2 November 2001

The US EPA has published a “Nonroad Diesel Emissions Standards Staff Technical Paper” (EPA420-R-01-052), which confirms the Tier 3 emission standard for combined non-methane hydrocarbons and nitrogen oxides (NMHC+NOx) as adopted in 1998. However, the Agency has not proposed any Tier 3 standard for particulate matter (PM) emission and shed little light on future plans in emissions regulations for mobile nonroad diesel engines.

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Under the 1998 nonroad engine regulation, Tier 3 standards for NMHC+NOx would take effect between 2006 - 2008, depending on engine category. Tier 3 engines would be required in 2006 for the 130-560 kW (175-750 hp) categories. No Tier 3 standard for PM emission was established in 1998; such standard was supposed to be adopted during the review of the regulation in 2001.

Industry observers believed that the EPA white paper would call for elimination of the existing Tier 3 NOx limit and abandoning the Tier 3 limits for PM. Instead, new NOx and PM limits would be set effective 2008 that would be equivalent to the US2007 regulation for highway engines. The new aftertreatment-forcing nonroad limits would be accompanied by a 15 ppm sulfur cap in nonroad diesel fuel, to enable particulate filters and NOx catalyst technologies.

Contrary to these expectations, the published EPA paper upholds all existing NMHC+NOx limits, as called for by some engine manufacturers (Caterpillar). It is not clear whether the EPA will yield to the diesel industry pressures and propose more relaxed nonroad standards than anticipated. The staff paper does not comment on the future directions in nonroad regulations, living it to a proposal to be published next year. A hint on future directions is given by the EPA in referring to a standard schedule which was suggested by Caterpillar as an approach that “may merit consideration”.

Source: US EPA