agencies before complaints get out ofhand. A dairy farmer working with communityleaders may lessen the demand for regulationsagainst odor.

Preventing/reducing odors

There are things that can be done to helpprevent or reduce odors that are being caused byyour facility:

• Develop an odor management plan• Use odor-control technologies• Cleanup old manure and feed stockpiles• Start a dialogue with neighbors, commu-

nity leaders and regulators

page 18

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heor

etic

al-n

ot te

sted

Sou

rce

redu

ctio

nA

nim

al fe

edR

atio

n m

anip

ulat

ion

MO

, I, D

Red

uce

prot

ein

requ

irem

ent a

nd in

crea

seID

SO

ME

feed

con

vers

ion:

incr

ease

dry

mat

ter,

synt

hetic

am

ino

acid

s, a

nd m

ore

dige

stib

lesu

pple

men

ts (

limit

feed

ing

corn

sila

ge,

bloo

d m

eal,

and

dist

iller

s gr

ain)

.

Drin

king

wat

erC

hem

ical

trea

tmen

tT

O, I

, DR

emov

al o

f pot

entia

l odo

rant

s so

urce

R

A, T

NO

elem

ents

(S

, Se)

from

pro

cess

and

drin

king

wat

er th

at w

ill u

ltim

atel

y en

d up

in m

anur

e st

orag

e.

Dis

pers

ion

Far

mst

ead

Nat

ural

win

dbre

aks

TI

Pla

nt h

ybrid

pop

lars

or

othe

r fa

st g

row

ing

IS, R

AS

OM

Etr

ees

to b

reak

win

dflo

w a

nd a

rial m

ixin

g.In

crea

sed

aest

hetic

s. W

ill r

equi

re ir

rigat

ion

and

seve

ral y

ears

to b

e ef

fect

ive

as w

indb

reak

.

Em

issi

ons

Sto

rage

bas

in /

lago

onIm

perm

eabl

e co

ver

TF,

IH

DP

E o

r si

mila

r co

ver

for

odor

con

trol

or

~$0

.65/

sq.ft

.ID

, IS

YE

Sca

ptur

e &

m

etha

ne c

aptu

re.

trea

tmen

tS

tora

ge b

asin

/ la

goon

Geo

text

ile—

perm

eabl

e co

ver

TF,

IG

eote

xtile

cov

er to

red

uce

odor

s, V

OC

s an

d H

2S.

~ $

0.18

/sq.

ft.IS

YE

S

Sto

rage

bas

in /

lago

onG

ranu

lar

foam

bio

cove

rT

F, I

Per

mea

ble

bioc

over

to r

educ

e od

or, N

H3,

VO

Cs.

H2S

.R

AN

O

Sto

rage

bas

in /

lago

onF

ixed

foam

& g

eote

xtile

cov

erT

F, I

Per

mea

ble

bioc

over

to r

educ

e od

or, N

H3.

VO

C &

H2S

.IS

, RA

YE

S

Sto

rage

bas

in /

lago

onS

traw

bio

cove

rT

F, I

Bar

ley

and

whe

at s

traw

bio

cove

rs fo

r w

inte

r st

orag

e.IS

, RA

YE

S

Out

door

sto

ckpi

les

Per

mea

ble

synt

hetic

bio

cove

rT

F, I

“Gor

Tex”

like

cov

er to

red

uce

odor

, NH

3em

issi

ons.

RA

YE

S

Out

door

sto

ckpi

les

Per

mea

ble

orga

nic

bioc

over

TF,

IM

anur

e st

ockp

iles

cove

red

in m

atur

e co

mpo

st.

ID, I

S, R

AY

ES

page

19

Tab

le 6

. Po

ten

tial

so

urc

es o

f o

do

r o

n a

dai

ry (

con

tinu

ed)

Ap

plic

atio

nL

oca

tio

nTe

chn

olo

gy

Typ

e o

f P

ract

ice

Mo

de

of

Pra

ctic

eD

escr

ipti

on

Co

st (

if a

vaila

ble

)S

tatu

s3r

d P

arty

T=

Tech

nolo

gyI=

Inte

nsity

ID=

Inst

alle

d on

E

val.

