Avatar photo

December 30, 2009 Vol. 5, No. 26

Just before Christmas a pretty interesting story cropped up, namely the news that Navistar has entered into a development and supply agreement with Amminex (, a Danish emissions-control systems provider, to produce an SCR-based solution for diesel engines in years to come.

Whaaat? Navistar exploring selective catalytic reduction?

That was my first reaction, not surprisingly, and the second was to want more information. I didn’t have the chance to explore any further at the time but my colleague Marco Beghetto did, asking a couple of questions of the International engine folks, whose responses I’ll include here. We need to know more, but given the holiday season, I haven’t yet had the chance to dive as deeply into this one as I’d like. That said, I did manage a long chat with an engineering friend of mine who knows the subject as well as anyone on the planet.

In fact I’m on holiday as we speak, by the way, so this newsletter will be more brief than most.

Anyway, right now we don’t know all that much about the technology or the Chicago truck and engine maker’s plans. It remains unclear what Navistar’s system would look like exactly, if it’s used at all, but the staple technology currently produced by Amminex differs little in principle from that seen on SCR engines used by Navistar’s competitors to meet the EPA’s 2010 nitrogen-oxide emission reduction targets. Both rely on ammonia released in a catalyst downstream of the DPF to create a chemical reaction that turns NOx into clean nitrogen and water vapour. The difference is in the ammonia storage and release systems.

Unlike today’s SCR engines — in which urea-based diesel exhaust fluid (DEF) is meshed with the hot exhaust stream in a catalyst, forming ammonia — Amminex’s AdAmmine system uses a solid, namely crystallized salt ammonium. It’s stored in a cartridge, which is heated to create “on-demand” ammonia in the catalyst, triggering the same sort of NOx conversion as with DEF. The cartridge would simply be replaced — as an OEM part — at every oil change.

Avatar photo

Rolf Lockwood is editor emeritus of Today's Trucking and a regular contributor to

Have your say

This is a moderated forum. Comments will no longer be published unless they are accompanied by a first and last name and a verifiable email address. (Today's Trucking will not publish or share the email address.) Profane language and content deemed to be libelous, racist, or threatening in nature will not be published under any circumstances.