Efficient Ammonia Cracking Technologies Can Unlock Maritime Decarbonization

A new suite of technologies is helping to position ammonia as the zero-carbon fuel of choice for the global shipping industry. Currently, vessels are primarily powered by fossil fuels, including heavy fuel oil, marine gasoil, and liquefied natural gas. Low carbon fuels make up less than 0.1% of overall shipping fuel demand, according to the International Energy Agency.

However, the industry is approaching a tipping point. The International Maritime Organization has established a target for a 50% reduction in CO2 emissions from international shipping by 2050. Given that the average vessel has a lifetime of between 25 and 30 years, maritime stakeholders understand that reaching this goal will require early action. 

The Getting to Zero Coalition, an alliance of more than 150 maritime, infrastructure, and energy companies, is calling for 5% of new vessels entering service by 2030 to be powered by zero-carbon fuels. Likewise, leading supply chain players have formed the Cargo Owners for Zero Emission Vessels group, with the aim of fully decarbonizing their freight operations by 2040. Ports are also moving in the right direction—Los Angeles and Shanghai have announced a partnership to develop a green shipping corridor, with the first zero-carbon trans-Pacific container ships set to enter service by 2030.

Ammonia’s Advantages as a Maritime Fuel

A recently published Guidehouse Insights white paper, Ammonia as a Fuel to Decarbonize Transportation, explains that ammonia can play a central role in helping the shipping industry and other transportation sectors reach their emissions reduction targets. Commissioned by Amogy, the paper assesses ammonia’s potential compared with competing fuel options, unpacks different ammonia propulsion technologies, and provides recommendations to accelerate adoption.

Unlike other low carbon fuel options available to vessels, ammonia combines a relatively high volumetric energy density with the promise of scalability and the advantage of zero CO2 emissions at the point of use. Alternatives such as hydrogen or lithium ion batteries take up much more space when used over long distances. Methanol and biofuels are more promising options from a fuel volume perspective, but supplies are likely to be constrained by the need for sustainable CO2 or feedstock inputs. 

Ammonia-Powered Propulsion Systems Are Approaching Market Readiness

There are several possible approaches to using ammonia as a fuel source for the shipping sector. In smaller vessels, ammonia can be paired with an onboard ammonia cracker to provide hydrogen to a fuel cell electric propulsion system. It can also be used directly in solid oxide fuel cell systems, although these remain expensive and technologically immature.

In larger vessels, ammonia can be combusted directly in internal combustion engines (ICEs). Engine manufacturers such as MAN Energy Solutions and Wartsila plan to release ammonia-compatible ICEs to the market by 2024-2025. Due to ammonia’s narrow flammability range in comparison with fossil fuels, ammonia-fueled ICEs also require a small amount of pilot fuel to be used for ignition purposes. Early models are likely to use diesel as a pilot fuel. However, hydrogen released from an onboard ammonia cracker can also be used, eliminating the need for a secondary fuel source. To achieve fully decarbonized operations, vessel owners will need to opt for the latter approach.

Underlying the rapid entry of ammonia-powered propulsion systems are step changes in technological performance. Ammonia cracking technologies were once perceived as too bulky and inefficient to be suitable for mobile applications, but such is no longer the case. As a result, ammonia-powered propulsion systems are well positioned to deliver emissions reductions in the shipping industry and other transportation applications sooner than many observers expect.