Saudi Arabia has banned the use of high-sulphur fuel oil (HSFO) with open-loop exhaust gas cleaning systems at its ports, according to ship services provider GAC.

The prohibition applies to all vessels entering Saudi Arabian ports and remains in force until further notice, GAC stated in an advisory dated December 3.

Ships calling at ports operated by Saudi Aramco must now comply with one of two options. Vessels can either use compliant fuel oil containing no more than 0.50% sulphur by mass, or 0.10% when operating in emission control areas where applicable. Alternatively, ships may operate their exhaust gas cleaning systems in closed-loop mode, or switch hybrid systems to closed mode, with strict prohibition on discharging wash water into the sea.

The measure affects vessels that have installed open-loop scrubbers—systems that use seawater to remove sulphur oxides from exhaust gases before discharging the wash water back into the ocean. These systems have allowed ships to continue burning cheaper HSFO while meeting the International Maritime Organization's 0.50% sulphur limit that came into force in 2020.

However, several port states and regions have implemented restrictions on open-loop scrubber discharge in recent years due to concerns about the environmental impact of wash water on marine ecosystems.

The Saudi Arabian ban adds to a growing list of jurisdictions that have restricted scrubber operations in their waters. Ships operating in the region will need to factor in the additional cost of low-sulphur fuel or ensure their exhaust gas cleaning systems can operate in closed-loop mode, which retains wash water onboard for later disposal.