796. Research on Asparagopsis Cultivation Contributes to Methane Gas Reduction

Methane is the second most important greenhouse gas contributing to climate change after carbon dioxide. It has more than 20 times the global warming potential of carbon dioxide. Reducing methane emissions is therefore an urgent issue for achieving the 2050 climate goals. Large amounts of methane are produced by the fermentation of gut microorganisms in ruminant animals such as cattle and sheep. The methane gas produced in the rumen is emitted to the atmosphere by these ruminants as burp and is considered the largest source of anthropogenic methane gas in the agricultural livestock sector. 

Recently, it has been shown that feeding Asparagopsis taxiformis, a red seaweed, to cattle and sheep can significantly suppress methane fermentation in the ruminal microorganisms. In 2014, a 98.9% suppression of methanogenesis was reported by the addition of the Asparagopsis seaweed to cattle feed in an experiment to test the potential of seaweeds for ruminal methane reduction under in vitro conditions. Further research on dairy cows in Australia also showed a significant reduction in methane emissions with Asparagopsis feeding under in vivo conditions. 

Bromoform, which is highly abundant in Asparagopsis, is a halogenated organic compound that strongly inhibits ruminal methanogenesis. Although bromoform is a common metabolite in many seaweeds such as kelp and sea lettuce, it does not remain in the cells of these seaweeds. Asparagopsis, however, has glandular cells that accumulate bromoform and other halogenated organic compounds, and is therefore thought to have a higher methane reduction efficiency than other seaweeds.

Today, research and development into the use of seaweed to reduce methane emissions is taking place around the world. In Australia, where research is advanced, Asparagopsis is fed to cattle and sheep to produce and sell "low methane" hamburger and wool products. Recently, trials to commercialize the cultivation have also been initiated in Japan.

Many problems remain to be solved before Asparagopsis can be commercialized, including the establishment of aquaculture technology for stable production, the development of processing methods without loss of the highly volatile active ingredients, and the evaluation of the effects of long-term feeding on livestock. In particular, the production output of companies currently engaged in aquaculture alone is not comparable to the number of ruminant livestock worldwide. In addition, with rising feed prices, there is no significant incentive for livestock farmers to use expensive seaweed feeds to reduce methane gas. Therefore, there is a need to develop technology to grow Asparagopsis cheaply and in large quantities.

Asparagopsis is a common seaweed species in tropical and temperate coastal environments and is also found along the coasts of Southeast Asia, which is the research area covered by JIRCAS. The Philippines, Indonesia and Malaysia are the powerhouse countries of seaweed cultivation due to their thriving cultivation of Eucheuma seaweed for carrageenan materials. However, production has been declining due to disasters such as typhoons and climate change, as well as disease outbreaks. Facilitating the implementation of Asparagopsis farming can create a new industry that will help revitalize the local economy and help combat climate change.

At JIRCAS, we are also involved in research on the cultivation and use of seaweed in Southeast Asia to reduce methane emissions from livestock.

References
Machado, L., Magnusson, M., Paul, N. A., de Nys, R., & Tomkins, N. (2014). Effects of marine and freshwater macroalgae on in vitro total gas and methane production. PLoS One, 9(1), e85289.
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. J Clean Prod, 234, 132-138.
755. GHG Emissions Continued to Increase in 2022 https://www.jircas.go.jp/en/program/proc/blog/20230411
701. Achieving Methane Reduction https://www.jircas.go.jp/en/program/proc/blog/20230123

Contributor: MATSUDA Ryuya (Fisheries Division)