Modelling and experimental determination of ammonia emissions rates from a scale model dairy-cow house

A simulation model was developed to predict ammonia emission from a scale model dairy-cow house. The model described the enzymatic urea degradation and volatilization of ammonia from a slatted floor after applying a mixture of urine and feces or after sprinkling of urine. The parameters needed as input for the simulation model to predict the ammonia emission for a period of 24 h were measured or taken from literature. Lack of fit occurred between the predicted and measured emission when urease-activity values from a laboratory analysis of a urine/feces mixture were used. A better agreement was obtained by using an urease-activity which was about ten times higher. The need for a higher urease-activity is in accordance with the observation that due to repeated fouling of the floor the height of the emission peak measured after the application of an urine/feces mixture increased and the time between the application of the mixture and the moment that the emission reached its peak became shorter. This indicated that due to repeated fouling, the amount of urease on the floor surface increased. The developed simulation model can be used as the basis for a model to predict the ammonia emission from a practical dairy-cow house.