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Old April 15th, 2007, 22:05   #4
Ernie Rogers
Veteran Member
Join Date: Oct 2001
Location: Pleasant Grove, Utah
Fuel Economy: 49/ 45/ 40
Default Care to run for president?

Hey, Meister,

You could have my vote if you want to run for president-- you can do math, and probably know how to read the words in books too.

Yes, the CO2 number for CNG looks very suspicious. You and I are too busy really to go around correcting everybody's mistakes, so let's go away with our suspicions intact. Before I go, I will offer a possible explanation for the high number. This is a well-to-wheels number. I didn't read the calculations behind it. I am imagining that along the path from the gas well to the pipeline, and finally to the fuel tank, that there might be a lot of spillage of NG. I think they count NG as maybe 50 to 100 times the weight as CO2 because of its higher infrared cross-section. That's the only possible explanation I can see.

If that is the cause, clearly it shouldn't be held against the car-- the oil and gas companies should clean up their act.

Ernie Rogers

Originally Posted by TDIMeister
I cannot accept the figure for CNG to be higher than gasoline than Diesel, even on a energy equivalent, well-to-wheel basis.

I can do a "tank-to-wheel" CO2 calculation rather easily, and I have actually done so for some fuels and can do so for the others, but well-to-wheel is so vaguely defined that the factors and assumptions can almost be pulled out of the air to make whatever result desired. I mean, what significant "well-to-tank" energy input is required in the CNG infrastructure other than compressing the gas at various stages of delivery from the well to the consumer?

I know of a reputable organization that has designed and built a prototype CNG-fuelled Audi A6 and claims a net 50% reduction in CO2 emissions on the NEDC test cycle with comparable performance to a gasoline engine of the same rated power. Who's to be believed, then?

Don't assume that just because an organization like ARL says something, that it means it's impartial, objective and infallible. Most of the time there are alterior motives and one is always advised to follow the money.
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