Japan Tests Direct Ocean Carbon Capture on Kume Island

Hitachi, Ltd., Mitsui O.S.K. Lines, Ltd. (MOL) and Japan Airlines Co., Ltd. (JAL) have signed a memorandum of understanding to conduct a pilot test of direct ocean capture (DOC) technology on Kume Island, Okinawa Prefecture. The project will examine the separation of dissolved CO₂ from seawater and collect operational and environmental data needed to assess potential deployment along Japan's coastline.

The cooperation combines process monitoring and equipment engineering with maritime expertise and regional infrastructure. Potential applications include carbon dioxide removal for hard-to-abate sectors such as shipping and aviation and, in the longer term, using captured CO₂ as a feedstock for synthetic fuels.

Testing Direct Ocean Capture
DOC removes dissolved CO₂ directly from seawater. Because seawater exchanges carbon dioxide with the atmosphere, extracting dissolved CO₂ changes this equilibrium, allowing treated seawater to absorb additional atmospheric CO₂ after it is returned to the marine environment.

According to the companies, CO₂ concentration in seawater is approximately 100 to 150 times higher than in the atmosphere. The pilot will provide data needed to evaluate the process under local marine conditions rather than relying only on laboratory-scale operation.

Containerized pilot equipment will be installed on land at Kume Island and connected to a seawater intake system. Seawater will be drawn from the surrounding marine environment, processed to separate CO₂ and subsequently discharged.

Dividing Technical Responsibilities
The partners have previously invested in U.S.-based DOC technology developer Captura Corp. and are combining their respective capabilities to evaluate the technology in Japan.

Hitachi will lead technical monitoring and analysis. Using analytical instrumentation and characterization methods from Hitachi High-Tech Corporation, the company will record operating conditions and seawater parameters including dissolved inorganic carbon and pH.

The collected data will be used to investigate operating conditions affecting energy efficiency. Hitachi will also measure captured CO₂ volumes and electricity consumption, providing data that could support measurement, reporting and verification (MRV) procedures. Hitachi Industrial Products, Ltd. will study core equipment requirements for possible commercial-scale systems.

MOL will use its existing cooperation with Kumejima Town to coordinate local stakeholders and establish the operating environment for the pilot. Its role also covers assessment of potential marine and regional applications for DOC.

JAL, together with Japan Transocean Air Co., Ltd. and Ryukyu Air Commuter Co., Ltd., will support regional coordination and evaluate potential links between captured CO₂ and future synthetic aviation fuel supply chains.

Evaluating an Island-Based Carbon Cycle
Kume Island already hosts ocean-based energy research, including Ocean Thermal Energy Conversion, which generates electricity using the temperature difference between warm surface seawater and cold deep seawater.

The DOC project will examine whether captured carbon can eventually be integrated into a local carbon cycle. One proposed pathway is E-SAF production, in which captured CO₂ is combined with hydrogen produced using renewable electricity to manufacture synthetic aviation fuel.

Operational data from the pilot, particularly CO₂ capture quantities, electricity consumption, seawater chemistry and environmental measurements, will determine the technical requirements for larger coastal installations and provide a basis for assessing the scalability of DOC technology in Japan.

Edited by Sucithra Mani, Induportals editor – adapted by AI.

www.hitachi.com