Air Quality Monitoring Based on Manure Chemistry and Emission Modeling

Outdoor animal manure basins and tanks emit various hazardous and odorous gases into the atmosphere. These gaseous emissions are subject to various local, state, and federal air quality regulations that require air quality monitoring. For example, Minnesota has an ambient air quality standard for hydrogen sulfide of 30 ppb (v/v). Missouri requires concentrated feedlot operations to have property-line scentometer readings below 5.4 dilutions to threshold, olfactometry measurements below 7 dilutions to threshold, and odor intensities below 225 ppm n-butanol in air. Provisions of the Comprehensive Environmental Response, Compensation, and Liability Act (40 CFR 302) require facility operators to notify the U.S. EPA when daily emission rates of listed hazardous gases exceed the specified reportable quantities. The reportable quantities of hydrogen sulfide, ammonia, and cresols are each 45.4 kg/day (100 lb/day). To meet these and other regulations, facility operators can face substantial costs for air quality monitoring. One option for reduced monitoring costs and improved precision in odor measurements is to characterize the chemistry of the manure, use emission models to estimate the emission rate of individual gases, and use dispersion-based air quality models to estimate ambient gas concentrations downwind of manure basins.