Navistar has acquired an interest in a Danish company that makes a type of NOX-reducing emissions technology -- a selective catalytic reduction process that does not rely on the addition of diesel exhaust fluid.

The company, Amminex, has developed a metal ammine-based NOx reductant delivery system. Navistar says its engineers will use the system to explore exhaust gas NOx reduction for specific applications.

The Amminex system is essentially a selective catalytic reduction (SCR) treatment technology, but it doesn't require urea-based diesel exhaust fluid that the SCR-based systems other manufacturers are using for EPA 2010 do. Amminex's system instead works by controlling the release and dosing of ammonia into the exhaust line.

Right now, Navistar is using advanced exhaust gas circulation to meet the Environmental Protection Agency's new stringent emissions regulations for 2010, and officials say that's still its "prime path."

"Our in-cylinder approach with MaxxForce Advanced EGR technology remains our prime path to achieve a tailpipe emissions compliance level of 0.2 NOx," said Jack Allen, president, Navistar's North American Truck Group. "The Amminex technology fits perfectly into our Advanced EGR prime path - assuring that the responsibility of emissions compliance remains with the OEM and eliminating the need for customers and third parties to invest in a new infrastructure for liquid urea."

The truck maker's main argument against its competitors' SCR systems is the need for the driver to add the liquid urea-based solution, or diesel exhaust fluid.

Amminex's AdAmmine system stores crystallized salt ammonium in a cartridge and then heats it for dosing of pure, "on-demand" ammonia directly to the exhaust line. Although Amminex has developed and tested the technology, a working system for a heavy-duty diesel engine doesn't yet exist and is still under development.