CO2 emissions of diesel vs. gasoline and ethanol fuel production

[bhtooefr]

Edit: This thread has been split off of the Electric vehicles (EVs), their emissions, and future viability thread. Some posts (including this post) from that thread have been duplicated for context.

UCS has updated their carbon footprint data to use 2016 grid emissions data, and expand the sales-weighting to include 2017: https://blog.ucsusa.org/dave-reichmuth/new-data-show-electric-vehicles-continue-to-get-cleaner

And here's a map using only the three most efficient EVs in the US - the Hyundai Ioniq BEV, the Tesla Model 3 LR, and (in charge depleting mode) the Toyota Prius Prime:

 

[turbobrick240]

I saw that first map the other day. The second one is even more revealing. It's quite dramatic when compared to the same maps from the previous five years. The grid is really cleaning up fast.

 

[Tin Man]

Lets see if some other not-so-political organization publishes data and how it ends up cost-wise per mile when the electrical grid becomes taxed and needs to upgrade with future boatloads of EV's.

The cost per mile currently may favor EV's, but conveniently UCS (using EPA data) compares EV emissions (power plant, not production or mining of rare earth metals and their transport) to gasoline cars (diesel emissions for new clean diesels are generally better).

Glad to see the grid may be getting cleaner too. But information about other important factors in health such as non-automotive emissions, such as indoor (cooking), tire and road particulates (all also higher in cities), is often ignored or misinterpreted.

TM

 

[turbobrick240]

The UCS is not a political organization any more than Scott Pruitt or Rick Perry are scientists. And indoor cooking is probably not a major player in global carbon emissions. It surely is a health concern in third world countries. In our wealthy part of the globe, what is being cooked has got to have greater health consequences than the indoor air pollution from the cooking itself.

As far as rare earth metals, the new switched reluctance permanent magnet motors (in Tesla model 3 & semi) actually require very little rare earth metals as compared to the older pm motor technology. The model S/X have essentially none. And guess what- the catalysts in ICE vehicles contain rare earth metals too. Far better to embrace the future than fight it.

 

[Tin Man]

UCS not political. Really.

Indoor emissions exist and likely affect city dwellers as do other non-diesel particulates. But diesels are targeted as we speak. I understand NOx emissions cause a lot of damage, but modern diesels emit about as much as any gasoline vehicle. But diesels are targeted almost exclusively.

Cobalt news: https://www.investors.com/news/ev-news-cobalt-price-key-ev-battery-ingredient-hits-10-year-high/

Pfffff.

 

[bhtooefr]

The cost per mile currently may favor EV's, but conveniently UCS (using EPA data) compares EV emissions (power plant, not production or mining of rare earth metals and their transport) to gasoline cars (diesel emissions for new clean diesels are generally better).

It is worth noting that they're only worrying, in these reports, about emissions with global warming potential. It'd be interesting to see their take on the criteria pollutant issue, but in this series of publications, they've not considered them.

Manufacturing emissions are something that they considered in their 2015 report, and determined that within the lifetime of the EV, the higher efficiency more than paid for itself. Grid decarbonization is only helping matters.

Diesel has ~13% higher tailpipe CO2 per gallon, dulling the efficiency gain, but I'm not sure how the refining emissions of diesel compare to gasoline. (They used GREET 2017, though, so it should be trivial to compare the well-to-pump GHG emissions for gasoline vs. diesel, for someone familiar with GREET.)

 

[kjclow]

With the hydrotreatment to remove sulfur, my assumption is that the refining effects of diesel and gasoline are probably close enough to call them equal. I've not heard how they are going to remove the excess sulfur from the gasoline, but that's just around the corner.

 

[turbobrick240]

It's the well to pump (and wheel) VOC emissions where diesel is far better than gasoline.

 

[Tin Man]

Diesel has ~13% higher tailpipe CO2 per gallon, dulling the efficiency gain,

Does that reflect the "true" seriously better efficiency of diesels vs pure gasoline vehicles or are they comparing diesels to hybrids? I know diesel has about 10% more energy per gallon, so CO2 should be much better with diesels. Apples to apples. Recently I've read about diesel hybrids....

