The use of 'blue bonds' as a CO2 credit from mariculture is something that will become increasingly important and fast-growing.
First in Japan to Receive CO2 Emissions Credit Certification for Mozuku Seaweed Farming
JAPAN
Friday, January 17, 2025, 21:00 (GMT + 9)

Uruma City, Okinawa Prefecture, Katsuren Fisheries Cooperative, and TOPPAN Digital achieve Japan’s first J Blue Credit® certification for mozuku seaweed.
The collaborative project showcases how blue carbon credits can drive sustainability in the fishing industry, contributing to a decarbonized society while maintaining and expanding Okinawa’s mozuku seaweed production.

Source: 'Implementation of blue carbon offset crediting for seagrass meadows, macroalgal beds, and macroalgae farming in Japan'. Author: Tomohiro Kuwae, Atsushi Watanabe, Satoru Yoshihara, Fujiyo Suehiro and Yoshihisa Sugimura.
Pioneering Certification
Uruma City, Okinawa Prefecture (Mayor: Masato Nakamura), the Katsuren Fisheries Cooperative Association (Chairman: Kenei Tamaki), and TOPPAN Digital Co., Ltd. (President and CEO: Kazunori Sakai) have secured Japan's first J Blue Credit® certification for mozuku seaweed. This milestone was achieved under the joint “Future of Fisheries” project, which focuses on natural mozuku harvesting and seaweed conservation in Uruma City—home to Japan’s largest mozuku production area.

Dried Okinawan Mozuku Seaweed
The project earned certification for capturing 21.7 tons of CO2 through mozuku seaweed farming, as verified by the Japan Blue Economy Association (JBE). This marks the first instance of mozuku seaweed being recognized under the J Blue Credit system.
Addressing Challenges Through Collaboration
Okinawa Prefecture accounts for over 90% of Japan’s mozuku production, with the Katsuren area contributing approximately 40% of Okinawa’s harvest. Despite its importance, mozuku farming faces significant challenges, including:
- Labor shortages due to an aging population.
- Climate change impacts, leading to unstable yields.
- Environmental threats, such as pumice from volcanic eruptions damaging seaweed beds.

In response, Uruma City, the Katsuren Fisheries Cooperative, and TOPPAN Digital launched a public-private partnership in September 2021 to sustain and expand mozuku farming. Their efforts have not only improved production practices but also established a framework for issuing blue carbon credits, with proceeds reinvested to amplify conservation activities.
Contributions by Each Partner
Uruma City
Uruma City integrated this initiative into its Basic Environmental Plan, prioritizing climate action through local projects. Efforts include:
- Promoting environmental conservation of mozuku beds.
- Incorporating mozuku into school meals to educate children on sustainable practices.
- Publishing mozuku recipes online to highlight its nutritional and culinary value.
Katsuren Fisheries Cooperative

Estimation results of seaweed bed area calculated using a tool developed by "ICT KŌBŌ®"
The cooperative demonstrated resilience by overcoming disruptions caused by pumice deposits in 2021 and maintained mozuku production. Key contributions include:
- Eco-friendly aquaculture: Using natural spores instead of artificial methods to minimize CO2 emissions.
- Efficiency improvements: Applying anti-fouling treatments to fishing boats, reducing fuel consumption.
TOPPAN Digital
TOPPAN Digital leveraged its InnoReef® fishery digital transformation solution to streamline mozuku production. Key actions included:
- Developing a weight management app to simplify credit application processes.
- Utilizing ICT expertise to measure seaweed bed areas and calculate CO2 absorption.

Using the weight management app provided by Toppan Digital during the mozuku harvesting process
Blue Carbon Credits: A Sustainable Path
Blue carbon refers to the CO2 absorbed by marine ecosystems, including seaweed, seagrass, and mangroves, which is sequestered in oceanic sediments. Like green carbon from forests, blue carbon offers a valuable tool for combating climate change. The J Blue Credit system converts this absorption into tradeable credits, incentivizing sustainable practices.
Future Goals
Revenue generated from blue carbon credits will support:
- Maintaining and expanding mozuku farming as a CO2 sink.
- Conserving seaweed beds to protect marine biodiversity.
- Addressing labor shortages by encouraging new talent in the fishing industry.

Source: 'Implementation of blue carbon offset crediting for seagrass meadows, macroalgal beds, and macroalgae farming in Japan'. Author: Tomohiro Kuwae, Atsushi Watanabe, Satoru Yoshihara, Fujiyo Suehiro and Yoshihisa Sugimura.
Additionally, the project will expand environmental education initiatives to foster awareness among local children about the importance of seaweed conservation and climate action.
Uruma City, the Katsuren Fisheries Cooperative, and TOPPAN Digital remain committed to sustaining mozuku production, advancing the fishing industry, and promoting environmental conservation. Together, they aim to enhance the local carbon cycle, strengthen the region’s resilience to climate change, and create a model for sustainable aquaculture.
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