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As of January 1, 2010, diesel engine manufacturers in the United States have to comply with new Environmental Protection Agency (EPA) emission standards. Diesel engines manufactured on or after January 1, 2010 will have to meet the following limits:
Particulate Matter (PM) of .01 grams per horsepower-hour, same as 2007 standards
Nitrous Oxide (NOx) of .2 grams per horsepower-hour
Engine manufacturers are responsible for engineering their technology to meet the standards set by the EPA, and different manufacturers take different paths to reach the same end result.
For 2010 and beyond, Blue Bird will be offering Cummins engines in their Type C and Type D school bus platforms. Cummins has chosen a path using Selective Catalytic Reduction, or SCR, to meet the 2010 emission standards. SCR is technology that is tried and tested, with more than half a million trucks using SCR every day in Europe.
To reduce NOx, SCR technology utilizes diesel exhaust fluid, or DEF, which is a solution of 32.5% urea and deonized water, and it is NOT toxic. It a simple automotive fluid, such as windshield washer fluid or coolant. The DEF is sprayed into the exhaust stream, and the DEF reacts with the NOx particles to convert to harmless nitrogen gas and water vapor. In most cases, the exhaust coming out of the tailpipe is cleaner and healthier than when the air came in the intake.
We've provided a sample DEF usage calculation form showing just how much (or how little) diesel exhaust fluid, or DEF, a typical buses operation will require annually.
Cummins Brochures & Literature for 2010
Cummins Aftertreatment Brochure
Cummins Diesel Exhaust Fluid (DEF) Brochure
Both Blue Bird and Cummins have further detailed information about the 2010 emission standards and the engine technology on their websites. We have provided multiple links to those sites, as well as other industry articles regarding emission standards and technology.
Cummins Diesel Exhaust Fluid Usage Calculator