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Summary of EPA's Proposed Program for Low Emission Nonroad Diesel Engines and Fuel

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EPA420-F-03-008, April 2003
Download PDF version formatted for print (5 pp, 19K, About PDF Files).

The U.S. Environmental Protection Agency (EPA) is proposing a comprehensive national program to reduce emissions from nonroad diesel engines by integrating engine and fuel controls as a system to gain the greatest emission reductions. To meet the proposed emission standards, engine manufacturers will produce new engines with advanced emission control technologies. The proposed exhaust emission standards would apply to diesel engines used in most kinds of construction, agricultural, and industrial equipment. (The proposed standards do not apply to diesel engines used in locomotives or marine vessels. EPA has previously established standards for these categories.) The proposed standards would take effect for new engines starting as early as 2008 and be fully phased in by 2014. The proposed standards are phased in over several years to provide adequate lead time to the engine and equipment manufacturers. The proposed exhaust emission standards will reduce emissions by more than 90 percent, and are similar to the requirements for engines used in highway trucks and buses.

EPA estimates that nonroad diesel engines that would be affected by the proposal currently account for about 44 percent of total mobile source diesel PM emissions and about 12 percent of total NOx emissions from mobile sources nationwide. These proportions are even higher in some urban areas. Because the emission control devices can be damaged by sulfur, EPA is also proposing to reduce the allowable level of sulfur in nonroad diesel fuel by more than 99 percent. Reducing nonroad emissions is essential to the efforts of federal, state, local, and tribal governments to improve air quality in all areas of the country and reduce the adverse health impacts.

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Why We Need To Reduce Emissions From Nonroad Diesel Engines

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Exhaust Emission Standards

Nonroad diesel engines built since 1996 have had to comply with modest emission standards, with the focus on reducing NOx emissions. Emission standards have generally not addressed PM emissions. Under the new proposed emission standards manufacturers are expected to use high-efficiency control systems to substantially reduce both NOx and PM emissions. This will achieve a level of control that compares with automobiles being built today. The table below shows the proposed emission standards and when these standards would apply for different sizes of engines. These standards are similar in stringency to the final standards adopted for 2007 and later diesel-powered trucks and buses.

Proposed Tier 4 Emission Standards (g/hp-hr)
Rated Power First Year that Standards Apply PM NOx
less than 25 hp 2008 0.30 --
equal to or more than 25, but less than 75 2013 0.02 3.5*
equal to or more than 75, but less than 175 2012-2014 0.02 0.30
equal to or more than 175, but less than 750 2011-2013 0.01 0.30
greater than or equal to 750 2011-2014 0.01 0.30

* The 3.5 g/hp-hr standard includes both NOx and nonmethane hydrocarbons.

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Nonroad Diesel Fuel

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Estimated Cost and Benefits

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Public Participation

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For further information or assistance regarding this web page, please contact the Assessment and Standards Division Information Line at (734) 214-4636 or E-mail: asdinfo@epa.gov.

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