Carbon Captured Transhipper concept – a key solution for decarbonizing maritime industry

Written by Agata Maderska, Chief Marketing Officer, Seatech Engineering

The marine sector is a crucial pillar of global trade, yet it is also a significant contributor to greenhouse gas emissions. As the urgency to combat climate change intensifies, the shipping sector faces rising pressure to reduce its carbon footprint. New legislation, especially Emissions Trading Systems (ETS) are triggering shipowners to reduce CO2 emissions from ships. Various strategies are being explored. One is to use alternative fuels with lower carbon emissions like synthetic methanol. Second solution are zero-emission fuels – ammonia and hydrogen (in compressed or liquid form) or even negative emission fuels like bioLNG from biologic waste like manure or slurry. A complementary solution is a concept of an innovative ship system able to receive captured CO2 via ship-to-ship tranfer, store it on board and discharge to shore facilities. Such promising solution is currently being developed by Polish ship design office Seatech Engineering together with Wavelength Technology Center . Carbon Captured Transhipper (CCT) is a ship concept designed to receive liquefied CO2 from vessels equipped with an on-board carbon capture technology, then store it and offload onshore.

Understanding CCT concept

Carbon Captured Transhipper combines advanced carbon capture technology with maritime logistics. The concept involves specialized costal vessel or a self-propelled barge with fully electric propulsion and high manoeuvrability designed for cost efficient ship-to-ship (LCO2 receiving) and ship-to-shore operations (LCO2 discharging). This flexible unit is being designed to receive captured CO2 from multiple sources and different types of ships like cruise vessels, container, bulk carries, ro-ro ships, tankers etc. and stay idle for as long as necessary without venting any cargo.

Transferred CO2 is to be stored in cargo containment systems consist of C-type tanks with enough capacity to collect it from several supply vessels. During this operation, received LCO2 is to be maintained at constant pressure and received boil-off gas is to be managed. Once CCT is fully loaded, it should head to the nearest receiving facility for final utilisation – permanent LCO2 storage in empty oil reservoirs or further conversion into synthetic alternative fuels like e.g. e-methanol.

Key technical features

CCT key technical features – ranging from advanced carbon handling system developed by Wavelength to tailor-made ship design based on LNG units, in which Seatech Engineering has extensive experience – position this vessel concept as a vital solution, offering a comprehensive approach of reducing emissions and enhancing operational efficiency.

• High manoeuvrability of the vessel is ensured by two azimuth thrusters aft and one or two bow tunnel thrusters forward. Optionally CCT could be equipped with retractable thruster forward.

• Designed CCT has good 360-degree visibility from the main conning position to the wheelhouse. CCTV should installed in shaded areas.

• CO2 transfer between the carbon capture facilities on board the supply vessel and the CCT is to be done via cryogenic hose connection equipped with all safety features. Transfer of hoses is provided by hose handling crane or specially designed LCO2 transfer boom located amidship. Additionally cryogenic hoses and specially purposed couplings, similar to those used for LNG, are to be applied to transfer liquefied CO2 to prevent formation of dry ice caused by sudden expansion of LCO2.

• CO2 transfer is possible with or without vapor return connection. If the supply vessel will be equipped with a vapor return connection, it will be possible to use CCT own CO2 compressors to push liquid back and unload the carbon capture system tank. In case of no vapor return connection on the supply vessel, it will need to be able to offload CO2 by own pump or PBU system.

• LCO2 is to be loaded and stored into type-C tanks operating at low pressure (7-10 barg). In case the supply vessel is storing CO2 at medium pressure (12-19 barg), CCT receives CO2 at first to a smaller deck tank prepared for that pressure, and gradually transfers it to dedicated cargo tanks using an on board reliquefaction unit to depressurize the gas.

• The temperature for LCO2 to be adjusted to volume of stored medium as well as mass of the storage tanks. Temperature to be from range -30 ⁰C down to -55 ⁰C.

