Should Cows Be Eating More Seaweed?

It’s a well-known fact that cow burps are a problem. Annually, the digestive system of each cow on the planet releases around 220 lbs (100 kg) of enteric methane, a potent greenhouse gas that contributes to climate change. With a global population of 1.5 billion cows, their methane emissions are roughly equivalent to the emissions of 650 million cars.

Contrary to popular belief, the vast majority of a cow’s methane comes from burps (just 5% comes out the other end). The microbes in a cow’s first stomach, the rumen, turn carbon and hydrogen from fermenting plants into methane. Interestingly, diet has a significant impact on the amount of methane a cow produces. For example, corn is much easier to digest than grass and results in significantly less methane being emitted.

Yet there may be a relatively simple solution to these powerful belches. In the past decade, numerous studies have found that sprinkling red algae from the genus Asparagopsis into cattle feed can reduce the amount of methane in their belches by as much as 90%. This is due to an organic compound in the seaweed known as bromoform that prevents carbon and hydrogen from becoming methane.

Research suggests that only a tiny fraction of a cow's total feed intake (as little as 0.2% in one recent study) would need to consist of seaweed. And besides reducing methane-filled burps, bromoform is associated with increased glucose, which may promote more efficient growth or better milk production.

Yet growing Asparagopsis on a scale that is viable for commercial use is another matter, though companies like Sea Forest, Blue Ocean Barns, and CH4 Global are making headway. However, in land-based tanks, large-scale seaweed cultivation has its own environmental impacts, including potentially high energy usage and nutrient runoff. On the other hand, there are many benefits associated with seaweed growth in the ocean, as this can help sequester carbon dioxide from the atmosphere and reduce ocean acidification.

The cattle burp conundrum: