Development and Sensitivity Analysis of a Dynamic Model for Estimating Ammonia Emissions from Naturally Ventilated Dairy Cattle Buildings

Abstract

Dairy cattle production system is one of the major emission sources in livestock sector, accounting for approximately 12% of the total yearly global ammonia emissions. It is very complicated to measure the ammonia emission rates directly with high accuracy from dairy cattle buildings because they are normally naturally ventilated. Thus a model with the function to predict the ammonia emission by using easily measured or obtained parameters from the available literature would be very helpful. In this paper, a dynamic model was developed based on the classical two-film theory to estimate ammonia emission rate from naturally ventilated dairy cattle buildings with slatted floors. Ammonia emission rates from the slurry pit and slatted floor in the building were calculated using the model, respectively. The overall measured ammonia emission rates were in the range of 11–88 g cow-1 d-1 at air temperatures of 2.3–22.4 oC, while the rates estimated by the model were in the range of 19–107 g cow-1 d-1 for the surveyed buildings. Compared to the filed measurement, the overall ammonia emission rate estimated by the model was approximately 10% higher. A sensitivity analysis was conducted to quantify the sensitivity of the model parameters on ammonia emission rate. The result showed that ammonia emission rate from the naturally ventilated dairy cattle building was highly sensitive to the pH value of the manure in the slurry pit and urine on the surface of the slatted floor.