Ammonia Measurements and Emissions Estimates from a California, USA Dairy Using Both Point and Remote Sensors.

Ammonia (NH₃) is an important trace gas species in the atmosphere that can have negative impacts on human, animal, and ecosystem health. Agriculture has been identified as the largest source of NH₃, especially livestock operations. Summer NH₃ emissions from a commercial dairy in California were investigated. Cattle were held in open lot pens, except for young calves in hutches with shelters. Solid manure was stored in the pens while liquid manure from feed lanes was passed through a solids settling basin and stored in a holding pond. Passive sensors and open path Fourier transform infrared spectrometers (OP-FTIR) were deployed around the facility to measure NH₃ concentrations. Emissions from pens and the liquid manure system (LMS) were estimated using inverse modeling. Average emission factors (EFs) were 140.5 ± 42.5 g d^-1 animal^-1 from the passive sampler data and 199.2 ± 22.0 g d^-1 animal^-1 from OP-FTIR data. These EFs are within the range of values reported in the literature. The facility’s summer time emissions were calculated at 265.2 ± 80.2 kg d^-1 and 375.4 ± 27.1 kg d^-1 based on the passive and OP-FTIR data, respectively, representing 38% and 54% of the facility’s estimated daily nitrogen excretion. Both concentrations and emissions exhibited a strong diurnal cycle, peaking in the late afternoon with a minimum in early morning. Total facility emissions exhibited significant positive correlations with temperature and wind speed. The findings of this study show that NH₃ emissions from a commercial dairy 1) can vary by a factor of 10 or more throughout the day and 2) EFs can vary by two orders of magnitude when compared to other U.S. dairies, based on literature values. Full details are available in Moore et al. (2014, Trans. ASABE, 57:181-198).