Emissions of ammonia, methane, carbon dioxide, and nitrous oxide from dairy cattle housing and manure management systems.

Concentrated animal feeding operations emit trace gases such as ammonia (NH₃), methane (CH₄), carbon dioxide (CO₂), and nitrous oxide (N₂O). The implementation of air quality regulations in livestock-producing states increases the need for accurate on-farm determination of emission rates. The objective of this study was to determine the emission rates of NH₃, CH₄, CO₂, and N₂O from three source areas (open lots, wastewater pond, compost) on a commercial dairy located in southern Idaho. Gas concentrations and wind statistics were measured each month and used with an inverse dispersion model to calculate emission rates. Average emissions per cow per day from the open lots were 0.13 kg NH₃, 0.49 kg CH₄, 28.1 kg CO₂, and 0.01 kg N₂O. Average emissions from the wastewater pond (g m(-2) d(-1)) were 2.0 g NH₃, 103 g CH₄, 637 g CO₂, and 0.49 g N₂O. Average emissions from the compost facility (g m(-2) d(-1)) were 1.6 g NH₃, 13.5 g CH₄, 516 g CO₂, and 0.90 g N₂O. The combined emissions of NH₃, CH₄, CO₂, and N₂O from the lots, wastewater pond and compost averaged 0.15, 1.4, 30.0, and 0.02 kg cow(-1) d(-1), respectively. The open lot areas generated the greatest emissions of NH₃, CO₂, and N₂O, contributing 78, 80, and 57%, respectively, to total farm emissions. Methane emissions were greatest from the lots in the spring (74% of total), after which the wastewater pond became the largest source of emissions (55% of total) for the remainder of the year. Data from this study can be used to develop trace gas emissions factors from open-lot dairies in southern Idaho and potentially other open-lot production systems in similar climatic regions.