Odor
• Has insignificant effects on the global or national
environment
• Has major effects on the local environment
– Nearest dwelling
– Greatest source of nuisance complaints
• Operations
Swine
Broiler
Layer
Beef feedlots
% of nuisance complaints from odor
95
75
66
50
– Sources
•
•
•
•
•
•
Animal buildings and lots
Manure treatment and storage
Land application
Silage
Feed processing
Dead animal disposal
– Difficult to define, quantify, and control
• Odor composed of 331 compounds in manure
– 30 compounds most common in swine manure
• Most objectionable compounds in manure
___Class___
Volatile fatty
Acids
Ammonia and
Amines
Indoles and
Phenols
Odor threshold
____ppm____
.001
20.0
1.0
46.8
___Compound___
____Smell_____
Butyric acid
Rancid butter
Isobutryic acid
Rancid butter
Caproic acid
Isocaproic acid
Valeric acid
Putred fecal
Isovaleric acid
Stinky feet
Propionic acid
Intense vinegar
Phenylpropionic acid
Lauric acid
Acetic acid
Vinegar
Ammonia
Acrid
Amines
Putrescine
Rotting flesh
Cadaverine
Rotting flesh
Trimethyl amine
Trimethyl pyrazine
Tetramethly pyrazine
Indole
Intense fecal
Skatole
Nauseating fecal
Phenol
Ethyl phenol
p-Cresol
Major odor in swine manure
.00021
.005
.001
Substrate
Carbohydrate
Protein
Carbohydrate
Protein
Carbohydrate
Protein
Carbohydrate
Protein
Carbohydrate
Carbohydrate
Protein
Protein
Protein
Protein
Protein
Protein
Protein
Protein
Protein
Protein
Protein
___Class___
___Compound___
Sulfur-containing Hydrogen sulfide
Compounds
Dimethyl sulfide
Diethyl sulfide
Methyl mercaptan
Ethyl mercaptan
Odor threshold
____Smell_____
____ppm____
Rotten eggs
.0072
Rotten eggs
.001
Skunk
.002
Skunk
.001
Substrate
Protein & TM
Protein & TM
Protein & TM
Protein & TM
Protein & TM
• Common divisions used in discussing odors
–NH3
–H2S
–Volatile organic compounds
•No single chemical has been identified as a good indicator of odor
•Difficult to control odor by any single approach
• Measurement of odor
– Gas measurement
• Air samples are collected and analyzed for specific, individual
gaseous compounds
• Measured with:
– Patches
– Indicator tubes
– Meters
– Electronic sensors
– Gas chromatograph/mass spectrometer
• Advantages
– Accurate measure of individual gases
» Allows for specific numeric standards
» Useful for measuring gaseous compounds with
specific health effects
• Limitations
– Manure odor is not associated with any single compound
– Olfactometry
• Odors are measured by a trained panel of humans
• May be measured
– On location
» Scentometer
» Field sniffer
– In laboratory
» Dynamic, triangular forced-air olfactometer
• Characteristics to describe odor
– Concentration
» Detection threshold
Volume of normal air needed to dilute odor sample to
the point where the difference is detected by 50% of
the panel members
» Recognition threshold
Volume of normal air needed to dilute an odor sample
to the point that the panel can recognize the
compound
– Intensity
» Describes the strength of the odor relative to different
concentrations of n-butanol
– Persistence
» Amount of air needed to dilute air around a livestock
unit to the point where the odor is not smelled
– Hedonic tone
» Measurement of the unpleasantness of an odor
» Scale of measurement is 1 to 10
– Character descriptors
» A description of the smell
• Advantages
– There is a direct correlation between odor and the sense of
smell
– Measures the complete mixture of gases
• Limitations
– Olfactometry is subjective
» Imprecise
» Difficult to regulate
• Health effects of odors
– Within buildings
• Toxicity of two compounds
– Ammonia
– Hydrogen sulfide
• Ammonia
Concentrations, ppm Exposure ________Effects____________
20
Decreased disease resistance
50
100
<150
500
<1000
>4000
5000
– Smells at 50 ppm
< 1 day
Eye and throat irritation
Severe cough
6 weeks Impaired pulmonary function
< 1 day Scarring of upper and lower airway
30 min Sore nose and throat
Irritation of upper respiratory
tract
Severe damage to upper and
and lower respiratory tract
< 30 min Death
• Hydrogen sulfide
