October 1997 - EPA establishes reduced Nox (Nitrogen Oxides) standard of 2.5 grams, combined with non-methane hydrocarbons, to take effect Jan 2004.
October 1998 - Seven diesel engine manufacturers agree to meet EPA emissions regulations by Oct 2002
January 2001 - EPA orders further reductions in NOx and particulate matter and caps sulfur content in diesel fuels to 15 ppm by 2006, phased in. Total compliance by 2010.
December 2003 - Engine manufacturers must have determined the technologies they will use for compliance in order to be ready to produce engines in production quantities by 2007.
January 2004 - All Heavy Duty diesel engines must meet EPA requirements for NOx and non-methane hydrocarbons. Mercedes Benz and others must comply.
2005 - ULSD (Ultra Low Sulfur Diesel) fuel must be available in quantitiy nationwide in order to run field test engines in sufficient quantities to prove each OEM’s chosen technology. Engine manufacturers need at least 1 year and one winter season to conduct field testing.
2006-2007 - Debut of EPA certified production engines to the aftermarket. At least half of manufacturers engines must comply, with averaging allowed.
June 2006 - ULSD availability must be 80% of a diesel refiners volume.
2007 thru 2008 - Standards tighten, by mid year 2008 half of engines produced must meet .2g NOx, .014g hydrocarbon and .01g particulate matter, averaging still allowed.
2009 - Heavy Duty gasoline engines must meet heavy duty diesel engine emission standards.
2010 - All HD diesel engines sold for on-highway use must meet 2007 standards. By December 2010 diesel fuel containing over 15 ppm sulfur (ULSD) may no longer be sold for highway use.
Particulate filters - Particulate matter suspended in the exhaust stream will have to be removed prior to entering the atmosphere. A particulate filter (trap) will be required in most instances to accomplish this. These will be a mechanical device which will capture the contaminant for later disposal. Particulate filter systems will require maintenance or replacement at set intervals in order to maintain their effectiveness. Emerging technologies include the particulate filter in the same location and housing as the muffler.
Catalytic Converters - One of two NOx control technologies similar to the component used in automotive emissions control today. Will be used to control NOx and other harmful emissions in conjunction with a particulate filter.
The technology is still being developed using various configurations and requires additional engine and chassis mounted hardware and electronic controllers. Diesel fuels with higher than 15 ppm sulfur content can not be used as they would destroy the converters effectiveness.
Catalytic converter technologies will have to be used in conjunction with EGR and other existing methods to reduce emissions. It is said that catalytic converters will increase operating temperatures, narrow oil change intervals, lower fuel economies, power output and negatively affect driveability.
Catalytic converters are the prevalent technology being investigated by domestic engine manufacturers, since there is readily available information and experience with them. Costs over a 5 year operating life are estimated to be approximately the same as the SCR method.
SCR-UREA - Selective catalytic reduction using urea solutions presents an alternative to the use of a catalytic converter; one or the other will have to be used to meet emissions requirements.
This technology involves the addition of a urea tank and injection system, it is not as easily damaged by the use of diesel fuels containing over 15ppm sulfur. It does not require the use of an EGR system and has no impact on engine operating temperatures.
SCR technology would also increase oil change intervals twofold, increase fuel economy and improve driveability. The system would require the availability of urea at diesel filling stations as well as a methodology of preventing operation in the event of urea tank depletion on the vehicle.
Offshore manufacturers and many fleet owners and operators favor this technology, since urea has been successfully used in Europe, systems are already available, and the technology is proven. Questions remain as to making urea available for distritbution nationwide, product availability from manufacturing sources is not an issue. Cost to operate over a 5 year lifespan is estimated to be the same as the Catalytic Converter technology, including urea purchases over the same period.