Scientist Ermias Kebreab has studied how to reduce cow methane emissions for more than a decade.
Photo: Gregory Urquiaga/ UC Davis

J dropcapudith Lewis Mernit writes in e360.yale.edu that an experiment being conducted by animal science professor Ermias Kebreab at the University of California, Davis, is testing 12 Holstein cows in an experiment to reduce methane emissions from livestock by supplementing their diets with a specific type of seaweed.

In California alone, 1.8 million dairy cows, together with a smaller number of beef cattle, emit 11.5 million metric tons of carbon dioxide equivalent every year — as much as 2.5 million cars. The enormity of those numbers, in part, motivated California lawmakers to pass a law to reduce methane emissions and other short-lived “climate pollutants” by 40 percent below 2013 levels by 2030. The California Air Resources Board subsequently ordered a majority of the reductions in the new law to come from the dairy industry.

The UC Davis study will contribute to a global store of knowledge on how to limit the methane produced by “enteric fermentation” — the digestive process in a ruminant’s upper stomach chamber, or rumen, where microbes predigest fiber and starch, releasing gases when they belch and exhale. It’s “one of a handful of options in various stages of development that seem to have the potential to reduce (enteric) methane by 30 percent or more,” says Ryan McCarthy, science advisor to the Air Resources Board.

Dr. Kebreab’s experiments with seaweed additives to cattle feed have now surpassed that 30-percent figure, with one type of seaweed slashing enteric methane by more than 50 percent: Asparagopsis taxiformis.

Ground-up Asparagopsis taxiformis, a type of seaweed, can reduce cow methane
emissions up to 50 percent when added to feed.
Photo: Gregory Urquiaga/ UC Davis

The dried Asparagopsis taxiformis seaweed are blended with molasses to produce a shiny, viscous slop that the cows evidently find delicious. Four of the cows eat a mixture of alfalfa and hay, heavily spiked with the seaweed-molasses mixture. Four more eat the same feed, with less seaweed added in. The rest are the control group — they’ll eat plain feed, without any additives at all.

When they finish eating, they’re enticed by the drop of a “cow cookie” to visit a compartment where an instrument, much like a breathalyzer, analyzes their emissions. Each cow wears a ring on its ear that transmits an identification code along with its breath analysis to a database.

The results have exceeded everyone’s expectations. The three-month study found that spiking cows’ ordinary rations with this specific marine macroalgae reduces enteric methane by 58 percent. More than other seaweeds, Asparagopsis contains compounds that inhibit the production of methane, or CH4, and interrupt the process by which carbon and hydrogen bind together.

Even though the California dairy industry at large fought hard against what farmers initially considered onerous regulation, at least some dairy farmers are tentatively enthusiastic about seaweed additives. “Methane is an indication of an inefficiency in the animal’s digestion,” says Jonathan Reinbold, sustainability program manager for Organic Valley, a cooperative of more than 1,800 dairy farmers, including 35 in California. “If you can increase the digestion efficiency of a cow by 5 percent you could remove 5 percent of the land you use for production for cows. It can go back to fallow or be used to grow other kinds of food.”

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