– Most dangerous of gases
– Colorless
– Can be smelled at 1 ppm, but concentrations > 150 ppm inhibits
smell
» Makes H2S particularly dangerous
» Requires monitoring equipment
– Gas is heavier than air
» Concentrates in pits and holding tanks
» Dangerous when agitated
– Acute toxicity
Concentration, ppm Exposure
100
> 1 hr
200
1 hr
375
4 hr
500
30 min
>500
1000
-
Human effects
Swine effects
Eye and nose irritation
None
Headache, dizziness
Pulmonary edema
Nausea, excitement,
insomia
Severe pulmonary edema
Unconsiousness,
Spasms, convulsions
death
cyanosis, death
– Chronic toxicity
» Occurs at long-term exposure at 300 ppm
» Symptoms
Asthma, bronchitis, sinusitis, hay fever, progressive loss of lung
function, chronic obstructive pulmonary disease
– Effects of H2S on lungs are uniform throughout the
respiratory tract
» Particularly damaging to deep pulmonary structures, causing
edema
– Toxicity effects
»
»
»
»
Binds mitochondrial cytochrome oxidase
Blocks oxidative phosphorylation and ATP production
Causes build up of lactic acid in body
Neurophysiological abnormalities
Impaired balance
Impaired hearing
Impaired memory
Impaired mood
Impaired intellectual function
– Workplace limit
» 10 ppm H2S
– Community effects
• Response to NH3, H2S, and VOCs
• Symptoms
–
–
–
–
–
–
–
Headache
Runny nose
Sore throat
Coughing
Diarrhea
Burning eyes
Negative mood (Tension, depression, anger, fatigue, confusion)
• Odor recommendations
– Based on dilution ratio of clean air:air from livestock operation
– Odor shall not exceed a 7:1 dilution at a residence in two periods/day for
more than 7 days per year
– Odor shall not exceed a 15:1 dilution at the property line for one
period/day for more than 14 days per year
• Factors affecting odor complaints
– Frequency of problem
» 86% of farmers tolerate neighbor’s odor if problem occurs > 2
days/year
» 50% of farmers tolerate neighbor’s odor if problem occurs > 10
days/year
– Intensity of problem
– Duration of problem
– Offensiveness of odor
– Relations with neighbors (Time of residence, previous contact)
– Odor plume (Direction, topography)
• Origin of livestock odor
Odor compound
Large intestine
Carbohydrates
(Starch, cellulose)
Protein
Volatile fatty acids
(Acetic, Propionic, Butyric acids;
may be absorbed or excreted)
H2S and mercaptans
(Passed as gas)
Other amines, phenols, and
indoles (Absorbed from LI &
excreted in urine)
Manure
Carbohydrates
(Secondary
fermentation
Lactic acid
greater at:
Manure pH > 4.5;
High manure moisture;
High ambient temperatures)
Air
Volatile fatty acids and alcohols
Protein
Butyric acid
NH3, H2S, mercaptans, branched
chain VFAs (Isobutyric, Isovaleric),
Amines (Putrescine, Cadaverine),
Phenols (Phenol, p-Cresol),
Indoles (indole, Skatole)
CH 4
Emissions increased with increased temperature, moisture, humidity, agitation,
dust, pH, wind, surface exposure
• Livestock management to reduce odors
– Reduce excessive protein feeding
• Reducing protein swine diets from 18 to 14% reduced odor
components by 40 to 86%
• Nonruminants
– Balance essential amino acids to create ideal dietary protein with
crystalline amino acids
– Use multi-phase and split-gender feeding
– Avoid safety margins in protein feeding
– Use genetically lean pigs
– Use growth promoters
– Minimize feed waste
• Ruminants
– Supply only enough ruminally degraded protein to meet the NH3
needs of the rumen bacteria
– Beyond the microbial NH3 needs, meet animal’s metabolizable protein
needs with ruminally undegrade protein sources or crystalline amino
acids
– Use phase feeding of beef feedlot or dairy cows
– Control feed wastes
– Reduce sulfur in mineral supplements
• Can reduce odor by 40%
• Utilize salts other than sulfates or sulfides for trace minerals
– Increase cellulose or other nonstarch polysaccharides in
swine diets
• Causes bacteria in large intestine to incorporate NH3 into
microbial protein
• Reduces NH3 by as much as 35%
• Ingredients to add:
– Soy hulls
– Sugar beet pulp
– Distillers grains
– Mask odor with other odors
