Hi Bill,
I have to disagree with your assertion that diesels are dirtier than
gasoline cars of the same type. It's just not true, or at least not
completely true.
I have seen and read the UCS "Diesel Dilemma" report, and found it very
disappointing, their preconceptions and bias are obvious from the
introduction and executive summary. Plus, their assertion is that
diesel is not a _cost-effective_ means of reducing emissions, not that
it is actually dirtier (though they do imply that idea).
Scientifically, I have a problem their use of at least two 'correction
factors', notably: the 19% lower "on-road performance" of diesel vs.
similar sized gasoline engines, and the conversion (25%!) of diesel mpg
into mpgge (miles per gallon of gasoline equivalent) simply because
there is a higher btu value in diesel fuel. Both of these are flawed
for obvious reasons. I can promise everyone out there that diesel
engines are plenty powerful (not like those old 30hp VW Rabbits of the
'80s), and drive as well or better than gasoline engines of the same
displacement. And every barrel of crude oil is converted into different
portions of gasoline, kerosene, diesel/heating oil, wax, asphault, etc.
see http://en.wikipedia.org/wiki/Image:Crude_Oil_Distillation.png), so
there's no reason to adjust for btu content.
Despite these issues, their results show marginal benefits, if any, of
gasoline over diesel. I can't even tell where in their results they
show that gasoline is better for the environment. In fact, it appears
that they show the opposite (see table 3, and look at the 'lifetime
global warming pollution savings' rows), where the current diesel
technology will result in 13 tons in lifetime pollution savings. The
meat of their study appears to show that diesel cars are slightly more
expensive than similar gasoline versions. But again, this is based on
the assumption that these cars have identical lifespans, which simply
isn't true, not to mention that cost is irrelevant in this particular
discussion.
Some other problems I would like to note:
Table 4 shows particulate emissions from 1977-1989 diesel vehicles, but
compares that with 1985-1997 gasoline vehicles.
Tables 5&6 show the potential health hazards of diesel exhaust, but no
gasoline exhaust as a comparison.
If I understand the report correctly, they are saying that it will be
better to focus on spending money on improving gasoline engine
technology rather than diesel. Why this is so important that it
warrants a public report, I can't say. Plus, their results appear to
show the opposite!
Anyway, enough about the UCS study. As far as real world data about
emissions...I haven't been able to find any simple assessments of this.
Best I can do is this recent summary from a NOAA climatologist (it's not
exactly peer-reviewed, but does have citations):
http://webpages.charter.net/lmarz/Diesel.pdf
The basic ideas that I have been able to collect are that NOx and
particulate matter (PM) are higher in diesels. Although both are being
addressed with new technology, and even the PM levels are debatable.
Diesels probably produce more large-particle PM (and total mass),
gasolines produce more small-particle PM (which may be more harmful to
human health). Gasoline-burning engines, even the newest technology,
produce more CO2, CO, O3, VOC, and other toxics like benzene. Add all
this to the notable difference in toxicity of the fuel itself (gasoline
has oxygenated additives [remember MTBE?]), and the fact that gasoline
vaporizes at something like 200x the rate that diesel fuel does. Plus,
the catalytic converters on modern diesels are pretty rudimentary, and
last quite a long time...the cats on most gasoline engines have a
limited lifespan, after which emissions are increased drastically.
So in summary, there is definitely a tradeoff. Diesels produce more NOx
and (probably) PM. Gasoline, more CO2 and a host of other toxic
chemicals. Hybrids = good, diesel hybrids = great. Riding a bike =
priceless!!!
Jay
William Adair wrote:
Hello Jay (and fellow ECOLOGGERS),
Your message describes the emissions associated with diesels as "negligible,"
which certainly comes as a surprise to me, a dedicated bicyclist (and motorcyclist) with
a history of respiratory problems.
As the situation currently stands, diesels certainly do have their advantages (efficiency
and longevity), but they also have considerable disadvantages too. Most notably, diesel
emissions are still quite dirty relative to comparable vehicles with gasoline engines.
