Hundreds of giant oil tankers that were stranded for months in the Persian Gulf because of the prolonged blockade of the Strait of Hormuz are now facing a different problem: heavy marine growth on their hulls. The article says that even after the strait reopened under a 60-day ceasefire agreement between the United States and Iran, the return of global oil shipments is being slowed by this unexpected obstacle.
While waiting at sea, the tankers accumulated thick layers of algae, shellfish, barnacles and other marine organisms on their undersides. This biofouling makes the hull rough instead of smooth, increasing drag, forcing engines to work harder and raising fuel consumption by 20% to 40%. For supertankers carrying oil over thousands of kilometers, that can mean millions of dollars in extra costs and serious risk of damage to engines, propellers and other mechanical systems.
The growth is especially damaging on propellers, where it causes severe vibration and can stop a ship from continuing its voyage. Operating in this condition can leave a vessel stranded at sea. There is also a regulatory barrier: strict international rules prohibit ships that are biologically contaminated from entering destination ports because of fears of spreading invasive species, effectively blocking these tankers from Western ports until they are thoroughly cleaned.
Cleaning is expensive and complex. Specialized divers, known as bottom cleaners, are needed to remove the buildup. Each tanker, which can be more than 300 meters long and about 45 meters wide, requires cleaning over roughly 14,000 square meters of surface. A team of five to six divers may need four to five hours per ship using hand scrapers and pressure-washing equipment, and the sudden demand has pushed prices up to tens of thousands of dollars per vessel.