• Garlic powder has been used for poultry
– Feeding sarsaponin
• Extracted from yucca plant
• Inhibits urease
– Feeding zeolites
• Minerals that have cation exchange capacity
– Binds odor compounds
– Reduce dust from animals’ skin
• Increase quality of dietary fat
• Feed adequate zinc
• Management of livestock facilities to manage manure
odor
– Frequent cleaning of wet manure and feed from facilities
• Manure standing for more than 5 days will cause considerable
offensive odor
– Use bedded systems
• Odor seems less offensive than liquid systems
• Addition of organic matter from bedding reduces odor
– Reduce dust within and outside buildings
• Approaches
– Frequent cleaning
– Spraying vegetable oils
» Reduce NH3 and H2S by 30%
» Spray once daily
» Use a medium droplet size
» Problem with oily facilities
– Installation of wet scrubbers
» Wetted pads 3 to 5’ in front of ventilation fans
» Traps dust with some NH3, H2S, and NOx
» Effectiveness on odors?
– Use of chemical additives
• Alum (K Al(SO4)) will reduce some NH3 emissions
– Use Biofiltration
• A system that uses aerobic bacteria to degrade gaseous odors
from ventilated air
• Process
Aerobic bacteria
VOC & inorganic gases
CO2 + H2O + Mineral salts +
Microbial biomass
• Fiber mat serves as media
– Shredded wood and compost (50:50)
– Shredded wood and soil (50:50)
– Straw and compost
• Less effective during periods of high ventilation
• Can be difficult to control vegetation and rodents
– Use Biomass filters
• Walls of corn stalks, corn cob or other materials placed
immediately outside ventilation fans
• Effects
– Reduces dust by 52 – 83%
– Reduces odor by 43 – 90%
– Use windbreak walls
• Walls placed 10 – 20 ft downwind from ventilation fans
• Effects
– Settle dust near barn
– Disperses odor plume upward to increase dilution
– Use natural windbreaks
• Rows of trees or other vegetation
• Effects
– Trap dust
– Aids in dispersion and dilution of odor
– Provides a visual barrier
• Management of manure storage to limit odor
– Aerobic treatment
• Liquid manure
– Air is pumped into liquid manure
– Should oxidize odor-causing chemicals
– Difficult to mix enough O2 to be effective
• Solid manure
– Composting
» Requirements
Appropriate moisture (50%)
Adequate C:N ration (>20:1)
Aerobic conditions (Frequent mixing)
Temperature
(130oF for 3 days)
– Oxidizes odor and incorporates N-containing compounds into
microbial protein
– Effects
» Reduces odor by 75% in 2 weeks
– Management of anerobic lagoons
• Complete anerobic digestion is effective at limiting odors
• Odors can be controlled if:
– Loading rate is slow and uniform enough to allow balance of
bacteria producing VFAs or CH4
» Allows development of purple sulfur-oxidizing bacteria
Metabolize VOCs
Reduce amines
A purple or pink color of lagoon is desirable
• Factors affecting odors in lagoons
– High loading rates
» Excess animal numbers
» Inadequate dilution water
– Windy conditions
» Disturbs surface
– Timing of agitation and pumping for application
» Should be done on clear, sunny days when warm air causes
odors to rise and disperse
– Early spring turnover
» Odor problems increase as bacterial action begins to
increase digesting nutrients that were incompletely
metabolized over winter
– Use covers over storage facilities
• Covers over manure structures
– Rigid covers
» Concrete, wood, fiberglass, plastic
» Materials must be noncorrosive
– Flexible covers
» Tarp over manure with a blower
• Floating covers
– Natural
» Crust floating on top of manure
– Artificial organic
» Straw, chopped corn stalks, wood shavings
– Artificial
» Polystyrene foam, air-filled clay balls, geotextile
– Effectiveness
» Provides a barrier between liquid manure and the
atmosphere
» Provides aerobic media to all microbes to degrade
odor compounds
» Limitations
Straw will only last from 2 weeks to 6 months
– Anerobic digesters
• Produce methane for biogas
• Reduce odors by 70 – 80%
– Additives
• Biological
– Microbial additives
» Cultures added to degrade odor compounds
» Effectiveness?
