Mitigating Methane in Cow Burps: Promising but Not Easy

July 21, 2018



Feeding seaweed to cows could slash the amount of climate change-inducing methane emissions from their burps.

Preliminary research has indicated a small amount of marine algae added to cattle food can reduce methane emissions from cattle gut microbes by as much as 99 per cent.

Now, scientists in California are hoping to help farmers meet strict new emissions targets by performing the first ever tests of seaweed feed in live dairy cows.

While their early results are yet to be released, team leader Professor Ermias Kebreab at the University of California, Davis, said their initial experiments were “very surprising and promising”.

“Results are not final, but so far we are seeing substantial emission reductions,” he said.

“This could help California’s dairy farmers meet new methane-emission standards and sustainably produce the dairy products we need to feed the world.”

Cow digestion relies on millions of microbes in their guts processing and fermenting high-fibre foods.

This process allows the animals to survive on a diet of grass, but it also produces large quantities of methane – a gas responsible for around a quarter of man-made global warming.

Cattle constantly burp and emit the methane being produced in their stomachs. The gas can also be expelled from their rear ends and from manure, but to a lesser extent.

Agriculture is a major contributor to greenhouse gas emissions, and around a third of the emissions from the sector are thought to come from livestock producing methane.

In an attempt to curb this source, California has introduced regulations calling for dairy farmers to cut methane emissions from their 1.7 million cows by 40 per cent over the next decade.

Achieving this goal will require drastic solutions, and Professor Kebreab thinks seaweed could be one of those solutions.


“Since much of a dairy’s methane emissions come from the animal itself, nutrition can play a big role in finding solutions,” he explained.

“The numbers we’re seeing are amazing – well beyond the target that farmers will need to reach.”

In the university’s barns, Professor Kebreab and his team have been testing an algae diet on 12 dairy Holstein cows, and intend to widen their experiments to include more cattle this summer.

To produce feed that the cows enjoy, the researchers cut a small amount of red seaweed with cattle feed and molasses.

Cows are then taken to a device four times a day that measures the amount of methane in their breath as they eat.

Harvard University:

A team of Australian scientists lead by Rocky De Nys (James Cook University) discovered that a certain type of red seaweed, called Asparagopsis taxiformis, can decrease the amount of methane produced by the bacteria found in a cow’s stomach.

Lauren Kuntz explains that methane is a very potent but short-lived greenhouse gas. Limiting methane produced by livestock, a major source of the gas, could help abrogate short-term dramatic global warming (on the scale of a few decades). It would not, however, eliminate the need to cut down on carbon dioxide emissions. Carbon dioxide contributes to the global warming via the greenhouse effect and remains in the atmosphere for a much longer time than methane.

De Nys’s research is still a ways off from being usable in commercial agriculture. To date, the seaweed has been tested in cow’s stomach fluid and in live sheep, but still needs to be tested in live cows. The seaweed is also only available naturally in small amounts. An environmentally sustainable way to grow and distribute the seaweed would be necessary for large scale use. Finally, the availability of future funding will determine the speed of continued research.

But nothing is simple.

But they also realised there was a hitch: like all seaweeds, the Asparagopsis seaweed produces a chemical called bromoform which leaks into the atmosphere and reduces the Earth’s protective ozone layer.

Dr Andy Reisinger, the deputy director of the New Zealand Agricultural Greenhouse Gas Research Centre (NZAGRC), said seaweed production of bromoform “would present a high risk of bromoform leakage into the atmosphere, which would be impossible to control fully in a seaweed farm”.

He said the main mitigation effect did not come from the seaweed itself but from the bromoform that the seaweed produces.

Because it was a simple enough chemical to produce in a laboratory, it would be easier to administer it to animals via a bolus rather than go to the trouble of growing seaweed.

“That would allow a much more accurate dosing and would avoid all the potential negative environmental side-effects of large-scale seaweed production,” Reisinger said.

He also raised the issue of the potential for the chemical to turn up as a residue in food.

He gave the example of how, as soon as residues of the nitrification inhibitor DCD (dicyandiamide) had been detected in food, it was banned outright.

“Given that experience, I for my side cannot imagine that the NZ industry (or any other industry that seeks to trade based on attributes of quality and safety, let alone ‘clean and green’ production) would support widespread use of bromoform in its production chain,” Reisinger said.

Kinley rejected the carcinogen fear. The only study that tested bromoforms on animals was where mice were force fed the chemical at levels 1500 times what livestock would be fed – “guaranteed to cause some problems at that level”.

Regarding bromoforms destroying the ozone layer, Kinley said their role was not yet well understood.

“At some point we have to make judgment calls. I know it’s not good to replace one problem with another but the problem of bromoforms haven’t been quantified whereas the benefits of the seaweed are far reaching.”

Meanwhile New Zealand scientists are working on a number of methane-reducing projects which are showing promise. They include:

* a vaccine that will inhibit methane by 20 per cent, although success is at least a decade away;

* a methane inhibitor or chemical compound fed to animals. This would be administered as a slow release tablet which kills the methanogens in an animal’s stomach;

* breeding low emission cattle and sheep. Selective breeding could reduce methane emissions from animals by 10-20 per cent without harming production, but it would take time;

* low emission animal feeds.


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