Effect of climate parameters on air exchange rate and ammonia and methane emissions from a hybrid ventilated dairy cow building

Naturally ventilated dairy cattle buildings are one of the major sources for ammonia and greenhouse gas emissions to the atmosphere. Generally it is difficult to clean the air from naturally ventilated buildings. In order to reduce the emissions, a hybrid ventilation system, which is natural ventilation combining with mechanical partial pit ventilation, has been developed. By full-scale measurement, this study was to quantify ammonia and methane emissions and to investigate the impacts of climate parameters on gaseous emissions, air exchange rate (ACH) and concentrations at sampling locations in a dairy cattle building with hybrid ventilation. The results revealed that 64–83% of ammonia emissions were collected by partial pit ventilation while 10–50% of methane emission was collected. The results showed that ammonia emission through natural ventilation was around 60% lower than the value found in literatures. ACH was significantly influenced by wind speed and wind direction (wind angle in the range of 135–270°) in summer. The ACH increased generally with wind speed in winter while it hardly changed with wind speed when the windows opening ratio was 6% and even lower. The paper further investigated the impact of wind speed and outdoor temperature on ammonia emissions.