ODOR MITIGATION FOR CONCENTRATED ANIMAL FEEDING OPERATIONS: WHITE PAPER AND RECOMMENDATION

Current Status Odor from Concentrated Animal Feeding Operations (CAFOs) • CAFOs affect air quality through emissions of odor, specific odorous gases (odorants), odorcarrying particulates (including organic, inorganic, and biological particulate matter), and volatile organic compounds (VOCs). • Odor from CAFO sources, as experienced by humans, is the composite of 170 or more specific gases in trace concentrations. • Odorous gases of primary concern often include hydrogen sulfide (H2S) and VOCs, including volatile fatty acids. • Odor research in the field and laboratory has largely focused on measuring concentrations in terms of dilutions to threshold (odor units per cubic meter) and odor intensity based on category or reference scaling. Emission Characteristics • Data on odor/odorant emission rates, flux, and emission factors are seriously lacking. • Systematic efforts have not yet been initiated to develop accurate emission factors for odorous gases (VOCs, H2S, etc.) that properly represent CAFOs in the U.S. and are needed to develop science-based permitting and abatement policies. Human Response • Odor from CAFOs can cause physiological or psychological health responses with regard to (a) frequently exposed neighbors at high concentrations, and (b) certain people with particular sensitivities for whom the health effects are of greater concern. Current Federal and State Policies • Federal and State policies regarding CAFOs primarily have addressed water quality protection from point sources under the Federal Clean Water Act and equivalent state statutes; however, only in a few cases have these policies addressed odor and odorants. Integrated Mitigation Programs • Approaches to control odor and odorants include: ration/diet modification, manure treatment, capture/treatment of emitted gases, and enhanced dispersion. Each of these mitigation approaches includes several specific technologies. • A particular CAFO may require implementation of one, two or more approaches in order to meet the environmental quality demands of the area in which it is located.