Diesel emissions-the truth - Page 2 - PeachParts Mercedes-Benz Forum

#16 02-05-2005, 10:01 PM

From what I've read, direct injection gassers emit even finer particulates than conventionally fuel injected gassers, thus increasing some of their environmental and health risks. This doesn't seemed to have stopped Saab from building DIGs for years. IIRC, the new VW 2.0 Turbo gasser is direct injection. They are more efficient, so I suppose that certain pollutants are reduced (CO2 for example).

TwitchKitty · #17 02-05-2005, 11:50 PM

Quote:

Diesel emissions-the truth

The truth about my diesel emissions is that they smell like french fries. Recently someone asked my why my car smells like a model airplane when it runs.

bullwinkle · #18 02-06-2005, 08:04 AM

Quote:

Originally Posted by MS Fowler

Not to pick a fight, but I have to challenge the allegation that global warming is a known fact. I would classify global warming as at least the result of junk science. There are serious debates on the topic. Only among the left, the main stream press and those who have accepted their view is it a "known fact".

Not to hijack, but anything that gives the EPA an excuse to exert more power and control over our lives will always be "acceptable science"

rurik · #19 02-06-2005, 05:54 PM

Right... "The Truth". Whenever I see a title like that I can't help it but get suspicious. It's like a name of a third-world country -- the more "people's" "republic" "democratic" etc. words it has, the less democratic the country actually is.

It is true that there's a lot of misconceptions regarding diesel emissions in the mind of common public, especially in US. A modern diesel is nowhere near as polluting as many people imagine. That said, certain types of emissions are a problem for diesels.

In US, most of the diesel fuel sold is pretty high in sulfur, and thus sulfur oxide/dioxide (SO and SO2, aka SOX) emissions are a problem. Once in the athmosphere, SOX form sulfuric acid which eventually comes down as acid rain (coal-fired power plans are well known for this). Also, SOX stink pretty bad and are strong irritants. However, they don't necessarily cause lasting health damage. A particularly nasty feature of SOX is the ability to "poison" catalytic converters, by reacting with the catalyst metals, thus inhibiting the ability of the car manufacturer to control other emissions (there's nothing that a catalytic converter can do to SOX themselves -- there's no more oxidation to be done). Catalyst poisoning is a big part of the reason the US is finally going to enforce low-sulfur diesel fuel. The use of biodiesel is very beneficial here as it has no sulfur to begin with.

Because the terperature of combustion is inherently higher in a diesel engine compared to a gasoline engine, NOX formation is facilitated. EGR and timing retardation help some, but not without a performance hit. Catalytic converters are capable of breaking down NOX into nitrogen and oxigen, provided an effective catalytic converter can be installed on the vehicle. Biodiesel is actually producing more NOX that dino-diesel in the same engine due to a higher temperature of combustion. BTW, NOX is an example of a "natural" pollutant -- it forms during lightning storms.

Hydrocarbons emissions represent the biggest problem, I think. Quantity is not as important as "quality" here. There's many different hydrocarbons, and while some are relatively harmless (e.g. octane or heptane), some represent the strongest cancerogens known (so-called policyclic aromatic hydrocarbons, or polyaromatics). Benzene is actually a pretty mild cancerogene, but something like anthrocene or benzopyrene is bad, bad $hit. Those molecules are extremely well suited for "intercalating" in DNA and causing mutations. The way raw petroleum is refined, with gas getting lighter fractions and diesel getting heavier fractions, dino-diesel fuel has a much higher content of heavy hydrocarbons, including polyaromatics. This issue, exacerbated by a challenge of attaching a well-functioning catalytic converter, is what I think is the biggest problem with US diesels today. Again, biodiesel is good here, because is has no polyaromatics. It also contains some oxygen which helps with more complete combustion.

Once low-sulfur diesel is the only stuff sold, a brand new diesel car equipped with a good catalytic converter should be able to produce less pollution than a comparable gasoline car, on the strength of simply burning less fuel. Who knows, maybe there'll even be some biodiesel in common use to help. As for today, it's not exactly the case -- one can still very much smell diesel exhaust of a new TDI, and as much as some people may like that smell, it's not a Good Thing for your lungs.

aklim · #20 02-06-2005, 06:13 PM

Quote:

Originally Posted by rickg

Yeah, they should have stated it as a "known theory".

