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Nonroad Engines, Equipment, and Vehicles

Ocean Vessels and Large Ships


Large ships such as container ships, tankers, bulk carriers, cruise ships, and Lakers are significant contributors to air pollution in many of our nation’s cities and ports. There are two types of diesel engines used on large ships: main propulsion and auxiliary engines. The main propulsion engines on most large ships are "Category 3" marine diesel engines, which can stand over three stories tall and run the length of two school buses. Auxiliary engines on large ships typically range in size from small portable generators to locomotive-size engines.

This page provides general and technical information on EPA’s coordinated strategy to address emissions from large ships, including ocean vessels and Lakers, flagged in the United States and in other countries. EPA’s coordinated strategy includes:

  • EPA domestic actions under the Clean Air Act; and
  • U.S. Government action through the International Maritime Organization, including:

Combined, these actions make a comprehensive program that is expected to significantly improve U.S. air quality and public health.

For more information on EPA’s requirements for marine diesel engines smaller than Category 3 installed on U.S. vessels, see Diesel Boats and Ships. For information on EPA's requirements for gasoline-powered marine engines, see Gasoline Boats and Personal Watercraft.

NOTE: You will need Adobe Acrobat Reader, available as a free download, to view some of the files on this page. See EPA's PDF page to learn more about PDF, and for a link to the free Acrobat Reader.

EPA Actions

Engine and Fuel Standards

In a rule published on April 30, 2010, EPA adopted standards that apply to Category 3 (C3) engines installed on U.S. vessels and to marine diesel fuels produced and distributed in the United States. That rule added two new tiers of engine standards for C3 engines: Tier 2 standards that begin in 2011 and Tier 3 standards that begin in 2016. It also includes a regulatory program to implement Annex VI to the International Convention for the Prevention of Pollution from Ships (a treaty called "MARPOL") in the United States, including engine and fuel sulfur limits, and extends the Emission Control Area (ECA) engine and fuel requirements to U.S. internal waters. The rule also revised our domestic CAA diesel fuel program to allow for the production and sale of diesel fuel with up to 1,000 ppm (0.10 %) sulfur for use in C3 marine vessels, phasing in by 2015.

On January 18, 2012, EPA published a Direct Final Rule that adds a provision to our large marine engine program to provide an incentive to repower Great Lakes steamships with new, more efficient, diesel engines. This consists of an automatic, time-limited fuel waiver that allows the use of residual fuel in the replacement diesel engines that exceeds the global and ECA sulfur limits that otherwise apply to the fuel used in ships operating on the U. S. portions of the Great Lakes. This automatic Great Lakes steamship repower fuel waiver is valid through December 31, 2025; after that date, repowered steamships will be required to comply with the Great Lakes ECA fuel sulfur limits for diesel engines. This automatic fuel waiver is available only 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.

See the electronic Code of Federal Regulations (e-CFR) for the full text of current CAA regulations at 40 CFR part 94 or 40 CFR part 1042 that apply to marine compression-ignition engines. See 40 CFR Part 80 Subpart I of the e-CFR for the full text of current regulations that apply to marine diesel fuels. See 40 CFR part 1043 for the full text of APPS regulations implementing MARPOL Annex VI and the North American ECA.

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Emission Control Area Designation

MARPOL Annex VI contains a program that applies stringent engine emission standards and fuel sulfur limits to ships that operate in specially designated Emission Control Areas. The quality of fuel that complies with the ECA standard changes over time.

The United States has obtained designation for the North American ECA and the US Caribbean ECA. The effective dates of the standards for an area depend on the area’s designation date. See Annex VI Amendments for more information about this international program.

On April 4, 2014, the Marine Environment Protection Committee (MEPC) of the International Maritime Organization (IMO), a United Nations agency, took action to protect the environmental benefits of the North American and U.S. Caribbean Sea Emission Control Areas by excluding them from an amendment to MARPOL Annex VI that will otherwise postpone the international Tier III NOx standards for marine diesel engines.  These technology-forcing engine standards will continue to apply to vessels operating in the ECAs adjacent to the United States, Puerto Rico, and the U.S. Virgin Islands beginning with new ships constructed in 2016, as originally specified in the 2008 amendments to MARPOL Annex VI.  For future NOx ECAs, the standards will apply to engines installed on ships constructed on or after the date of adoption of such an emission control area, or a later date as determined by the country applying for the NOx ECA designation.

U.S. Caribbean Emission Control Area

On July 15, 2011, the IMO officially designated waters around Puerto Rico and the U.S. Virgin Islands as an area in which stringent international emission standards will apply to ships. For this area, the effective date of the first-phase fuel sulfur standard is 2014, and the second phase begins in 2015. Stringent NOx engine standards begin in 2016.

The documents that describe and support the U.S. Caribbean ECA are available below.

North American Emission Control Area

Carnival Corporation is the most recent of several shipping companies, including other cruise lines, to apply for flexibility under the International Maritime Organization requirements to support the development of exhaust gas cleaning technology. Over the next three years, Carnival Corporation intends to develop and deploy a new type of exhaust gas cleaning system for ships—one that provides the potential to exceed the fuel sulfur standard ECA requirements, as well as provide additional benefits in the reduction of particulate matter and black carbon, at a lower cost than using lower sulfur fuel.

On March 26, 2010, the IMO officially designated waters off North American coasts as an area in which stringent international emission standards will apply to ships. For this area, the effective date of the first-phase fuel sulfur standard is 2012, and the second phase begins in 2015. Beginning in 2016, NOx aftertreatment requirements become applicable.

The documents that describe and support the North American ECA are available below.

EPA has also completed a study to examine the economic impacts on Great Lakes shipping of the requirement to use ECA-compliant fuel. This peer-reviewed study examines three potential impacts: transportation mode shift, source shift, and production shift. It also provides information about the benefits and costs associated with applying the requirements to the Great Lakes and a description of the Great Lakes shipping sector. Documents related to this economic study are available below.

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International Standards

EPA participates on the U.S. delegation to the International Maritime Organization (IMO). The IMO is the United Nations agency concerned with maritime safety and security and the prevention of marine pollution from ships. The international air pollution standards are found in Annex VI to the International Convention on the Prevention of Pollution from Ships (MARPOL).

Related IMO Activity

The United States regularly submits position papers to IMO committees such as the Marine Environment Protection Committee, in support of advances in measures to reduce air pollution and greenhouse gas emissions from ships. Committees of the IMO meet periodically to consider and adopt revisions to the various annexes of MARPOL and related treaties.

At its 65th session in May 2013, MEPC approved a draft amendment to MAPROL Annex VI that would delay the international Tier III NOx limits from 2016 to 2021. The United States joined with Canada, Denmark, Germany, and Japan on a paper that provided information challenging the reasoning behind that decision and recommending that the Committee reconsider its decision and retain the original implementation date of January 2016. At its 66th session in April 2014, the Committee agreed to retain the 2016 effective date for the North American and U.S. Caribbean Sea ECAs.  For future NOx ECAs, the standards will apply to engines installed on ships constructed on or after the date of adoption of such an emission control area, or a later date as determined by the country applying for the NOx ECA designation.

At MEPC 62 in July 2011, the IMO amended MARPOL Annex VI to include energy efficiency standards for new ships through the designation of an Energy Efficiency Design Index.

To learn more about U.S. participation at the IMO in discussions of various MARPOL provisions, you may visit the U.S. Coast Guard’s IMO web page, or contact EPA.

Annex VI to the International Convention for the Prevention of Pollution from Ships (MARPOL) – 2008 Amendments

In October 2008, member states of the IMO adopted new international standards for marine diesel engines and their fuels (2008 Amendments to MARPOL Annex VI) that apply globally as of July 1, 2010. The amendments also established additional, more stringent emission requirements for ships that operate in designated coastal areas where air quality problems are acute, called Emission Control Areas (ECA’s). These new global and geographic standards have the potential to significantly reduce air pollution from ships, and provide important benefits to our national air quality.

Under the new global standards, NOx emissions will be reduced, and the fuel sulfur cap will drop to 5,000 ppm in 2020 (pending a fuel availability review in 2018). Under the new geographic standards, ships operating in designated ECA’s will be required to use engines that meet the most advanced technology-forcing standards for NOx emissions beginning in 2016, fuel with a sulfur content not exceeding 10,000 ppm in the first phase of the program, and 1,000 ppm in the second phase of the program. Documents describing the amendments and the amendment process are available below.

Main U.S. Submittals to Amendment Process:
Other U.S. Submittals to the Amendment Process:
Other Documents Relevant to the Amendment Process:

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Guidance and Publications

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Related Links

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