Greenhouse gases trap heat in the atmosphere. Methane accounts for 11% of U.S. greenhouse gas emissions and are emitted from livestock for agriculture, the production and distribution of natural gas and crude oil, and coal mining (EPA 1, 2022). Around 58% of global methane emissions come from humans (EPA 1, 2022).
The agriculture sector is the largest source of methane emissions in the United States (EPA 1, 2022). When livestock such as cows, pigs, and sheep digest food, they produce and emit methane. This process is estimated to produce around 27% of the United States' methane emissions (EPA 1, 2022).
Preliminary experiments have introduced seaweed for up to 1% of dairy and beef cattle diets. In these tests, different types of red seaweed resulted in the largest methane emissions reductions. This may be due a compound in the seaweed called bromoform that reduces gut microorganisms that emit methane (Vijn, 2020).
The difference in the reduction in methane emissions between beef and dairy cattle could be due to the different types of seaweed used or the different breeds of cattle used.
Beef and dairy cattle fed with seaweed required less feed in order to gain weight (Lean, 2021). In some cases, dairy cows fed diets with seaweed produce more milk than cows without seaweed (Roque, 2019; Sefenoni, 2021).
Beef and milk from cows fed seaweed have elevated levels of iodine (Stefenoni, 2021). While beneficial for those with insufficient iodine, excess iodine intake can lead to thyroid problems (Vijn, 2020; IM, 2001). The National Academies of Science has defined upper limits for safe iodine consumption based on age and other factors such as pregnancy (IM, 2001).
In 2018, 32 million tonnes of seaweed was produced globally, tripling since 2000 (Figure 1) (FAO, 2020). Over 95% of the production is in China, Indonesia, South Korea, and the Philippines (FAO, 2020).
Financial incentives may be necessary for seaweed adoption if increased beef or milk yields do not outweigh feed costs (Vijn, 2020). Improved feed efficiency could decrease the amount of feed necessary to raise cattle and reduce feed costs, which often comprise a large portion of costs on a farm (Roque, 2021). However, currently there are no scientific studies that have comprehensively investigated the economic costs for farmers to implement seaweed in cattle feed.
These seaweeds are not required to undergo premarket review and approval by the FDA. More research may be needed to classify the types of seaweed that reduce methane emissions as generally safe according to FDA regulations (Vjin, 2020).
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Lean, I. J., Golder, H. M., Grant, T. M., & Moate, P. J. (2021). A meta-analysis of effects of dietary seaweed on beef and dairy cattle performance and methane yield. PLOS ONE, 16(7). https://doi.org/10.1371/journal.pone.0249053
Roque, B. M., Salwen, J. K., Kinley, R., & Kebreab, E. (2019). Inclusion of Asparagopsis Armata in lactating dairy cows’ diet reduces enteric methane emission by over 50 percent. Journal of Cleaner Production, 234, 132–138. https://doi.org/10.1016/j.jclepro.2019.06.193
Roque, B. M., Venegas, M., Kinley, R. D., de Nys, R., Duarte, T. L., Yang, X., & Kebreab, E. (2021). Red Seaweed (asparagopsis taxiformis) supplementation reduces enteric methane by over 80 percent in Beef Steers. PLOS ONE, 16(3). https://doi.org/10.1371/journal.pone.0247820
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Vijn, S., Compart, D. P., Dutta, N., Foukis, A., Hess, M., Hristov, A. N., Kalscheur, K. F., Kebreab, E., Nuzhdin, S. V., Price, N. N., Sun, Y., Tricarico, J. M., Turzillo, A., Weisbjerg, M. R., Yarish, C., & Kurt, T. D. (2020). Key considerations for the use of seaweed to reduce enteric methane emissions from cattle. Frontiers in Veterinary Science, 7. https://doi.org/10.3389/fvets.2020.597430