A theory has to have some sort of proof behind it, does it not?

phidauex · #21 02-06-2005, 06:17 PM

Quote:

Originally Posted by bullwinkle

Not to hijack, but anything that gives the EPA an excuse to exert more power and control over our lives will always be "acceptable science"

Not to be a jerk, but this statement turns around perfectly to become:

Anything that changes my personal way of life will always be "junk science".

----

As to emissions.. Biodiesel is a good choice for lowering most of these emissions. B100 lowers PM emission by 47%, hydrocarbons by 67% (it also changes the nature of these hydrocarbons as rurik mentioned, less polyaromatics), CO by 48% and more. The NOx issue is still there, but advancements in ULSD and diesel catalytic converters will solve two problems at once.

peace,
sam

aklim · #22 02-06-2005, 06:19 PM

Problem with this who thing is that people are used to gassers. They see them everyday. Once again, NIMBY is at work. Since I don't have a diesel, let me point fingers at the diesel crowd. Also the fact that the best car doesn't belch out black smoke like a diesel semi would. Never mind that the engine is much bigger. Never mind that it is just hauling a larger load. We see the black smoke and we point the finger.

aklim · #23 02-06-2005, 06:21 PM

Quote:

Originally Posted by phidauex

Not to be a jerk, but this statement turns around perfectly to become:

Anything that changes my personal way of life will always be "junk science".

We can't even predict the weather for next week and they are telling us that in 50 years this, that and the other will happen? Kinda of a hard item to swallow.

So, if it is not junk science, do they have proof positive? If not, what would you call it?

sleeeper · #24 02-06-2005, 06:56 PM

This may be a little long...
I think it is good to be skeptical when we are handed "facts" from the media and in particular the government but I find it hard to dismiss the overwelming evidence of global warming and climate change along with it's widespread acceptance among scientists as "junk science". One would pretty much have to consider science in general to be junk to discount the rise in atmospheric C02 levels and rising global temperatures.

The fact is that C02 levels are quite a bit higher than they were pre industrial revolution and are still rising. There is a natural carbon cycle that involves huge quantities of c02 emitted into the atmosphere and taken up by plants but it is the balance of that cycle that matters and the quantities of C02 produced by people is more than enough to tip the balance. Here is what seems to be a reasonable link with good references that describes it : http://www.radix.net/~bobg/faqs/scq.CO2rise.html
one of the better snipets is :

Ice cores show that during the past 1000 years until about the year
1800, atmospheric CO2 was fairly stable at levels between 270 and
290 ppmv. The 1994 value of 358 ppmv is higher than any CO2 level
observed over the past 220,000 years. In the Vostok and Byrd ice
cores, CO2 does not exceed 300 ppmv. A more detailed record from
peat suggests a temporary peak of ~315 ppmv about 4,700 years ago,
but this needs further confirmation. [Figge, figure 3] [Schimel 94,
p 44-45] [White]

In addition to generating more C02 we have also reduced the capacity of the planet to reuse carbon through deforestaion and development.

It is well documented that C02 in the atmosphere traps heat.( I can look for some refrences if people really have a hard time with this one)

It is also well documented that the average global temperature is in fact steadily rising. (again I would be happy to pull references but the super bowl is starting!)

All of the climate change models I have seen predict just that-change, weather patterns will change, some areas will be warmer others colder, some wetter others drier so we should be carefull about anticdotal evidence from individual places.

One more good discussion can be found here:
http://www.newscientist.com/channel/earth/climate-change

I think a discussion and even a debate about the facts and myths of global warming is a good idea but lets try and leave politics out of it. I don't want to believe it is happening (it is an unpleasant thought for sure) but I do.

Now back to the Game!

phidauex · #25 02-06-2005, 06:57 PM

Quote:

We can't even predict the weather for next week and they are telling us that in 50 years this, that and the other will happen? Kinda of a hard item to swallow.

So, if it is not junk science, do they have proof positive? If not, what would you call it?

Edit: Sleeeper beat me to a few of these points, posted at the same time.

We have atmospheric CO2 data stretching back thousands of years that can be gleaned from deposition layers of algae and silt. We know how much CO2 the earth naturally produces, and how much it naturally buffers. In the last few hundred years CO2 levels have been steadily increasing, showing that we are overwhelming the earth's natural ability to buffer CO2 increases.

This CO2 is not coming from volcanoes, and its not coming from sunspots.

Simultaneously, we are seeing increases in worldwide temperature. It has been a cold winter in Minnesota, and a warm one in St. Louis, but individual localities are just a part of the larger average.

