Modeling Gaseous Emissions From Liquid Swine Waste.

Swine animal feeding operations (AFOs) are sources of emissions for various gases [ammonia (NH3), hydrogen sulfide (H2S), carbon dioxide (CO2), volatile organic carbons (VOCs)], and fine particulate matter. Gaseous emissions from simple aqueous systems are typically controlled by temperature, pH, wind speed, total dissolved concentration of the chemical species of interest (e.g. NH3+NH4 = TAN), and the Henry's law coefficient. Using a simple flow-through Teflon-lined chamber (0.3m × 0.2m × 0.15m), we have compared emissions of NH3 from liquid swine waste obtained from shallow pits from a finisher swine AFO in eastern North Carolina to pure solutions of (NH4)2SO4 under conditions of identical pH, temperature and TAN. Wind speed in the chamber is < 0.05 m/sec. Both liquid formulations exhibit the expected response in emissions with changes in temperature and pH. However, NH3 emissions from the pit liquid are ~ 5 times those from pure solutions of (NH4)2SO4. The large difference in emissions with solutions of equivalent TAN (steam distillation + MgO) suggests the possibility of a synergistic mechanism that is enhancing NH3 emissions. Concurrent measurements as part of the National Air Emissions Monitoring Study (NAEMS) document the emissions of CO2, H2S and VOCs (primarily acetic, propionic and butyric acids) at levels that are comparable to observed NH3 emissions. Controlled experiments are underway to investigate further the potential for enhanced emissions of NH3 due to the concurrent release of other volatile species. If successful, this work will be extended to determine the potential for other synergistic reactions that influence gaseous emissions across the air-liquid interface of swine manure liquid. An additional goal is the potential modification/utilization of existing computer models (e.g. U.S EPA WATER 9) to accurately predict gaseous emissions from liquid swine waste.