Decarbonising international shipping

Decarbonising international shipping
12 July 2019

Decarbonising international shipping

The maritime sector is critical to the UK and global economy – transporting products, materials and food internationally. However, it is also vital that the maritime sector addresses the global threat of climate change.

So there was welcome news when the International Maritime Organisation (IMO) set its first greenhouse gass (GHG) reduction targets in 2018. Against scenarios of significant increases in GHG to 2050, the IMO committed to reduce emissions by 50% compared to 2008 levels.

This important first target will require a combination of adoption of energy efficiency measures and a switch to low and zero carbon fuels.

Energy efficiency has been regulated under MARPOL Annex VI since 2013 with incremental tightening every five years thereafter. However, if the industry is to achieve the IMO’s GHG reduction targets, it will need to go beyond incremental energy efficiency improvements and switch to new fuels within the next decade. Two factors drive this timeline:

  1. The operational life of international vessels can be 20 to 30 years, so to meet the 2050 target, the switch to zero carbon fuels needs to be incorporated in vessels launched from 2025 onwards;
  2. The need to certify and demonstrate these new solutions requires that work starts in the next 5 years to be able to launch vessels designed for zero carbon fuels from 2025.

These aspects became clear in an assessment that Ricardo undertook for the Environmental Defense Fund: Sailing on Solar.

This Sailing on Solar study examined the case for zero carbon fuels, with a focus on green ammonia as an example. The report examined each stage in the supply chain from generation of renewable energy, production of hydrogen and nitrogen, conversion to green ammonia, through to distribution and use on vessels.

The aim was to establish if there were any blockers that might prove an unmovable barrier to green ammonia as a zero carbon marine fuel. Evidence from stakeholders, and from the present methods of manufacturing and transporting ammonia, showed that there were no significant blockers. Comparison with other zero carbon fuels, such as green hydrogen and biofuels, also showed that green ammonia has some advantages, e.g. the space and temperature needed on board for fuel. The comparative analysis is shown below:

 However there are important issues to be solved, these include:

  • Cost: Zero carbon fuels are significantly higher in cost than traditional fossil fuels. Though the cost of renewable energy continues to fall, which will have a knock-on impact on fuel cost.  
  • Air Quality: Combustion of green ammonia creates nitrous oxides (NOx). So abatement systems will be needed, though this is will be a requirement soon for fossil-fuelled vessels anyway in the North Sea and other maritime Emission Control Areas.

The potential role for green ammonia was highlighted in yesterday’s publication of the UK Clean Maritime Plan (CMP) ( This aligned with Ricardo’s work in concluding that energy efficiency improvements alone will not be sufficient and that the use of alternative fuels (such as green hydrogen, green ammonia or methanol) will be required.

The research that informed the CMP also identified green hydrogen and green ammonia production technologies as offering the most significant potential economic benefits to the UK. So there are additional reasons to examine the case for these zero carbon options.

Ricardo and the Environmental Defense Fund (EDF) Europe are offering you the chance to examine the case in more detail at a joint webinar on Renewable energy’s role in decarbonising international shipping on Thursday 25 July.  The webinar will be run twice on 25 July. There will be a morning session at 9:00am to 10:00am (BST) and a second afternoon session at 3:00pm to 4:00pm (BST).

To register or for more details, visit: