Compliance Summary
Compliance Summary Tool
Transportation Modes
Service Functions
All Topics
Please note: This summary is provided to help you understand the regulations. Consult the references provided for links to the full text of the regulations.

Marine Diesel EngineDiesel Fuel Requirements (Marine)

Road Rail Air Water

Commercial oceangoing vessels operating within 200 nautical miles of the U.S. Coastline must use diesel fuels with limited sulfur content. These regulations apply to waters that are designated as Emission Control Areas (ECAs) by the International Maritime Organization (IMO), the United Nations agency concerned with maritime safety and security and the prevention of marine pollution from ships, under the International Convention for the Prevention of Pollution from Ships (MARPOL) Annex VI. The ECA includes those areas adjacent to the Pacific coast, the Atlantic/Gulf coast, waters around Puerto Rico and the U.S. Virgin Islands, and the main Hawaiian Islands and U.S. Inland waters (e.g., Great Lakes).

Air pollution can travel long distances, and emissions from ships can extend far inland. Many countries around the world have agreed to a common set of rules that apply to all ships registered in those countries. The rules require large ships that operate in a designated ECA to use cleaner fuel and improved engine technology.

The globally-applicable requirements of MARPOL Annex VI became enforceable in the U.S. through the Act to Prevent Pollution from Ships (APPS).

This section covers fuel standards for marine engines. For information on standards covering marine engine design, operation, and maintenance, see Engine Emissions (marine engines).

Who is covered by the regulations?

All ships flagged under countries that are signatories to MARPOL are subject to its requirements, regardless of where they sail and member nations are responsible for vessels registered under their respective nationalities. There are approximately 150 countries that are part of the MARPOL agreement, including the U.S.

The MARPOL fuel standards include globally applicable standards, as well as more stringent ECA standards. The standards must be met by commercial oceangoing vessels 400 tons and above (e.g., container ships, tankers, bulk carriers, and cruise ships) with Category 3 diesel engines.

MARPOL Annex VI is implemented by U.S. Law through the Act for the Prevention of Pollution from Ships. APPS grants authority to both the EPA and the U.S. Coast Guard with respect to implementation and enforcement. EPA has authority to issue regulations to implement the standards. The Coast Guard and EPA each have enforcement authority, although the Coast Guard has the lead with respect to vessel surveys and compliance actions.

What is the purpose of the regulations?

The diesel fuel used in international shipping can contain extremely high sulfur content as compared to that that used for road vehicles. Sulfur contained in fuel causes emissions of sulfur dioxide (SO2) and also contributes to the formation of secondary particulate matter (PM) that is particularly harmful to human health. SO2 emissions also cause environmental problems such as acid rain that can result in widespread damage to forests and lakes.

Enforcing the Emission Control Area standards will reduce sulfur content in fuel by 98 percent, which should result in an 85 percent decrease in particulate matter emissions.


MARPOL Annex VI is an international agreement to limit emissions of nitrogen oxides and sulfur oxides from ships. Nitrogen oxide levels are primarily determined by engine operating conditions, but sulfur oxide levels are primarily determined by the sulfur content of fuels. MARPOL Annex VI therefore sets limits on the maximum sulfur content of fuel allowed under the standards. These global standards for the sulfur content of fuel apply to ships at all times, without regard to location.

Some geographic areas may be more susceptible to harmful impacts from the emissions. MARPOL Annex VI recognizes that such areas may require further control, and provides special geographic-based standards. Ships operating in designated Emission Control Areas (ECAs) are required to comply with more the stringent fuel sulfur limits.

Table 1 summarizes the Annex VI fuel standards that apply globally and within all ECAs. The sulfur content of fuel referred to this table must be documented by its supplier.

Table 1. MARPOL Annex VI International Vessel Fuel Standards

Area Year Fuel Sulfur Content
(parts per million)
Emission Control Area (ECA) 2008 - 2009 15,000 ppm
2010 10,000 ppm
2015 1,000 ppm
Global 2008 - 2011 45,000 ppm
2012 35,000 ppm
2020 5,000 ppm

On March 26, 2010, the IMO amended the MARPOL agreement designating specific portions of U.S., Canadian and French waters as an Emission Control Area (ECA). The proposal for ECA designation was introduced by the U.S. and Canada, reflecting common interests, shared geography and interrelated economies. In July 2009, France had joined as a co-proposer on behalf of its island territories of Saint-Pierre and Miquelon, which form an archipelago off the coast of Newfoundland. Overall, the designated area is referred to as the North American ECA and it became enforceable in August 2012.

In anticipation of the North American ECA fuel sulfur standard, EPA codified regulations affecting marine diesel fuel composition. This rule requires that beginning June 1, 2014, all ECA marine fuel produced or imported to the U.S. is subject to a maximum sulfur limit of 1,000 ppm.

On January 18, 2012, EPA published a Direct Final Rule that adds a provision to their marine engine program to provide an incentive to repower Great Lakes steamships with new, more efficient, diesel engines. This rule is an automatic fuel waiver available to steamships that operate exclusively on the Great Lakes, that were in service on October 30, 2009 and that are repowered with a Tier 2 or better diesel engine. This Great Lakes steamship repower fuel waiver is valid through December 31, 2025; after that date, repowered steamships will be required to comply with the ECA fuel sulfur limits. For more information see: Great Lakes Steamship Repower Incentive Program.

On 1 January 2020, a new limit on the sulfur content in the fuel oil used on board ships came into force, marking a significant milestone to improve air quality, preserve the environment and protect human health.

Known as "IMO 2020", the rule limits the sulfur in the fuel oil used on board ships operating outside designated emission control areas to 0.50% m/m (mass by mass) - a significant reduction from the previous limit of 3.5%. Within specific designated emission control areas the limits were already stricter (0.10%). This new limit was made compulsory following an amendment to Annex VI of the International Convention for the Prevention of Pollution from Ships (MARPOL).

Compliance Options

The current ECA fuel standard can be met through use of multiple fuel tanks and fuel switching. In most cases, ships already have the capability to store two or more fuels. As an alternative to using lower sulfur fuel, ship operators may choose to equip their vessels with exhaust gas cleaning devices ("scrubbers"). In this case, the scrubber extracts sulfur from the exhaust. Development of an approval standard for such systems is ongoing at IMO.

Ships using separate fuel to comply with the regulation must carry a written procedure showing how the fuel change-over is to be accomplished. The volume of fuels in each tank as well as the date, time, and position of the ship when any fuel-change-over operation is completed must be recorded the ship's log-book.

More Resources

Designation of North American Emission Control Area to Reduce Emissions from Ships (March 2010). Fact sheet.

Enforcement of MARPOL Annex VI Memorandum of Understanding (MOU) Information Sheet.