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TDI (Diesel) Emissions This is a discussion about emissions from TDI's. Pro's cons of Diesels (including biodiesel) effects on the environment and how they compare to Gasoline and other fuel sources for Internal combustion engines.

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Old March 13th, 2018, 17:10   #16
wxman
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Originally Posted by bhtooefr View Post
Interesting - so 22.3% of the gasoline GHG emissions are from feedstock or fuel (well to tank), 20.8% of the diesel GHG emissions are from feedstock or fuel.

However, I do find it interesting how much lower the feedstock stage is for gasoline (E10 doesn't fully explain it), and how much higher the fuel stage is.
Can you explain?

According to the GREET user's manual, "Feedstock" (in the case of petroleum) is "Extraction of oil and its transportation to the refinery." Why would there be any difference between the two fuels in the case of E0 gasoline?

Last edited by wxman; March 13th, 2018 at 17:23.
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Old March 13th, 2018, 17:38   #17
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I'm surprised by the higher total CO output of diesel. Guess I can't say diesel exhaust is as safe as I thought!

Thanks wxman!
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Old March 13th, 2018, 17:51   #18
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Originally Posted by Tin Man View Post
I'm surprised by the higher total CO output of diesel. Guess I can't say diesel exhaust is as safe as I thought!

Thanks wxman!
Yeah, I'm not sure about that either, Tin Man.

The tailpipe CO emissions in the ICCT/WVU study that discovered the VW TDI defeat device in the first place showed very low emissions for all three of the diesel cars they tested - 0.1 g/mile or less.

I think ANL got the tailpipe emissions data from EPA, but I'm not sure why the default CO emissions are relatively so high.
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Old March 13th, 2018, 20:11   #19
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Quote:
Originally Posted by wxman View Post
Can you explain?

According to the GREET user's manual, "Feedstock" (in the case of petroleum) is "Extraction of oil and its transportation to the refinery." Why would there be any difference between the two fuels in the case of E0 gasoline?
But the "feedstock" GHG emissions are significantly lower than diesel - more than 10% lower. (And 10% lower would assume zero emissions from ethanol, which, no.)

Which tells me that there's something going on - maybe they're having to crack other fractions of the barrel of oil, increasing emissions, to get diesel?
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Old March 13th, 2018, 22:08   #20
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Maybe because the refineries are getting more gallons of gasoline per barrel of crude than diesel fuel?
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Old March 14th, 2018, 08:13   #21
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I believe GREET considers the Carbon fixation of the ethanol crops in it's net CO2 feedstock numbers. So that 10% has a lot more than a 10% net effect.
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Old March 14th, 2018, 10:03   #22
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I think the feedstock value difference is a combination of the ethanol factor and the higher yield of gasoline per barrel crude. Our refineries get twice as many gallons of gas as diesel from a given amount of crude oil.

I think it very unlikely that corn ethanol crops are fixing carbon into the soil. The best they could do really would be carbon neutral- also quite unlikely. Some forms of cellulosic ethanol could be close to carbon neutral though.

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Old March 14th, 2018, 10:28   #23
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totally depends on what the non-sugar carbons are doing from the crops.
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Old March 14th, 2018, 10:41   #24
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Even with the best no till practices (thanks Monsanto), I can't see corn ethanol crops building the soil. The cover crops planted between rotations perhaps. Hopefully there will be a shift to cellulosic ethanol soon.
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Old March 14th, 2018, 11:04   #25
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I believe the jury is still out as to whether cellulosic ethanol is economically viable. Even on a very large scale the data isn't back. Unless they make some enzymatic breakthrough it seems marginal.
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Old March 14th, 2018, 11:17   #26
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Originally Posted by CraziFuzzy View Post
I believe GREET considers the Carbon fixation of the ethanol crops in it's net CO2 feedstock numbers. So that 10% has a lot more than a 10% net effect.
That is my understanding.
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Old March 15th, 2018, 04:45   #27
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Even with the best no till practices (thanks Monsanto), I can't see corn ethanol crops building the soil. The cover crops planted between rotations perhaps. Hopefully there will be a shift to cellulosic ethanol soon.
Carbon fixation is not just the storage of carbon in soil, it's the storage of it in any non-CO2 form. Even as much as using the non-digested solids as physical fillers represents a form of carbon fixation.
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Old March 15th, 2018, 17:44   #28
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Carbon fixation is not just the storage of carbon in soil, it's the storage of it in any non-CO2 form. Even as much as using the non-digested solids as physical fillers represents a form of carbon fixation.
Yeah, I checked out the latest Argonne and USDA life cycle analyses for corn ethanol ghg emissions. It looks as though they are carbon crediting the domestic corn-ethanol production for land use change (mostly carbon sequestration in soils I think), and co products like distillers grain for animal feed & corn oil for biodiesel. Also something about domestic rice methane- not sure what that's about. It's worth mentioning that there is quite a lot of variation in different life cycle analyses over the past 10 years- especially in the land use change category.

Of course there are other environmental impacts from the fertilizer, herbicide, pesticide, and water use completely separate from the GHG emissions. I'm all for biofuels, I just don't think corn ethanol is all that great.
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Old March 16th, 2018, 07:52   #29
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Our refineries get twice as many gallons of gas as diesel from a given amount of crude oil.
The amount of gasoline versus diesel will vary depending on the source of the crude oil. I think your "twice the gallons" generalization is grossly overstated.
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Old March 16th, 2018, 08:34   #30
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I suspect I'm correct about this, but the US exports refined diesel and imports refined gasoline from Europe.

Gasoline traditionally is a waste product of diesel production, which if my econ 101 knowledge is correct, makes production of diesel the profit center and gasoline not so much. Therefore, gasoline is cheaper per gallon (keeping in mind higher taxes on diesel as well as various regulations on gasoline qualities) and is the secondary product. It would surprise me if refineries were not set up to bring more diesel and less gasoline. This explains the price differential but also makes gasoline production irrelevant to energy output. Diesel production drives our use of transportation crude oil, not gasoline. So to create less CO2, as well as other "pollutant" production (which arguably is better for diesel) improve the efficiency of everything, but concentrate on diesel.

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