PL

 

[bhtooefr]

The 13% higher CO2 per gallon figure ignores the higher thermal efficiency of diesels, because it's purely the fuel.

Burn a gallon of diesel, get 22.4 pounds of CO2, end of story. Burn a gallon of gasoline, get 19.6 pounds of CO2 (although it's worth noting that E10 is lower tailpipe CO2). Basically, there's no free lunch - the added energy in a gallon of diesel fuel comes from a higher density of hydrocarbons.

In any case, diesels aren't actually considered in this data at all - it's purely gasoline-fueled vehicles versus electric vehicles. You have to get 80 miles per gallon of gasoline to match the average EV on the roads, using 2016 grid data, and 2011-2017 sales data.

So, a diesel, emitting 13% more per gallon, needs to get 90.4 MPG to match the EV, assuming that the amount of CO2 from producing the energy in diesel fuel is the same as gasoline. That's independent of how the energy is handled by the car (whether it's a hybrid or not) - if you can get 90.4 MPG combined in your diesel, more power to you. (However, an EV that's that efficient could likely beat your 90.4 MPG diesel.)

 

[Tin Man]

I'd prefer if they use "real world" data which would favor diesel, no matter the energy density of the fuel. CO2 is definitely better in diesels due to efficiency of burning.

How To Lie With Statistics: https://www.amazon.com/s/?ie=UTF8&k...qmt=e&hvbmt=be&hvdev=c&ref=pd_sl_8r0u192p7n_e

I'd rather stick with my current diesel, knowing things may change when there is more experience with EV's (I do favor them to some extent) and not rely on biased futurist proclamations and "data" from groups like the EPA and OCS who have their own agendas.

TM

 

[bhtooefr]

Keep in mind that they're not talking about diesels. I'm talking about diesels. They're only talking about gasoline cars, because in the grand scheme of things, diesels are utterly irrelevant to the US discussion.

And, it'd be nice if there was real-world data on every car, although reproducibility on real-world data is difficult. The EPA does collect real user data, though.

 

[wxman]

...Diesel has ~13% higher tailpipe CO2 per gallon, dulling the efficiency gain, but I'm not sure how the refining emissions of diesel compare to gasoline. (They used GREET 2017, though, so it should be trivial to compare the well-to-pump GHG emissions for gasoline vs. diesel, for someone familiar with GREET.)

Here are the output files of GREET1_2017 for the default gasoline and diesel passenger cars in GREET:

Note that gasoline has lower "feedstock" GHG emissions because GREET assumes the gasoline is E10.

 

[oilhammer]

Keep in mind that they're not talking about diesels. I'm talking about diesels. They're only talking about gasoline cars, because in the grand scheme of things, diesels are utterly irrelevant to the US discussion.
.

Please tell this to the EPA, so some of us can drive what we want to drive.

 

[bhtooefr]

Here are the output files of GREET1_2017 for the default gasoline and diesel passenger cars in GREET:
http://webpages.charter.net/lmarz/muncie/GREET1_2017_Gas_Output.png
http://webpages.charter.net/lmarz/muncie/GREET1_2017_Diesel_Output.png
Note that gasoline has lower "feedstock" GHG emissions because GREET assumes the gasoline is E10.

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.

 

[wxman]

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?

 

[Tin Man]

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!

 

[wxman]

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.

 

[bhtooefr]

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?

 

[turbobrick240]

Maybe because the refineries are getting more gallons of gasoline per barrel of crude than diesel fuel?

 

[CraziFuzzy]

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.

 

[turbobrick240]

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.

 

[CraziFuzzy]

totally depends on what the non-sugar carbons are doing from the crops.

 

[turbobrick240]

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.

 

[ToxicDoc]

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.

 

[wxman]

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.

 

[CraziFuzzy]

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.

 

[turbobrick240]

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.

 

[kjclow]

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.

 

[Tin Man]

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.

TM