Finally, note that after the standards finalized in this final rule go into effect, engines meeting these national standards will also meet the less stringent MARPOL Annex VI NOx limits and separate emission testing will not be required. However, engines intended for use on foreign-trade vessels or for sale in foreign countries will still be required to comply with the administrative, recordkeeping, and survey requirements that will be mandated when MARPOL Annex VI goes into force for the United States.
2. Tier 2
The Clean Air Act provides guidance for setting emission standards for nonroad engines in section 213(a)(3), instructing us to set standards that achieve the greatest degree of emission reduction achievable through the application of technology the Administrator determines will be available for the engines or vehicles to which such standards apply, giving appropriate consideration to the cost of applying such technology within the period of time available to manufacturers and to noise, energy, and safety factors associated with the application of such technology.
As described in the Final Regulatory Impact Assessment, manufacturers of marine diesel engines typically start with a partially or fully completed land-based nonroad diesel engine or, in some cases, a highway diesel engine, and adapt it for use in the marine environment. The emission standards that apply to land-based nonroad diesel engines therefore serve as the primary basis for the standards that apply to marine diesel engines. The land-based nonroad diesel engine standards in turn were designed to expand the use of highway engine technologies. The marine diesel new emission standards, and the underlying technology assumptions, are similarly derived from highway engine emission standards and technologies.
Table 3 contains the emission standards for commercial marine diesel engines at or above 37 kW. We are setting a standard of 7.2 g/kW-hr NOx+HC for most Category 1 engines. For engines under 0.9 liters per cylinder, a 7.5 g/kW-hr applies to correspond with the standard for land-based nonroad engines. The PM standards vary by engine size, as shown in Table 3; these values generally match the limits that apply to the counterpart land-based engines. The CO emission standard is 5 g/kW-hr for all engines. New Category 1 engines under 0.9 liters per cylinder produced starting in 2005 must comply with these standards. For Category 1 engines over 2.5 liters per cylinder, the starting date is 2007. For the rest of Category 1, these standards apply to new engines produced beginning in 2004.
For Category 2 engines between 5 and 15 liters per cylinder, the NOx+HC and PM standards are 7,8 g/kW-hr and 0.27 g/kW-hr, respectively. Bigger Category 2 engines are subject to graduated NOx+HC standards and a PM standard of 0.5 g/kW-hr, as shown in Table 3. These standards apply to new engines produced beginning in 2007.
These dates refer to the point at which the manufacturer concludes the final assembly of the engine. This also applies to remanufactured and imported engines that qualify as new marine engines. In addition, an engine can become new without being manufactured, remanufactured, or imported, if it is an engine that has been placed into service in non-marine application before being installed on a vessel. In this case, these dates refer to the point at which the engine is installed on a vessel.
We are finalizing requirements to ensure that engines meet the emission standards during real-world operation, not only under laboratory testing (see Section IV.G.). Under these requirements, marine engines may not exceed the applicable emission standards by a fixed percentage while the engine is operated in any load/speed combination contained in specified not-to-exceed (NTE) zones.
B. Total Hydrocarbons
The emission standards specify total hydrocarbons (THC) rather than nonmethane hydrocarbons. Organic emissions are sometimes expressed as nonmethane hydrocarbons because methane is significantly less reactive than other hydrocarbons in the formation of ozone. However, for diesel engines, methane makes up only about two percent of the total hydrocarbons. In addition, HC generally makes up less than five percent of the combined HC+NOx from diesel engines. The combination of these two factors makes the methane fraction a mathematically insignificant portion of the HC+NOx emission standard.
C. Crankcase Emissions
We are requiring that all naturally aspirated marine diesel engines have closed crankcases, where blowby gases are routed into the engine intake air stream. For turbocharged engines, manufacturers may have a closed crankcase or route blowby gases directly to the atmosphere. If manufacturers do not have a closed crankcase, they must make it possible to readily route blowby gases into the exhaust stream or otherwise measure them for an in-use test. This approach is similar to the approach we adopted for locomotives. The purpose of this requirement is to provide manufacturers the incentive to reduce crankcase emissions to the maximum extent possible, or eliminate them altogether.
