AMMONIA DISPERSION FROM MULTI-FLOOR VERSUS STANDARD SINGLE-FLOOR PIG PRODUCTION FACILITIES BASED ON COMPUTATIONAL FLUID DYNAMICS SIMULATIONS

Abstract

● NH3 dispersion from a multi-floor pig building was compared to a single-floor building.● NH3 dispersed much further from the multi-floor pig building.● Wind speed, direction and source concentration were important for NH3 dispersion.● NH3 tended to accumulate in the east and west yards of the multi-floor pig building.● Higher wind speed was the likely cause of more NH3 accumulation in the yards. Multi-floor buildings for raising pigs have recently attracted widespread attention as an emerging form of intensive livestock production especially in eastern China, due to the fact that they can feed a much larger number of animals per unit area of land and thus alleviate the shortage of land available for standard single-floor pig production facilities. However, this more intensive kind of pig building will pose new challenges to the local environment in terms of pollutant dispersion. To compare the dispersion air pollutants (ammonia as a representative) emitted from multi- versus single-floor pig buildings, ammonia dispersion distance and concentration gradients were investigated through three-dimensional simulations based on computational fluid dynamics. The validation of an isolated cubic model was made to ensure the simulation method was effective. The effects of wind direction, wind speed and emission source concentration at 1.5 m (approximate human inhalation height) during summer were investigated. The results showed that the ammonia dispersion distance of the multi-floor pig building was far greater than that of the single-floor building on a plane of Z = 1.5 m. When the wind direction was 67.5°, the wind speed was 2 m·s−1 and the emission source concentration was 20 ppmv, the dispersion distance of the multi-floor pig building could reach 1380 m. Meanwhile, the ammonia could accumulate in the yard to 7.68 ppmv. Therefore, future site selection, wind speed and source concentration need to be given serious consideration. Based on the simulation used in this study with source concentration is 20 ppmv, the multi-floor pig buildings should be located 1.4 km away from residential areas to avoid affecting residents. The results of this study should guidance for any future development of multi-floor pig buildings.

Keywords

• pig building|computational fluid dynamics|ammonia|dispersion