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Greenwire -- Friday, March 30, 2007
AIR POLLUTION: EPA issues guidance for diesel engine NOx controls
Daniel Cusick, Greenwire reporter
Tens of millions of tons of diesel fuel pollution, including nitrogen oxides
(NOx) and particulate matter, could be reduced under new U.S. EPA guidance
that allows automakers to install selective catalyst reduction (SCR)
technology on diesel-powered cars and trucks, the agency said today.
The [2]guidance, issued this week in a 10-page memo from Karl J. Simon,
EPA's acting compliance and innovative director, to automakers, will help
manufacturers comply with tough new emissions standards for NOx emitted from
diesel engines.
The standard, set at 0.20 grams of NOx per brake horsepower-hour, is being
phased in between model years 2007 to 2010, according to EPA. NOx is a
primary component of ground-level ozone, the nation's leading air pollution
threat, and is also a precursor pollutant in the formation of fine
particulate matter, or soot, that affects millions with asthma, bronchitis
or other lung ailments.
Since EPA published its diesel engine NOx standard in 2001, engine makers
have experimented with a variety of technologies to control the pollutant.
Selective catalytic reduction, which is already widely used to control NOx
from area source emitters such as industrial plants, ultimately won favor
with EPA and manufacturers because it can achieve as high as 90 percent
reductions in NOx.
In a release, EPA said the new guidance on emission certification procedures
for on-road diesel engines using SCR technology "helps pave the way for
putting more innovative and fuel-efficient clean diesel cars and trucks on
America's roads."
While endorsing the move toward greater use of SCR on diesel engines, Simon
noted that the technology "is still evolving" and added that EPA "reserves
the right to make any necessary changes" to the guidance as conditions
warrant.
One concern about SCR's use in motor vehicle engines is that the technology
requires regular replenishment of a NOx reducing agent, usually ammonia or
urea, to be effective. If an engine were to run out of its reducing agent
while in use, its NOx reduction capability would drop to zero, according to
EPA.
"Because the NOx efficiency and thus the NOx emissions performance of an SCR
system is so dependent upon a nitrogen-containing reducing agent, it is
critical than a vehicle using SCR never operate without the reducing agent,"
Simon wrote in the guidance letter.
Yet many manufacturers have warned that they would not be able to store
sufficient volumes of ammonia or urea on a motor vehicle to allow for
federally recommended maintenance intervals of between 100,000 and 150,000
miles.
As such, "It may be appropriate for EPA to approve an industry-wide
scheduled maintenance change, as we have done previously in similar
situations," the guidance states.
Manufacturers will need to gain approval for their SCR strategies as part of
the EPA certification process. Among the other requirements for
certification are driver warning systems and inducement measures, a track
record of system durability and reliability, and reducing agent quality and
availability, EPA said.
Diesel engine manufacturers, represented by the Diesel Technology Forum,
have assured that all new engines being produced for highway use will meet
EPA's air pollution standards, including for NOx and particulate matter.
In January, the group announced that all new big rigs are equipped with
innovative new PM-trapping filters and that NOx emissions have also been
significantly cut due to improved technology. The enginemakers said model
year 2007 trucks are 90 percent cleaner than the previous generation of
trucks.
Allen Schaeffer, director of the Diesel Technology Forum, said this morning
that the new SCR guidance comes after nearly two years of conversations
between EPA and enginemakers over how to make further reductions in NOx
emissions. He said it "sets the stage closer to a time when we'll have even
cleaner diesel engines that are delivering even higher fuel efficiency."
Dieter Zetsche, chairman of DaimlerChrysler and head of its Mercedes car
division, also issued a statement saying his company "welcomes and supports"
EPA's guidance on SCR technology for on-road diesel engines, adding it
"serves to reinforce diesel's benefit as a viable alternative to help reduce
fuel consumption and ultimately, reduce oil imports."
[3]Click here to read the diesel engine guidance memo.
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References
1. http://www.greenwire.com/
2. http://www.eenews.net/features/documents/2007/03/30/document_gw_02.pdf
3. http://www.eenews.net/features/documents/2007/03/30/document_gw_02.pdf
4. http://www.eenews.net/trial/
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