UNSW Researchers Track Cattle Methane Emissions for Climate Impact Study
A team of scientists from UNSW were recently awarded a grant to verify the measurements of atmospheric methane from the newly launched high-resolution methane-sensing satellite, MethaneSAT, opens in a new window.
The UNSW methane science team leader, Associate Professor Bryce Kelly from the School of Biological, Earth & Environmental Sciences, opens in a new window, says the belching and manure from bulls, steers, heifers and cows is responsible for nearly one third of Australia’s reportable methane emissions.
He and the team will measure these methane emissions directly from feedlots, using high-precision methane analysers attached to cars and aircraft.
The data collected from these surveys will be used to validate the rate of methane emission estimates derived from MethaneSAT’s measurements.
The findings will then inform the Australian agricultural sector on how to improve the management of their methane emissions.
The project was funded just ahead of the release of the Global Methane Budget 2024, opens in a new window, which found methane emissions from human activities increased by 20% in the past two decades.
Why verify methane emissions?
In response to a Climate Change Authority assessment, opens in a new window that Australia has “failed to keep pace with global developments and investment in methane measurement capability”, the federal government this year announced a new initiative to accurately measure—and report—methane emissions.
The Authority then released their ‘Sector Pathways Review, opens in a new window’, to help Australia reach net zero emissions by 2050. The report outlines pathways for six sectors, including agriculture and land.
“The accurate measurement of emissions is a crucial first step for implementing reduction strategies,” Prof. Kelly says.
However, he says the world relies largely on bottom-up accounting methods of greenhouse gases, and that these are often prepared by financial accounting firms.
“These are guesstimates of our net emissions, not a true rate of annual emissions,” Prof. Kelly says.
“For the bulk of Australia’s greenhouse carbon accounting, we do not measure the true rate of atmospheric emissions or removals,” he says. “Rather, we estimate the emissions using Excel calculations that use emission factors and productivity data.”
The Intergovernmental Panel on Climate Change (IPCC), opens in a new window and Australian Government-approved approaches for measuring methane emissions are currently both over- and under- estimating by millions of tonnes for various industrial and agricultural sectors.
This is where the team from UNSW come in.
Do cattle really cause that much harm?
The more we eat, the more gas we produce. But cattle need to let out a whole lot more gas than humans do: they emit an estimated 50 to 95 kg of methane per head, per year.
A/Prof. Kelly says there is still uncertainty associated with these estimates. Australia’s cattle population is approximately 30 million—and in 2022 it was estimated that they produced 1.4 million tonnes of methane emissions from enteric fermentation, via their burps.
Australia reports its emissions using standardised carbon dioxide equivalents – which means methane emissions are converted to a carbon dioxide equivalent. One molecule of methane has a global warming potential equivalent to 28 molecules of carbon dioxide over a 100-year period.
“Methane emissions from cattle account for approximately 33% of Australia’s reportable methane emissions, or approximately 10% of Australia’s reportable carbon dioxide equivalent emissions,” A/Prof. Kelly says.
As the human population grows, so too do the number of cattle we need for meat, dairy and other animal products. The global cattle population has increased from 410 million in 1890 to a current estimate of 1.5 billion. This growth contributed to the rise of methane in the atmosphere from a pre-industrial concentration of approximately 700 parts per billion (ppb) to 1931 ppb today.
A/Prof. Kelly says a United Nations Environment Programme (UNEP), opens in a new window review demonstrates that reducing methane emissions is the most cost-effective way to achieve the initial aim of the Paris agreement: to keep the global average temperature increase to well below 2°C above pre-industrial levels.
A brief history of measuring methane
A/Prof. Kelly has been mapping methane emissions throughout Australia since 2014.
He was part of the UNEP Methane Science team that undertook the world’s first airborne study, opens in a new window in 2018 to quantify the rate of methane emissions from coal seam gas (CSG) production in Queensland’s Surat Basin.
Many feedlots in the region use the groundwater produced by the CSG sector. So, as part of that study, the team also quantified the methane emissions from many feedlots.
The UNEP Methane Science project is now used internationally as an example of best practice inventory verification. It has been cited every year since in The Australian Government Australian National Greenhouse Accounts submission to the UN FCCC.
“During the Surat Basin study we also noticed that similar sized feedlots and similar grazing cattle properties had different rates of methane emissions,” A/Prof. Kelly says.
“It is likely that different farm management practices influence the rate of emissions.
“If we can identify best management practices with respect to emissions, we can then use these insights to educate other beef producers on how they can lower their emissions through simple measures.”
Looking to the future
This research is part of a long-term project. In Australia, feedlots range from a few hundred to 75,000 cattle. The methane plumes from the largest yards can be mapped for tens of kilometres.
MethaneSAT is already measuring methane concentrations in the atmosphere. The verification of these data with direct measurements from the ground and air will improve the way the data are interpreted.
A/Prof. Kelly says, “We’ll be using MethaneSAT to identify mitigation opportunities and track net zero progress. We’ll also develop products that will help government, industry and the agricultural sector identify mitigation opportunities, determine if methane abatement programs are effective, and track net zero progress.
“Overall, we aim to improve the quality of data being used for carbon management and accounting.”
What will help reduce methane emissions?
A/Prof. Kelly says measurements of methane will take place both before and after attempts to reduce emissions from feedlots and grazing cattle landscapes.
The latest solution to reduce cattle burps and manure methane emissions is adding red seaweed, Asparagopsis, to cattle feed. Early trials, opens in a new window show this can reduce the amount of methane emitted by a single animal by up to 98%.
“However, it remains to be demonstrated that seaweed projects can scale industry wide,” A/Prof. Kelly says. “I suspect it will be a partial solution.”
A recent Murdoch University research review, opens in a new window found that Asparagopsis fed to cattle could cause ulceration, haemorrhaging and inflammation in their stomachs. The review also found they generally tend to avoid Asparagopsis.
Other research into reducing methane emissions from cattle includes methane vaccinations, methane inhibitors and manure management treatments.
But the first step? Just knowing what’s there.
“Best practice management requires high quality data to test ideas and guide optimising emission reduction programs,” A/Prof. Kelly says.
“We hope our work inspires others to join this collaborative research to reduce Australia’s methane emissions.”