Red Algae: A Potential Solution to Methane Emissions from Cow Waste


Earth has a problem with cows. Cow agriculture is one of the greatest contributors to global warming methane emissions. However, adding a type of red algae with methane-inhibiting properties to bovine feces could be beneficial. This reduces methane production in defecation by approximately 44%, according to a study published on July 13 in Frontiers in Sustainable Food Systems. According to scientists, this offers a promising new way to reduce overall methane emissions from cattle.

Nearly a quarter of the world’s methane emissions, a potent greenhouse gas, are caused by the dairy industry (SN: 11/18/15; SN: 5/5/22). During digestion, cows produce methane in their intestines, which is then released primarily through burps. During decomposition, cow excrement also emit a lesser, but not negligible, amount of methane.

Researchers have actively sought solutions to the methane produced by the digestive tract. Adding a pinch, or 0.5% of the dry feed, of the red algae Asparagopsis taxiformis to the calves’ food can reduce methane production by approximately 65%.

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Bromoform and Iodine Concerns in Dairy Products and Human Health

Photo by: Johnmartindavies via wikimedia commons

A. taxiformis, which is abundant in tropical ocean waters, contains bromoform, an organic compound that inhibits an enzyme that typically promotes the methane reaction. This research has raised concerns that the milk and meat of dairy cows fed the phytoplankton may contain toxic levels of bromoform and iodine. The Environmental Protection Agency of the United States has classified bromoform as a probable human carcinogen, and an excess of iodine can result in thyroid dysfunction.

In the current investigation, Ramin and his colleagues added algae to the feces of four dairy cows. Two were fed the algae, while the other two were not. Each stool sample was further subdivided, with one subsample receiving additional algae and the other remaining untreated. In the laboratory, all stool samples were allowed to incubate and decompose slowly.  After nine weeks, the subsamples were analyzed to determine how much methane they contained.

As anticipated, adding phytoplankton to the cows’ diet initially reduced the amount of methane in their manure. However, once the dung began to decompose, the cows’ consumption of phytoplankton had no effect on the production of new methane. The team also examined the microbial communities living in the various types of feces and discovered that there was little difference between the feces of cows fed algae and those fed a control diet. This indicates that algae dietary supplements are not particularly effective at inhibiting methane production outside the stomach. However, adding the algae directly to the defecation significantly reduced the amount of methane produced by decomposition. The team concludes that this would be an effective component of the solution to the larger cow-methane issue.

A. taxiformis may continue to be most effective at inhibiting fermentation in a cow’s intestines as opposed to its manure. The good news, according to Glasson, is that cutting-edge feed additive technologies that utilize specific algae extracts as opposed to the entire biomass significantly reduce the risk of iodine or bromoform toxicity.

And the conclusion of the study that algae in the cows’ feed has no effect on the production of methane in their feces may also be positive, says Place. The conversion of methane into biogas is one proposed strategy for reducing emissions from cow manure. She adds that if feeding phytoplankton to cattle for methane mitigation has no effect on the manure, this could be beneficial for biogas production — a possible twofer for the industry.

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Source: Science News

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