• John Lin

Red Seaweed Could Curb Methane Emissions

As climate change increasingly threatens the habitability of Earth, one lab group finds that curbing methane emissions may be as simple as adding a bit of seaweed to cow feed.

Polluted air cloaks a Texas feedlot operation where cattle emit methane as they digest (Steinmetz/NYT).

Methane is an extremely prevalent and potent greenhouse gas, contributing to 20 percent of global emissions which makes it the second most emitted gas after its more well-known counterpart carbon dioxide. While it may remain in the atmosphere for only 12 years (compared to the 100-year life span of carbon dioxide), methane eventually disintegrates into water and carbon dioxide which means it essentially replaces one greenhouse gas with another long-lasting one. Furthermore, in a 100-year period, methane traps 28 times more heat than carbon dioxide in the atmosphere. Alarmingly, methane emissions have risen by a record 10 percent for the past two decades.

All these factors make reducing methane emissions a high priority for climate policy and environmental advocacy.

One of the biggest sources for methane emissions is livestock, particularly ruminants (animals with complex digestive systems to digest plants), which make up a quarter of methane emissions. While these animals, such as cows and goats, release the gas through belching or flatulence, methane is actually produced by a group of microbes known as methanogens.

The relationship between bacteria and ruminants is symbiotic. As herbivores that eat complex plant material, cows and goats rely on the bacteria in their stomach to break down their diet into simpler bits for further digestion. From this process, the bacteria produce byproducts such as carbon dioxide. Methanogens take up carbon dioxide for their own energy and convert it to methane, which is then released from the body and becomes a greenhouse gas.

As meat consumption continues to rise in the majority of the world, methane emissions have also gone up to 227 million tons in 2017, which is a 12 percent increase from decades earlier. In response to rising methane numbers, environmental advocates have called for completely removing livestock from the equation.

This, however, is ultimately not feasible or sustainable. “Only a tiny fraction of the earth is fit for crop production. Much more land is suitable only for grazing, so livestock plays a vital role in feeding the 10 billion people who will soon inhabit the planet,” said Ermias Kebreab, an agricultural scientist, in a statement.

Researchers are looking at alternative methods to feed cows in the effort to reduce methane emissions. For one group at the University of California Davis, including Kebreab, the solution came in the form of seaweed.

Known as Asparagopsis taxiformis, red seaweed has been a promising agent to curb ruminant methane production for almost a decade. In 2005, an Australian study found that adding small amounts of this seaweed in fluid containing cow stomach microbes reduced methane production by 99 percent. The laboratory findings, however, were not yet tested in live cows until earlier this year.

These exciting findings have led to a red seaweed shortage and the proliferation of seaweed farms (Getty).

For the study, the scientists added small amounts of seaweed to the cows' diets and measured their methane production over the span of 21 days.

In the end, cows that were fed seaweed reduced their methane production by up to 80 percent while also maintaining a healthy weight.

Furthermore, the study also found that adding seaweed could increase energy efficiency in cows by 20 percent. As a result, farmers could feed their cows less with seaweed to achieve similar nutrition results while cutting feeding costs by an average of $40,320. The reduced cost could make seaweed feed much more appealing to farmers in developing countries which emit some of the highest amounts of methane from livestock.

This effect of seaweed on methane can primarily be attributed to its reaction with enzymes made by methanogens. The methane-producing bacteria in cow stomachs require a series of biological and chemical reactions, which involve proteins called enzymes to gain energy. These enzymes consequently produce methane as byproducts. Seaweed contains inhibitors which prevent the enzymes in methanogens and disrupts the methane production process.

While the results from the study mark a significant breakthrough in the effort to curb methane emissions, there are still a few key challenges that must be addressed. There are over a billion cows in the world, and each cow requires roughly 27 pounds of food daily. Red seaweed only grows in temperate seawaters, specifically around Australia and the Mediterranean. The imbalance in the supply of seaweed to that of cows makes it difficult to harvest enough seaweed in their natural environment to be widely used in cows.

Scientists and agriculturists are working around these issues by developing methods to cultivate seaweed farms. Last September, one farm in New Zealand received 3 million dollars in funding to begin exploring methods to grow red seaweed on a larger scale. As greenhouse gases continue to rise, adding a few ounces of seaweed to cow diets might be the key for a more effective and efficient method of decreasing methane emissions for one of its largest contributors.

John Lin is a rising freshman at Harvard University studying history and science originally from Boston, Massachusetts. He writes about medicine, educational equity, and social forces.

This piece was edited by Will Cover, a sophomore at Rice University studying public policy originally from Columbia, Missouri.

Cover: NYT


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