• Chemical
– Oxidizers and pH control
» Limited effectiveness
– Masking agents
» Volatile compounds that smell pleasant
» Sprayed on or above manure
» May separate from manure downwind
– Absorbents and Adsorbents
» Activated carbon, zeolite, bentonite, or sphagnum moss
» Effectiveness?
– Antimicrobial oils
» Includes plant oils like thymol and carvacol
» Inhibit microbial degradation of manure during anerobic
storage, but degrade in aerobic conditions after application
» Preserves nutrients and reduces odor emissions
» Still in research
» Economics?
– Natural windbreaks
• Creates a visual barrier
• Filters, disperses and dilutes odor
– Separation of manure solids and liquid
• Can be mechanical or gravity
• Separates urea in urine from urease in feces
• Effects
– Reduces NH3
– Reduces odor by 50%
• Manure application management to control odors
– Manure odor problems are directly proportional to the surface
area for emissions
• The area of manure application is the greatest source of manure
odor
– Factors affecting manure odor during application
• Form of manure
– Earthen basin > Below barn pit > Anerobic lagoon > Solid > Compost
• Lagoon management
– Lagoon should be large enough to leave a permanent pool to
stabilize microbial population
– Apply in June through fall
» Odors reduced when microbes are most active
– Dilute manure with water liberally
» 2 – 3 parts H2O : 1 part manure
– Test for salt and NH3 concentration
– Stop lagoon feeding 2 weeks before pumping
» Allows bacteria the opportunity to degrade odor
• Application method
– Injection of manure into soil
» Most effective at preventing odors
– Surface application with incorporation
» Must be done immediately after application
– If surface applying liquid manure by irrigation make sure
to:
» Set sprayer for large droplets
Reduce droplet surface area
» Adequately dilute manure with clean water
2:1
» Monitor wind direction
Shut down if wind blows towards neighboring residences
» Monitor wind spead
Shut down if wind speed exceeds 5 mph
Prevents dilution of odor
• Consideration of neighbors as a method to control
manure odor nuisance complaints
– Siting of operation and fields for manure application
• Major tool to limit odor nuisance complaints
• Considerations
– Distance
» Odors decreases exponentially with distance
» Distances (Required to use the Master Matrix)
> Residences
>¼ mile from buildings
>750 ft from manure application-Surface applied
> Residential development
>1 mile from buildings
>750 ft from manure application-Surface applied
– Topography
» Don’t build uphill from residences
– Prevailing winds
» Don’t build so residences are downwind of the
prevailing winds
Especially during the spring
– Building orientation
» Short side of livestock facility should be perpendicular
to the neighbor’s residence
– Timing of manure application
• Tell neighbors when you plan to spread manure
• Select days when wind is blowing away from neighbors
• Avoid spreading manure on weekends, holidays, or on days
when neighbors have a social event planned
– Facility maintenance
• Maintain buildings and grounds around facilities
– Mow grass
– Control weeds
• Proper dead animal disposal
• Avoid spilling manure on roads