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Oceangoing Vessels

Diesel engines on oceangoing vessels such as container ships, tankers, bulk carriers, and cruise ships are significant contributors to air pollution in many of our nation’s cities and ports.  Their emissions are expected to increase even more in the future, as our trade with other countries increases, and ship emissions will represent a larger share of our national emission inventories.

This page provides general and technical information on EPA’s Clean Air Act regulations for the largest marine diesel engines as well as the U.S. government's international efforts to reduce air pollution from oceangoing vessels.

There are two types of diesel engines used on oceangoing vessels.  The main propulsion engines on most oceangoing vessels are very large Category 3 marine diesel engines (those with per-cylinder displacement at or above 30 liters).  Auxiliary engines on oceangoing vessels typically range in size from small portable generators to locomotive-size engines with power of 4,000 kilowatts or more. Auxiliary engines on U.S.-flagged oceangoing vessels are subject to EPA’s marine diesel engine standards for engines with per-cylinder displacement up to 30 liters per cylinder.  More information about EPA's programs for smaller marine engines is available on Diesel Boats and Ships and Gasoline Boats and Personal Watercraft.

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EPA Regulations

Category 3 engines on U.S.-flagged oceangoing vessels are currently subject to "Tier 1" emission standards that rely on engine-based technologies to reduce emissions.  These Tier 1 standards -- which were adopted by EPA in 2003 and went into effect in 2004 (see 68 FR 9746; Feb. 28, 2003) -- are equivalent to the standards adopted by the International Maritime Organization (IMO) in Annex VI to the International Convention for the Prevention of Pollution from Ships (a treaty called "MARPOL". Exit EPA disclaimer)

EPA is developing a rule for additional tiers of emission standards for new marine compression-ignition engines at or above 30 liters per-cylinder displacement.  These new tiers will be based on the application of high efficiency after treatment, and will closely match the program that the United States government first advanced at the IMO in February 2007 and that was reflected in our Advance Notice of Proposed Rulemaking in December 2007.

See the electronic Code of Federal Regulations for the full text of current regulations that apply to marine compression-ignition engines. The documents that established these regulations are available below.

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Emission Control Area Designation

One component of EPA’s coordinated strategy for addressing emissions from oceangoing vessels is the designation of an Emission Control Area (ECA).  The United States submitted a joint proposal with Canada to the IMO on March 27, 2009, to designate specific areas of our coastal waters as an ECA.  By 2020, an ECA designation with tough geographic-based emissions standards that apply to large ships would prevent between 3,700 and 8,300 premature deaths annually, and avoid approximately 3.4 million instances of respiratory ailments, such as asthma.

Compared to fuels used in ships today, ECA standards will lead to a 96 percent reduction in sulfur in ships’ fuels, as well as a cut in emissions of PM by 85 percent and NOx by 80 percent.  To achieve these reductions, ships must use fuel with no more than 1,000 parts per million (ppm) sulfur beginning in 2015, and new ships will have to use advanced emission control technologies beginning in 2016.

Designation of this ECA will deliver substantial public health benefits to many people living in the U.S. and Canada, as well as to marine and terrestrial ecosystems.  Air pollution from large engines on ships affects not just U.S. and Canadian ports and coastlines, but is also carried hundreds of miles inland.  When people breathe this polluted air, their health is adversely affected leading to lost productivity due to increased illnesses, hospitalizations and even premature deaths.  As of early this decade, more than 100 million people in the U.S. and Canada were living in areas with air pollution at levels exceeding our respective national ambient air quality standards.  Moreover, scientists have not identified any safe ambient threshold for particulate matter, thus the health of people in areas currently attaining our standards can be enhanced by improving air quality.  In addition, the gains that have been made by extensive domestic regulations to control emissions from land-based sources over the last four decades could be eroded or even reversed by expected growth in human and economic activity, including shipping.  To maintain and improve air quality, public health and the environment, decisive action must be taken to realize the benefits that can be gained from additional emissions reductions.

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

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International Standards

The International Maritime Organization (IMO) facilitates development of standards to control air exhaust emissions from the engines that power ships.  The IMO is the United Nations agency concerned with maritime safety and security and the prevention of marine pollution from ships.  The international standards are found in Annex VI to the International Convention on the Prevention of Pollution from Ships (MARPOL).

The effective date for the current Annex VI Tier 1 NOx limits was January 1, 2000.  Now that the Annex has entered into force for the United States (as of January 8, 2009), vessel owners will be required to comply with these standards, although most have voluntarily complied in the interim.

Current Annex VI Tier 1 NOx Standards

IMO MARPOL Annex VI Amendments

In October 2008, Member States of the International Maritime Organization adopted new international standards for marine diesel engines and their fuels (2008 Amendments to MARPOL Annex VI) that apply globally, and establishes additional, more stringent emission requirements for ships that operate in specially-designated coastal areas where air quality problems are acute.  These new global and geographic standards will dramatically reduce air pollution from ships, and will provide important benefits to our national air quality.  We will also take these international standards into account as we continue to develop our Category 3 marine diesel engine rulemaking.

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 areas will be required to use engines that meet the most advanced technology-forcing standards for NOx emissions, and to use fuel with sulfur content at or below 1,000 ppm. To obtain the full benefits of the program, the United States has proposed designation of an Emission Control Area off our coasts.

This important new program matches closely the program that the United States government first advanced at the IMO in February 2007 and that was reflected in our Advance Notice of Proposed Rulemaking in December 2007.

Main U.S. Submittals to Amendment Process:

Other U.S. Submittals to the Amendment Process:

Other Documents Relevant to the Amendment Process:

Original MARPOL Annex VI (adopted September 1997 and took effect May 2005)

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Press Releases

March 2009 Press Release announcing ECA proposal. (March 30, 2009)

President signs the Maritime Pollution Protection Act of 2008. (July 22, 2008)

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Guidance and Publications

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Related Links

For more information, contact EPA's Assessment and Standards Division at asdinfo@epa.gov or 734-214-4636.

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