Non-interference measurement of CH4, N2O and NH3 emissions from cattle

Abstract

A technique combining open-path Fourier transform infrared spectroscopy with an inverse-dispersion model was used to quantify methane (CH4), nitrous oxide (N2O) and ammonia (NH3) emissions from an isolated cattle pen in south-eastern Australia. Twenty-eight Angus steers (1-year old, initial average liveweight 404 kg) were fed a 60% grain diet and kept in a pen (20 × 20 m) for 41 days. Gas concentrations were measured downwind of the pen using an open-path Fourier transform infrared spectroscopy with a path length of 100 m, having a detection sensitivity of 2, 0.3 and 0.4 ppb for CH4, N2O and NH3, respectively. Daily emission rates were 232, 14 and 192 g/cattle.day for CH4, N2O and NH3, respectively. The measured CH4 emissions were in agreement with predictions based on Australian National Inventory recommendations, however, measured N2O and NH3 emissions were much higher than the predicted values. Extrapolation of our measurements would mean that CH4 and N2O emissions from beef feedlot cattle contribute 3.1% and 5.9% of the Australian agricultural CH4 and N2O emissions, respectively.