Contents lists available at ScienceDirect Agricultural and Forest Meteorology journal homepage: www.elsevier.com/locate/agrformet Ammonia and greenhouse gas emissions at beef cattle feedlots in Alberta Canada S.M. McGinn a, ⁎ , T.K. Flesch b a Agriculture and Agri-Food Canada, Lethbridge, T1J 4B1, AB, Canada b Department of Earth and Atmospheric Sciences, University of Alberta, Edmonton, T6G 2E3, AB, Canada ARTICLE INFO Keywords: Cattle Feedlot Ammonia Methane Nitrous oxide Carbon dioxide ABSTRACT This study was conducted at beef cattle feedlots, over two years in southern Alberta Canada, and focused on deriving the ammonia, methane, nitrous oxide and carbon dioxide emissions from two feedlots from June/July to October. Line-averaging sensors were used to measure ambient gas concentrations in the vicinity of the feedlots, and an inverse dispersion method was used to calculate emissions. Results show that ammonia and methane emissions were consistent with that measured from other studies. Both feedlots lost about 40% of the nitrogen feed intake as ammonia. The emission of nitrous oxide, when compared on a greenhouse gas bases, was similar to the methane emission. A diet difference between feedlots coincided with a slight difference in feedlot methane emission. There was good agreement between previously reported ammonia and methane emission rates and those derived in our feedlot study. Further evaluation of the underlying relationships causing variation in emissions should follow. A key to understanding emissions at commercial feedlots is to fully engage the management data available. 1. Introduction Beef cattle feedlots, where thousands of cattle are grouped together to enable greater control of feed management and meat production, are hot spots in the agricultural landscape for ammonia (NH 3 ), methane (CH 4 ) and nitrous oxide (N 2 O). Ammonia emitted from cattle manure is affiliated with various ecosystem and human health concerns, and is also an indirect greenhouse gas (GHG). Feedlots are also sources of direct GHG’s including CH 4 eructated from the cattle rumen and N 2 O and CH 4 emitted from cattle manure (Rahman et al. 2013). As well, cattle respire carbon dioxide (CO 2 ); however, this source is not gen- erally considered a net GHG contributor since the carbon is assumed to be re-cycled within the agricultural system. Quantifying the emission rate of these environmentally important gases is essential to our un- derstanding of the impact of agriculture on the ecosystem. Ideally, the emission rates of these different gases should be measured simulta- neously to account for any interactions between their emissions (Leytem et al. 2011; Bai et al. 2015). For example, Hünerberg et al. (2014) found that an increase in dietary dried distillers’ grain (DDG) coincided with a reduction in cattle enteric CH 4 emissions due to an response to fat, but a corresponding increase in DDG crude protein (CP) equated to greater manure NH 3 emission and the potential for increased deposition and more surface N 2 O emission. There are several methods available to measure gas emissions from distinct sources (Harper et al. 2011; McGinn 2013), where each method is generally associated with a specific spatial scale. For example, at the individual animal scale, face masks, head-hood chambers, whole-an- imal chambers and tunnels, and a ratiometric approach using a tracer gas (e.g., SF 6 ), are used. At a larger scale encompassing emissions from entire animal facilities, micrometeorological approaches such as the inverse dispersion method (IDM) have the advantage of not interfering with the management of the animals. Quantifying the enteric CH 4 emissions from a cattle feedlot using an IDM technique can be a difficult task, where the scale is large and the source distribution is not uniform due to cattle movement within the facility. Similar concerns exist for NH 3 , but with the added difficulty that monitoring concentration is complicated due to its highly reactive nature, e.g., deposition to a crop. Despite these limitations, advance- ments in measurement techniques and sensors have allowed for si- multaneous measurements of gas concentrations at cattle feedlots (Bai et al. 2015).] The objective of our study was to evaluate whole-feedlot emission measurements of NH 3 , CH 4 ,N 2 O and CO 2 using IDM at two https://doi.org/10.1016/j.agrformet.2018.01.024 Received 17 July 2017; Received in revised form 6 January 2018; Accepted 18 January 2018 ⁎ Corresponding author. E-mail address: sean.mcginn@agr.gc.ca (S.M. McGinn). Abbreviations: bLS, backwards Lagrangian stochastic; FTIR, Fourier Transfer Infrared; IDM, inverse dispersion method; LAL, line-averaging laser; N, nitrogen; NC, number of cattle; TAN, total ammonical nitrogen Agricultural and Forest Meteorology xxx (xxxx) xxx–xxx 0168-1923/ Crown Copyright © 2018 Published by Elsevier B.V. All rights reserved. Please cite this article as: McGinn, S.M., Agricultural and Forest Meteorology (2018), https://doi.org/10.1016/j.agrformet.2018.01.024