It was feeding time for the steers in a research barn at the University of California, Davis. Using a cement mixer, an intern blended a special additive into some of the cattle feed — made from seaweed. It’s part of a study to determine whether steers that eat the seaweed will emit less methane through their digestive process.

“We have three groups in the trial,” explained postdoctoral fellow Paulo de Meo Filho, who runs the day-to-day operations in the study. 

The control group receives no intervention. The short-term treatment group is exposed to the seaweed additive from their second day of life until they’re three months old. The third, or long-term treatment group, gets the additive from two months old to about 18 months, when they go to slaughter.

“We hope these animals, over their life, produce less methane compared with the control group, even when we stop the additive in early life,” de Meo Filho said. 

Researchers estimate livestock production contributes between 12% and nearly 20% of global greenhouse gas emissions, mostly from methane. Seaweed has a compound called bromoform that blocks the production of methane in the calves’ rumen, the first of their four stomach chambers. 

To see how the treatment is working, de Meo Filho lures the animals to a machine that deposits tasty alfalfa pellets to attract them. While they enjoy their snack, sensors measure their emissions.

“It's important to highlight, like 95% of the emissions come from the mouth, the nostrils,” de Meo Filho said. “It’s the expiration and the belching from the rumen.”

A steer named Sheepy, part of the long-term treatment group, stuck his head into the machine. As he ate, an app on de Meo Filho’s phone showed a small spike in methane.

“So this is probably his first belch the machine could capture,” he said. 

Previous research of feedlot cattle has found that a seaweed-based supplement can reduce methane emissions by as much as 90%. But Ermias Kebreab, a professor of animal science who’s leading the UC Davis study, said cattle spend most of their lives grazing before they get to the feedlot, making it difficult to feed them an additive. If Kebreab and his team can prove that early intervention has long-lasting effects, that could be a game-changer.

So far, the results are promising. Five months after they stopped receiving the treatment, the steers in the short-term group still had a 20% reduction in methane.

“I'm really hoping that this will continue until they are harvested, but we'll have to do the work and find out,” Kebreab said. 

He’s also working with researchers at UC Berkeley to use gene editing to modify cattle’s microbiome to produce the same effect.

Critics of the effort say that, even if it works, it doesn’t address the other climate impacts of livestock production — from deforestation for grazing to petroleum-based fertilizers and transportation.

But Kebreab said if we want cleaner beef, reducing methane has to be part of the equation. 

“It is the main contribution from livestock,” he said. “So if you are able to reduce that, then we have a long way in trying to limit the effect on climate.”