Methane emissions from beef cattle – a comparison of paddock- and animal-scale measurements

摘要: Methane (CH4) emissions from a herd of 58 grazing cattle were determined in field experiment using paddock-scale (micrometeorological) methods. The also measured daily each animal, the sulfur hexafluoride tracer method. methods exploit how gas, once emitted cattle, is transported and dispersed by wind. Hence, emission rate may be calculated measurements windspeed, wind direction turbulence statistics, as well CH4 concentration upwind downwind herd. include mass-budget approach, flux-gradient method gas dispersion model. Accuracy can assessed unprecedented detail because animal-scale (reference) included all individuals herd, measurement site was ideal for micrometeorological (flat, usually windy free obstructions that alter turbulent airflow). hand-reared steers average weight 325 ± 20 kg. Based on method, over 9 days 161 ± 20 g/steer.day. model, when utilising vertical profiles, yielded 27% greater emissions. other agreed with provided at least 22 m away location measurements. When allowed to graze closely 5 m instruments, gave than method; reasons this are discussed.