understanding livestock odors ron sheffield animal waste extension specialist l.
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Understanding Livestock Odors Ron Sheffield Animal Waste Extension Specialist. Odors from Livestock Facilities. Odors from Livestock Facilities. Highly emotional issue Rural development Economic importance of livestock industry

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odors from livestock facilities
Odors from Livestock Facilities
  • Highly emotional issue
  • Rural development
  • Economic importance of livestock industry

Only after we understand the problem can we work towards acceptable solutions.

olfaction sense of smell
Olfaction-Sense of Smell
  • Complex
  • Evokes a reaction
  • Humans detect > 10,000 odors
  • Mixtures of gases
  • Able to detect extremely low concentrations
conception of odors and smells
Conception of Odors and Smells
  • Describe a childhood odor memory
  • What is your favorite odor? Why?
  • Describe your most unusual odor memory
normal olfactory sensitivity
Normal Olfactory Sensitivity

Ansomic Condition

Hypersensitive Condition

Population Detecting Odor (%)

Normal Sense of “Smell”

Odor Concentration

how are odors produced
How are odors produced?
  • By-products of microbial degradation of manure and organic matter
  • Uncontrolled anaerobic conditions
  • Highly dependent on the amount and type of microbial activity
manure decomposition
Manure Decomposition
  • Over 80 to 200 different gasses identified
  • Manure gasses related to anaerobic decomposition
    • Ammonia (NH3+)
    • Methane (CH4)
    • Hydrogen sulfide (H2S)
  • Odorants
    • volatile fatty acids
  • Dust and other particulate matter
manure gasses
Manure Gasses
  • Hydrogen Sulfide
  • Methane
    • colder climates, poor ventilation, anaerobic decomposition of stored manure
  • Ammonia (NH3)
    • dominates in warmer climates
    • anaerobic by-product
    • compounded by recycling of lagoon effluent for waste handling
  • Sources
    • Feed
    • Dried Manure
    • Dander (dead skin)
    • Hair
  • Other particulate matter
    • viral, bacterial, and fungal agents
    • endotoxin, glucans
  • Dual role as possible odorant and odor carrier
odor and gas emissions
Odor and Gas Emissions
  • Parameters that effect odor and microbe production
    • moisture content
    • temperature
    • pH
    • oxygen concentrations
    • environmental conditions (season, wind patterns)
manure gases
Manure Gases
  • Nose detection at low levels
    • Hydrogen Sulfide (H2S)
  • Nose detection at high level
    • Methane (CH4)
  • Some gases may have a compounding odor effect
odor emission sources
Odor Emission Sources
  • Livestock buildings
  • Manure storage units
  • Land application sites
  • Method of land application
  • Feed storage
  • Mortality storage or disposal units
odor sources
Odor Sources
  • “Background” odor
    • buildings
    • lagoons or storage ponds
  • Seasonal variations in odor
  • “Short-term” odors
    • agitation
    • land application / spray irrigation
odor and gas emissions18
Odor and Gas Emissions
  • Can be controlled through design and management
    • ventilation system
    • management and “housekeeping” practices
    • waste management system
    • waste application system
odor chemistry
Odor Chemistry
  • Odorous Compounds
    • Aliphatic (fatty) Acids
    • Amines
    • Ammonia
    • Aromatics
    • Sulfur (inorganic and organic)
compounds produced through anaerobic decomposition
Compounds Produced through Anaerobic Decomposition
  • Methane
  • Carbon Dioxide
  • Carbon Monoxide
  • Ammonia
  • Hydrogen Sulfide
  • Acetic, Propionic, Butyric Acids
  • Cadaverine and Putresine - bacterial breakdown of amino acids
  • Odors are caused by this group of radicals

CHO- Aldehydes

CH2OH- Carbinols

CO-2 Carbonyls

COOH- Carboxyls

OH- Hydroxyl compounds

SH- Sulphydryls

  • Odor/smell is due to the presence of different molecules

C2H5OH Ethyl Alcohol, sweet-smelling

C3H5OH Allyl Alcohol, irritating smell

C9H19OH Nonyl Alcohol, offensive smell

oxygen transfer
Oxygen Transfer
  • Replacement of oxygen by sulfur
  • Non-odorous compounds