M=

Man

agem

ent

D=

Dur

atio

nD

airy

Far

mF

=F

requ

ency

IS=

Inst

alle

d on

O

=O

ffens

iven

ess

Sw

ine

Far

mR

A=

Re-

App

licat

ion

of T

echn

olog

yT

=T

heor

etic

al-n

ot te

sted

Man

ure

colle

ctio

n F

arm

stea

dM

anur

e cl

eanu

pM

F, I

Agg

ress

ive

and

com

preh

ensi

ve m

anag

emen

t ID

, IS

--&

trea

tmen

tan

d cl

ean-

up o

f exc

ess

man

ure

on fa

rm.

Add

ition

al b

enef

it of

red

uced

dus

t and

flie

s.

Sto

rage

bas

in /

lago

onA

naer

obic

trea

tmen

t lag

oon

T/M

I, F,

OA

naer

obic

trea

tmen

t and

sto

rage

lago

on to

ID

, IS

YE

Sre

duce

odo

rs, B

OD

and

TS

S. U

ncov

ered

an

aero

bic

trea

tmen

t lag

oons

will

res

ult i

n th

e lo

ss o

f >60

% o

f man

ure

nitr

ogen

(N

).

Sto

rage

bas

in /

lago

onA

naer

obic

dig

estio

nT

/MI,

F, O

Ana

erob

ic d

estr

uctio

n of

org

anic

mat

ter

in

Cov

ered

lago

on

ID, I

SY

ES

man

ure

to e

ncou

rage

the

prod

uctio

n of

$4

00–7

00/c

ow;

met

hane

(C

H4)

. Pro

duce

s re

lativ

ely

odor

free

co

mpl

ete

mix

liqui

d. P

oten

tial f

or e

nerg

y re

cove

ry (

heat

ed

$450

–600

/cow

;w

ater

, ele

ctric

al c

o-ge

nera

tion)

. Wor

ks b

est

plug

flow

$40

0–50

0/co

ww

ith c

once

ntra

ted

man

ure

hand

ling

syst

ems

(scr

ape,

aut

omat

ed s

crap

ers

and

vacu

um).

Sto

rage

bas

in /

lago

onA

erob

ic d

iges

tion

T/M

I, F,

OA

erob

ic d

iges

tion

of o

rgan

ic m

atte

r. #3

00–6

00/c

ow p

lus

ID, I

SY

ES

Pro

duce

s re

lativ

ely

odor

free

liqu

id.

Dep

endi

ng o

n ae

ratio

n ra

te—

may

res

ult i

n la

rge

prod

uctio

n of

bio

mas

s op

erat

ing

cost

to

be la

nd a

pplie

d or

dig

este

d. E

lect

rical

cos

ts o

f ae

ratio

n m

ust b

e co

nsid

ered

.

Man

ure

stab

iliza

tion,

C

ompo

stin

gT

I, F,

O

Aer

obic

ally

dig

est s

olid

man

ure

or s

epar

ated

ID

, IS

SO

ME

hand

ling

& s

tora

gem

anur

e so

lids.

Mai

ntai

n ad

equa

te p

oros

ity,

moi

stur

e co

nten

t (50

-60%

) an

d C

:N (

25-3

0:1)

.E

xces

sive

moi

stur

e an

d lo

w C

:N m

ay le

ad to

high

NH

3lo

sses

and

odo

rs.

Fre

esta

ll / O

pen

lot a

lley

Aut

omat

ed s

crap

e T

I, O

Rem

oval

of m

anur

e fr

om fr

eest

all o

r ou

tdoo

r ID

--re

mov

al s

yste

ms

feed

ing

alle

y vi

a a

slid

ebar

and

cab

le/c

hain

. C

once

ntra

ted,

hig

h so

lid %

man

ure.

Fre

quen

t m

anur

e re

mov

al is

req

uire

d.

Fre

esta

ll / O

pen

lot a

lley

Vac

uum

rem

oval

sys

tem

sT

I, O

Rem

oval

of m

anur

e fr

om fr

eest

all o

r ou

tdoo

r ID

--fe

edin

g al

ley

via

vacu

um ta

nker

s. C

once

ntra

ted,

hi

gh s

olid

% m

anur

e. F

requ

ent m

anur

e re

mov

al is

req

uire

d.

