Mitigation of methane emissions from the northern Australian Beef herd – extension to field laser research

Summary

Methane (CH4) emissions associated with beef production systems in Northern Australia are yet to be quantified for commercial sized herds. Methodologies are available to measure individual emissions, but application in extensive grazing environments is challenging. A micrometeorological methodology for estimating herd scale emissions using an indirect open-path spectroscopic technique and an atmospheric dispersion model is described. Livestock emissions have been measured for properties in Queensland and Northern Territory. As part of the extension to the original project B.CCH.1004, Mitigation of methane emissions from the northern Australian beef herd, methane measurements using open path lasers (OPL) have also been obtained from two sites in the Northern Territory; Douglas Daly Research Farm, and AACo Brunette Downs. 
These additional campaigns have measured methane flux from Brahman cross and composite heifers grazing predominantly unimproved pastures typical of northern Australia. At both sites methane emissions were measured using OPL for up to 5 h per day for at least 12 days and estimated with a bLS dispersion model. Calculated daily methane emissions (g CH4/d) for 12 valid measurement periods (11 to 22 August 2011) obtained at Kidman Springs for Brahman and Brahman x Senepol cross heifers (mean  sem liveweight 316  4.5 kg) ranged from 65  18.4 g/d to 257  25.8 g/d. Data obtained at Brunette Downs (27/04/2012 to 14/05/2012) on the Barkly Tablelands for composite heifers (mean  sem liveweight 287  6.2 kg) grazing an Astrebla sp. dominated sward has yet to be processed. 
An additional campaign is proposed for August 2012 on Hamersley Station, WA and will add further emission data for benchmarking heterogeneous grazing systems across northern Australia. This report documents two campaigns conducted as part of the project extension (B.CCH. 1063).