The place you see climate change is not in the middle of temperate america, but in fringe environments, areas that hover on the boundry of aerable and non-aerable. Like deserts and taiga. Desert areas are increasing, and border farmland is subject to desertification. Likewise, the permafrost regions of Siberia are receding, creating new farmland.

To give you an interesting perspective, Russian scientists have come to the same conclusion that the rest of the world's scientific community has come to, that global warming is occuring. However, their solution is not to stop global warming, but to speed it up! New farm land in Siberia is increasing yield and quality of food from that region, and has given its economy a shot in the arm. "Why stop a good thing?" they say.

If we have a steady increase in CO2 levels, correlated perfectly with a steady increase in global temperatures, as well as historic data about what causes climatic change, and information about CO2's ability to trap heat in the atmosphere, then what about this conclusion does not fit? Now, it is just a theory, but it is based on very solid science. If you don't think the theory fits the data at hand, then please help find new theories that explain the data, but none of the other theories explain all the phenomena. Don't just argue against the theory on the basis of someone's personal interests (since big financial interests are on both sides of this debate).

peace,
sam

aklim · #26 02-06-2005, 07:02 PM

Quote:

Originally Posted by phidauex

If we have a steady increase in CO2 levels, correlated perfectly with a steady increase in global temperatures, as well as historic data about what causes climatic change, and information about CO2's ability to trap heat in the atmosphere, then what about this conclusion does not fit? Now, it is just a theory, but it is based on very solid science. If you don't think the theory fits the data at hand, then please help find new theories that explain the data, but none of the other theories explain all the phenomena. Don't just argue against the theory on the basis of someone's personal interests (since big financial interests are on both sides of this debate).

I don't believe what they say. By the same token, I don't disbelieve it either. I just haven;t investigated it that much. So, have they rules out any other reasons that could cause it to occure?

phidauex · #27 02-06-2005, 07:23 PM

Quote:

I don't believe what they say. By the same token, I don't disbelieve it either. I just haven;t investigated it that much. So, have they rules out any other reasons that could cause it to occure?

The great thing about science is that you don't have to believe what 'they' say, you can read about it and decide for yourself. I teach science for a living, and every day I tell people, "Scientists aren't wizards, and you don't need to take their words as dogma. The reason they publish their findings is so you can decide for yourself." The problem is that it can take some time to do the background reading, so most people either don't have any thoughts on the subject, or have generated their thoughts based on either a complete trust of scientists (not wise), a complete distrust of scientists (also not wise), or a few soundbites from either a conservative or liberal media source (again, not wise).

Another link: http://www4.nationalacademies.org/onpi/webextra.nsf/44bf87db309563a0852566f2006d63bb/f6335bf011038bb185256a84005838c7?OpenDocument

The national academy of sciences has a good summary of global warming data, with many links to research done around the world and how they fit into the overall findings.

peace,
sam

aklim · #28 02-06-2005, 07:39 PM

The Intergovernmental Panel on Climate Change (IPCC) concluded that global warming in the last 50 years is likely the result of increases in greenhouse gases, which accurately reflects the current thinking of the scientific community, the committee said. However, it also cautioned that uncertainties about this conclusion remain because of the level of natural variability inherent in the climate on time scales from decades to centuries, the questionable ability of models to simulate natural variability on such long time scales, and the degree of confidence that can be placed on estimates of temperatures going back thousands of years based on evidence from tree rings or ice cores.

This is just one paragraph. It is the uncertainty that bugs me. I prefer to hava a nice neat package where they have more certainty. It makes me think of psychology. Everything is a definate maybe which will explain my absolute and total (redundency) distrust of it.

BobK · #29 02-06-2005, 10:17 PM

I kinda have a different question: Does anyone know for sure the cause of this mini ice age we are living in now? 1000 years ago, it was warmer. Like we all lived 500 miles further south. Heck, Greenland used to actually be green!

dannym · #30 02-07-2005, 10:57 AM

I have a hard time believing in global warming. even a 1 or 2 degree average temp rise would melt the polar ice enough to raise the sea levels enough to be noticed. Most of Florida would be lost.
I think it could definitely happen if we keep going on the course we are on but there is no evidence of it now.
Temperatures are cyclical anyway. Everyone knows about the Ice Age but what not too many people realize is that there were many Ice Ages during the life span of our planet.

Also someone mentioned that electric cars cause polution because power plants burn coal. Modern gas/electric cars are charged by the braking system. Therefore not indirectly burning coal. Maybe during the initial charging. If they even do that. But definitely not during the lifesan of the vehicle.

Danny