LNG for propulsion of non-LNG carriers

Hi all

As far as I can tell LNG is becoming a topic for propulsion. What are people’s opinions? And since I don’t have a clue, how would you feel if a port charged a different (aka lower) mooring fee for LNG powered vessels compared to Diesel powered ones?


Don’t really see a problem in using LNG as fuel - been working on a few designs lately. Lower NOx, SOx, PM and even CO2 emissions (methane slip is still an issue, though) and no risk of persistent pollution in case of a spill (not to mention that many ships don’t even store LNG in hull tanks which may be breached in case of grounding). I’ve heard the engine rooms are cleaner as well as there’s no HFO around.

…aside from the storage issues? Not to mention logistics…

Are you thinking cryo or pressurized?

True. LNG is much more bothersome to store and handle than fuel oil.

As for storage tank technology, I reckon both Type C and membrane have their pros and cons, and the selection must be done on a case-by-case basis.

More and more LNG powered vessels to be seen.
Main problem is lack of bunkering possibilities around the world, but improving by the day.
Many LNG storage tanks are on open deck for safely dispersing of any gas in case of leakage, overfilling or boil-off, but not always the case

My understanding is that the current crop of dual fuel LNG container ships cannot maneuver in and out of port on LNG so they have to switch over to MGO or ULSFO when below sea speed. I would imagine the auxiliaries could remain on LNG for the port call though. This is just something I’d heard from an engineer while talking about these ships so it may just be completely false.

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Ah OK. I was thinking fully pressurized would be the only way to go, albeit at a construction cost that I wouldn’t know how to justify. What do you do with boil-off in periods of inactivity? Keep the boilers hot? Dump it in a flare? Run a big Stirling cooler to limit the problem? The surface area to volume ratio is pretty high for the tiny tanks we’re talking about…

How much modern ships see “periods of inactivity”, especially unplanned ones, anyway?

Type C is a bit more forgiving when it comes to holding time as you can allow it to exceed atmospheric pressure, but it’s true that eventually, regardless of the tank type, you’ll have to react somehow as more and more LNG boils off. The second-to-last solution is to burn off the excess gas in a boiler which acts then like a small GCU.

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I skimmed through WinGD X72DF project guide and didn’t find any limitations for gas mode except for very low load (below 10 %?) MCR. Perhaps this is some teething issue that has been ironed out from modern engines?

DNV-GL has some short (and some longer) explanations on the complexity and solutions to problems in using LNG as fuel on ships:


There is a link to download the full 60 page report for those interested enough to do so.

The boil-off problem have apparently been solved (at least when in normal operation):

BTW, DNV-GL recons that LNG is just en intermittent solution to the emission from ships while waiting for Hydrogen, Methanol or possibly other solutions.

Would reducing mooring fees for LNG and raising them for HFO have any kind of positive effect on uptake?

Who do you represent?

This is a question for ship owners, which can’t be answered before the technological issues have been dealt with.

I am a political activist with a degree in transport who is currently writing a transport policy for a political party. I have worked in forwarding, but never in the shipping industry itself.

Doubtful, and a difficult policy since most ships are dual fuel so what governs? Going to pure LNG is not likely a cost decision that one would pursue solely on the basis of mooring fees.

And what incentive would there be for the port? Why would they lower their fees for LNG? They’d be providing the same services at presumably same costs so they’d have to increase non LNG fuel fees to cover a discount and that risks driving away ships. Actually, if they begin allowing LNG bunkering, the port would incur new costs, since the port would have new issues to deal with that require specialized planning, training and risk management over traditional fuel.

Small, localized, incentives like mooring fees are not likely to drive behaviors in any meaningful way. The shift to using LNG fuel is being driven by macro level approaches and international emission targets more than this could produce. The technology has to be available to be selected and in trying to change an industry’s traditional energy model it only develops in broad target based schemes such as the emissions regulations implemented by phases for ships leading to increased use of LNG seen ongoing now. It has to be a force large enough to create a market for the tech.


I was thinking doing this on tax level. Same as introducing a legal requirement to provide LNG bunkerage as well as potential subsidies for this.

But it looks like trying to modify behaviour with tax is not sensible - providing LNG bunkerage OTOH might.

Ah, well, if it’s something broad based, then impacts can occur. Mooring fees sound ‘localized’ and thus small. But, it sounds… expensive, good for LNG bunker and fuel system component makers and LNG sellers, but large investment that won’t be offset. Picking a ‘winning’ fuel is not the best approach, it just creates an ethanol Iowa corn market thing and that can become an albatross. it’s the emissions objectives that need to be encouraged and maybe offset. Consider the Harbor Maintenance Fee. What if this was skewed to favor ships with better EEDIs by dropping it a fraction, with long term targets? That could create meaningful incentives for ship builders and operators contemplating a twenty year lifecycle of a container boat trading in the US.

Caveat - this is for a small country with mostly short sea and feeder trade. My thinking is to try this at home and then possibly try and persuade the EU to adopt it.

What kind of documentation do ships currently have to carry regarding emissions? Can we check things like carbon emissions per ton of fuel or something like that?

Maybe spend some time studying this before giving politicians even more bad advice.

The questions tell more about how bad policy is created than an answer might lead to good policy.

There is a reason why I am asking questions here - so I don’t write up ignorant sh*te. And yes, this has given me a few directions for reading.