National Air Emissions Monitoring Study (NAEMS) Finisher Hog Site NC3B: Observations of Farm Operation and Management

Wayne P. Robarge1*, Jihoon Kang1, Albert Heber2, Erin Cortus3, Lilong Chai2, Kaiying Wang4 and Jiqin Ni2

The NAEMS provides a unique opportunity to continuously observe individual animal confined feeding operations over long periods of time (~ 2 years). Information is presented on the operation and management of a representative swine finisher farm (7200 head permitted capacity; 9 barns) in eastern North Carolina. Animal numbers in the three tested barns (880 capacity) being monitored ranged from ~700 to ~830 hogs/barn for each 20 week growth cycle. Death rates are low (< 2 head/barn/week). Growth rate varies within the population, with an initial grade out of 110 – 120 kg hogs at 16 wks (~185 hogs). A second grade out typically occurs between 17 – 19 wks, prior to final “runout” at 20 wks (~ 500 hogs). Five different feed formulations available on demand are used each cycle. Percent total nitrogen content of these formulations ranges from 2.2 to 3.5% N. Total feed consumed is over 180,000 kg per barn per 20 wk growth cycle. The barns are tunnel-ventilated (3 122-cm dia. and 2 91-cm dia. fans), but also contain baffles above the side-curtain walls that work in combination with the end wall curtain to ensure a well-mixed and uniform environment for the hogs. Default duty cycle is 10 min. for the stage 1 fan (91-cm dia.), till overridden by the difference between internal and exterior temperatures. As internal temperatures increase, various combinations of fans turn on and off changing the total volume of air exiting the barn. At the final fan stage, all fans are operating and the end wall curtain is fully lowered. Waste generated by the hogs is handled through a shallow pit (~48 cm from animal floor to bottom of the pit). The pit is drained (pull-plug) once per week and then flushed and filled with liquid from the nearby anaerobic lagoon. Sludge depth within the pit varies the length of the barn (2.5 to 12.5 cm) and undoubtedly with age, complicating attempts to quantify a nitrogen balance. TAN content and pH of pit liquid is sometimes higher (~ 1800 mg TAN/L; pH 7.6) than that found in the primary lagoon, depending on season of the year. Presence of a surface crust on the pit liquid will complicate modeling the air-water exchange of gases. The supplemental information gathered by the NAEMS project will facilitate the development of process-based models to describe gaseous emissions from animal confined feeding operations

* Wayne P. Robarge: ; 919-515-1454
1 North Carolina State University, Department of Soil Science, Raleigh, NC 27695-7619
2 Purdue University, Agricultural and Biological Engineering, West Lafayette, IN 47907
3 South Dakota State University, Ag. and Biosystems Engineering, Brookings, SD 57706
4 Zhejiang University, Ag. Bio-Environment Engineering Inst., Hangzhou, P.R. China