Traffic through the Strait of Hormuz has resumed under a U.S.-Iran end-of-war agreement, but an analysis said ships that were stuck in the strait for months face another task before they can return to normal operations: cleaning their hulls.
On the 23rd, CNN said, "Tankers trapped in the Strait of Hormuz cannot move until they remove the organisms attached to their hulls," adding, "After months of war caused the largest energy supply disruption in history, this will be another obstacle to normalizing global oil supplies."
As ships remained anchored for months in the warm waters of the Persian Gulf, a large number of marine organisms such as barnacles, mussels, shellfish, and seaweed have clung to their hulls.
Like aircraft, ships are designed to minimize water resistance. But when "biofouling" occurs—barnacles or seaweed attaching to the hull—water resistance increases and fuel efficiency drops sharply. The worse the biofouling, the more fuel is consumed and the operating expense also surges.
In particular, for tankers that transport crude over thousands of miles from the Middle East to Asia or Australia, the impact of hull fouling is inevitably greater. Neil Roberts, head of the marine and aviation institutional sector at the Lloyd's Market Association (LMA), an industry group for marine insurance, said about 50% of ship operating expense is fuel. Increased fuel burn due to fouling on the underside of the hull can significantly raise total transport expense.
Carolyn Shearlock, operator of the boat-specialist website "The Boat Galley," noted that if heavy debris adheres to a ship's propeller, propulsion performance can drop sharply over time. She also said there are many cases in which marine organisms settle inside intake valves and cause cooling-system failures.
It is also a problem that hull cleaning takes considerable time. Ultra-large tankers are more than 1,000 feet (about 305 meters) long and about 150 feet (about 46 meters) wide. The area to be cleaned on the underside of the hull alone reaches about 150,000 square feet (about 14,200 square meters). A team of five to six divers using metal scrapers and high-pressure washers is known to take about 4 to 5 hours to remove biofouling from a single ship.
As about 600 ships that had been stuck in the Strait of Hormuz rush to clean their hulls to clear the strait, demand for related services is also surging. Cleaning firms are likely to raise work expense by thousands of dollars due to the explosion in demand. Earlier, Bloomberg, citing an industry source, reported that when U.S. President Donald Trump announced a peace deal with Iran, the expense to wash a single ship, which had been around $5,000 (about 7.7 million won), soared to $8,000 (about 12 million won) in a matter of days.
Even after hull cleaning is completed, it is uncertain whether ships will immediately return to normal operations. CNN said, "Hull cleaning is just one step in a long process that ships must go through before transporting hundreds of millions of barrels of oil to their final destinations," adding, "With the truce agreement encountering new variables and twists every day, it remains uncertain whether financial institutions and insurers will permit ship operations."