Acr

ony

ms

use

d in

Tab

le 6

BO

D—

Bio

chem

ical

oxy

gen

dem

and

C:N

—C

arbo

n to

nitr

ogen

rat

ioH

2S—

Hyd

roge

n su

lfide

HD

PE

—H

igh

dens

ity p

olye

thyl

ene

MC

—M

oist

ure

cont

ent

NH

3—A

mm

onia

OM

P—

Odo

r m

anag

emen

t pla

n

OR

P—

Oxi

datio

n re

duct

ion

pote

ntia

lP

SI—

Pou

nds

per

squa

re in

chS

—S

ulph

urS

e—S

elen

ium

TS

S—

Tota

l sus

pend

ed s

olid

sV

FA—

Vol

atile

fatty

aci

dsV

OC

—V

olat

ile o

rgan

ic c

ompo

unds

page

20

Tab

le 6

. Po

ten

tial

so

urc

es o

f o

do

r o

n a

dai

ry (

con

tinu

ed)

Ap

plic

atio

nL

oca

tio

nTe

chn

olo

gy

Typ

e o

f P

ract

ice

Mo

de

of

Pra

ctic

eD

escr

ipti

on

Co

st (

if a

vaila

ble

)S

tatu

s3r

d P

arty

T=

Tech

nolo

gyI=

Inte

nsity

ID=

Inst

alle

d on

E

val.

M=

Man

agem

ent

D=

Dur

atio

nD

airy

Far

mF

=F

requ

ency

IS=

Inst

alle

d on

O

=O

ffens

iven

ess

Sw

ine

Far

mR

A=

Re-

App

licat

ion

of T

echn

olog

yT

=T

heor

etic

al-n

ot te

sted

Man

ure

colle

ctio

n &

Tre

atm

ent (

cont

inue

d)

Fre

esta

ll / o

pen

lot a

lley

Flu

sh s

yste

ms

TI,

OF

requ

ent r

emov

al o

f man

ure

from

free

stal

l or

ID--

outd

oor

alle

ys v

ia h

ydra

ulic

con

veya

nce.

D

ilute

, low

sol

id %

man

ure.

RE

QU

IRE

S fu

rthe

r tr

eatm

ent i

n ad

ditio

n to

sol

id s

epar

atio

n (m

axim

um to

tal s

uspe

nded

sol

ids

of 1

%).

Man

ure

hand

ling

&

Man

ure

sepa

ratio

nT

/ M

I, O

Red

uce

solid

s to

liqu

id s

tora

ge: r

educ

e B

OD

V

arie

sID

, IS

SO

ME

stor

age

basi

n / l

agoo

nlo

ad, i

mpr

ove

hand

ling.

Cre

ates

sec

ond

was

te

stre

am a

nd p

oten

tial o

dor

sour

ce. G

ravi

ty

sepa

ratio

n ~

50%

rem

oval

, mec

hani

cal

~35

% m

axim

um (

how

ever

, effi

cien

cy is

qui

te

varia

ble

betw

een

tech

nolo

gies

, app

licat

ions

, an

d m

anuf

actu

rers

).

Fre

esta

ll / o

pen

lot a

lley

Ozo

natio

n of

flus

h w

ater

TI,

OO

xidi

ze o

dora

nts

and

VO

Cs,

incr

ease

OR

P.

T, ID

NO

Mus

t con

side

r th

e po

or e

fflue

nt q

ualit

y (h

igh

% s

olid

s) a

nd p

umpi

ng d

ista

nce

whe

n ca

lcul

atin

g pi

pelin

e re

tent

ion

time.

Ozo

ne

gene

rato

rs h

ave

trad

ition

ally

bee

n ve

ry fr

agile

an

d ex

pens

ive

to o

pera

te (

high

ele

ctric

al c

ost)

.

Fre

esta

llA

cidi

ficat

ion

of fr

eest

all

MI,

D, F

, OA

dditi

on o

f low

pH

sol

utio

ns to

red

uce

T, R

AN

Oco

mpo

st b

eddi

ngam

mon

ia e

mis

sion

from

free

stal

l bed

ding

(A

lCl)

in g

ranu

lar

or c

once

ntra

ted

liqui

d fo

rms.

Ope

n lo

tM

anur

e re

mov

ial /

M

F, I

Rem

oval

of a

ccum

ulat

ed m

anur

e an

d be

ddin

g R

AY

ES

Dus

t sup

ress

ion

from

cor

rals

. Dus

t sup

pres

sion

to m

aint

ain

~30

% M

C o

n co

rral

sur

face

. MC

>40

% w

ill

caus

e hi

gher

odo

r em

issi

ons.

