As of 1 January 2020, Annex VI reduced the allowable sulphur content in marine fuel from 3.5 percent to 0.5 percent. This will yield significant global health and environmental benefits, especially in coastal areas and port cities.
Ships can meet the sulphur limit by using either compliant (low-sulphur) fuel, or through the use of an ‘alternative’ way of meeting the limit, such as an exhaust gas cleaning system (scrubber).
Scrubbers systems use either seawater or modified freshwater to remove gases and other combustion products from the ship’s exhaust. They then sometimes discharge scrubber effluent back into the ocean. The discharges contain a number of contaminants, and the type and amount of effluent depends on whether the scrubber is a ‘closed’ or ‘open’ loop system.
Some ships carry hybrid scrubbers which can operate in both open and closed loop mode. The main concerns are around the contaminants in the effluent and uncertainty as to the potential risks to the marine environment.
The Ministry for the Environment is currently in the process of assessing the risks relating to the use of scrubbers.
Read our guidance page for ship operators and port/regional authorities.