LAUSR

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.