Scrubbers on ships

In ship construction, scrubbers, or exhaust gas cleaning systems, are installed on ships to reduce air pollution caused by sulfur oxides (SOx) emitted when burning heavy fuel oil. A prevalent type is the open loop scrubber, which uses seawater to wash exhaust gases and then discharges the resulting polluted washwater directly into the sea. These systems have sparked significant environmental debate due to their impacts on marine ecosystems.

Open loop scrubbers became widespread after the International Maritime Organization (IMO) implemented a global sulfur emissions cap in 2020. They allow ships to continue using less expensive, high-sulfur heavy fuel oil while meeting air quality regulations, shifting the environmental burden from air to water. As of 2022, in some regions like the Baltic Sea, the number of ships fitted with these systems has quadrupled in recent years.