Ammonia Emissions Affected by Airflow in a Model Pig House: Effects of Ventilation Rate, Floor Slat Opening, and Headspace Height in a Manure Storage Pit

摘要

Laboratory experiments were performed to study the influence of airflow on ammonia emissions from pig house slurry in a model growing/finishing pig house with slurry in the pit and a clean slatted floor with various opening areas, 100%, 33.3%, and 16.7%. The 100% opening area meant that the headspace was an integral part of the room air space, and this configuration was used as the reference treatment. The pig house model had two sidewall inlets and exhaust in the middle of the ceiling. The liquid slurry used was from a growing/finishing pig building and consisted of 1% to 2% dry matter, had pH of 8.05, and TAN (total ammonia nitrogen) of 2.38 g/L. Experiments in a model growing/finishing swine barn were conducted to determine the effects of room ventilation rate, slurry pit air exchange rates, slatted floor openings, and pit headspace on ammonia emissions. The results showed that ammonia emission rate increased as ventilation rate increased with a constant inlet opening. Increase in the slatted floor opening ratio increased the air exchange rate in the slurry pit, resulting in a higher ammonia emission rate. Different correlations between the ammonia emission rate and the air headspace height in the slurry pit caused by the type of flow in the boundary layer influenced the ammonia transport from the slurry surface to the ventilation air. A statistical model was developed to calculate the ammonia emission rate as a function of ventilation rate, slatted floor opening ratio, and slurry pit headspace (R 2 = 0.93). It was found that the NH 3 emission rate was more sensitive to the ventilation rate than to the slatted floor opening ratio and air headspace height in the pit. In addition, the NH 3 emission rate was much more sensitive to variations in the ventilation rate at low ventilation rates than at high ventilation rates. Similar sensitivity responses were obtained for both slatted floor opening ratio and air headspace height.