SCR stands for Selective Catalytic Reduction and requires the use of a fluid known as Diesel Exhaust Fluid. Most major engine manufacturers have chosen the SCR technology to meet the new nitrogen oxide emission standards in the EPA's latest revision to the Clean Air Act. SCR has proven to be the most cost effective method for meeting these new standards.
SCR technology is designed to reduce NOx emissions by using ammonia (urea) as a reducing agent within the catalyst system. The reducing agent reacts with the NOx causing it to convert to nitrogen, water and small amounts of carbon dioxide. The reducing agent is most commonly automotive grade urea otherwise known as Diesel Exhaust Fluid (DEF). SCR technology has proven to reduce NOx emissions by over 90%.
SCR technology has also proven to yield a boost of 3-5% in fuel economy according to many major engine manufactures of commercial truck engines. SCR is proving to be a win-win technology by not only reducing harmful emissions to near zero, but also proving to be good for business by providing a cost savings to commercial truck operators.