Scientists around the world are studying the amount of methane in cow burps and Argentine researchers say they have come up with a unique way.

Attaching a red plastic tank to a cow's back and connecting it through a tube to the animal's stomach, scientists say they can trap bovine burps and analyze them.

"When we got the first results, we were surprised. Thirty percent of Argentina's (total greenhouse) emissions could be generated by cows," said Guillermo Berra, a researcher at the National Institute of Agricultural Technology.

One of the world's biggest beef producers, Argentina has some 55 million heads of cattle grazing on the famed Pampas grasslands.

Berra said the researchers "never thought" a cow weighing 550 kg (1,210 lb) could produce 800 to 1,000 litres (28 to 35 cubic feet) of emissions each day.

At least 10 cows are being studied, Berra said, including some in a corral whose burps are collected in yellow balloons hanging from the roof.

Greenhouse gases are widely blamed for causing global warming. Methane, researchers say, is 23 times more potent than carbon dioxide in trapping heat in the atmosphere and can be found in animal waste, landfills, coal mines and leaking natural gas pipes.

Scientists are working to develop new diets for cows that could make it easier for them to digest food, moving them away from grains to plants like alfalfa and clover.

"We have done a preliminary study and have found that by using tannins, you can reduce methane emissions by 25 percent," said Silvia Valtorta of the National Council of Scientific and Technical Investigations. (Additional reporting by Nicolas Misculin; Writing by Kevin Gray; Editing by John O'Callaghan)