Measurement of Atmospheric Ammonia, Methane, and Nitrous Oxide at a Concentrated Dairy Production Facility in Southern Idaho Using Open-Path FTIR Spectrometry

Abstract

The number of dairy cows in Idaho has increased by approximately 80% in the last decade, with the majority of these facilities located in southern Idaho, causing air quality concerns in this region. To determine the potential air quality impacts of these facilities, we measured ammonia (NH3), methane (CH4), and nitrous oxide (N2O) concentrations over the pens, wastewater storage pond, and composting area on a 700-cow open-lot dairy using open-path Fourier transform infrared spectrometry (OP/FTIR). Concentrations were measured for one or two days at each location during January, March, June, and September. Median NH3 concentrations over the pens, storage pond, and composting area ranged from 0.14 to 0.39 ppmv, 0.04 to 0.17 ppmv, and 0.06 to 0.22 ppmv, respectively, with concentrations tending to be lower in January. Average CH4 concentrations over the pens, storage pond, and composting area ranged from 2.07 to 2.80 ppmv, 1.87 to 2.15 ppmv, and 1.71 to 1.76 ppmv, respectively. Average N2O concentrations ranged from 0.31 to 0.33 ppmv for all areas, which was similar to global background N2O concentrations. Combined ammonia emissions for the pen and storage pond areas, calculated with a backward Lagrangian stochastic inverse-dispersion technique, were 0.04, 0.25, 0.19, and 0.15 kg NH3 cow-1 d-1 for January, March, June, and September, respectively, and methane emissions were 0.34, 0.55, 0.21, and 0.20 kg CH4 cow-1 d-1 for the same months. Assuming this limited monitoring was representative of the entire year, annual emissions from the pens and storage pond were 57 kg NH3 cow-1 and 120 kg CH4 cow-1. These emission rates were similar to the limited number of comparable studies that have been published. However, more extensive monitoring is needed to better quantify variations in emissions throughout the year and among locations.