Navistar's last-ditch SCR challenge

(chinatrucks.com, Mar.09, 2010)Truck maker Navistar's loudly proclaimed objections to selective catalytic reduction (SCR) technologies to control oxides of nitrogen (NOx) diesel emissions look like going down to the wire - the wire in this instance being the January 1 2010 deadline for new trucks and buses in the US to comply with tougher emission limits.

The US Environmental Protection Agency (EPA) has asked a federal appeals court to delay, for 60 days, proceedings instigated by Navistar requiring the agency to 'review and reconsider' its 2009 guidance on the use of SCR for NOx reduction. Earlier this year the manufacturer sued the agency, alleging that it did not follow the proper rule-making procedures in issuing SCR guidance.

For several years SCR, despite its widespread adoption in Europe, was frowned on by the EPA. This was largely because of perceived problems of enforcement, in ensuring the replenishment of the system's additional consumable: the urea-water solution needed to activate the SCR catalyst. The reductant, already familiar in Europe under the name AdBlue, is now being referred to in North America as diesel exhaust fluid (DEF). There was an added concern that cheap sub-standard DEF, typically (and literally) watered down, would find its way on to the market. Establishing coast-to-coast availability of approved-quality fluid was regarded by the EPA as a major obstacle.

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