Site, environmental and airflow characteristics for mono-slope beef cattle facilities in the Northern Great Plains

Authors: CORTUS, ERIN - South Dakota State University; AL MAMUN, MD RAJIBUL - South Dakota State University; Spiehs, Mindy; AYADI, FEROUZ - South Dakota State University; DORAN, BETH - Iowa State University; KOHL, KRIS - Iowa State University; POHL, STEPHEN - South Dakota State University; CORTUS, SCOTT - South Dakota State University; STOWELL, RICHARD - University Of Nebraska; NICOLAI, RICHARD - South Dakota State University

Submitted to: Transactions of the ASABE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/2014
Publication Date: 2/26/2015
Publication URL: http://handle.nal.usda.gov/10113/61655
Citation: Cortus, E.L., Al Mamun, M.R.H., Spiehs, M.J., Ayadi, F.Y., Doran, B.E., Kohl, K.D., Pohl, S., Cortus, S.D., Stowell, R., Nicolai, R. 2015. Site, environmental and airflow characteristics for mono-slope beef cattle facilities in the Northern Great Plains. Transactions of the American Society of Agricultural and Biological Engineers (ASABE). 58(1):123-135.

Interpretive Summary: Mono-slope buildings are a popular form of roofed and confined cattle feeding facilities in the Northern Great Plains. Cattle producers consider mono-slope barns for various reasons including lower risk of runoff, ease of labor, manure management and better performance compared to open lot feedlots. These facilities are generally east-west oriented with openings on the north and south side of the barn. The north side has a smaller opening with adjustable curtains that allow the producer to increase or decrease airflow through the facility. Airflow is a critical parameter for understanding the barn environment. Measuring airflow and air quality parameters in a naturally ventilated barn, and in particular mono-slope barns, is complicated by large openings and variable wind velocity and direction within the openings. Production-scale barn airflow data for mono-slope barns were not found in the literature. A two-year monitoring study was conducted using four mono-slope beef barns in the Northern Great Plains region to determine air flow through these facilities. Airflow was measured on the north and south sides of the barns during open and closed curtain conditions. The results indicated that insignificant or minimal temperature and relative humidity differences were measured between the north wall opening and ambient conditions outside the barn. Airflows through the north wall openings were more consistent and predictable than airflows through the south wall openings. Airflows were consistent between pens for the north wall opening. In the south wall opening, closed curtain conditions created differences in air velocity and direction between pens. The north wall opening airflow measurements provide a more realistic and representative value for the building airflow. For every unit of wind velocity (m s-1), there were 7 air changes per hour for closed curtain conditions and 33 air changes per hour for open curtain conditions.

Technical Abstract: In conjunction with an emission monitoring study, long-term airflow and environmental data were collected from four regional producer-owned and -operated mono-slope beef cattle facilities in the Northern Great Plains. The barns were oriented east-west, with approximate dimensions of an 8-m south wall opening height, and 27 m deep in the north-south dimension. The north wall curtain openings were adjusted by the producers seasonally or daily, and classified as Open (> 1.5 m, mean = 2.1 m) or Closed (< 1.5 m, mean = 0.5 m). The temperature, relative humidity and air velocity through the north and south wall openings were monitored at a fixed height near the center of the openings. On-site weather towers provided corresponding ambient temperature, relative humidity and air velocity and direction data. The airflow was calculated as the product of the air velocity and opening area. The hourly mean airflows for the north and south wall openings were modeled as functions of perpendicular (to the barn opening) ambient air velocity (10-m height) and curtain opening. Theoretical airflows using the wind pressure coefficient method were also calculated. Based on comparisons between monitoring locations within an opening, north and south wall opening airflows, and measured versus theoretical values, greater confidence was given to airflow measurements for southerly airflow and Open conditions. Airflow measurements for northerly flow and Closed conditions were low compared to south wall opening measurements and theoretical values. In light of the systemic and random uncertainties associated with the monitoring method, the north wall opening airflow was deemed a reasonable measurement of airflow through the barn (i.e., for emission calculation purposes) for Open and Closed conditions. As the ambient wind velocity increased, the airflow through the barns increased from near zero air changes per hour in still air in a linear pattern. With a 5 m s-1 south wind, there were approximately 10-70 air changes per hour (ACH) for Closed conditions in the four barns, and 160 ACH with Open curtains. The average relationships between airflow and ambient wind velocity were 7 and 33 ACH (m s-1)-1 for Closed and Open conditions, respectively. These data inform emission estimating methodologies, as well as producers, for this type of beef cattle facility in the Northern Great Plains.