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United States Air and Radiation EPA420-F-03-001 

Environmental Protection January 2003 

Agency 

Office of Transportation and Air Quality 

Regulatory 

Announcement

Emission Standards Adopted for 

New Marine Diesel Engines 

The Environmental Protection Agency (EPA) is adopting emission 

standards for new marine diesel engines that will be installed on vessels 

flagged or registered in the United States. The near-term, Tier 1 

standards in this rule are equivalent to the internationally negotiated 

emission limits for oxides of nitrogen (NOx). These standards will go into 

effect in 2004 and are based on readily available emission-control 

technology. We will also undertake another rulemaking in a few years to 

consider a second tier of more stringent standards. This fact sheet 

contains an overview of the new standards and information about the 

future rulemaking. 

Which marine diesel engines are covered by the new 

standards? 

The Tier 1 standards apply to marine diesel engines manufactured January 1, 2004 or later if they will be installed on vessels flagged or registered in the United States1

. The Tier 1 standards will apply to older 

engines only if (1) they are converted from land-based to marine engines 

or (2) they are installed on a new vessel. More specifically, the engines 

that will be required to meet the standards are: 

1 This final rule applies to "new" marine diesel engines and to "new" marine vessels 

that include marine diesel engines. In general, a "new" marine diesel engine or a "new" 

marine vessel is one that is produced for sale in the United States or that is imported 

into the United States. The emission standards established in this final rule, therefore, 

will typically apply to marine diesel engines that are installed on vessels flagged or 

registered in the Unites States. 

Printed on Recycled Paper 
•	 Marine diesel engines with per-cylinder displacement at or above 

30 liters 

These engines are also known as Category 3 marine diesel engines. 

They range in size from about 2,500 to 70,000 kilowatts (3,000 to 

100,000 horsepower). These are very large marine diesel engines 

used for propulsion power on ocean-going vessels such as container 

ships, oil tankers, bulk carriers, and cruise ships. 

•	 Marine diesel engines with per-cylinder displacement between 2.5 

and 30 liters 

These engines are also known as Category 1 and Category 2 marine 

diesel engines. They range in size from about 500 to 8,000 kilowatts (700 to 11,000 horsepower). These engines are used to provide propulsion power on many kinds of vessels including tugboats, 

pushboats, supply vessels, fishing vessels, and other commercial 

vessels in and around U.S. ports. They are also used as stand-alone 

generators for auxiliary electrical power on many types of vessels. 

In 1999, we adopted emission standards for commercial marine diesel 

engines smaller than 30 liters per cylinder (Category 1 and Category 2). 

Under that program, the internationally negotiated NOx standards would 

be voluntary until EPA's more stringent Tier 2 standards begin to apply. 

EPA's Tier 2 standards are more stringent than the MARPOL Annex VI2 

NOx standards. EPA's Tier 2 standards also include limits for particulate 

matter, carbon monoxide, and hydrocarbon emissions. Information about 

these standards can be found in our fact sheet entitled, “Emission Standards for New Commercial Marine Diesel Engines” (EPA420-F-99-043, 

November 1999) and on our Web site at www.epa.gov/otaq/marine.htm. 

What are the new Tier 1 standards? 

The near-term Tier 1 standards we are adopting are equivalent to the 

internationally negotiated NOx limits adopted by the International 

Maritime Organization (IMO) in MARPOL Annex VI. These Tier 1 

standards will be enforceable on U.S. vessels with engines manufactured 

January 1, 2004 or later. These standards were voluntary for Category 1 

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 MARPOL is the International Convention on the Prevention of Pollution from Ships, 

1973, as Modified by the Protocol of 1978 Relating Thereto. You can obtain more 

information about this Annex and the associated NOx Technical Code in Docket A97-50, Document II-B-01. Copies of updated versions can be obtained from the 

International Maritime Organization (www.imo.org). 

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and Category 2 marine diesel engines under our 1999 rule; they are now 

mandatory for those as well as Category 3 marine diesel engines. As 

shown in the figure, the NOx standard varies from 9.8 to 17.0 grams per 

kilowatt-hour (g/kW-hr), depending on an engine’s maximum operating 

speed. 

These near-term standards are achievable with less than one year of lead 

time because manufacturers are already certifying their engines to the 

equivalent international standards under our program for Voluntary 

Statements of Compliance. These near-term standards are being 

achieved through the application of currently available technology, 

including optimized turbocharging, higher compression ratios, and 

optimized fuel injection. Engines meeting the Tier 1 standards have 

emission levels about 20 percent lower than uncontrolled levels. 

The Tier 1 standards will continue to apply to Category 3 marine diesel 

engines until we adopt more stringent standards in a future rulemaking. 

The Tier 1 standards will continue to apply to Category 1 and Category 

2 marine diesel engines until 2007, when the more stringent Tier 2 

standards we adopted in 1999 go into effect. 

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Why is EPA adopting the Tier 1 standards if they are 

the same as the international limits? 

The international standards apply to engines installed on vessels constructed on or after January 1, 2000, but they are not yet enforceable. 

The MARPOL Annex VI NOx limits will go into force twelve months 

after the Annex has been ratified by 15 countries representing at least 50 

percent of the world merchant shipping tonnage. Adopting the international NOx limits in this rule makes them enforceable for engines on 

U.S. vessels under U.S. law. 

As of January 2003, more than four years after it was adopted, the 

Annex has been ratified by six countries representing about 26 percent 

of the world’s merchant shipping.3 We expect that it will be ratified by 

several other countries, including the United States, and will go into 

effect in the next few years. 

What are EPA’s plans for the Tier 2 standards for 

Category 3 marine diesel engines? 

