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

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.

Assessing the inter-annual variability of separation distances around odour sources to protect the residents from odour annoyance

In recent years, there has been a growing concern about potential impacts on public health and wellbeing due to exposure to environmental odour. Separation distances between odour-emitting sources and residential areas can be calculated using dispersion models, as a means of protecting the neighbourhood from odour annoyance. This study investigates the suitability of using one single year of meteorological input data to calculate reliable direction-dependent separation distances. Accordingly, we assessed and quantified the inter-annual variability of separation distances at two sites with different meteorological conditions, one in Brazil and the other in Austria. A 5-year dataset of hourly meteorological observations was used for each site. Two odour impact criteria set in current regulations were selected to explore their effect on the separation distances. The coefficient of variation was used as a statistical measure to characterise the amount of annual variation. Overall,for all scenarios, the separation distances had a low degree of inter-annual variability(mean coefficient of variation values from 8% to 21%). Reasonable agreements from year to year were therefore observed at the two sites under investigation, showing that one year of meteorological data is a good compromise to achieve reliable accuracy. This finding can provide a more cost-effective solution to calculate separation distances in the vicinity of odour sources.