Cleaning Up Diesel Pollution - Union of Concerned Scientists

10 l Union of Concerned Scientists 0.3 g/bhp-hrFigure 4 Comparing Nitrogen Oxide (NOx) Emissions Standardsfor Diesel Engines: Highway vs. Heavy EquipmentGrams per Brake Horsepower Hour (g/bhp-hr)1413121110987654321Highway Trucks and BusesHeavy Diesel Equipment01989 1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009NOTE: Standards for heavy diesel equipment are for 25 horsepower and greater. Some of the standards include nonmethane hydrocarbons.SOURCE: Heavy diesel equipment standards from U.S. EPA, 2002C; highway truck and bus standards for 2004 and earlier from U.S. EPA, 1997;highway standards for 2007 from U.S. EPA, 2000.into effect (Figure 5). The model indicates thata 180 hp excavator built in 2006 will releaseone-third as many nitrogen oxides as a 1995model. The Tier 3 standards, however, do notgo far enough in protecting the public from thedangers of diesel exhaust. Stronger standards thatmore closely mirror the standards for highwaytrucks and buses could further reduce nitrogenoxide emissions by 90 percent relative to Tier 3standards.Figure 5 Pollution from an Excavator:Impact of Progressively Stronger StandardsPounds per Year2,5002,0001,5001,000500Yearly Emissions of Nitrogen Oxides6.9 g/bhp-hrNOx only4.9 g/bhp-hrNOx + HC3.0 g/bhp-hrNOx + HC0NOx onlyNo Tier 1 Tier 2 Tier 3 Tier 4Standards (1996) (2003) (2006) (Future)NOTE: g/bhp-hr stands for grams per brake horsepower hour, which is a measurefor expressing the amount of pollution released per unit of power.SOURCE: UCS calculation is based on the U.S. EPA’s NONROAD model andbackground support documents located at: www.epa.gov/otaq/nonrdmdl.htm.