Urea selective catalytic reduction

Mack and Siemens are working on the NOx emissions-reducing technology for heavy-duty trucks, though infrastructure hurdles still exist.

With emissions regulations driving heavy-duty (HD) diesel engine development, urea selective catalytic reduction (SCR) integrated with modern engine technology is gaining attention as a potential means of meeting future oxides of nitrogen (NOx) standards while maintaining acceptable driveability and fuel economy. Emissions standards for Europe and the U.S. show that NOx and particulate matter (PM) aftertreatment will be mandatory.

Urea SCR has been widely used since the 1980s to reduce NOx emissions from exhaust gas in stationary applications such as gas turbines, waste incineration, and diesel engines used for power generation. More recently, the technology has been applied to mobile diesel engines in applications such as ships, locomotives, and prototype on-road HD vehicles. Since 1990, urea has been increasingly used to replace anhydrous ammonia and aqueous ammonia as the reducing agent for improved handling and storage safety.