The Environmental Protection Agency has issued its first guidelines for selective catalytic reduction on diesel-powered vehicles. Several engine makers have expressed interest in using SCR to meet nitrogen-oxide pollution cuts for construction trucks in 2010 and later for off-road equipment. The systems would require drivers to fill up regularly with a reducing agent, such as urea, to catalyze pollution in the tailpipe.

EPA said in a March 27 letter that it will disqualify SCR systems that enable engines to be operated without urea. EPA also wants manufacturers to prove urea will be “widely available and readily accessible” at dealerships, truck stops and other outlets. Sources say SCR is expected to add several thousands of dollars to the price of new trucks and heavy equipment.