The green transition at sea: new fuels and propulsion technologies

The UN's maritime organization IMO has set the goal that international shipping should be CO2-neutral by 2050 with sub-targets to reduce CO2 emissions by respectively around 20 percent in 2030 and around 70 percent in 2040. These are ambitious goals for an industry where ships typically operate for decades and where engines have traditionally run on heavy fuel oil. As a ship fitter you are part of that transition because it is ultimately you who must service the new engine types.

Methanol is today considered one of the most promising candidates for a green ship fuel. In 2020, the IMO already issued guidelines for the use of methyl and ethyl alcohol (methanol) as fuel in ships, and several shipping companies have since ordered ships with methanol dual-fuel engines that can run on both methanol and conventional fuel. The challenge is that methanol is still more expensive than traditional heavy fuel oil and that global green methanol production capacity is still far from the level a full transition requires.

Ammonia is another major hope because no CO2 is released during combustion itself. The first commercial ships with ammonia engines are expected to be launched in 2026. On the other hand, ammonia poses major technical and safety challenges: the substance is toxic, it is aggressive toward copper alloys, and it has a boiling point of minus 33 degrees, so it must either be stored under pressure or cooled. During combustion, NOx can also form, which must be handled with post-treatment.

• 01Methanol — liquid at ordinary temperature, already in commercial operation on several ships
• 02Ammonia – no CO2 during combustion, but toxic, aggressive toward copper and must be stored cold/under pressure
• 03LNG (liquefied natural gas) — reduces CO2 somewhat, but is still a fossil fuel
• 04Biofuels and e-fuels — can in many cases be used in existing engines with minor modifications

Much of the challenge is not the engine itself, but the infrastructure around it. Bunkering facilities — that is, facilities where ships can refuel with the new fuels — currently exist only in limited scope in the world's ports, and this slows down how quickly shipping companies can really convert their fleets. This means that the transition period with dual-fuel engines, which can run on both old and new fuel, will probably be long.

Regardless of which fuel advances in the coming years, the point for you as a ship fitter is the same: the fundamental ability to understand and troubleshoot an internal combustion engine system is the foundation you build on — but you should be prepared for the technical details and safety requirements to change as new technologies are adopted.