[Vwdiesel] environmental concerns

[James Hansen]

Yes, but there is more...   Gas engines have been forced to have pollution
controls for a long time, and have been getting it fairly right for a while.
 Diesels, on the other hand have had similar controls for only a few years,
previously they were considered as exempt. When the technology for cleaning
diesel exhaust has progressed anywhere near the level of technology used to
clean gas emissions (which is getting near) diesel will kick major butt on gas
engines not only from the performance end of things which they do now, but from
the emissions side as well.  North Americans need to get the picture of a
crapped out 290 with the pump dialed way up slugging up a steep grade trying to
burn what they scraped off the bottom of a refinery worker's shoe as fuel.
 This doesn't have to be.  It's a pity the wheels of change work so slowly in
NA when it comes to the stuff we burn in our cars, trucks etc.  At present,
diesel cars produce more nox than a gasser, but one third less greenhouse gases
at the very minimum.  If the fuel was cleaner, urea nox traps could be used to
deal with it, but not as long as current fuel standards prevail.  People just
can't seem to get over the idea that they can SEE that puff of particulate
soot.  That and the idea that their 8mpg suv is okay, cause the epa sez so, and
it makes no puff of smoke like that dirty smelly diesel thing....   Just how on
earth can anyone say a car getting 50-60mpg is dirtier than a something getting
10mpg.  Now you know why diesel drivers are SMARTER and better looking.
Biodiesel just sweetens the pie.
-James


> That is misinformation.
>
> Diesels have higher combustion temperatures than gasoline engines. This is
> part of why they have higher efficiency. Diesels have no throttle plate to
> create a vacuum. They pull in the full displacement of air each stroke. These
> lower pumping losses also improve the efficiency.
> The bad side is that the higher temperatures and more residual oxygen once
> the meager fuel has burned means that more, not less, NOx compounds are
> produced. The oxygen that remains once the fuel is consumed combines with
> nitrogen due to the higher pressure and temperature into the smog producing
> compounds collectively called NOx. Exhaust Gas Recirculation goes a long way
> in reducing the excess O2 available for combining, but the relatively high
> sulfur content in petroleum diesel fuel limits the amount of EGR before the
> SO2 condenses and begins eating the intake. Once the US joins the rest of the
> world and forbids the use of high sulfur diesel fuel then this last argument
> against diesels will be moot.
> Oh, Did I mention? Biodiesel, unlike petroleum diesel, contains NO Sulfur! No
> limits to the amount of EGR for NOx reduction. Retarding injection timing by
> 2 degrees will do the same reduction without EGR.
> Jonathan Bartlett
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