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Diesel-powered trucks are the workhorses of today's society, delivering the vast majority of all goods either used or consumed in North America. After two decades of dramatic emissions reductions, the North American heavy truck industry has been challenged to develop even cleaner diesel engine solutions to meet the Environmental Protection Agency's latest standards.


An outstanding solution is Selective Catalytic Reduction (SCR) - an emissions-reduction technology with the ability to deliver near-zero emissions of nitrogen oxides (NOx), a smog-causing pollutant and greenhouse gas. SCR's performance has been proved in millions of miles of real-world truck operations in other countries, as well as in long-term field tests in the U.S.

SCR reduces NOx emissions to minute levels, while at the same time delivering improved fuel efficiency and engine performance. This technology doesn't change the design or operation of the basic engine. Rather, SCR is a simple aftertreatment system which converts NOx in the exhaust stream into harmless gases. Modern diesels already use exhaust aftertreatment systems, called diesel particulate filters, to control emissions of another pollutant, soot (also known as particulate matter or PM).

SCR works by injecting Diesel Exhaust Fluid (DEF) into the exhaust stream only as required. DEF is nothing more than a solution of water and urea, which is a common nitrogen-containing compound. DEF works with the heat of the exhaust and a catalyst to convert NOx into nitrogen and water vapor - two harmless and natural components of the air we breathe.

The end result is cleaner air, excellent fuel efficiency (which reduces the amount of imported oil needed) and a reliable emissions control system for today's modern diesels.

Click here for more information about SCR.

Talking SCR
Click here to ask and get answers from Mack's SCR expert, and to view past Q&A.

Click here for information on Diesel Power's Current and Future Importance.

Press Coverage
Click here to see what the press has to say about SCR.

Click here to visit the Mack corporate web site.