Methane emissions from ruminant livestock are one of the big contributors to agriculture’s carbon footprint – but the amount of ozone-layer-depleting methane emitted by Australia’s cattle herd has been overestimated significantly, thanks to the use of outdated methodology, say researchers.
A multi-institutional team led by CSIRO scientists used new methodology to analyse data collected over the past eight years as part of Meat and Livestock Australia’s (MLA’s) methane abatement research program. Using the new system of data analysis, the team found that annual emissions of methane gas from the national cattle herd were around 24 percent lower than had been estimated previously.
The adjusted emissions rate for the national cattle herd is equivalent to 12.6 million tonnes of carbon dioxide annually.
The National Greenhouse Gas Inventory (NGGI) has been updated to reflect the new information.
Employing the new methodology to analyse the data brings the NGGI estimates into line with those of the Intergovernmental Panel on Climate Change (IPCC), the world’s leading international body on the assessment of climate change, established by the United Nations Environment Programme (UNEP) and World Meteorological Organization (WMO) in 1988.
Why the discrepancy?
CSIRO’s Dr Ed Charmley said the new research into Australia’s cattle herd emissions was conducted to address concerns about the large differential between NGGI estimates and those made by the IPCC, and subsequent doubt regarding the accuracy of previous methods used to calculate methane emissions for Aussie cattle, particularly northern Australian cattle.
“Different methods used to calculate emissions from livestock in temperate and tropical regions were based on studies done in the 1960s and 1990s, mainly with dairy cattle,” explained Dr Charmley. “Both of these past methods were found to be likely overestimating the emissions from cattle.
The revised methodology
“The revised method, which is based on improved ways of estimating ruminant methane emissions from forage-fed beef and dairy cattle, be they in temperate or tropical regions, has been tested against international defaults provided by the IPCC and found to give consistent methane yields.”
According to MLA General Manager for On Farm Innovation Matthew McDonagh, the new Australian research yielded a more accurate dataset, which shows that Australia’s cattle population contributes substantially less to overall methane emissions than was believed previously.
“This revelation clearly shows livestock-based emissions are nowhere near what they were thought to be, and will help improve the accuracy of Australia’s national greenhouse gas emissions estimates,” Dr McDonagh said.
“This is positive news for the Australian livestock sector as it seeks to continually improve its production efficiencies and demonstrate its environmental credentials.”
Management measures to reduce cattle methane emissions
MLA Manager for Sustainable Feedbase Tom Davison said the latest findings from the National Livestock Methane Program (NLMP) also showed that there are several simple management measures producers can implement to reduce methane emissions substantially, simultaneously boosting productivity.
“Some of these are as simple as integrating leucaena into grazing systems, improving growth rates or herd reproductive performance, while other future techniques may include feeding red-algae to livestock and have been prioritised for further research,” Dr Davison said.
“We look forward to continuing to make further gains in this field for the mutual benefit of both our livestock industries and environmental sustainability.”
The analysis of Australian cattle research data was conducted by CSIRO; the Victoria State Government Department of Economic Development, Jobs, Transport and Resources; the New South Wales Department of Primary Industries (NSW DPI); University of New England (UNE); and the Queensland Government Department of Agriculture and Fisheries (DAF), with technical input from the Australian Government Department of Environment.
The new methodology for estimating cattle methane emissions was published online in the journal Animal Production Science in January 2016.