A dynamic model of ammonia emission from urine puddles

Urine puddles have been identified as one of the main sources of ammonia in pig-rearing houses. Ammonia emission and puddle characteristics were measured for 36 simulated urine puddles under different temperatures, air velocities and initial urea concentration conditions. The measurements were used to calibrate and validate a dynamic urine puddle model that considers the processes of evaporation, urea conversion, change in liquid concentration and puddle pH, in order to simulate the amount of ammonia emitted from a puddle. Based on general agreement (correlation coefficient, R) and bias (fractional or normalised bias, FB) tests between measured and simulated values for water volume (R=0.99, FB=0.007), total ammoniacal nitrogen concentration (R=0.90, FB=−0.157) and total emission (R=1.00, FB=0.003), the model was deemed reliable and accurate. The measurements and simulations in this experiment show the impact of puddle pH and changing environmental conditions on the average puddle emission rate, and that ammonia emission will continue to occur as long as there is a liquid surface.