Ope

n lo

tA

cidi

ficat

ion

of

MI,

D, F

, OP

oten

tial a

pplic

atio

n of

alu

m o

r ot

her

acid

s to

T,

RA

NO

corr

al s

urfa

cere

duce

am

mon

ia e

mis

sion

s. W

inte

r ap

plic

atio

ns

will

larg

ely

redu

ce e

mis

sion

dur

ing

sprin

g cl

eano

uts;

sum

mer

app

licat

ions

will

red

uce

odor

and

dus

t dur

ing

sum

mer

. Res

earc

h re

quire

d to

det

erm

ine

appl

icat

ion

rate

s,

appl

icat

ion

inte

rval

s, a

nd s

yste

m c

ost.

Acr

ony

ms

use

d in

Tab

le 6

BO

D—

Bio

chem

ical

oxy

gen

dem

and

C:N

—C

arbo

n to

nitr

ogen

rat

ioH

2S—

Hyd

roge

n su

lfide

HD

PE

—H

igh

dens

ity p

olye

thyl

ene

MC

—M

oist

ure

cont

ent

NH

3—A

mm

onia

OM

P—

Odo

r m

anag

emen

t pla

n

OR

P—

Oxi

datio

n re

duct

ion

pote

ntia

lP

SI—

Pou

nds

per

squa

re in

chS

—S

ulph

urS

e—S

elen

ium

TS

S—

Tota

l sus

pend

ed s

olid

sV

FA—

Vol

atile

fatty

aci

dsV

OC

—V

olat

ile o

rgan

ic c

ompo

unds

page

21

Tab

le 6

. Po

ten

tial

so

urc

es o

f o

do

r o

n a

dai

ry (

con

tinu

ed)

Ap

plic

atio

nL

oca

tio

nTe

chn

olo

gy

Typ

e o

f P

ract

ice

Mo

de

of

Pra

ctic

eD

escr

ipti

on

Co

st (

if a

vaila

ble

)S

tatu

s3r

d P

arty

T=

Tech

nolo

gyI=

Inte

nsity

ID=

Inst

alle

d on

E

val.

M=

Man

agem

ent

D=

Dur

atio

nD

airy

Far

mF

=F

requ

ency

IS=

Inst

alle

d on

O

=O

ffens

iven

ess

Sw

ine

Far

mR

A=

Re-

App

licat

ion

of T

echn

olog

yT

=T

heor

etic

al-n

ot te

sted

Land

App

licat

ion

Pre

-pla

nt a

pplic

atio

nM

anur

e in

corp

orat

ion

MI,

D, F

, OIn

corp

orat

e br

oadc

aste

d or

irrig

ated

man

ure

~ $

5.00

/acr

e ap

plie

dID

, IS

, RA

YE

Sim

med

iate

ly fo

llow

ing

appl

icat

ion

as p

ossi

ble

or w

ithin

24-

hour

s (m

axim

um).

Pre

-pla

nt a

pplic

atio

nM

anur

e in

ject

ion

M /

TI,

D, F

, OD

irect

inco

rpor

atio

n of

man

ure

via

tank

or

~ $

0.00

1/ga

llon

appl

ied

ID, I

S, R

AY

ES

hose

-dra

g ap

plic

ator

s. In

ject

or o

ptio

ns in

clud

e:

disc

inco

rpor

ator

s, s

wee

p, n

o-til

l, ch

isel

, and

ro

tary

aer

ator

.

Pos

t-pl

ant a

pplic

atio

nM

anur

e in

ject

ion

M /

TI,

D, F

, OLi

mite

d in

ner

row

inco

rpor

atio

n on

ear

ly

~ $

0.00

1/ga

llon

appl

ied

ID, I

S, R

AY

ES

grow

th c

rops

(ta

nker

s) o

r in

ject

ion

into

new

ly

harv

este

d al

falfa

(ta

nker

s or

hos

e-dr

ag).

Irrig

atio

nF

resh

wat

er d

ilutio

nM

I, D

, OD

ilute

app

lied

man

ure

with

5 to

10

times

the

fres

hwat

er.

