A new robot may help keep ships’ bottoms clean

ALL SHIPS suffer from fouling: the build-up below the waterline of shellfish, seaweeds and other organisms. This causes drag, which slows the affected craft and increases its fuel consumption. Regular hull cleaning thus makes a considerable difference to the profitability of shipping. It also results in a useful reduction in the amount of planet-warming carbon dioxide emitted by the world’s merchant shipping—an industry that many environmentalists think is notoriously dirty and which could therefore do with burnishing its green credentials.Roar Ådland, a shipping economist at the Norwegian School of Economics, in Bergen, says that a midsized oil tanker’s fuel consumption (and also, consequently, its emission of carbon dioxide) drops by around 9% after its hull is cleaned at sea—something that happens, on average, once every six or seven months. If the cleaning is done in a dry dock, which allows the process to be more thorough, that figure can be as much as 17%.