WASHINGTON, D.C. — Despite the Environmental Protection Agency’s refusal earlier this year to extend by two years the deadline for 2010 engine emission standards, as Navistar had requested, the truck and engine maker has launched a new challenge. In fact, a petition was filed in the federal Court of Appeals, District of Columbia Circuit, on March 31 but it’s only recently come to light.

Essentially, Navistar is questioning the legitimacy of the EPA’s allowing selective catalytic reduction as a 2010 emission-control strategy when it represents a reversal of the agency’s 2001 position. Can the EPA certify 2010 SCR engines without going through a lengthy review process to amend the 2001 rules? Navistar’s petition says ‘no.’

Its lawsuit uses words like "arbitrary," "capricious," and "an abuse of discretion" in describing the EPA’s actions.

When the 2010 0.20 g/hp-hr nitrogen oxide limit was created in 2001, Navistar says the EPA stated clearly that SCR would not be a feasible technology because, among other reasons:

1. There was not or would not be a distribution infrastructure for DEF (erroneously called ‘urea’ back then); 2. There were no safeguards in place to ensure that DEF is used for the life of the vehicle; 3. There were no safeguards in place to ensure that drivers fill DEF tanks; 4. There were “considerable uncertainties regarding the effectiveness of SCR” in reaching the 0.20 g/hp-hr NOx limit; and 5. there were expectations that a “substantial number” of failures to replenish DEF would result in a “total loss of NOx control.”

Navistar and the EPA are, not surprisingly, unwilling to comment on the court action. The head of one other truck and engine maker says this suit is unlikely to delay things, however.

Navistar, of course, is the sole engine maker planning to use exhaust gas recirculation to meet the coming standard, admitting that it will have to use accumulated emissions credits to do so in 2010 and for some undetermined period afterwards. It’s not at all clear how long those credits will last.

Getting to 0.50 g/hp-hr is more or less readily possible using advanced or ‘massive’ EGR, but the SCR camp says going down to 0.20 g/hp-hr is impossible if fuel economy and driveability are to be maintained.