Effect of ventilation on distributions, concentrations, and emissions of air pollutants in a manure-belt layer house

Abstract

Air pollutants from poultry operations pose a potential threat not only for bird health, but also for the environment outside. Ventilation is believed to be an effective way of regulating house environment. To improve understanding of ventilation effects on house environment, distributions, concentrations and emissions of ammonia, carbon dioxide, total suspended particulates, and particulate matter 2.5 (fine particles with a diameter of 2.5 μm or less) were investigated in a manure-belt layer house using 9 ventilation stages (VS) with different ventilation rates (VT). Distributions of pollutants were assessed visually using contour plots and coefficient of variation. Emission rates of pollutants were estimated by multiplying VT by concentration. Spatial distributions of 4 pollutants were not homogeneous throughout the house, regardless of VS, and increased VT aggravated the spatial disparity. In the house, pollutant concentrations were controlled under harmful levels during the 9 VS. Ventilation, as expected, can decrease pollutant concentrations. However concentrations of ammonia and carbon dioxide did not decrease proportionately to increased VT. The highest emission rates of 4 pollutants were observed during VS1, a stage with maximum ventilation, which reflected VT as a key factor determining emission rate. The study indicated that it is difficult to balance house environment and control pollutant concentrations depending only on ventilation. Several additional factors, such as temperature, humidity, manure handling, bird management, and ventilation system design, should be comprehensively considered to control air pollutants from poultry operations.