Ammonia Emission Characteristics at a Livestock Manure Composting Facility: A Preliminary Assessment Using Passive Air Samplers

Ammonia (NH3) is an important precursor of secondary particulate matter and a major odor-causing compound emitted during livestock manure management. The applicability of passive air samplers (PASs) for spatial NH3 monitoring was evaluated, and a preliminary assessment of NH3 emissions from a livestock manure composting facility was conducted. NH3 uptake by the PASs increased linearly during daytime exposure periods of 30–150 min. Ion chromatography was selected as the quantification method based on comparative evaluation with visible spectrophotometry. The mean NH3 concentrations decreased progressively along the agitation tank, from 39.4 mg/m3 at the tank inlet to 28.6 mg/m3 in the middle and 24.9 mg/m3 at the tank outlet. During the daytime, lower concentrations near windows and entrances suggested dilution by natural ventilation, whereas nighttime concentrations increased to 85.9 mg/m3 after the doors were closed. Vertical measurements revealed lower NH3 concentrations near the floor, whereas concentrations at higher sampling points remained relatively uniform. Based on the daytime and nighttime mean concentrations in the agitation tank, NH3 emissions through mechanical ventilation were preliminarily estimated at 108 kg/day (28 kg during the daytime and 80 kg during the nighttime). These results demonstrate the applicability of PASs for high-resolution spatial monitoring and indicate that both the composting stage and ventilation conditions influence NH3 distribution in composting facilities.