This final rule commits us to adopt technology-forcing Tier 2 standards 

for Category 3 marine diesel engines by April 2007. We will consider 

the availability of advanced technologies such as those used in other 

diesel engine applications as well as water emulsification and selective 

catalytic reduction. Engine manufacturers are already developing ways 

to apply these technologies to marine diesel engines. While there is a 

certain amount of information available about these advanced technologies now, there are several outstanding technical issues concerning their 

widespread commercial use, including the impacts of fuel sulfur on 

emissions, emissions at low engine loads, and particulate matter emissions. Adopting the standards at a later date will allow us to obtain 

important additional information on the use of these advanced technologies that we expect to become available over the next few years. This 

will also allow us to pursue further negotiations in the international 

arena to achieve more stringent global emission standards for marine 

diesel engines. 

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 The countries that have ratified Annex VI are Sweden, Norway, Bahamas, Singapore, Marshall Islands, and Liberia. Information about Annex 

VI ratification can be found at www.imo.org (look under Conventions, 

Status of Conventions - Complete List). 

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Is EPA adopting standards for particulate matter 

from Category 3 engines? 

We are not adopting emission standards for particulate matter (PM) from 

Category 3 engines in this final rule. The majority of PM emissions from 

large marine diesel engines comes directly from the high concentration 

of sulfur in the residual fuel they use, so the simplest way to reduce 

these emissions is by removing sulfur from the fuel. Annex VI provides 

a mechanism to control the sulfur content of fuels used by vessels that 

operate in specially designated SOx Emission Control Areas (SECAs). 

After the Annex goes into force, ships operating in these designated 

areas must use marine fuel with a sulfur content below 15,000 ppm or 

aftertreatment technology to achieve equivalent emission reductions (for 

comparison, sulfur levels in marine residual fuels may be as high as 

45,000 ppm). We intend to investigate this special designation for one or 

more areas in the United States. We will also reconsider this issue in our 

future rulemaking. 

Are the testing and certification requirements similar 

to the international program? 

The certification and testing requirements we are adopting for Category 

3 engines are similar, but not identical to the provisions contained in 

Annex VI and the associated NOx Technical Code. The differences 

between the two programs are intended to ensure that test data be representative of actual in-use conditions and that manufacturers demonstrate 

that the emission controls will be durable for the full useful life of the 

engine. We specify that this useful life for Category 3 engines is three 

years, based on the time that engines operate before being rebuilt for the 

first time. To allow manufacturers time to incorporate these changes in 

their testing and certification procedures, we are adopting a provision 

that will allow manufacturers to certify their engines with EPA by using 

the international procedures on an interim basis, after which they must 

use the procedures in this final rule. 

For Category 1 and Category 2 engines, we specify certification and 

testing requirements based on the requirements we adopted for these 

engines when we set the Tier 2 standards in 1999. Similar to the provisions for Category 3 engines, we allow manufacturers to certify their 

engines using the international procedures until the Tier 2 standards 

apply. 

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What is a Statement of Voluntary Compliance? 

As noted above, manufacturers are already producing engines that meet 

the Annex VI standards. EPA issues Statements of Voluntary Compliance for engines that meet the requirements of Annex VI using the 

procedures in the NOx Technical Code. This certification process addresses the need for manufacturers to sell compliant engines before the 

Annex goes into force. An EPA-issued Statement of Voluntary Compliance is similar to an EPA-issued Certificate of Conformity, which we 

issue for engines that meet the emission standards and other requirements in 40 CFR part 94. We expect that engine manufacturers will be 

able to apply for both of these documents in a single application. 

For more information about our voluntary certification program, see 

“Guidance for Certifying to MARPOL Annex VI,” VPCD-99-02. This 

letter is available on our Web site at: www.epa.gov/otaq/regs/nonroad/ 

marine/ci/imolettr.pdf. 

How will EPA’s future rule interface with international 

action? 

As explained above, we are making a commitment to develop more 

stringent standards under the Clean Air Act for marine diesel engines 

used on U.S. vessels. The Act requires us to adopt standards that reflect 

the greatest degree of emission reductions achievable through the application of technology that will be available, taking into consideration the 

availability and costs of the technology, and noise, energy, and safety 

factors. We will also consider whether we have the discretion under the 

Clean Air Act to apply any second tier of standards to engines on foreign 

vessels that enter U.S. ports. 

Most ocean-going vessels that come to the United States are flagged in 

other countries and are subject to the international standards. The United 

States will be participating in discussions under the International Maritime Organization to advocate a new set of more stringent emission 

standards for marine diesel engines that would apply to engines on both 

U.S. and foreign vessels. These discussions are expected to begin in the 

next few years. The schedule for our future rulemaking will allow us to 

take into account progress in the international arena toward more stringent emission standards for marine diesel engines. 

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Will EPA consider mores stringent standards for 

Category 1 and Category 2 marine diesel engines in 

the future rule? 

As part of our future rule, we also intend to consider more stringent 

standards for Category 1 and Category 2 marine diesel engines. We 

proposed Tier 3 standards for these engines in 1998 but did not finalize 

them in 1999 due to concerns about the emission-control technology 

necessary for greater reductions. We expect that additional information 

will be available soon that will help us determine if the more advanced 

technologies that will be applied to the land-based counterparts of these 

engines can be used on marine diesel engines. 

Where Can I Get More Information? 

You can access documents on marine diesel engines on the Office of 

Transportation and Air Quality Web site at: 

www.epa.gov/otaq/marine.htm 

You can also contact us at: 

U.S. Environmental Protection Agency 

Assessment and Standards Division 

2000 Traverwood Drive 

Ann Arbor, MI 48105 

voice-mail: (734) 214-4636 

e-mail: asdinfo@epa.gov 

You can access documents related to MARPOL Annex VI on the International Maritime Organization Web site at: www.imo.org 

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