Editorial: The Choice for 2010
This editorial appears in the April 30 print edition of Transport Topics. Click here to subscribe today.
From the outset, the Environmental Protection Agency has not been a fan of selective catalytic reduction — one of the technologies for cutting diesel emission of nitrogen oxides to the bone.
Exhaust-gas recirculation, the current technology, won’t reduce NOx as much as the law requires. Another step is needed to meet the 2010 target.
SCR works by injecting urea, water-based ammonia, into the exhaust stream. The urea increases the ability of catalysts to break down NOx molecules.
Federal clean-air regulators would have preferred a more “passive” approach. They favor addition of adsorbers — something like diesel particulate filters, in that they would capture NOx molecules in coatings of sponge-like minerals. And like DPFs, the adsorbers would have to be “regenerated,” or cleaned, periodically, probably requiring an injection of fuel.
Critics maintain that adsorber technology is still not ready for prime time.
EPA has its own concerns about SCR: Its success will depend on driver action — keeping the truck’s urea tank topped off. And that means making urea universally available, as well as enforcing its use.
As with all federal agencies, EPA must take a technologically neutral stance in its rulemakings. It may set the goals, but it cannot dictate the means of meeting those goals. Still, the agency wants assurances on this key step in achieving exceptionally clean diesel engines.
That is why it is significant that EPA has issued guidelines on the adoption of SCR. The agency reiterates its lingering concerns while recognizing that at least a portion of the U.S. engine-manufacturing community is committed to going in this direction.
Freightliner and Volvo Trucks North America are both early SCR adopters, drawing on parental experience, so to speak. DaimlerChrysler, which owns Freightliner, and Volvo AB are Europe-based companies with roots in European trucking, which already has embarked on the SCR road. And now that Volvo owns Mack Trucks, the bulldog, too, is opting for the SCR solution for 2010.
But, as they say, the jury is still out.
Market clout aside, nothing these companies, nor EPA, have done forces the other engine makers to reject the alternate technology.
At this date, what remains to be seen is whether trucking ends up with a “dual regime,” come 2010 — some engines working with SCR and others with adsorbers in their exhaust lines.
