Capturing carbon on board

Carbon capture and storage (CCS) technology has been used in shore installations for decades and is now being explored as a possible solution for the decarbonisation of shipping.

How carbon capture works

In very simple terms, a post-combustion carbon capture system will block CO₂ from reaching the atmosphere. The system traps CO₂ at the emission source and transfers it to an isolated storage location.

For a system fitted on board a vessel, the CO₂ is extracted from the exhaust gases either through scrubbing or by bubbling the gas through an absorber column packed with liquid solvents. Once the CO₂ has been captured, it is compressed into liquid state. The liquid will then be stored on board in cryogenic storage tanks until the vessel reaches a port connected to a suitable transfer and storage infrastructure.

From there, underground geological formations may be used for storage and isolation from the atmosphere.

The CO₂ captured by the system could be re-used for other purposes, such as in ‘enhanced oil recovery’, where it is injected into oil and gas reservoirs to increase extraction. This is known as carbon capture and utilisation (CCU).

Other than the risk of leakage during storage, one of the main reported drawbacks with current CCS technologies in general, is that they are energy intensive. A vessel with a carbon capture system will require adequate power capacity, which may mean increased fuel consumption.

Global and regional policies

Under the European Union’s carbon trading scheme, ships fitted with carbon capture systems could benefit from reduced costs. The EU’s emissions trading system (EU-ETS), expected to include shipping from 2023, currently proposes that installations are not required to surrender carbon credits (known as EU Allowances) when CO₂ is captured for subsequent transportation by pipelines and geological storage.

However, current IMO regulations do not recognise CCS as a means of improving the carbon intensity (CII) rating.

Charterparty considerations

In the future, there may well be scenarios where a vessel fitted with a CCS system would be attractive to charterers, such as low fossil-fuel prices or if the cost of carbon credits increases significantly.

However, owners should check if the installation of a system reduces the cargo-carrying capacity of the vessel, which may depend on the size and location of the liquid CO₂ storage tanks.

Based on current knowledge, certain charterparty clauses will require consideration and, potentially, amendment. For example, the provision to address the time and cost of installing the CCS system, as well as the right for owners to deviate to dry dock or repair berth to do so should that be necessary. Description clauses and performance warranties may need to be revisited if the CCS system increases fuel consumption or requires a greater power generation capacity.

As the CCS system will form part of the vessel’s machinery and equipment, in the event of any breakdown it is likely that the time lost and/or delays arising because of such a breakdown would be covered by the off-hire provision in a time charterparty.

Parties should investigate whether the liquid CO₂ storage tanks are capable of being discharged at the same time as cargo operations, so to ensure there are no delays caused to the vessel from that perspective.

Furthermore, consideration of the trading pattern of the ship will be important because infrastructure to transport the captured CO₂ may not be available in every port.

The CC-Ocean Project

Mitsubishi Shipbuilding, part of Mitsubishi Heavy Industries (MHI) Group, are leading the world’s first marine based test of CO₂ capture system in their “Carbon Capture on the Ocean” (CC-Ocean) project.

The project is taking place on CORONA UTILITY, a coal carrier for Tohoku Electric Power Co., operated by “K” Line, in conjunction with classification society ClassNK.

We spoke to Maetoko Takeshi (senior deputy manager) of Mitsubishi Heavy Industries to find out more about the CC-Ocean project.

Q: How do you expect CCS systems will be used on the different ship types in the future?

A: When the infrastructure to manage the captured CO₂ is more advanced, we see carbon capture systems being widely used regardless of the type of ship.

For example, carbon capture may lend itself well to crude oil tankers because crude oil ports are generally close to the oil field where captured CO₂ is used for enhanced oil recovery (EOR). CO₂ EOR is gaining popularity globally and it assists with major increases in oil well production.

Q: How will you marinize the technology of the CCS systems used ashore?

A: The technology is well established ashore. It’s now just a case of downsizing it for the marine market and preventing damage from the conditions experienced on board a ship, such as vibration and corrosion.

Q: What are the space requirements for the storage of carbon capture?

A: The amount of captured CO₂ varies depending on capture rate and type of fuel. Capacity is further determined by the ship’s trading pattern and the frequency of discharging captured CO₂.

Q: How is the transportation of carbon capture going to be handled?

Answer: Pipelines, containers and road tankers will be used ashore. At sea, liquified CO₂ carriers (LCO₂), currently under development by Mitsubishi Shipbuilding, will be used.

Q: What equipment needs to be installed on the vessel?

A: The key components are the towers that capture the CO₂, the equipment to liquefy it and the storage tanks.

Q: Is fuel pre-treatment required for CO₂ capture system?

A: Fuel pre-treatment is not required.

Find out more

Click Here to view our Navigating Decarbonisation page

Click Here to read Signals 124 article “Navigating Decarbonisation: Understanding the EU-ETS”

Click Here to read the latest press release on the CC-Ocean project from MHI