A Rolls-Royce spokesperson for the mtu brand, a power solutions provider for power passenger ships, ferries and yachts, recently offered Singapore bunkering publication Manifold Times its perspective on the adoption of ammonia, Hydrotreated Vegetable Oil (HVO), and methanol as marine fuels for the shipping sector.

Ammonia is amongst future bunker fuels being considered, but it seems is there is no operating ammonia-fuelled marine engine yet. Why is it so?

We are watching closely where the use of alternative fuels is going. In Rolls-Royce Power Systems’ markets, it does not currently look like ammonia is going to become a big thing. For operators and owners of vessels that are often used for coastal passenger transport, we see the trend moving towards HVO and methanol, which are easier to handle.

The high toxicity of ammonia is a big threat especially on board of vessels with limited space and limited escape routes. But on the other hand ammonia may offer CO2 free propulsion with a comparably low cost fuel. This makes it attractive enough to be observed.

What is Roll-Royce’s forecast of the future marine fuels mix leading towards IMO 2030 and IMO 2050?

From today’s perspective, the different sectors in the marine industry – deep sea shipping, coastal passenger shipping, yachts and naval – will develop differently when using alternative and climate-friendly fuels.

For large-scale shipping – container ships, for example – ammonia is emerging as an alternative fuel as well as for come cases laughing gas. However, this is not the market in which Rolls-Royce’s business unit Power Systems operates with its mtu brand.

For our mtu marine engines, which often power passenger ships, ferries or yachts, the trend is moving towards two other alternative fuels that are technically easier to handle than ammonia and that enjoy greater acceptance in the passenger shipping industry:

HVO (Hydrotreated Vegetable Oil), a second-generation plant-based fuel made from waste materials e.g. from the food industry, has the potential to replace partly fossil diesel. Most mtu engines are already approved for it. HVO is already available today and will soon be available in larger volumes as demand for it increases. With HVO, a CO2 reduction of up to 90 percent can be achieved on balance. This is because during combustion, the CO2 that the plants absorbed during photosynthesis from the air is released into the atmosphere. Some yacht manufacturers already deliver their new yachts with HVO in the tanks.

Methanol can be produced in a climate-friendly way with electrical energy from renewable sources and CO2 which was captured from a sustainable source. On balance, Methanol is virtually climate-neutral. It is easy to store and handle on the ship and the necessary ship infrastructure can be realised at reasonable expense. mtu methanol engines for marine use are currently under development. The most important thing here is that sufficient green methanol is available in the foreseeable future.

In principle, it is not only technical feasibility, supply and demand that govern the market, but regulatory framework conditions such as laws and ordinances as well as government support for the use of such fuels and their production can have a decisive influence. Powertrain manufacturers such as Rolls-Royce must recognise the trends in their markets and provide appropriate technical solutions. They have comparatively little influence on the future fuel mix.

Since methanol and ammonia are acidic fuels in nature, what steps/technologies are the engine manufacturer taking to protect their power plants from these new types of fuels?

Of course for every new fuel the compatibility of materials needs to be checked. Depending on the fuel specification components containing fuel like fuel tanks and fuel lines need to be adapted for its fuel. For methanol this is a solvable task, as there is experience in racing and other types of engines. Methanol compatibility with stainless steel is good, but of course coatings are also reasonable options. Depending on the use, other materials and manufacturing processes are used, for example other coatings, seals or lubricants.

More or less the same applies to ammonia. Ammonia is highly toxic, but it is used since decades, therefore there is experience with materials.

Photo credit: Rolls-Royce
Published: 31 July, 2023