Ultra low sulphur fuel oil (ULSFO)
ULSFO is the 0.10 percent sulphur residual grade used for ECA compliance where a ship wants a residual fuel rather than distillate, with its own handling regime.
Ultra low sulphur fuel oil (ULSFO) is a residual bunker blended to meet the 0.10 percent m/m sulphur limit that applies inside an emission control area under MARPOL Annex VI Regulation 14. It occupies the position between distillate and 0.50 percent VLSFO, and it exists because some operators prefer to keep a residual fuel system in service inside an ECA rather than switch to a distillate that sits at the low end of the engine inlet viscosity window.
The full article will cover what distinguishes ULSFO in handling. Unlike marine gas oil it requires heating, and the required storage and separator temperatures differ sharply from those for distillate: engine builder guidance places distillate separation around 40 to 50 degrees C and ULSFO near 98 degrees C, so a ship carrying both must treat them as separate fuels rather than as points on one scale.
The article will address the stability and compatibility questions that follow from the high paraffin content of many ULSFO blends, the wax appearance temperature that governs storage, and the commingling risk when two ULSFO stems from different suppliers meet in one tank. It will compare ULSFO against marine gas oil on price, engine wear and system complexity for a ship trading in emission control areas .