Understanding livestock odors ron sheffield animal waste extension specialist
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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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Understanding livestock odors ron sheffield animal waste extension specialist l.jpg

Understanding Livestock OdorsRon SheffieldAnimal Waste Extension Specialist

Odors from livestock facilities l.jpg
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.

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Olfaction-Sense of Smell

  • Complex

  • Evokes a reaction

  • Humans detect > 10,000 odors

  • Mixtures of gases

  • Able to detect extremely low concentrations

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Conception of Odors and Smells

  • Describe a childhood odor memory

  • What is your favorite odor? Why?

  • Describe your most unusual odor memory

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Normal Olfactory Sensitivity

Ansomic Condition

Hypersensitive Condition

Population Detecting Odor (%)

Normal Sense of “Smell”

Odor Concentration

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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

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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

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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

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  • 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

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Odor and Gas Emissions

  • Parameters that effect odor and microbe production

    • moisture content

    • temperature

    • pH

    • oxygen concentrations

    • environmental conditions (season, wind patterns)

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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

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Odor Emission Sources

  • Livestock buildings

  • Manure storage units

  • Land application sites

  • Method of land application

  • Feed storage

  • Mortality storage or disposal units

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Odor Sources

  • “Background” odor

    • buildings

    • lagoons or storage ponds

  • Seasonal variations in odor

  • “Short-term” odors

    • agitation

    • land application / spray irrigation

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Odor and Gas Emissions

  • Can be controlled through design and management

    • ventilation system

    • management and “housekeeping” practices

    • waste management system

    • waste application system

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Odor Chemistry

  • Odorous Compounds

    • Aliphatic (fatty) Acids

    • Amines

    • Ammonia

    • Aromatics

    • Sulfur (inorganic and organic)

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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

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  • Odors are caused by this group of radicals

    CHO- Aldehydes

    CH2OH- Carbinols

    CO-2 Carbonyls

    COOH- Carboxyls

    OH- Hydroxyl compounds

    SH- Sulphydryls

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  • 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

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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

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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)

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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

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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

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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

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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

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Gas vs Odor Measurement

  • Gas

    • Identify individual gases

    • Measure concentrations

  • Odor - Olfactometry

    • Analyze mixture

    • Correlates with odor

    • Uses human sense of smell

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Gas Measurement

  • Instantaneous

  • Integrated average

  • Precision & detection limit

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Gas Measurement

  • Patches

  • Tubes - Indicator & Diffusion

  • Jerome® meter - H2S

  • Electronic Sensors

  • GC / Mass Spectrometer

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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

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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

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Dust & Lagoon Interaction Related to Odor Transport


Odorous Compounds

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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

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Technologies to Control Odor

  • Prevent odor generation

  • Capture or destroy odors before any release to the atmosphere

  • Dispersion or disguise of odors

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Odor Prevention Technologies

  • Anaerobic treatment

  • Aeration or Oxidation

  • Feed additives

  • Manure pit or lagoon additives

  • pH control

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Technologies to Capture Odors

  • Manure storage covers

    • synthetic

    • organic mats

  • Biofilters

  • Biomass filters

  • Washing walls

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Technologies to Disperse Odors

  • Site Selection

  • Ventilation Design

  • Vegetated Wind Breaks

  • Windbreak Walls

  • Stacks or Chimneys

  • Perfumes

  • Masking Agents