Ammonia emissions from a beef cattle feedyard on the southern High Plains

Concentrated animal feeding operations (CAFOs) are major sources of ammonia emitted into the atmosphere. There is considerable literature on ammonia emissions from poultry and swine CAFO, but few comprehensive studies have investigated large, open lot beef cattle feedyards. Ammonia emission rates and emission factors for a 77-ha, 45 000-head commercial beef cattle feedyard on the southern High Plains were quantified using measured profiles of ammonia concentration, wind speed and air temperature, and an inverse dispersion model. Mean summer emission rate was 7420 kg NH 3 d −1, and winter emission rate was about half that, at 3330 kg NH 3 d −1. Annual NH 3–N emission rate was 4430 kg NH 3–N d −1, which was 53% of the N fed to cattle. Daily per capita NH 3–N losses increased by 10–64% after the daily per capita N in feed rations increased by 15–26%. Annual emission factors for the pen area of the feedyard were 19.3 kg NH 3 (head fed) −1, or 70.2 kg NH 3 Mg −1 biomass produced. Annual emission factors for the retention pond of the feedyard were estimated to be 0.9 kg NH 3 (head fed) −1, or 3.2 kg NH 3 Mg −1 biomass produced.