AutoEcoRating Blog, Prius more green than Leaf?

I've seen several press articles that quote from the http://autoecorating.wordpress.com/2010/12/04/prius-still-tops/ blog. The author gives an analysis that shows that the Prius (rating: 203) is greener than the Leaf (rating 193) or Volt (rating 160). He claims that the coal fired electrical plants plus the increased manufacturing costs bring the LEAF below the Prius. This seems to contradict a lot of the other analysis I've read. Can you figure out where the difference in analysis comes from?

LindsayNB said:

He claims that the coal fired electrical plants plus the increased manufacturing costs bring the LEAF below the Prius.

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Which coal fired electrical plants are those? My electrical plant is on my roof. Prius is an awesome automobile, I actually wish we had one instead of our Civic Hybrid (which is fine in and of itself), but it still uses fossil fuels, and the LEAF doesn't have to. (I know I'm mostly preaching to the choir here, and my comment is somewhat gratuitous without actually answering the original post - sorry)

LindsayNB said:

The author gives an analysis that shows that the Prius (rating: 203) is greener than the Leaf (rating 193) or Volt (rating 160).

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As we say in my homeland.....bunch of bollocks!

I just figured they really like the Prius!

Seriously though, they provide no information to determine how they came up with that exact "AutoEcoRating" and as far as I can tell, is just a random number...

Perhaps his analysis is sound IF you assume the average leaf buyer is similar in to the average American when it comes to power consumption.

This is probably a false assumption, however.



Furthermore, even if true, it would be considering only the immediate short term contribution. In the long term, moving our transportation power requirements to an electrical grid gives us immeasurably higher flexibility to adopt new technology. If we figure out how to extract clean energy from bird poop, it'll be a LOT easier to change our power production infrastructuer than change our transportation infrastructure to adopt that new tech.

Not to mention, many of the areas where the leaf is expected to be popular already run on cleaner electricity than the average American home.

LindsayNB said:

Can you figure out where the difference in analysis comes from?

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I think it all depends on what you look at. Quite a few issues with their scale:

• It uses the MPG number, which we've talked about elsewhere just doesn't make a lot of sense to use with an EV
• Counting the "coal" usage is... a whole thing in and of itself - for me the two big ones are that they aren't counting the emissions to make and transport gas, and that an existing Leaf will get a better rating just by us cleaning up the way we generate electricity while an existing Prius can not improve
• We can't tell if the Leaf is getting 'credit' for the use of recycled materials
• We can't tell if the Leaf is getting 'credit' for the end-of-use recycling plans that Nissan has announced
• Probably many other things...

The only thing I will give them is that I completely believe that actually building a Prius might be 'greener' than building the Leaf. Toyota has been making the Prius for quite a while, so I would imagine they have gotten very efficient at doing so to maximize profits.

Frankly, anyone that wants to give out some kind of hard number scale without showing where those numbers come from is 'suspect' in my book. I'm not saying they don't mean well, but it just isn't transparent enough for my taste.

JasonT said:

The only thing I will give them is that I completely believe that actually building a Prius might be 'greener' than building the Leaf. Toyota has been making the Prius for quite a while, so I would imagine they have gotten very efficient at doing so to maximize profits.

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The Prius uses NiMH batteries. Nickel is not very environmentally friendly to mine, and it requires energy intensive extractive metallurgy (roasting, reduction, smelting). Lithium is extremely clean by comparison. It's common natural form is a salt dissolved in water. It is purified using electrolysis instead of extractive metallurgy.

Prius also has both an electric motor and ICE, so there is the added environmental costs of producing the ICE itself.

It's probably pretty close when all is said and done, and I can't really see the Leaf passing the Prius by much, if at all... but I don't think the author's analysis is as comprehensive as he'd like to believe.
=Smidge=

Oh yes, the ever present "coal powered car" argument. ZZZZZZZZZZZZZ

For the EV they want to look at emissions from the plant to the wheels. For an ICE car they want to look at the emissions from the tank to the wheels. Plant does not equal tank, and what they claim is an "apples to apples" comparison is more like an "apples to potatoes" comparison.

If you really want to do an "apples to apples" comparison then, if want to go all the way back to the electrical plant for an EV, you have to go all the way back to the refinery for an ICE vehicle. When you do that you find that it takes quite a bit of electricity to just refine a gallon of oil. Nissan says 7.5 kWh. The DOE says 6 kWh. This is the amount used, not the amount of electricity produced before transmission and distribution losses. If transmission is 93% efficient then it takes 6.5 kWh or 8 kWh at the plant just to refine a gallon.

But of course it doesn't stop there. Once a gallon of gas is refined it has to be stored and delivered. That takes more energy and involves more emissions. Once the electrons have been captured by the battery that's it -- no energy is expended and no emissions are created.

