The stricter rules come into effect under MARPOL Annex VI, Reg. 14, which covers emissions of sulfur oxides and particulate matter from ships. These requirements were adopted in October 2008 by consensus and entered into force in July 2010.
The emission control areas established under MARPOL Annex VI for SOx are the Baltic Sea area, the North Sea area, the North American area (covering designated coastal areas off the United States and Canada); and the US Caribbean Sea area (around Puerto Rico and the US Virgin Islands).
Outside ECAs, the current limit for sulfur content of fuel is 3.5%, falling to 0.5% on Jan. 1, 2020. The 2020 date is subject to a review, to be completed by 2018, as to the availability of the required fuel oil. Depending on the outcome of the review, this date could be deferred to January 2025.
Ships may also meet the SOx requirements by using gas as a fuel or an approved equivalent method, for example, exhaust gas cleaning systems or scrubbers, the solution chosen by major cruise operators for a number of ships, including Carnival Corp. & plc, Royal Caribbean Cruises Ltd. and Norwegian Cruise Line Holdings.