Maritime Transport of CO2

Maritime Transport of CO2, is one of the elements of the Capture Carbon Utilization Storage (CCUS) and Capture Carbon Storage (CCS) value chain. It refers to the transport of CO2 in a specific form, from port to port or in an offshore pipeline by ship, in order to store it in a geological or other formation. According to the literature it started in the 1990s with demonstration projects and intensified in the decade 2010-2020 in the Nordic countries with a main aim to prove that maritime transportation of CO2 is a cost effective solution for the value chain.

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The global carbon dioxide market size was valued at USD 7.80 billion in 2020  and the food and beverage industry is the largest end user of CO2. Commercial food - grade CO2 is currently transported by truck, train or ship, and typically as refrigerated liquid. This is generally high purity CO2, typically captured from hydrogen production facilities1 or other fermentation or chemical processes with a high CO₂ concentration by-product.

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For the food and beverage industry, CO₂ is usually transported in ships with capacities lower than 2 kt CO₂. For example, CO₂ is today captured from fertilizer producer Yara, and routinely shipped for commercial use (e.g. food and beverage) by Larvik Shipping for Praxair . These ships have a capacity of up to 1.8-2.0 kt per shipment . This CO2 is transported in liquid form at 15-18 barg and  approximately -22 to -28°C . This is a smaller scale than it would be necessary for CCS . For example, with the current Northern Lights specifications, each shipment will carry more than 8.2 kt2.

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Benefits of Shipping

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Shipping is an attractive alternative for CO₂ transport, especially for early movers, because it is a flexible option that does not require fixed infrastructure. It is also scalable, and it is less sensitive to fluctuations in capture profile than piping.

The technology for CO₂ shipping is ready and there are ongoing projects for building the ships that will transport the CO₂ for the early mover CCS projects (e.g. Northen Lights). 

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               Figure 2. - Offshore Transport and Storage overview  (Source: globalccsinstitute.com)

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Technology and  short-term deployment

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As mentioned above, LCO₂ shipping is done commercially, but at a smaller scale compared to what would be required for CCS. However, the shipping part of the CCS value chain is on time and advanced for the ongoing CCS projects.

Northern Lights in Norway adapted ship designs used for transporting liquefied petroleum gas (LPG), adding a liquefied CO₂ carriage system and insulation to maintain a temperature that keeps the CO₂ in a liquid state. Northern Lights Joint Venture announced on 11 October 2021 that they have ordered two dedicated LCO₂ carriers that will be ready for delivery by mid-2024. LCO₂ will be transported at cryogenic conditions (15 barg and equilibrium temperature). The ships will be built by Dalian Shipbuilding Industry and have a cargo size of 7500m3 (~7.5 kt) and a length of 130 m. The primary fuel in this design is LNG.

Carbon Collectors in The Netherlands have received Approval In Principle for the design of their tug- barge combination and the offshore mooring system. LCO₂ will be transported at temperatures above 0 °C, pressures above 40 barg. The nominal capacity for each barge is 5500m3 (~4.7 kt) and a length overall (LOA) of 130 m (barge only) and 150 m (tug-barge combination).

In addition, specialized companies for CO₂ seaborne transport are emerging. An example is Dan-Unity CO₂, collaborating with Carbfix (storage), which recently announced they are able to build purpose-built CO₂ vessels with a capacity of 12500m3 and 22000m3 .

Flexibility of CO₂ shipping

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Compared to pipelines, shipping of LCO₂ has some benefits in terms of flexibility which are especially attractive to emerging projects. For example,

• Scalability, for projects developed in more than one phase it will be possible to expand the ship fleet according to the project's needs.

• Ability to transport to different storage sites (if/when available), depending on costs and availability.

 The density of LCO₂ is 1101 kg/m3 and the Northern Lights specification require a ship capacity of 7500 m3 (Northern Lights Project).  Other project may require bigger capacity.

• Flexible with respect to fluctuations in capture profile (utilization rate), which have less effect on shipping costs compared to pipeline .

• Water bound inland industry can be flexibly connected to seaports, giving access to several permanent storage sites.

• Barges can be "built to purpose", optimizing design and volumes, considering waterway restrictions. Ideally, ship size should be customized for each specific CCUS chain, also considering cost .

• Fast development cycle. Ships have in general shorter construction times than pipelines. As reference, the Northern Lights ships were ordered in October 2021 and are expected to be ready by mid-2024  (~32 months). Barges have an average construction time of 26 months. In comparison, the construction time of pipelines usually lies between 1 and 4 years, depending on the length and complexity .

Costs of CO₂ shipping

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Regarding costs, shipping has some advantages for emerging CCS projects. Shipping costs are dominated by OPEX, while costs for pipelines are dominated by CAPEX. In other words, shipping is less capital intensive. In general, high transport capacity leads to a significant economy of scale for pipelines, which is less important for shipping. In general shipping is more economically favourable than pipelines with lower CO₂ flowrates (less than ~5 Mtpa), shorter project durations (less than ~20 years) and longer transport distances.

The discount rates used for project evaluation and calculating impacts the CAPEX annuity depend on the type of project investors. National authorities use a lower discount rate than average companies, while oil and gas companies and companies dealing with risks use a higher discount rate and risk premium. This will lead to different net present values for the same project costs and revenues. At higher discount rates, the CAPEX annuity increases and marine transport becomes more cost-effective than pipeline.

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  Source: CO₂ ship transport: Benefits for early movers   

                and aspects to consider - EU CCUS PROJECTS NETWORK 23-12-2021