How Scientists Tackle Methane Emissions With Killer Viruses and Algae Regimes


The intestine of a cow is a whole foreign world. In the digestive tract of cattle, dozens of organisms settle into position, digesting and fermenting the grass and the food that passes through them. Some of these microbes convert sugars into other molecules, others suck in carbon dioxide and hydrogen and, as a result, produce methane.

Cows and other ruminants spit out this methane – a particularly troublesome problem on a warming planet. Methane is a powerful greenhouse gas, with an even greater warming potential than carbon dioxide. The vast majority of methane emissions come from human activities such as burning fossil fuels and consumer waste, but ruminant emissions are a significant contributor, accounting for around 15%.

Fortunately, the methane-producing microbes in the gut are themselves “food”, hunted down by even smaller enemies: viruses.

Viruses land on the microbe, like a NASA rover landing on Mars, pierce the outside of the body and inject their own genetic code. As part of this process, they destroy microbes. Scientists believe they could ally with viruses to control methane-producing microbes, or methanogens, in the intestines of livestock or synthesize new compounds that lower methane emissions. And that’s not the only potential ally they’ve turned to.

Researchers are also study the potential of algae to neutralize methane in the intestine. Introducing small amounts of red algae to livestock feed reduced methane emissions by about 80%. The development of mitigation strategies like these could reduce agricultural methane emissions without harming the overall health of the animal.

As world leaders, activists and academics gather in Glasgow, Scotland for COP26, the first United Nations conference on climate change, CNET Science examines some of the technological advancements being developed to help tackle the climate crisis. While technology can help us adapt or mitigate the effects of climate change, it alone is not a solution to the problem. A drastic reduction in carbon emissions is needed for the world to limit global warming to 1.5 degrees Celsius by the turn of the century – the main goal of the 2015 Paris Agreement.

Nonetheless, research and development of new technologies will allow more tools to be added to the climate change toolbox. One of these tools is the germ-killing viruses that naturally inhabit a cow’s gut. Algae, another. So how can we use them?

It’s not a phage, it’s a way of life

Life is divided into three “areas”. Eukarya, which includes everything from mushrooms and frogs to cows and humans, contains only a tiny fraction of all organisms on Earth. It is overshadowed by the other two areas: bacteria and archaea.

These two domains are made up of all the single-celled microbes, invisible to the naked eye, that have colonized virtually every corner of the planet. Bacteria and archaea look the same under a microscope, but they differ in the way their cell walls are built.

Archaea are found in some of the most extreme environments on earth – some species thrive in boiling waters near hydrothermal vents, while others can withstand extreme levels of ionizing radiation. A cow’s intestine is not as wild as some of these environments, according to Rosalind Gilbert of the Queensland Department of Agriculture and Fisheries, but it is an unusual environment filled with a wide range of microorganisms.

Phages are extremely unusual organisms that resemble alien landers. This illustration shows a bacteriophage landing on a bacterial membrane.


Archaea are the main methane production plants. They absorb carbon dioxide and hydrogen produced by other bacteria (and fungi) and spit out methane. This process can result in an energy loss of between 2% and 12% in the feed, which is energy that could be converted into protein to help a cow gain weight or into milk for dairy products. . Destroying methane plants or preventing them from functioning means that the cow gets more energy from its feed and emits less greenhouse gases.

And that’s where viruses come in. “Anywhere you have bacterial populations, you’ll have viral populations associated with them,” says Gilbert. It is the same story for the archaea. Viruses also like to chase them away.

Viruses that attack bacteria and archaea are called “phages”, from the Greek “devour”. Identifying phages in a cow’s intestine that naturally attack methanogens would be a unique way to reduce methane emissions.

Gilbert recently conducted a phage search in a cow’s intestine, but says it was a difficult project because the microbes that viruses feed on are difficult to grow in the lab. Unfortunately, her team couldn’t locate any phage, but, she says, it may be possible in the future to find viruses that will infect and burst archaea.

Examining the DNA of these phages can give even better results.

