By now, you’ve probably heard the news that supplementing cattle with seaweed could reduce methane belched by livestock. In fact, researchers in Australia and the U.S. have found that feeding as little as .5% “Asparagopsis taxiformis, a red seaweed that grows in the tropics, can decrease methane emissions by 80 percent or more.
But there are still unresolved challenges to this solution, the first being finding enough seaweed. Alexander Hristov, distinguished professor of dairy nutrition at Penn State, says that to get enough seaweed to make a difference globally, the scale of production would have to be immense. With nearly 1.5 billion head of cattle in the world, harvesting enough wild seaweed to add to their feed would be impossible. Even to provide it as a supplement to most of the United States’ 94 million cattle is unrealistic.
“To be used as a feed additive on a large scale, the seaweed would have to be cultivated in aquaculture operations,” he said. “Harvesting wild seaweed is not an option because soon we would deplete the oceans and cause an ecological problem.”
Australian researcher Dr. Rob Kinley agrees that supplying enough seaweed is a significant challenge, but he is more optimistic. Kinley is the Technology Lead for Future Feed, an offshoot of Australia’s Commonwealth Scientific and Industrial Research Organization (CSIRO) that is also researching this seaweed. His team’s research has demonstrated a 99% reduction in methane output in a laboratory setting, and an 85% reduction in sheep fed the seaweed supplement. According to Future Feed, millions of tons of seaweed are already cultivated and harvested each year, so it should be possible to grow this seaweed as well.
So, Where Does Cow Methane Come From and Why Do We Care?
Ruminants are able to process highly fibrous materials like grasses thanks to the diverse microbial ecosystem living in their rumens. The microbes don’t actually care about the cow at all. They’re simply breaking down whatever comes in to meet their own needs. Some are focused on sugars, others on fiber, cellulose or lignin. As the microbes break down forage into something they can use, the cow benefits from many of the byproducts they produce. The microbes also produce waste products as they work away in the rumen including carbon and hydrogen. These are food for another type of microbe, methanogens. As they eat up the carbon and hydrogen, they produce their own waste product, the methane ruminants burp out.
The more difficult something is to digest, the more methane is produced. As Future Feed points out in their FAQs, grass is generally more difficult to digest and is less efficient than grain for converting feed into meat, milk and wool. “The net result is more product with less feed energy lost as methane gas in an equation of reduced methane emissions intensity, or more product for the same or less methane.” About 12% of what an animal eats is lost to methane production. By reducing methane output by feeding seaweed, we also increase the efficiency of converting feed into meat.
Cows are often named climate villains, in part due to the methane they produce. As a greenhouse gas, methane has a global warming potential 104 times greater than CO2 in a 20-year time frame. The Future Feed team notes that if just 10% of the livestock industry fed the seaweed supplement, it would have the same positive climate effect as removing 100 million cars from the road.
That’s a lot of cars – but a very small portion of the 1.2 billion cars that are currently on the road. As Penn State’s Hristov points out, “Methane from animal agriculture is just 5 percent of the total greenhouse gases produced in the United States. Much, much more comes from the energy and transportation sectors.”
“Do we want to look at this?” Hristov asks. “I definitely think that we should, and if there is a way that we can reduce emissions without affecting profitability on the farm, we should pursue it.”
What Are Researchers Looking At?
With that in mind, researchers are continuing to explore the possibilities of using seaweed as a supplement. Challenges include:
“We know that it is effective in the short term; we don’t know if it’s effective in the long term,” Hristov explained. “The microbes in cows’ rumens can adapt to a lot of things. There is a long history of feed additives that the microbes adapt to and effectiveness disappears. Whether it is with beef or dairy cows, long-term studies are needed to see if compounds in the seaweed continue to disrupt the microbes’ ability to make methane.
So far, studies in Australia feeding sheep the seaweed supplement for 72 days and beef cattle for 90 days, shows there was no adaptation and methane continued to be mitigated. This is a hopeful sign as most adaptations happen within a few weeks.
There are also questions about the stability over time of the active ingredients – bromoforms – in the seaweed. These compounds are sensitive to heat and sunlight and may lose their methane-mitigating activity with processing and storage.
It appears that at least some cows do not like the taste of seaweed. When Asparagopsis was included at 0.75 percent of the diet, Penn State researchers observed a drop in the feed intake by the animals.
Currently the supplement is whole seaweed that has been dried and is mixed in with the ration just before it is delivered to the feed bunkers, or as a seaweed flake with the roughage. Future feed says, “Other technologies are expected to be developed as the feed formulators and livestock producers work together to refine their systems. This depends on the feeding system that varies between feedlot style (high grain), dairy style (medium grain), and grass fed (low grain),” says Kinley.
4. Long-term Effects
The long-term effects of seaweed on animal health and reproduction and its effects on milk and meat quality yet to be determined. A panel judging milk taste is part of ongoing research at Penn State.
5. Providing supplement to pasture-based livestock
When I spoke to Dr. Kinley I asked specifically if he’d looked at how to provide the supplement to livestock on pasture since that seems to be where it would be the most beneficial. They are continuing to look for ways to make this possible.
What Can You Do With All This?
This article was requested by one of our readers in Ireland who has ready access to seaweed. She wanted to know if it was the kind that might reduce methane output of her livestock. Though it isn’t, it may still have some impact on methane reduction. As noted above, the Kelp and Rockweed that was the catalyst for the research did reduce methane output by 20% and also improved animal productivity. If you can add this input at little or no cost, you might run your own small experiment to see if there is enough of a difference to warrant any additional expense or labor involved. If you do that, we’d love to hear about it!