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Japan Plans to Report 360,000 Tons of ‘Blue Carbon’ to U.N.; First Such Calculation in the World

The Yomiuri Shimbun
Blue carbon absorbed by seaweed, seagrass

Japan had about 360,000 tons of “blue carbon,” or carbon dioxide absorbed and stored by seaweed and seagrass, in fiscal 2022, the government intends to report to the United Nations.

Japan will calculate its net emissions, meaning emissions from human activities minus the amount of CO2 absorbed by plants through photosynthesis and other means. For the first time in the world, the amount of CO2 absorbed by kelp forests and seagrass meadows will be measured.

As a countermeasure against global warming, nations have set greenhouse gas reduction targets by calculating their net emissions. Japan is aiming to reduce its net emissions by 46% compared to the fiscal 2013 level by fiscal 2030, and to achieve net zero emissions by fiscal 2050. Japan reports its latest figures to the United Nations annually.

Nations have not reported the amount of CO2 absorbed by seaweed and seagrass to the United Nations, as there is no established method for calculating it. Japan has devised a method based on the amount absorbed by each type of seaweed and seagrass, such as wakame and eelgrass, and the area of seaweed beds in coastal areas.

According to the government, Japan’s blue carbon amounted to about 360,000 tons in fiscal 2022, equivalent to the annual CO2 emissions of about 140,000 households. The figure will be officially confirmed by an Environment Ministry panel of experts on Jan. 22.

Most of the 47.6 million tons of CO2 absorbed by plants in Japan in fiscal 2021 came from forests. As existing terrestrial forests are expected to decrease in the future as they age, some estimates predict blue carbon will account for 10% of total carbon sequestration in 2030.

Taking advantage of the fact that Japan is surrounded by oceans, the ministry hopes to promote decarbonization through blue carbon, for example by creating kelp beds.