The Union of Concerned Scientists has described this trade-off as "The Diesel
Dilemma," and has examined the problem in great detail:
http://www.ucsusa.org/clean_vehicles/fuel_economy/the-diesel-dilemma.html
Certainly the quality and kind of fuel is an important consideration. Here in
Utah, the federal low-sulfur-fuel standards have made a huge difference. For
example, getting passed by a typical diesel pickup truck is no longer a
life-threatening experience. UCS addresses the biodiesel question here:
http://www.ucsusa.org/clean_vehicles/big_rig_cleanup/biodiesel.html
If anyone can offer data that contradicts their conclusions, I would be glad to
see it.
Hopefully the situation will start to change in 2009, when new Tier II diesels
must satisfy a far more stringent set of standards. In the meantime, I will
rely on the UCS analysis and my own personal experience, which suggests that
diesels are good for their drivers and bad for everyone else.
happy trails
bill a
-----Original Message-----
From: Ecological Society of America: grants, jobs, news [mailto:[EMAIL
PROTECTED] On Behalf Of L. Jay Roberts
Sent: Monday, March 03, 2008 1:07 PM
To: ECOLOG-L@LISTSERV.UMD.EDU
Subject: Re: [ECOLOG-L] McDonough thread tangent...most "ECO" cars
Not entirely sure if this option has been brought up yet, but those of
you looking for 'eco-conscious' cars should consider the VW TDIs.
I agree with Malcolm that there is no excuse for our current line of
automobiles to be so inefficient. Except of course that we all drive
80mph on the highway, you probably weren't driving quite that fast in
your '83 Escort, right?
Anyway, of the current vehicles available, diesels are probably the
best. That means your choice is a Mercedes Benz, or a Volkswagen. This
is soon to change (Honda, Ford?). So, for the VW Jetta, Golf, Beetle TDIs;
Advantages:
40-50mpg on plain old diesel
Negligible emissions (despite the reputation)
10k+ mile oil changes
Outstanding longevity (200k+ miles conservatively)
High crash-test ratings, lots of airbags, heavier than other small cars
You can buy -or make your own- biodiesel (which has a smaller carbon
footprint and better energy balance than ethanol)
Diesel fuel has a lower vapor pressure than gasoline so additional
emissions savings due to negligible evaporation
Biodiesel is completely non-toxic
You can run your car on plain old oil or grease (although this WILL
affect the longevity of the engine, so it's NOT worth doing)
Excellent online community for repair and maintenance advice (tdiclub.com)
Disadvantages:
Relatively poor mileage on short trips (30-40mpg)
Warms up slowly (efficient combustion = little waste heat produced), so
cold-climates are an issue
VW not the most problem-free brand (e.g. windows break, radio and other
electrical problems)
High resale value, so used cars are pricey (my wife and I recently
bought a high-mileage 2004 Jetta for ~$12,000)
Mechanics (especially dealers) are unfamiliar with the design so they
create problems and destroy engines (problem solved by using tdiclub for
all maintenance and repairs [also saves $])
Price of diesel is more volatile than gasoline (at least for now, it
might even out in the future)
Summary (of my opinions):
If you HAVE to have a new car, buy a Prius (or small efficient gasoline
powered car) if you drive in the city, buy a TDI if you drive on the
highway - otherwise keep your old car running efficiently so as not to
use up resources in the production of your new vehicle.
Jay
Carrie DeJaco wrote:
I recently bought a Toyota Yaris for ~$13K (couldn't afford the Prius).
It gets between 35-40 in the city, over 40 on the highway. It's small,
but it does have a good-sized backseat and is a hatchback. I've been
surprised at how much stuff I can fit into it. I saw a Smart Car the
other day-- it doesn't get any more mpg than mine!
My old '91 Toyota Tercel got a consistent 35 mpg, and my '82 Mazda
before that. I don't know how anyone could justify buying a car with
lower mpg unless they had special hauling or off-road needs.
America has got to wake up and start making compromises.
