The Yomiuri ShimbunMany people may be unaware of blue carbon, or carbon dioxide absorbed by oceans containing marine plants such as sea grass and seaweed. More than half of the CO2 captured by plant life on Earth is actually stored by saltwater plants, and moves are spreading to find ways to use blue carbon to help put the brakes on global warming.
“It’s good for the global environment and also good for our health as a foodstuff. The potential of kelp is incalculable,” said 63-year-old Minoru Watanabe, representative director of the SATO UMI initiative, a Yokohama-based general incorporated association involved with kelp culturing.
Blue carbon is an antonym of green carbon, which is captured by land plants at the time of photosynthesis. The term was coined by the United Nations Environment Programme (UNEP) in 2009. Reducing the amount of CO2, a chief source of greenhouse gas emissions, is a global challenge.
Watanabe’s association started culturing kelp together with local fishermen in 2015 off Hakkeijima, a man-made islet in Yokohama. Harvesting six to seven tons of kelp annually, the association wholesales raw kelp to restaurants in Yokohama and sells processed product to hotels. The proceeds are used for new culturing, in an attempt to increase blue carbon.
According to the Port and Airport Research Institute (PARI), a national research and development agency, kelp is one of the leading capturers of CO2 among marine creatures.
The SATO UMI initiative is conducting kelp-culturing experiments at five locations across the country. “We want to promote this as an effective business model for curbing global warming,” Watanabe said.
The municipal government of Yokohama is deploying what it calls the “Yokohama Blue Carbon” initiative, monitoring the amount of blue carbon at its experimental facilities and along its coastal areas. The city plans to implement a carbon offset system, under which CO2-emitting business enterprises will buy “credits” based on CO2 absorption gauged.
The proceeds will be utilized for the rejuvenation of seaweed beds, and companies buying credits can get favorable publicity for their efforts to fight global warming.
The city of Fukuoka is nurturing eelgrass beds in Hakata Bay, organizing events for children with their parents and others to grow their seedlings there. “Eelgrass beds also are important as a habitat for fish. We want to pass these endeavors down to the next generation,” said Tomoko Kobayashi, chief of the Environmental Affairs Section of the city government.
Nippon Steel & Sumitomo Metal Corp., a leading steelmaker based in Tokyo, is resuscitating beds for such seaweed as kelp in coastal areas covering a total of about two hectares in Hokkaido and elsewhere. The company is using a fertilizer made with byproducts generated in the creation of steel products.
Local governments and private companies are paying attention to blue carbon, as the absorbing capacity of blue carbon in Japanese waters is high. The overall length of Japan’s coastlines, which turn back on themselves repeatedly, is about 35,000 kilometers, exceeding that of the United States and ranked sixth in the world. Along the coastlines, there is a vast stretch of seaweed beds, including those for kelp, wakame and eelgrass.
Business enterprises and university professors who have noticed the potential of blue carbon in Japan established a study group in 2017. As Japan has set a long-term goal of curbing greenhouse gas emissions by 80 percent by 2050, officials of the Land, Infrastructure, Transport and Tourism Ministry and those of the Environment Ministry are taking part in the study group as observers.
According to estimates by the study group, up to a total of 9.1 million tons of CO2, nearly 1 percent of Japan’s total emissions, can be captured by blue carbon.
However, methods of gauging the amount of absorption currently differ, and developing seaweed beds takes time and money.
“To increase beds for marine plants, it’s also necessary to coordinate views with local fishermen. The challenge is how the public and private sectors could cooperate in this endeavor,” said Tomohiro Kuwae, 48, chief of the Coastal and Estuarine Environment Group at PARI.Speech