Air Quality


Standards for New Generators

New Source Performance Standards (NSPS) for New Stationary Diesel-Powered Engines

Do you plan on purchasing a new power generator set that runs on diesel fuel, or simply any engine that is powered by diesel fuel?

If your answer to this question yes, then it is important to consider if your new diesel-powered engine meets the recent emission limits established by the United States Environmental Protection Agency (USEPA), called the New Source Performance Standards (NSPS) Title 40, Code of Federal Regulations, Part 60, Subpart IIII, (40CFR60).

Is my stationary diesel-powered engine subject to the federal NSPS?

If you are purchasing a new diesel engine, take note of the manufactured stamp date of the stationary diesel-powered engine. The Federal Regulations state that all new stationary diesel-powered engines manufactured after April 1, 2006 are subject to the NSPS.

If you are reconstructing or modifying an existing diesel engine, with modification/reconstruction taking place after July 11, 2005, it is subject to the new NSPS. Modification under 40CFR60.14 is defined as any physical or operational change to an engine which results in an increase in the emission rate to the atmosphere of any specified pollutant. Under 40CFR60.15, reconstruction is defined as the replacement of components of an existing engine (irrespective of any change in emission rate) to such an extent that the fixed capital cost of the new components exceeds 50 percent of the fixed capital cost of a new engine.

If you currently own a diesel generator that was manufactured prior to April 1, 2006 and was not modified or reconstructed after July 11, 2005, the generator is not subject to the NSPS.

What actions do I need to take to ensure I am in compliance with the NSPS?

If you are purchasing a new generator, the burden of compliance with NSPS is primarily on the manufacturers, therefore, it is important that you are purchasing a generator that has been certified to meet the NSPS.  When purchasing a new engine (2007 model year or later), make sure that it is accompanied by a certification of compliance (stating that it is a certified engine that meets the 2007 EPA regulations). Without the engine certification, an air permit to install and operate cannot be granted. There are two engine classifications based on size identified under 40CFR60.4202 that must have the emission standards certification for 2007 model year or later.

The first covers 2007 model year or later engines that are less than 37 kilowatts (kW) or 50 horsepower (HP). The engines must be certified to meet the emission standards in 40CFR89.112 and 40CFR89.113 for all specified pollutants. The second classification covers 2007 model year or later engines that are 37 kW (or 50 HP) to 2231 kW (or 3000 HP) in size.  Please see the attached document, NSPS for Diesel Generators withTable 1 for a more complete listing of the emission standards.

Any 2007 to 2010 model year engine that is larger than 2231 kW with a displacement of less than 10 liters per cylinder must follow the Tier I (or Table 1 of 40CFR60, Subpart IIII) emission standards. The 2007 model year or later engines that have a displacement between 10 to 29 liters per cylinders have to follow the emission standards in 40CFR94.8. To determine the emissions from engines this large basically requires actual stack testing. Most of the engines found in the CNMI are below 2231 kW with the exception of those engines used at the local power plants owned by the Commonwealth Utilities Corporation.

Are there any other rules about the NSPS I need to know about?

According to the latest information from the U.S. Environmental Protection Agency regarding the applicability of 40CFR60, Subpart IIII, to emission sources in the CNMI, there are two special exemptions to the NSPS (found in 40CFR60.4215) that pertain specifically to diesel-powered engines used in the Commonwealth of the Northern Mariana Islands (CNMI), Guam, and American Samoa. They are both very significant.

First, CNMI sources do not need to meet the standard for non-emergency generators found in 40CFR60.4204. Rather, the CNMI must meet the emission standards outlined under 40CFR60.4202 for all its stationary diesel-powered engines, regardless if they are used as emergency or non-emergency.

Second, the CNMI does not have to meet the fuel requirement in 40CFR60.4207 for the maximum sulfur content in diesel fuel. The maximum sulfur content for diesel fuel used in the CNMI remains at 0.50% or 5000 parts per million by weight. The local petroleum suppliers in the CNMI currently supply this grade of diesel fuel.

For any additional information regarding the NSPS or other air quality permitting issues, please contact the Division of Environmental Quality’s Acting Clean Air Program Manager, Kate Fuller, at 664-8500 or 8503. 


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