Finisher Hog Production in the Southeastern United States: Ancillary Measurements Derived from the National Air Emissions Monitoring Study (NAEMS)
Sang R. Lee1, Wayne P. Robarge1* and John T. Walker2
Measurements of emissions of gases and fine particulate matter from swine animal feeding operations (AFOs) in the southeastern US have typically been confined to relatively short periods (days to several weeks) and have generally focused on the waste lagoons. Access to swine animal housing units and other ancillary information has often been limited. The National Air Emissions Monitoring Study (NAEMS) project provided a unique opportunity to characterize emissions from swine housing units for an extended period of time (~ 2 years), and allowed access to ancillary measurements regarding nutrient flows (feed amounts and composition), manure dynamics, animal inventories, water usage and farm management. Presented here is a summary of the observations made for a NAEMS finisher site (NC3B) selected as being representative of swine production in the southeastern US. Finisher hogs are raised in rotations (~ 140 days) with a target market weight of 123 kg/hog. Among the population in a barn during a rotation (700-800 hogs) the actual growth rate varies with a series of “grade-outs” of market-weight hogs starting ~ 110 days from initial load-in. Derivation of the standing live-weight in the barns during a rotation therefore requires use of a growth model and summation over several different “populations” of hogs within a single barn. Up to 5 different feed formulations are fed during a rotation with %N content ranging from (3.4 to 2.2% N). Across 4 complete rotations, N consumed was ~50 g N per hog per day. Of this amount, we estimate ~ 70% is excreted as fecal matter and urine. The TAN (NH3 + NH4 +) content of the shallow pits is consistently higher (~1885 ±389.27 mg TAN L-1) than that found in the anaerobic lagoon (802 ±72.78 mg TAN L-1), except immediately after recharge following pit-pull (pH of the two liquids was similar). The presence of a recalcitrant layer of sludge in the shallow pits (depths ranging from 5-10 cm, total N content = ) complicates attempts to construct a N mass balance for the barns, and may represent a source of N and S that elevates pit liquid content in addition to daily additions from fecal matter and urine from the hogs. The ancillary information collected during the NAEMS project will provide critical information in order to facilitate the development and test the predictions of processbased models of emissions from shallow-pit hog barns typically used on AFOs in the southeastern United States.
*Corresponding author: Wayne P. Robarge ; 919-515-1454
1North Carolina State University, Department of Soil Science, Raleigh, NC 27695-7619
2U.S. Environmental Protection Agency, NRMRL, Research Triangle Park, NC 27711