• The vessel could be optionally equipped with cascade type LCO2 liquefication system. The unit will then use cargo compressors and a refrigerant loop to keep CO2 boil-off gas from increasing the tank pressure. To reduce boil-off, LCO2 tanks are to be covered by thermal insulations (PU sprayed foam with hard top lining).

• The vessel is additionally equipped with a Custody Transfer System (CTS) system to provide fiscal metering of received volumes and provide the source vessel with a 3rd party certified transfer note for the received amount. The CTS system is based on tank level measurements, and vessel trim.

• To offload LCO2, CCT should be brought to the nearby CO2 hub terminal where collected cargo will be discharged by deepwell pumps. The cargo unloading is possible without vapor return if needed. A small amount of liquid CO2 will always be kept at the tank bottom in order to maintain the tanks cold and ready to receive next load.

What are the benefits?

Carbon Captured Transhipper concept offers a range of benefits that significantly contribute to the decarbonization process of the maritime industry.

Reducing shipping emissions

The maritime sector accounts for approximately 3% of global greenhouse gas emissions, primarily from the burning of heavy fuel oil. Designed CCT addresses this issue by capturing CO2 emissions at the source, enabling shipping companies to significantly reduce their overall emissions profile and comply with international regulations. This approach to carbon capture can lead to substantial reductions in overall maritime GHG emissions.

Supporting regulatory compliance

With the International Maritime Organization (IMO) setting ambitious targets to halve greenhouse gas emissions by 2050, CCT provides a viable solution for shipping companies seeking to meet these regulatory demands. By implementing carbon capture technology, companies can demonstrate their commitment to sustainability and enhance their competitive edge.

Economic viability

CCT concept not only contributes to environmental goals but also offers economic incentives. Shipping companies that adopt carbon capture technologies can benefit from potential regulatory credits, reduce fees related to CO2 emissions, and improve brand image as environmentally responsible operators.

Enabling carbon utilization

Captured CO2 can be repurposed in various ways, creating new economic opportunities. For instance, it can be utilized in the production of synthetic fuels, contributing to a circular economy and reducing reliance on fossil fuels. This approach not only mitigates emissions but also paves the way for innovative applications in various industries.

Circular Economy

The utilization at scale of synthetic fuels like e-methanol depends deeply on the access to biogenic CO2 sources. By combining the use of e-fuels with carbon capture technology and logistics it is possible to partially recirculate the carbon content between e-fuel producer and consumer, thus reducing the pressure on the primary biogenic CO2 sources.

There are also challenges …

Despite its great potential, CCT concept faces several challenges. The main obstacle for now is the lack of onshore receiving infrastructure for LCO2 captured on board ships. Many ports lack necessary facilities ready to accept, store, and process it. This includes specialized tanks for storage, pipelines for transport, and processing plants for utilization or sequestration. This infrastructure gap limits the potential for the maritime industry to contribute to decarbonization efforts, while having a ready-to-go CCT design for carbon capture on sea. Developing necessary infrastructure to support those operations, including transhipment hubs and carbon storage facilities, will require significant investment and time, but it’s worth an effort. In addition a clear solution for the use of captured CO2 is needed. Synthetic fuels using carbon are a future, especially when combined with green hydrogen.

Carbon Captured Transhipper concept represents a forward-thinking solution to the maritime industry’s environmental challenges. By integrating carbon capture technology into ship operations, CCT units could significantly reduce emissions, enhance operational efficiency, and support sustainable economic practices. As the maritime industry navigates the transition to a low-carbon future, CCT concept stands out as a key player in facilitating meaningful change and achieving decarbonization goals. Seatech Engineering and Wavelength plan to further develop this concept together, and look forward for shipowners willing to take on the challenge of building such unit. And in the meantime, they are already working on the concept of a multipurpose option – a combination of a multi-fuel bunkering vessel combined with a CCT functionality addressing even broader spectrum of support – collecting LCO2 and supplying ships with necessary fuels. They believe that readiness to receive carbon dioxide from ships operating at sea, as well as pressing regulations and high emission fees, will encourage other shipbuilding players to install the equipment for CO2 capture on board their vessels.

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