Carrie
-----Original Message-----
From: Ecological Society of America: grants, jobs, news
[mailto:[EMAIL PROTECTED] On Behalf Of Jane Shevtsov
Sent: Sunday, March 02, 2008 1:00 PM
To: ECOLOG-L@LISTSERV.UMD.EDU
Subject: Re: [ECOLOG-L] McDonough - I don't think so
Here's a Prius driver conversation about raising MPG that you may find
interesting.
<http://www.hybridcars.com/forums/help-increasing-06-t929.html>
Folks are getting 50+ MPG.
Jane
On Sat, Mar 1, 2008 at 7:51 PM, Malcolm McCallum <
[EMAIL PROTECTED]> wrote:
I don't know where we are in this conversation now, but MY 1983 escort
station wagon got 30-40 mi/gal on average with up to 50 mi/gal on the
highway. that wasn't a rating, that was what it actually got. So,
why is it that all the new cars (including the hybrids) do so puke
poor on mileage????
As for me, I'm waiting for the $60,000 price tag on the electric ZAP-X
to drop about 15 grand, then I'll get one for every day driving. It
goes 350 mi on one charge, and to recharge you simply plug it in for
10 min. Its a small car, but it looks like an everyday compact
(unlike the nutty looking e-cars of the past).
No kidding! If you were driving in city traffic all the time, $60K
would be a bargain next to the gas you were dumping out your endpipe
sitting in traffic. And, with projections of $4/gal gas soon, its
sounding like a bigger bargain!
On Thu, February 28, 2008 8:32 pm, Paul Cherubini wrote:
David Bryant wrote:
I'm not sure of your point here or where you get your data.
A 72 VW "micro-bus" got around 20 mpg (less than a Subaru Forester,
replete with airbags, crumple zones, and cup holders) and was one
of the most dangerous vehicles on the road.
OK, I'll try outlining another example. If you took a 3,300 pound
2007 Subaru Forester and installed a 80 HP 4 cyl engine in place of
it's 171 HP engine, a manual transmission in place of it's
automatic, and front wheel drive in place of all wheel drive, it's
weight would drop to about 2,800 pounds and it's highway fuel
economy would climb to about 37 MPG from 26 MPG. Then strip away
the air bags and crash protection structural reinforcements and
weight declines to 2500 lbs and fuel economy would rise to about 40
MPG. Along with this large (54%) increase in fuel economy there
would be a corresponding large (54%) reduction in carbon emissions.
At this point you'd have a vehicle with the same genera level of
power, comfort, convenience and safety features as a early 1980's
era vehicle and a vehicle like early 80's era ecologists and
activists in
the
USA were willing to drive, but not present day ecologists.
In addition, early 80's ecologists embraced the national 55 MPH
speed limit, which further boosted highway fuel economy 15%.
Paul Cherubini
El Dorado, CA
Malcolm L. McCallum
Assistant Professor of Biology
Editor Herpetological Conservation and Biology
http://www.herpconbio.org [EMAIL PROTECTED]
[EMAIL PROTECTED]
--
-------------
Jane Shevtsov
Ecology Ph.D. student, University of Georgia co-founder, <a
href="http://www.worldbeyondborders.org";>World Beyond Borders</a> Check
out my blog, <a href="http://perceivingwholes.blogspot.com";>Perceiving
Wholes</a>
"But for the sake of some little mouthful of flesh we deprive a soul of
the sun and light, and of that proportion of life and time it had been
born into the world to enjoy." --Plutarch, c.46-c.120 AD
--
-----------------
Lance Jay Roberts
PhD Candidate/Graduate Research Assistant
Department of Fisheries and Wildlife/EEBB
20 Natural Resources
Michigan State University
Office phone: 517-353-3030
Home phone: 517-243-1061
http://www.msu.edu/~rober245/index.html
--
-----------------
Lance Jay Roberts
PhD Candidate/Graduate Research Assistant
Department of Fisheries and Wildlife/EEBB
20 Natural Resources
Michigan State University
Office phone: 517-353-3030
Home phone: 517-243-1061
http://www.msu.edu/~rober245/index.html