A book in a book

Viruses that infect archaea are among the most poorly understood microorganisms on Earth. Only a few dozen archephagi that attack methanogens have been discovered and described. Thanks to advances in DNA sequencing techniques over the past decade, scientists are starting to learn more about them, even though they can’t find them under a microscope.

Sometimes when an archaephage infects a microbe, it integrates into the body’s DNA and leaves behind a fingerprint of its existence. If you think of DNA as a book, it’s like the phage is copying and pasting its own book inside the arches; a copy of the Sorcerer’s Stone inside the Goblet of Fire. This copy of DNA is known as a prophage.

Researchers can work back and study the prophage to identify proteins and enzymes that could be used to attack the microbe’s outer membrane. Gilbert says it’s easier to find the viral enzymes that break open methanogens than it is to find the viruses and grow them to make our offer.

A search for enzymes has already given initial positive results.

A research group, from New Zealand, was able to isolate an enzyme which can burst open methanogens and place them inside a nanoparticle. When the nanoparticle was delivered to methanogen cultures in the lab, it was able to inhibit methane production. Notably, proof-of-concept work has shown that the enzyme has broad effects against different species of methanogens.

“It hasn’t been developed into something that can be delivered to cows at this time,” says Gilbert.

Sea food

Something that is already fed to the cows comes from the sea.

In mid-2020, scientists showed that add small amounts of red algae, Asparagopsis taxiformis, to cow feed reduces methane emissions by up to 98% – without any negative effects on health.

Another study, published in the journal PLOS One in March 2021, showed reduced methane production in steers more than 80%. The trial took place over three weeks and the microbial communities did not appear to develop resistance to the algae.

There are also significant advantages over using natural viruses or viral enzymes. You don’t need a lab to make it, and it’s common in all tropical climates around the world, restricting carbon-intensive supply chain movements. Companies like FutureFeed, set up by Australia’s leading scientific body, CSIRO, in 2020 are already trying to establish the algae supply chain.

Red algae under the sea

Red algae, a type of seaweed, is used to reduce methane emissions from livestock.


The seaweed contains a fragrant chemical known as bromoform which blocks the pathway for methane production in archaea and, in culture, has been shown to reduce the abundance of methanogens. It also helps release carbon dioxide and hydrogen in the gut, which provides energy for other microorganisms and may even help the cow gain weight. “It is energetically beneficial, because instead of losing the carbon, they use it themselves,” explains Gilbert.

Importantly, when tested on beef cattle, the algae additive did not alter the quality of the meat or the sensory properties of the steaks – a win for farmers and consumers.

However, one of the key questions to be answered is whether the bromoform released in the cow’s intestine can return to the atmosphere. Bromoform can become an ozone-depleting substance, so it will be important to calculate its potential effects on the atmosphere before farmers switch to algae for good.

Another compound, known as 3-nitrooxypropanol (3-NOP), produces a similar effect in ruminants, but it has a more modest reduction in emissions and can affect milk production and fat content. Research on both is ongoing.

Control methanogens

It is likely that by 2050, an additional 2 billion people will live on the planet. Those additional 2 billion stomachs will need food, and as developing countries like China and India continue to thrive, demand for meat could increase by almost 75%.

It’s a simple equation, as it is: more meat means more methane.

The alien world in a cow’s gut provides an opportunity to help decouple this increase in meat production from an increase in methane. In recent decades, scientists have explored the fauna that inhabit the alien world. Understanding the killer viruses that attack microbes and discovering a powerful methane-inhibiting algae are just two ways we learn how to counter cow burping.

But on their own, these advances will not be enough to prevent the worst effects of climate change. We may need to further reduce meat consumption, increase the efficiency of feeding livestock, improve land use practices, and perhaps even increase the amount of synthetic meats, places like Impossible Foods, which we include in our diet.

If we can’t control methanogens and dramatically reduce our carbon emissions, it could be our world that becomes increasingly alien – hotter, drier, and much more extreme.

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