Researchers are feeding cows seaweed in the hope of taming their infamous burps, which are contributing to climate change.
Scientists at the University of New Hampshire (UNH) are feeding cows a mixture of different kinds of seaweed – along with their normal food – to see if they can reduce their burps, NHPR reported.
Cattle herds and other ruminants are responsible for up to 37% of methane emitted worldwide.
The greenhouse gas is 21 times more potent than carbon dioxide at trapping heat in the atmosphere.
But while cow gas is often the emission that make the headlines, cow burps are the main problem – with up to 95% of methane emissions coming via their mouths.
Andre Brito, associate professor of dairy cattle nutrition and management at UNH, told NHPR: "Cattle is the second largest source of methane in the United States. The industry as a whole is very interested in results to mitigate methane."
Some types of seaweed have compounds that disrupt the ability of microbes in cow stomachs to produce methane, Brito said.
But so far, the seaweed known to disrupt this grows mainly in Australia – and researchers are racing to find seaweed that can be grown easily in other territories, including the US.
Nichole Price, a senior research scientist at the Bigelow Laboratory for Ocean Sciences, based in Maine, and who works with Brito, said: "The question is, are there seaweed species that are native to different regions around the world, and specifically for us to the northeast [US]... that can be produced at a scale necessary to feed to the thousands head of cattle that we generate?"
The researchers believe that seaweed that could be grown in the US might be able to reduce methane by up to 30%, in contrast to 80% for Australian seaweed.
Even that would be equivalent to taking 10 million cars off the road for a year, the researchers said.
In January, methane – a powerful greenhouse gas – passed the alarming milestone of 1,900 parts per billion (ppb) in the atmosphere.
Experts have since called for measures to limit emissions of the gas, which is thought to have contributed 0.5C of warming since pre-industrial times, according to Nature.
Natural gas has become more popular as a relatively 'clean' fossil fuel, with demand soaring by up to 50% in recent decades.
But the problem is not simply due to the fossil fuel industry, according to Euan Nisbet, professor of Earth sciences at Royal Holloway, University of London.
Writing for The Conversation, Nisbet said: "Agriculture, producing about 150 million metric tons a year, is the largest overall source. As are urban landfills and sewage systems, contributing about 70 million metric tonnes annually."
Nisbet said that scientists could monitor the sources of atmospheric methane by studying the proportion of two different isotopes of carbon – carbon-12 and carbon-13.
'Biogenic' methane, which comes from vegetation, is high in carbon-12, while methane from fires and fossil fuels is richer in carbon-13.
Nisbet said: "For two centuries, rapidly expanding gas, coal and oil industries steadily drove atmospheric methane richer in carbon-13. Since 2007, that trend has reversed, and the proportion of carbon-13 in atmospheric methane has decreased.
"Although fossil fuel emissions may still be growing, soaring methane emissions are now primarily the result of faster-growing biogenic sources."
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