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Marine engine choices – Which fuel? Newbuild, ready or retrofit?

Photo: MAN Energy Solutions Dr Uwe Lauber, CEO of MAN Energy Solutions
Dr Uwe Lauber, CEO of MAN Energy Solutions
Dr Uwe Lauber, CEO of MAN Energy Solutions, believes shipping is headed towards a more complex future with multiple fuel and engine types.

In this multi-fuel future methanol, LNG and ammonia are all set to play their part. In an interview with Seatrade Maritime News Dr Lauber discusses the different types of engines and the choices between newbuildings, retrofits, or opting for engines that are alternative fuel “ready”.

“Definitely, the future will be complex. And this is I think, specifically for the shipping industry, a major concern,” he explains. “I don't see that we going to have like we had in the past, where a one size fits all strategy will work.”

So, when ordering a newbuilding with dual fuel capability which fuel and engine types will owners choose and why?


Methanol, which has seen a sharp take up in orders over the last 18 months, he believes will be the most commonly used fuel in the medium term.

MAN Energy Solutions already has a number of years of working with methanol and has over 500,000 hours of operating experience on methanol carriers that also use methanol as fuel. “That gives us a fairly good level of comfort that the concept is such is proven technology,” Dr Lauber says.

Having already proven the operation using methanol over the last one and half years there have been over 180 new orders for methanol dual fuel engines. Last year saw the first large containership to run on green methanol – the Laura Maersk – come into service. Developments on the engine side have happened faster than MAN expected and they are more advanced in terms of engine development than the fuel side supply of the equation. “The ships are ready, the engines are ready to go, so the question is how fast can we ramp up green fuel?”


Looking to ammonia he notes there are still a lot of concerns around safety, but certain vessel types could be well suited to using it as a fuel.  “I see huge potential for container vessels, vessels who transports goods from A to B, ammonia is there could be the fuel of choice,” he says. However, he sees it as highly unlikely that anyone would choose ammonia to fuel a passenger vessel any time in the near future.

In terms of developing an ammonia engine MAN Energy Solutions carried out its first firing in the middle last year and has achieved very positive results since then.  It also has a launch customer in the shape of Mitsui OSK Lines for a containership with installation next year and operations in 2025 – 26.

Dr Lauber does not expect to see large scale adoption of ammonia before 2028 with a ramp up in fuel production and engine technology going hand-in-hand to 2027 at which point it might be the right time to develop a serial product.


With the drive to get towards net zero emissions, LNG, the most widely used alternative fuel to date would seem to be falling out of favour for new orders compared to methanol but Dr Lauber very much believes it still has a role to play. “I think one should not forget about the LNG. I still believe that LNG offers a huge potential because we have the infrastructure available for LNG.”

A dual-fuel engine that operates on LNG and heavy fuel oil can reduce CO2 emissions by around 20% just by switching to using LNG. On the issue of methane slip Dr Lauber says this can be solved using a high-pressure injection system, although this does increase capital cost. He said though if the need to reduce emissions is the driver a high-pressure injection system of 300 BAR or higher will work to reduce methane slip.

Dr Lauber expects owners to continue to order LNG dual fuel vessels, although in terms of volume it could slow down, with the fuel available in quantity and backed by the necessary supply infrastructure. “LNG is available today, e-methanol in the quantities, which we really need today is not there, so production needs to be ramped up first.”

How ready is ready?

An increasing number of vessels are being ordered with engines that are classed as being “ready” for methanol or ammonia. While Dr Lauber says that the amount of work done does depend on ship type in the case of a methanol ready vessel today around 40% - 50% of the work can be done upfront. The advantage of doing this work at the newbuilding phase it is easier than converting all the systems at a later stage.

So should how should an owner choose between ordering a dual fuel engine today, or a ready one for later. He says it depends on the economics and fuel type of the vessel.

For example, an owner looking to move straight to ammonia when its available Dr Lauber explains, “I will say you should choose the ammonia ready concept… because if you have to do a retrofit later on when nothing is ready for ammonia, the system components are so complex, it will end up being nearly a newbuild.”

The scope for retrofits

With the pressure to decarbonise sooner rather than later the question comes as to whether it is worthwhile to retrofit an existing vessel with a dual fuel engine. Dr Lauber says that potential demand for retrofits is really high, but the question is how many of them actually make sense financially.

MAN Energy Solutions has around 20,000 two-stroke engines in service, for those on vessels of 20 years or older retrofits simply don’t make sense. An electronically controlled engine is also prerequisite for a dual fuel conversion. Then there is the size of the vessel – for example is it 1,000 teu containership of a 20,000 teu vessel.

“We consider that there are around about between 3,000 to 5,000 vessels, which really would make sense to convert to dual fuel application,” he says.

However, even with no than a quarter of the existing two-stroke engine fleet suitable for retrofit there is a question engine maker and shipyard capacity. Both MAN Energy Solutions and the shipyards need to train more qualified people to carry out these retrofits. The company expects to be able to carry out 50 retrofits annually worldwide, moving up to 70 – 80 per year if it has the resources.