Greenhouse gas emissions from Australian beef cattle feedlots

Summary

The project was the first Australian study to measure greenhouse gas emissions from beef cattle feedlots using open-path spectroscopy and atmospheric dispersion modelling.

The average methane (CH4) emission was 113 g head-1 d-1, about 40% lower than estimates using the standard Moe and Tyrrell model, but close to average estimates using the IPCC Tier II model. Thus, results support the use of IPCC Tier II for modelling CH4 emissions in beef cattle feedlots.

Average ammonia (NH3) emission was 176 g head-1 d-1 (nearly three times IPCC Tier II modelled estimates), while average nitrous oxide (N2O) emission was 3.3 g head-1 d-1 (half that of IPCC-modelled emissions). This suggests that the greater-than-expected volatilisation of NH3 may have resulted in less-than-expected nitrogen remaining available for N2O production via nitrification-denitrification.

Indirect N2O emissions from land-deposited NH3 and NOx may be substantial (an additional 75% of the direct N2O emissions). Thus the total greenhouse contribution of N2O emissions (in CO2-e) was estimated at 60% of the feedlot CH4 emission. Average carbon dioxide (CO2) emission was 12.9 kg head-1 d-1. This is somewhat higher than modelled estimates, although livestock-respired CO2 is not considered a net anthropogenic greenhouse gas emission.