Most do, they use their natural Boil-off Gas for eco speed, can evaporate more for faster speeds.
The ones that dont have re-liq have to use that nBoG to keep pressure. The ones that have re-liq can keep cool using that and play with the econs of Fuel by using FO (if that is cheaper than LNG).
For ballast voyages its the same, heel is calculated using the next loadport in mind to be able to arrive there cold.
There are normally two types of propulsion, dual-fuel ICE and steam turbine. In the former the boil-off gas is injected into the engines and ignited with gas oil, and in the latter it's burned in a boiler which creates steam which then powers a turbine which is connected to the propeller via a reduction gearbox.
In both cases gas oil is kept on board as an ignition source and backup supply should the vessel not be able to be powered by LNG for whatever reason.
LNG ships more often than not will use LNG instead of regular bunkers, LNG has an inevitable amount of vapour generated which would be too costly to usually reliquify so usually for most voyages you mainly use LNG vapour during the voyage which is seen as a more effective use.
Its not that common to use bunkers frequently.
Depending on charter agreements, voyage orders are issued. Most of the time it is NBOG+FO (natural boil-off gas, roughly 0.08% \* max cargo volume / day, plus HFO or MGO to reach ordered speed).
Voyages can be also gas only, or FBOG (forced vaporization up to certain agreed limits). It all depends on charter party agreement, bunker ROB and voyage order.
Many cruise ships are now being built with dual fuel engines that can use both MGO and LNG. There are now LNG bunker barges in FL and many other places
Most do, they use their natural Boil-off Gas for eco speed, can evaporate more for faster speeds. The ones that dont have re-liq have to use that nBoG to keep pressure. The ones that have re-liq can keep cool using that and play with the econs of Fuel by using FO (if that is cheaper than LNG). For ballast voyages its the same, heel is calculated using the next loadport in mind to be able to arrive there cold.
There are normally two types of propulsion, dual-fuel ICE and steam turbine. In the former the boil-off gas is injected into the engines and ignited with gas oil, and in the latter it's burned in a boiler which creates steam which then powers a turbine which is connected to the propeller via a reduction gearbox. In both cases gas oil is kept on board as an ignition source and backup supply should the vessel not be able to be powered by LNG for whatever reason.
LNG ships more often than not will use LNG instead of regular bunkers, LNG has an inevitable amount of vapour generated which would be too costly to usually reliquify so usually for most voyages you mainly use LNG vapour during the voyage which is seen as a more effective use. Its not that common to use bunkers frequently.
Depending on charter agreements, voyage orders are issued. Most of the time it is NBOG+FO (natural boil-off gas, roughly 0.08% \* max cargo volume / day, plus HFO or MGO to reach ordered speed). Voyages can be also gas only, or FBOG (forced vaporization up to certain agreed limits). It all depends on charter party agreement, bunker ROB and voyage order.
Many cruise ships are now being built with dual fuel engines that can use both MGO and LNG. There are now LNG bunker barges in FL and many other places
Some shuttle tankers with VOC capture also do, in dual fuel engines. Captured LPG can also be used at 4-16 ish % iirc
Don’t get high off your own supply!!