IOW for a Prius to go 50 miles it needs one gallon of gas and at least 8 kWh of electricity. A Leaf can go the same distance using, at most, 17 kWh of electricity. Even forgetting that the Leaf in a place like CA with a relatively clean grid will emit far less of every pollutant and emission than a Prius even if you don't count the kWh needed to produce the gallon of gas, once you do count the electricity needed to produce the gallon of gas the Leaf will emit less and pollute less even if it runs on electricity which comes exclusively from coal fired plants.

Not to mention that the "green" index doubtless only looks at CO2, as if all other emissions and pollutants don't matter.

This entertaining and more complete summary of why the "coal powered car" argument doesn't make any sense was posted earlier. If you missed it it's worth a look: http://www.evtalk.org/453/episode-10-the-coal-powered-car/

I was just looking at this MIT report:
http://web.mit.edu/sloan-auto-lab/research/beforeh2/otr2035/On%20the%20Road%20in%202035_MIT_July%202008.pdf
which gives well to wheels numbers.

Although it is based on projected 2035 vehicles Figure ES-1 on page ES4 (12th page) shows HEV and PHEV-30 (30mile all-electric range) vehicles producing lower greenhouse gas emissions/km than a BEV.

The two aspects of the analysis that jump out at me are that it gives 143 gCO2e/km for the BEV based on current blend of generation, with 200 if it is completely coal generated, 115 if produced with natural gas. Secondly, I'm not sure but I think they are assuming enough batteries to provide a 200 mile range, which would increase materials and reduce efficiency due to weight.

Most of the electricity here is hydro-electric and nuclear so that would produce a much much lower number, but there's more nuance here than I would have thought. The 100% coal generation scenario still produces 200gCO2e/km versus 277 for current SIE vehicles though. Too bad it doesn't give a current HEV number.

LindsayNB said:

I was just looking at this MIT report:
http://web.mit.edu/sloan-auto-lab/research/beforeh2/otr2035/On%20the%20Road%20in%202035_MIT_July%202008.pdf
which gives well to wheels numbers.

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I didn't read it all, but overall pretty good report. Their conclusions seems to favor PHEVs by 2035. However, I noted that the report was done in 2008, and quote "The vehicle [talking about BEV] with a 100-mile range is plausible from both a weight and cost perspective..." (page 28-29). It's been only 2 years, and we're about to have an affordable 100-mile range BEV. So their prediction is already seemingly underestimating actual progress in battery technology and advancement.

its probably based on BS like most other articles on the same subject. remember the one that said the Hummer had a smaller carbon footprint than a Prius because of the amount of fuel spent to mine the small amount of rare earth metals used in the traction battery and elsewhere??

but anyway when it comes to controlling greenhouse gas emissions, what is easier? changing 300,000,000 exhaust pipes or 10,000 power plants? most new power plants today have emission rates far far below that of a car. problem is that newer cleaner plants which are "required" (too many granted variances though) are much more expensive to build so most power companies have elected to run the older plants harder. there is a growing group of older coal plants that have had minimal upgrades and have not been forced to upgrade due to "hardship" costs that we need to run out of business.

SanDust said:

Oh yes, the ever present "coal powered car" argument. ZZZZZZZZZZZZZ

For the EV they want to look at emissions from the plant to the wheels. For an ICE car they want to look at the emissions from the tank to the wheels. Plant does not equal tank, and what they claim is an "apples to apples" comparison is more like an "apples to potatoes" comparison.

If you really want to do an "apples to apples" comparison then, if want to go all the way back to the electrical plant for an EV, you have to go all the way back to the refinery for an ICE vehicle. When you do that you find that it takes quite a bit of electricity to just refine a gallon of oil. Nissan says 7.5 kWh. The DOE says 6 kWh. This is the amount used, not the amount of electricity produced before transmission and distribution losses. If transmission is 93% efficient then it takes 6.5 kWh or 8 kWh at the plant just to refine a gallon.

But of course it doesn't stop there. Once a gallon of gas is refined it has to be stored and delivered. That takes more energy and involves more emissions. Once the electrons have been captured by the battery that's it -- no energy is expended and no emissions are created.

IOW for a Prius to go 50 miles it needs one gallon of gas and at least 8 kWh of electricity. A Leaf can go the same distance using, at most, 17 kWh of electricity. Even forgetting that the Leaf in a place like CA with a relatively clean grid will emit far less of every pollutant and emission than a Prius even if you don't count the kWh needed to produce the gallon of gas, once you do count the electricity needed to produce the gallon of gas the Leaf will emit less and pollute less even if it runs on electricity which comes exclusively from coal fired plants.

Not to mention that the "green" index doubtless only looks at CO2, as if all other emissions and pollutants don't matter.

