In 2010, the U.S. Environmental Protection Agency will again cut the amount of nitrogen oxides (NOx) in heavy-duty diesel engine emissions.  With the US 2010 regulations in place, the amount of NOx allowed in diesel engine emissions will be reduced more than 90 percent from the limits in place at the end of the last decade. 

As with US 2007, Volvo plans a “total vehicle solution” approach to comply with US 2010.  In addition to the proven technologies of high-efficiency exhaust gas recirculation (HEGR) and the diesel particulate filter (DPF), Volvo will introduce an advanced emissions control technology known as SCR.

SCR stands for "Selective Catalytic Reduction."  It is an exhaust aftertreatment technology that injects diesel exhaust fluid into an engine's hot exhaust stream to reduce emissions of nitrogen oxides.  The fluid is a water-based solution containing urea, an organic nitrogen-containing compound commonly used in agriculture as a fertilizer and classified by EPA as a nonhazardous substance.

The diesel exhaust fluid, in conjunction with a catalyst in the exhaust aftertreatment system, breaks down the NOx into harmless nitrogen and water vapor.  The amount of the fluid injected into the exhaust stream is precisely regulated by the vehicle's electronic control system, based on the engine's need for emissions reduction at the time.  The vehicle's driver is alerted when the diesel exhaust fluid reservoir needs to be refilled, which will be done at truck stops, service centers, truck dealer facilities and trucking firms' terminals.