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Oceangoing Vessels

Diesel engines on oceangoing vessels such as container ships, tankers, bunk carriers, and cruise ships are significant contributors to air pollution in many of our nation’s cities and ports.  As trade with other countries increases, these emissions will represent an even larger share of our national emission inventories. There is an opportunity to gain large additional public-health benefits from Category 3 marine diesel engines through the application of advanced technology emission controls including high-efficiency catalytic aftertreatment.

Under the Clean Air Act, we are working on an additional tier of federal emission standards for Category 3 marine diesel engines (those with per-cylinder displacement of 30 liters or greater).  We issued an Advance Notice of Proposed Rulemaking in November 2007.  In addition to engine and aftertreatment technologies, we will also consider the role of fuel quality in achieving future emission reductions and the impact of emissions from foreign vessels that enter U.S. ports. EPA also provides support to the U.S. delegation to the International Maritime Organization as it considers a new tier of international consensus standards for marine engines and fuels.

This page provides general and technical information on EPA’s Category 3 marine diesel engine rulemaking and the U.S. government's efforts at the IMO to reduce air pollution from oceangoing vessels. Category 3 marine diesel engines are those with per-cylinder displacement at or above 30 liters. Information about EPA's other marine engine programs is available on Gasoline Boats and Personal Watercrafts and Diesel Boats and Ships.

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Press Release

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

EPA Regulations

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. Category 3 engines 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 rules adopted by the International Maritime Organization in Annex VI to the International Convention for the Prevention of Pollution from Ships (a treaty called "MARPOL").

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.  Engines of this type 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.

New Standards

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Existing Standards

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 provisions are available below.

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IMO MARPOL Annex VI Amendments

The United States in February 2007 formally proposed a series of amendments to Annex VI of the MARPOL treaty. The emission program described in that proposal would dramatically reduce air pollution from ships by establishing a new tier of performance-based standards for marine diesel engines on all vessels and by establishing stringent emission requirements for ships that operate in coastal areas where air-quality problems are acute.

Negotiations for amended standards are continuing and are expected to be completed in 2008.

U.S. Submittals to Amendment Process:

Other Documents Relevant to the Amendment Process:

MARPOL Annex VI was adopted September 1997 and took effect May 2005.

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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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