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US EPA signs final emission standards for Category 3 marine diesel engines

4 February 2003

The US Environmental Protection Agency (EPA) finalized emission standards for large ocean going vessels. The rule, proposed in April 2002, was signed on 31 January 2003. The emissions standards apply to “Category 3” engines of over 30 liters of displacement per cylinder, such as those used for propulsion power on ocean going ships.

The adopted Tier 1 standards for Category 3 engines are equivalent to the internationally negotiated MARPOL Annex VI limits for nitrogen oxides (NOx) emissions, as adopted by the International Maritime Organization (9.8 to 17 g/kWh NOx, depending on the engine speed). They are enforceable for new engines built in 2004 and later, installed on vessels flagged or registered in the United States. These limits can be achieved by engine-based controls, without the need for exhaust gas aftertreatment.

The EPA said it will develop more stringent Tier 2 standards, which will be proposed by April 2007. The EPA will also consider if the Tier 2 standards should also apply to engines on foreign vessels that enter US ports.

In 1999, EPA adopted emission standards for new commercial marine diesel engines. The “Category 3” engines were left unregulated in an expectation that they would comply with the MARPOL Annex VI limits. This triggered a law suit against the EPA by environmental organizations. A court settlement required the EPA to propose NOx emission limits for Category 3 engines no later than 30 April 2002. The court settlement, however, did not specify the stringency of the limits, which was up to the EPA to decide.

Indeed, most large marine engines built today do comply with the MARPOL Annex VI limits. In the US, engine manufacturers are already achieving and certifying to the Tier 1 standards under the EPA Voluntary Statement of Compliance program for Annex VI. Therefore, the adopted standards bring little, if any, emission benefit over the existing status quo. Environmental organizations and other critics called the regulation “toothless” and indicated the possibility of another court action against the EPA.

The adopted rule includes also other provisions, as follows:

The adopted rule does not include any provisions in regards to the sulfur content in marine fuels used in Category 3 engines. With regard to fuels used by Category 1 and Category 2 engines, the EPA said it is considering fuel controls as part of the rule for mobile nonroad diesel engines that is currently under development.

EPA Marine Engines page

Source: EPA