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I want to know if they include the emissions for the military to keep the mideast oil flowing, the emissions for the gulf oil spill, the emissions from the many oil well fires after the Kuwait war, what about the lives lost in these wars, and what about the cost to our economy for importing all that oil. Is all that in there? And surely there is more to add. I am not trying to save the world but the coal powered car argument holds no water to me.

SanDust said:

For the EV they want to look at emissions from the plant to the wheels. For an ICE car they want to look at the emissions from the tank to the wheels. Plant does not equal tank, and what they claim is an "apples to apples" comparison is more like an "apples to potatoes" comparison.

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Look, I'm convinced that my LEAF will be much greener than my Prius is, but I have to wonder how carefully you read the article, SanDust. The author specifically states:

But in an apples-to-apples comparison that tallies pollution from the tailpipe to refineries and power plants and beyond, ...

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and also:

The process of extracting, shipping and refining petroleum pollutes a lot, too.

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Clearly the author was aware of the need to look at the whole cycle, and that makes much of your post sound like a rant.

I'm with JasonT and others here. I find the results very suspicious. Show us how those numbers were derived and then we can decide if they are believable.

LindsayNB said:

I've seen several press articles that quote from the http://autoecorating.wordpress.com/2010/12/04/prius-still-tops/ blog. The author gives an analysis that shows that the Prius (rating: 203) is greener than the Leaf (rating 193) or Volt (rating 160). He claims that the coal fired electrical plants plus the increased manufacturing costs bring the LEAF below the Prius. This seems to contradict a lot of the other analysis I've read. Can you figure out where the difference in analysis comes from?

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The author is an idiot! AND, you can't charge a Prius with PVs, like with the LEAF. It also depends on what state the author is talking about...some states use a LOT of renewables instead of coal. Here, we're only 35% coal and decreasing every day.

See the CO2/cost calculator posted here:

http://www.mynissanleaf.com/viewtopic.php?f=13&t=1725

The leaf is not only less polluting, but far less expensive to operate, than any other car.

Also, remember the CO2 pollution of the grid is generally declining each year, as natural gas and renewable energy is displacing coal, and the CO2 content of gasoline is going up each year, as more energy intensive extraction and refining methods (like Canadian tar sands) replace conventional crude oil as the hydrocarbon feedstock.

CO2 is not the only pollutant we should worry about and CO2 pollution is not the issue if the transportation system moves to primarily coal power.

I think the article is completely off base, but the point that we're moving pollution from one source to another *is* a valid point. If our transportation grid were driven from primarily coal, SO2, NOx, and other such pollutants would be quite a bit inflated as compared to our current rates of pollution.

Still, it this article ignores quite a number of critical facts, and I'm guessing its conclusions are completely off base.

Maybe this is what they mean.



Certainly cant get a LEAF in this color.

palmermd said:

Maybe this is what they mean.
[image - green Prius]
Certainly cant get a LEAF in this color.

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HaHa. Thanks for bringing a little levity into the discussion. People get so serious on this forum when people criticize the Leaf!

planet4ever said:

Look, I'm convinced that my LEAF will be much greener than my Prius is, but I have to wonder how carefully you read the article, SanDust.
...
Clearly the author was aware of the need to look at the whole cycle, and that makes much of your post sound like a rant.

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The difference between us is that you accepted his claim that he was was making an apples to apples comparison. I didn't. I actually figured out what he was and wasn't doing.

If you look at the articles on his web site you can find considerable discussion about the need to consider emissions and pollutions from electrical power plants when looking at BEVs but nothing about looking at the efficiency of oil refining operations. Hard to find anything about his methodology either. However, you can find it over at greenercars.org. He considers:

1. Tailpipe emissions as given by the emissions standard to which a vehicle is certified
2. Fuel economy based on EPA test cycles
3. Vehicle mass (curb weight).

If you look at his car comparisons it's clear that all he did when looking at BEVs was to consider the pollution attributable to electrical generation. I won't even bother getting into why treating mass the same way for BEVs and ICEs makes little sense nor why CARB certification isn't a good proxy for emissions much less pollutions. What I will say is that IF he was going to consider the emissions and pollution attributable to refining, at a minimum he would have had to (1) use 36.4 kWh (the higher DOE number) as the energy content of gasoline since that's what you get when you treat gasoline like you do electrical generation and (2) account for refining as being, at most, 85% efficient. If you do that the Leaf gets 126 MPGe. But he uses the EPA number of 99 MPGe. Since this number most certainly does not account for the refining process it's safe to conclude that he is not considering refining in his comparisons and that his "apples to apples" comparison is in fact an "apples to potatoes" comparison.

If you consider that a rant you're entitled to your opinion.

I'm having a conversation with the author in this post.

http://autoecorating.wordpress.com/2010/12/01/nissan-leaf-twice-as-green/