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Enteric and Simulated Pen Surface Emissions of Nitrous Oxide from Beef Cattle Feedyards

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  10th International Livestock Environment Symposium (ILES X)  .(doi:10.13031/iles.18-093)
Authors:   David B Parker, Kenneth D Casey, Heidi M Waldrip, Jenny Jennings, Kristin Hales, Richard Todd
Keywords:   Air quality, animal feeding, beef cattle, emissions, feedlot, feedyard, global warming, greenhouse gas

Abstract. Nitrous oxide (N2O) is a greenhouse gas with a global warming potential higher than methane (CH4) or carbon dioxide (CO2). The objectives of our research were to 1) quantify enteric N2O emissions from beef cattle, and 2) quantify N2O emissions from beef feedyard pen surfaces. Live animal enteric emissions were measured using respiration calorimetry chambers. Non-steady state chambers were used to quantify simulated pen-surface emissions. Air-dried feedlot manure was subjected to simulated rainfall (6, 12, 25, or 51 mm), real and artificial urine (6 kg m-2) or fresh feces (2.4 and 4.8 kg m-2) at varying temperatures (6°C, 11°C, 21°C, 27°C, 31°C, 38°C, or 46°C) and monitored for 20 to 45 d. In all experiments, gas concentrations were measured with real-time continuous instruments. Mean live animal enteric N2O emission rates were 10.3 and 19.0 mg N2O-N animal-1 d-1. Cumulative manure N2O emissions were positively correlated with rainfall. A single N2O episode was observed following rainfall addition to dry manure between 6°C and 27°C, while two N2O episodes were observed ≥ 31°C. Cumulative manure N2O emissions from rainfall on dry manure were positively correlated with temperature, with a step-increase at 31°C. Cumulative N2O emissions from urine on dry manure were 31% to 70% of emissions from equal mass of water. Cumulative N2O emissions from cattle feces on dry manure were 8.6% of emissions from equal mass of water. The magnitude of N2O emissions from feedyards was attributed to the following processes: rainfall > urine >> enteric ≈ feces. Information learned from this research will be useful for developing emission factors, and for selecting best management practices for reducing greenhouse gas emissions from beef cattle feedyards.

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