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Liquid CO2 carriage by sea: An introduction

29/06/22

As awareness grows about the harmful effects of carbon emissions, we have seen a surge in demand for knowledge about how to carry CO₂ on seagoing vessels, in bulk. This article provides an overview of the challenges and opportunities involved.

What makes CO₂ so special as a cargo?

Most other gases can be carried in a liquid form provided they are at or below their boiling point and either:

  • Under pressure alone
  • Under refrigeration alone
  • Under a combination of pressure and refrigeration.

CO₂ however is different. To carry it in its liquid form, CO₂ requires both pressure and refrigeration to prevent it directly converting from its gaseous state into its solid state (dry ice). These combined pressure/refrigeration requirements are not fixed but are sometimes referred to as “high pressure”, “medium pressure” and “low pressure”. These constraints have important implications for vessel design and capacity.

What pressure/temperature criteria are realistic for bulk liquid CO₂ carriage? (Provisional figures)

  Smaller-scale Vessels* Large Vessels
Pressure Range Low/Medium Low
Min Temperature -35 degrees celsius -55 degrees celsius
Max Temperature 19 bar 5.5 bar

How is CO₂ carried today?

CO₂ has been shipped by sea since the late 1980s, initially on converted dry cargo vessels. The existing fleet of CO₂ vessels comprises only four units (see table below). These have mostly been trading within Europe on short-haul business, supplying CO₂ to the food and drink industries.

 

Vessel Name Capacity Built Yard Owner
Helle 1,265 1999 Frisian SY Nippon Gasses Europe
Gerda 1,800 2004 Royal Bodewes SY Nippon Gasses Europe
Embla 1,800 2005 Royal Bodewes SY Nippon Gasses Europe
Froya 1,800 2005 Royal Bodewes SY Nippon Gasses Europe

Can any other types of gas ships carry CO₂?

The realistic answer is no. While there are six existing gas vessels of 10,000 CBM capacity with a rating that enables them to carry CO₂, they have never done so. The intake and sloshing-related challenges they would face makes CO₂ carriage impractical.

What about LNG carriers?

Again, the simple answer is no. LNG carriers are not able to withstand the pressure required to handle CO₂ cargo. There are some small-scale LNG carriers which have a relatively high-pressure rating, but still not high enough for this purpose.

Could further dry cargo vessels be converted for CO₂ carriage?

This would be impractical for cargo volumes of significant scale.

What are Clarksons doing about CO₂ carriage?

Clarksons Gases is firmly established at the heart of the global gas markets with an unrivalled track record in providing shipping and trade-related services for LPG, ammonia, petrochemical gases and LNG. As part of our commitment to becoming equally proficient in the emerging, seaborne CO₂ business, we have formed a specialist team, within Gases Department. The team is working closely with the Clarksons Green Transition, Carbon and Research teams to ensure we remain at the forefront of developments in the sector. We are already assisting several parties on CO₂ projects and welcome your enquiry to find out how we can help you.

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