If you eat kangaroo meat thinking it is free of the environmentally harmful greenhouse gases produced by the bucketloads by farm animals, think again.
Researchers have busted that myth, finding that kangaroos produce as much gas as other herbivores such as horses.
A collaboration between researchers from University of Wollongong, University of New South Wales and the University of Zurich in Switzerland found that kangaroos produce about three litres of methane each day, although that amount can vary depending on how much and what each animal eats.
"Kangaroos are not mysteriously low methane-producing creatures, but herbivores with an active methane-producing microbe community," researcher Marcus Clauss said.
It was previously thought that kangaroos had a unique gut bacteria that meant they produced little to no greenhouse gas. Environmentalists and kangaroo meat producers have long marketed the meat as an alternative to beef and lamb; researchers said dairy cows each produce up to 200 litres of methane every day.
In 2011, scientists floated the idea of transplanting this gut bacteria to cows and sheep to reduce their carbon footprint.
Researcher Adam Munn said kangaroos could still be considered environmentally friendly, as they produced significantly less methane than cows. They also eat less food and drink less water than traditional livestock.
John Kelly, executive officer of the Kangaroo Industries Association of Australia, was sceptical of the research, saying kangaroos remained a more environmentally friendly choice.
"There's a whole range of reasons to eat kangaroo; harvest is the only mechanism to control the population, which is essential to manage grazing pressure and encourage a whole lot of plant diversity," he said.
"The industry has been steadily growing for a number of years."
Dr Munn and his long-time collaborator, Mr Clauss, spent months measuring the output of two groups of kangaroos, one fed a controlled diet, and the other allowed to eat as much as they wanted. They found that if a kangaroo is well fed, it will produce less methane than its hungry cousin. This is because fermentation is part of kangaroo's digestive system, which means that food passes through the gut faster and there is less time for microbes to break down the food and produce gas.
Methane is a greenhouse gas that is 22 per cent more potent than carbon dioxide and contributes to global warming and climate change.
The findings follow a 2012 report that found that wallabies also produced methane.
A study published in the journal Conservation Letters in 2008 recommended Australia reduce its cattle and sheep populations and increase its kangaroo numbers to 175 million by 2020, which would lower greenhouse gas emissions by 16 megatonnes annually.
Worldwide, 28 per cent of all greenhouse gas emissions come from livestock.
