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Many transit agencies are using DPFs and ULSD for new buses and as retrofits to older diesel engines to minimize fleet PM levels.By the end of 2006,nearly all diesel fuel for on-road applications is required to be ULSD.The PM level is planned to be restricted for all on-road diesel vehicles to 0.01 g/bhp-hr starting in 2007,and DPF technology has been proven to reliably address this PM levelall on-road diesel vehicles to 0.01 g/bhp-hr starting in 2007,and DPF technology has been proven to reliably address this PM level
NOx levels were reduced from 4.0 g/bhp-hr in 1998 to 2.4 g/bhp-hr combined NOx and HC in 2004 (CNG levels are 2.5 g/bhp-hr NMHC + NOx with a limit of 0.5 g/bhp-hr NMHC).The 2004 level was actually moved up to 2002 based on an agreement between EPA and diesel engine manufacturers.The emissions reduction down to 2.4 g/bhp-hr HC + NOx caused several diesel engine manufacturers to use EGR to help reduce NOx levels.The use of EGR has been reported in some locations to result in significant soot in the engine oil,caused major maintenance problems when combined with the use of DPF technology,and has been reported to have had some negative impact on fuel economy.
NOx certification levels are to be lowered to 0.2 g/bhp-hr by 2010 with a phase-in period from 2007 through 2009.During the phase in period,only half of the new engines (of a particular engine family) need to meet the 0.2 g/bhp-hr NOx level or all of the engines (of that particular family) must have NOx emissions levels less than 1.2 g/bhp-hr (or half the current standard).Most heavy diesel engine manufacturers are choosing the latter option (all engines in a family meeting the 1.2 g/bhp-hr NOx) during the phase-in period.The PM level is to be 0.01 g/bhp-hr regardless of the NOx reduction strategy.At the same time,the HC level is also being restricted down to 0.14 g/bhp-hr (or NMHC for natural gas) with a phase-in similar to NOx.For more details on this topic,see EPA’s latest public report,Highway Diesel Progress Review Report 2,March 2004,EPA420-R-04-004.
For the 2010 model year and beyond,the heavy diesel engine manufacturers are exploring selective catalytic reduction (SCR) and NOx adsorber technologies to keep NOx emissions at these extremely low levels.These emissions control technologies require low sulfur levels in the diesel fuel for the catalysts to work effectively.These emissions reductions are expected to comewith significant fuel economy penalties that have not yet been reported.CNG propulsion has already achieved the 2007 emissions certification level for NOx at 1.2 g/bhp-hr and CNG engine manufacturers are working to meet the 2010 certification levels early.Both Cummins and Deere have reported the availability of 0.2 g/bhp-hr NOx levels in their heavy natural gas engines by 2006.
Many transit agencies are using DPFs and ULSD for new buses and as retrofits to older diesel engines to minimize fleet PM levels.By the end of 2006,nearly all diesel fuel for on-road applications is required to be ULSD.The PM level is planned to be restricted for all on-road diesel vehicles to 0.01 g/bhp-hr starting in 2007,and DPF technology has been proven to reliably address this PM levelall on-road diesel vehicles to 0.01 g/bhp-hr starting in 2007,and DPF technology has been proven to reliably address this PM level
NOx levels were reduced from 4.0 g/bhp-hr in 1998 to 2.4 g/bhp-hr combined NOx and HC in 2004 (CNG levels are 2.5 g/bhp-hr NMHC + NOx with a limit of 0.5 g/bhp-hr NMHC).The 2004 level was actually moved up to 2002 based on an agreement between EPA and diesel engine manufacturers.The emissions reduction down to 2.4 g/bhp-hr HC + NOx caused several diesel engine manufacturers to use EGR to help reduce NOx levels.The use of EGR has been reported in some locations to result in significant soot in the engine oil,caused major maintenance problems when combined with the use of DPF technology,and has been reported to have had some negative impact on fuel economy.
NOx certification levels are to be lowered to 0.2 g/bhp-hr by 2010 with a phase-in period from 2007 through 2009.During the phase in period,only half of the new engines (of a particular engine family) need to meet the 0.2 g/bhp-hr NOx level or all of the engines (of that particular family) must have NOx emissions levels less than 1.2 g/bhp-hr (or half the current standard).Most heavy diesel engine manufacturers are choosing the latter option (all engines in a family meeting the 1.2 g/bhp-hr NOx) during the phase-in period.The PM level is to be 0.01 g/bhp-hr regardless of the NOx reduction strategy.At the same time,the HC level is also being restricted down to 0.14 g/bhp-hr (or NMHC for natural gas) with a phase-in similar to NOx.For more details on this topic,see EPA’s latest public report,Highway Diesel Progress Review Report 2,March 2004,EPA420-R-04-004.
For the 2010 model year and beyond,the heavy diesel engine manufacturers are exploring selective catalytic reduction (SCR) and NOx adsorber technologies to keep NOx emissions at these extremely low levels.These emissions control technologies require low sulfur levels in the diesel fuel for the catalysts to work effectively.These emissions reductions are expected to comewith significant fuel economy penalties that have not yet been reported.CNG propulsion has already achieved the 2007 emissions certification level for NOx at 1.2 g/bhp-hr and CNG engine manufacturers are working to meet the 2010 certification levels early.Both Cummins and Deere have reported the availability of 0.2 g/bhp-hr NOx levels in their heavy natural gas engines by 2006.
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