Exhaust Gas Cleaning System (EGCS)

An exhaust gas cleaning system, or scrubber, removes sulfur oxides from a ship’s exhaust so that a vessel burning high-sulfur fuel can meet the MARPOL Annex VI sulfur limit on an equivalent basis under Regulation 4. Open-loop systems wash the exhaust with seawater and discharge the effluent overboard; closed-loop systems recirculate treated freshwater dosed with alkali and retain a bleed-off; hybrid systems switch between modes. The wash-water discharge criteria and monitoring are set by IMO Resolution MEPC.259(68), and a growing number of ports restrict open-loop discharge.