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Odor - Assessment and Treatment Alternatives

CTU = Conservation Treatment Unit
NCPS = National Conservation Practice Standard
CAFOs = Concentrated Animal Feeding Operations

Odor - Affects air quality through emissions of specific odorous gases (odorants), odor-carrying particulates (including organic, inorganic and biological particulate matter,) and volatile organic compounds (VOCs). Agricultural sources of odor come primarily from the uncontrolled decomposition of animal waste. As experienced by humans, odor is the composite of 170 or more gases in trace concentrations. Odorous gases of primary concern often include: hydrogen sulfide (H2S), ammonia (NH3), methane (CH4) and VOCs, including volatile fatty acids. Odor is measured in terms of dilutions to threshold (odor units per cubic meter). Odor from CAFOs can cause direct or indirect (physiological or psychological) health responses in people with regard to neighbors frequently exposed at high concentrations, and certain people with particular sensitivities for whom the health effects are of greater concern. Treatable factors affecting odor emitted by animal waster are: moisture content, pH, temperature, and oxygen availability. Currently, there are no federal or Montana state-specific statutes or rules that directly regulate or control odors or establish setback limits.

Is the CTU within 10 miles (upwind) of a neighbor, concentrated population (>1 house per acre), a city or town or a major transportation facility (freeway, interstate highway, state highway, or commercial airport)?

Yes or No. This question addresses concerns with safety factors and nuisance odors, so proximity, prevailing wind direction and speed are considerations in determining if odor is a resource concern. If yes, consider practices/management techniques that will reduce or eliminate generation of gases associated with nuisance odors (H2S, NH3, CH4, etc.) such as:

  • Bio-filter installation on building exhaust and Amendments for Treatment of Agricultural Wastes (NCPS Number 591)
  • Feed management (NCPS Number 592)
  • Avoid �fertigation’ with sprinkler systems using animal waste
  • Manure moisture control
  • Manure management (NCPS Numbers 590, 313, 633)
  • Liquid waste injection (Waste Utilization, NCPS Number 633), timing and notification
  • Same day solid waste incorporation (Waste Utilization, NCPS Number 633)
  • Composting (NCPS Number 317)
  • Waste Facility Cover (NCPS Number 367) or aeration system
  • Waste utilization, handling and management (NCPS Numbers 313, 633, and 317)
  • Frequent waste transfer/removal/scraping (NCPS Number 634)
  • Comprehensive Nutrient Management Plan (CNMP)
  • Construction of living and/or artificial windbreaks, herbaceous wind barriers and/or hedgerow plantings (NCPS Numbers 380, 386, 561, 589c, 603), to benefit air flow patterns as needed
  • Anaerobic Digester (NCPS Number 366)
  • Constructed wetlands for wastewater treatment.
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