ID, I

SY

ES

Irrig

atio

nLo

w-p

ress

ure

appl

icat

ion

T /

MI

Use

low

pre

ssur

e (3

5psi

max

.) d

rop

nozz

les

IS, T

NO

with

rot

atin

g sp

rinkl

ers

that

enc

oura

ge la

rge

drop

let p

rodu

ctio

n.

Irrig

atio

nE

nd-g

un p

rohi

bitio

nM

I, F

Cea

se u

se o

f cen

ter

pivo

t end

-gun

s.R

A, I

D, I

S--

Irrig

atio

n“D

ribbl

e” d

rop

hose

sT

/ M

IU

se lo

w p

ress

ure

drop

hos

es w

ith a

pplic

atio

nR

A, I

D, I

S??

blad

ders

or

drib

ble

nozz

les

to a

pply

hig

h vo

lum

es d

irect

ly to

soi

l sur

face

. Mus

t con

side

r lo

wer

app

licat

ion

unifo

rmity

and

hig

h pr

ecip

itatio

n ra

tes.

Hig

h ru

noff

pote

ntia

l.

Irrig

atio

nIn

ner-

cano

py a

pplic

atio

nsM

IE

xten

ded

low

pre

ssur

e dr

op h

oses

use

d R

A, I

SY

ES

prim

arily

whe

n cr

op g

row

th is

abo

ve s

prin

kler

. M

ust c

onsi

der

low

er a

pplic

atio

n un

iform

ity a

nd

high

pre

cipi

tatio

n ra

tes.

Irrig

atio

nP

re-a

pplic

atio

n ae

ratio

n /

T /

MI,

D, F

, OA

erat

ion

of s

tore

d m

anur

e/ef

fluen

t prio

r to

app

licat

ion.

T,

ISox

idat

ion

Oxi

dize

odo

rant

s an

d V

OC

s, in

crea

se O

RP.

Irrig

atio

nP

re-a

pplic

atio

n oz

onat

ion

/ T

/ M

I, D

, F, O

Sim

ilar

to P

re-a

pplic

atio

n ae

ratio

n. O

xidi

ze

T, ID

, IS

NO

oxid

atio

n od

oran

ts a

nd V

OC

s, in

crea

se O

RP.

Mus

t co

nsid

er th

e po

or e

fflue

nt q

ualit

y an

d pu

mpi

ng

dist

ance

whe

n ca

lcul

atin

g pi

pelin

e re

tent

ion

time.

O

zone

gen

erat

ors

have

trad

ition

aly

been

ver

yfr

agile

and

exp

ensi

ve to

ope

rate

(hi

gh e

lect

rical

cos

t).

Acr

ony

ms

use

d in

Tab

le 6

BO

D—

Bio

chem

ical

oxy

gen

dem

and

C:N

—C

arbo

n to

nitr

ogen

rat

ioH

2S—

Hyd

roge

n su

lfide

HD

PE

—H

igh

dens

ity p

olye

thyl

ene

MC

—M

oist

ure

cont

ent

NH

3—A

mm

onia

OM

P—

Odo

r m

anag

emen

t pla

n

OR

P—

Oxi

datio

n re

duct

ion

pote

ntia

lP

SI—

Pou

nds

per

squa

re in

chS

—S

ulph

urS

e—S

elen

ium

TS

S—

Tota

l sus

pend

ed s

olid

sV

FA—

Vol

atile

fatty

aci

dsV

OC

—V

olat

ile o

rgan

ic c

ompo

unds

page

22

Issued in furtherance of cooperative extension work in agriculture and home economics, Acts of May 8 and June 30, 1914, in cooperation with theU.S. Department of Agriculture, Charlotte V. Eberlein, Director of University of Idaho Extension, University of Idaho, Moscow, Idaho 83844. TheUniversity of Idaho provides equal opportunity in education and employment on the basis of race, color, national origin, religion, sex, sexual orien-tation, age, disability, or status as a disabled veteran or Vietnam-era veteran, as required by state and federal laws.

Published May 2 © 2008 University of Idaho online only

About the Authors

Ron E. Sheffield was formerly with theUniversity of Idaho Extension and Department ofBiological & Agricultural Engineering in southernIdaho.

Pius Ndegwa is with Washington StateUniversity’s Department of Biological SystemsEngineering in Pullman, Wash.

Mike Gamroth is with Oregon State University’sDepartment of Animal Science in Corvallis, Ore.

Mario de Haro Marti is a Gooding County dairyeducator with the University of Idaho Extension.