H2O Water

H2O2Hydrogen Peroxide

CO2 Carbon Dioxide

  • Compounds become odorous

H2S Hydrogen Sulfide

H2S2Hydrogen Persulfide

CS2 Hydrogen Disulfide

biochemical oxidation
Biochemical Oxidation
  • Proteins, amino acids & carbohydrates are plentiful energy source for bacteria
  • Aerobic or anaerobic process
  • Bacteria “transfer” oxygen from compounds to a hydrogen acceptor

2NO3- + 12H+ = N2 + 6H2O

CO2 + 8H+ = CH4 + 2H2O

SO4 + 10H+ = H2S + 4H2O (odorous)

purple sulfur bacteria psb
Purple Sulfur Bacteria - PSB
  • Biochemical Oxidation in Anaerobic Lagoons in NC and southern US
  • Purple lagoon color
  • Photosynthetic bacteria
  • Use H2S as an electron acceptor instead of O2 and NO3
  • Reduces emission of sulfur compounds and sulfur based odors


Light-dependent reactions (photophosphorylation)



Dark reaction (CO2 fixation)




Oxygenic: Green plants, algae, cyanobacteria

Anoxygenic: Purple, green and Heliobacteria


Light-dependent reactions (photophosphorylation)



Dark reaction (CO2 fixation)



*** H2O is electron donor

*** H2S is electron donor

anaerobic lagoons
Anaerobic Lagoons
  • Studies have been inconclusive relating environmental conditions to the presence of PSB in lagoons
    • loading rate (TS, VS, NH3, SO4)
    • class of animals
    • Temperature
    • Lagoon start-up procedures
odors and gases
Odors and Gases
  • Odor Intensity
    • measure of detection sensed by the nose
  • Gas Concentration
    • actual concentration of gas in the air
  • The relationship between odor intensity and gas concentration is different for each gas
gas vs odor measurement
Gas vs Odor Measurement
  • Gas
    • Identify individual gases
    • Measure concentrations
  • Odor - Olfactometry
    • Analyze mixture
    • Correlates with odor
    • Uses human sense of smell
gas measurement
Gas Measurement
  • Instantaneous
  • Integrated average
  • Precision & detection limit
gas measurement33
Gas Measurement
  • Patches
  • Tubes - Indicator & Diffusion
  • Jerome® meter - H2S
  • Electronic Sensors
  • GC / Mass Spectrometer
odor intensity vs gas concentration
Odor Intensity vs. Gas Concentration
  • Weak positive correlation's for some gases
    • Ammonia (NH3)
    • Hydrogen Sulfide (H2S)


    • High odor intensities indicate high gas concentrations of NH3 and H2S
    • However, high gas concentrations do not necessarily indicate a high odor intensity
odor transport
Odor Transport
  • Difficult to document the impact area of gases
  • Transmitted via air currents
    • wind direction
    • wind speed
    • weight of gas
    • adsorption to dust particles
limits to measuring odors
Limits to Measuring Odors
  • Changes in weather or micrometeorological conditions
    • temperature, humidity, inversions
  • Odor emissions change with time
  • Wind speed and direction
  • A snap-shot in time may not reflect the conditions an hour/day before or after a measurement
technologies to control odor
Technologies to Control Odor
  • Prevent odor generation
  • Capture or destroy odors before any release to the atmosphere
  • Dispersion or disguise of odors
odor prevention technologies
Odor Prevention Technologies
  • Anaerobic treatment
  • Aeration or Oxidation
  • Feed additives
  • Manure pit or lagoon additives
  • pH control
technologies to capture odors
Technologies to Capture Odors
  • Manure storage covers
    • synthetic
    • organic mats
  • Biofilters
  • Biomass filters
  • Washing walls
technologies to disperse odors
Technologies to Disperse Odors
  • Site Selection
  • Ventilation Design
  • Vegetated Wind Breaks
  • Windbreak Walls
  • Stacks or Chimneys
  • Perfumes
  • Masking Agents