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183 comments on Countdown to $200 oil (3) - no gas tax needed...erm, right...
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The math does not work out for me, sorry.
It takes 8 gallons of diesel to farm 1 acre, which is equivalent of 13 gallons of ethanol.
http://www.extension.umn.edu/newsletters/ageconomist/components/ag237-69...
the ethanol yield provided per bushel in your link is around 2.8 gallons per bushel.
Average US corn crop yield per acre is around 130 bushels/acre.
http://www.agriculture.com/ag/story.jhtml?storyid=/templatedata/ag/story...
so the average acre of corn yields 364 gallons of ethanol. It takes 13/364 = .036 gallons of ethanol to farm a gallons worth.
According to your info the average dry-mill uses 31,070 btu's per gallon, Thats from table 9 of your link..
I'll go ahead and use your fertilizer cost of 6,500 btus.
76000 btu per gallon of ethanol/ ( 31,070+(.036*76000)+6,500) ) == 1.88 EROI, also I'm sure this corn and ethanol is transported to a filling station somehow.
Also the average fuel economy of a midsize car in the united states is around 21 mpg and the average distance to a gas station is somewhere around 1 mile. so 1/21 * 124,000 Btu so 5904 btus are spent on getting to the gas station...
if you include that the ratio would be something like 1.64 and if you included those transportation cost it would be even lower.
How'd you get 4.5 to 1?
How'd you get 4.5 to 1?
Without auditing your calculations or following the links, it looks like:
(a) kdolliso is using best-in-class process energy efficiency, you are using average. This is legitimately arguable - technology only ever gets better, but not so quickly for a mature process with a large installed capital base, like distillation.
(b) He is blandly asserting that one gallon of ethanol exactly replaces one gallon of gasoline, which is Just Plain Wrong and always will be.
(c) Your driving-to-the-gas-station term is questionable - maybe I just drive past it on the way to work or some other value-adding activity. But it's a relatively small term in your calculation.
Cheers,
PUD
Saildog,
Plucky Underdog (below) has it exactly right. If you will notice my link shows at least one refinery (corn plus, in Winnebago, Mn, I believe it is) uses only 17,706 btus of nat gas, and electricity to produce one gallon of ethanol.
The average yield in the U.S. last year was 151 bushels of corn/acre. Remember, corn is cattle feed; and, anywhere from 33% to 40% of that livestock feeding ability is returned in the form of distillers grains. I used 33% to match the corn plus plant.
This gave me 675 gall/acre. I, also, used this number to calculate the amount of seed, and fertilizer that went into the ethanol.
I don't do Anything blandly. The below link is a test the State of Minnesota did using 40 identical pairs of cars. The bottom line was their cars only lost 1.6% mileage using a 20% blend of ethanol. The DOE states that you will, on average, lose 0.5% mileage using a 10% mixture. The New cars will do even better.
http://www.mda.state.mn.us/news/publications/renewable/ethanol/e20drivab...
Yes, cars get more efficient but that has nothing to do the eroi of corn ethanol. Also keep in mind the average life of a car in the US is about 16 years. Isn't that what they refer to as a red herring?
I don't understand your cattle feed calculation.?
the average yield last year of 151 bushels * 2.8 the gallons of ethanol per bushel = 422.8, far short of 675 gallons.. I don't know how you got this? could you elaborate.
New cars will do better with gasoline too, Also we never included the transportation cost of the ethanol from the farm and too the plant and from the plant to the refinery?
All this considered I still don't get 4.5 to 1?
If you could show me this id be glad to listen
Strewth! If you guys can't agree, what hope do we mere mortals have?
Sure, keep in mind: this is a real-world, for all practical purposes type calculation.
First: I used 2.96 gallons/bu. If you noticed in my link some refineries are reaching this level. I'm sure many, many more will be in the future.
Now, to the "Cattle Feed." Remember, almost 90% of all field corn goes to feed livestock, mostly cattle. This is a very important concept to keep in mind.
When you process a bushel of corn you get back 17.5 lbs of distillers grains. This is, for all practical purposes, corn with the starch, and CO2 removed. All of the vitamins, nutrients, and protein is still there. A ration that's 65% corn, and 30% dgs will actually yield 10% More weight on a cow than a ration with 95% corn.
For that reason, I, normally, figure that we've used 60% of the corn to realize our 2.96 gallons of ethanol, and retained 40% - .30 + .33(.30) of our cattle feeding ability.
*in the above calculation I used 33% instead of 40% because I knew that 17,706 btus signified that it was the Corn Plus Plant, and that they gassified some of their "syrup" thus cutting back, slightly, on the "feed" returned.
Anyway, let's take 3 gal/by (it's easier than using 2.96) and multiply by 3/2 (remember, we only used 2/3 of our corn for the ethanol) to get 4.5 gal/bu. Now, we'll multiply that by 150 bu/acre, and come out with 675 gal/acre.
Now, I adjust the tilling, planting, harvesting, and fertilizer production, and seed drying inputs accordingly; but I don't mess with the Refinery inputs since that process would never be undertaken absent the need to make ethanol.
Here's where I, really, take a "Liberty." I've given several links of real, honest to goodness, real-world tests that show that ethanol in ten, twenty, or thirty percent blends are basically mileage-neutral compared to gasoline. So, for a little "shock" value I used the 116,000 btu content of gasoline, not the 76,000 btus of ethanol. It's shady, of course; but, it's also "real-world" accurate, inasmuch as ethanol's 30% Higher Octane compensates where it really matters - at the gas pump.
Hi kdolliso,
PUD: He is blandly asserting that one gallon of ethanol exactly replaces one gallon of gasoline, which is Just Plain Wrong...
k: I don't do Anything blandly.
Calorific values at this link. You need to use the lower calorific value, i.e. with water remaining as vapor, to get the heat available to an internal combustion cycle (you're welcome). Multiply by density to get volumetric energy density. Strictly speaking you should adjust to exhaust temperature, but that's not going to make much difference. I don't know the mixing volume loss for gasoline/ethanol blends - anyone?
http://en.wikipedia.org/wiki/Calorific_value#Lower_heating_value_for_som...
Ethanol=28.9, Gasoline=44.4 MJ/kg
I'd be interested in your comments. Hint: "irrelevant" won't cut it. As SwordsOfDamocles says (paraphrasing), there's probably a lot of efficiency improvement to be made in mass-market IC engines, irrespective of fuel type, but those numbers aren't going to change.
Two questions. Is the electricity that is included in the 17.7kBTU energy input that you quote fully-burdened with generation cycle efficiency?
And, just out of curiosity - as a teenager, did you get whacked upside the head with a copy of Atlas Shrugged?
Cheers,
PUD
Hey, PUD
Read it when I was young; don't remember much about it.
I'm just interested in the "Real" World. BTUs don't mean a thang if you can't get the energy out. In the Real World you need Octane. Ethanol has gobs of it. 113 - 116, depending on how you measure.
Throw some compression to it, and you can knock gasoline's socks off. At low to medium blends you don't need too much compression to equal gasoline's performance. Two Links: First one on "Efficiency," Second on on EPA cycle test using midlevel blends.
http://www.methanol.org/pdf/ISAF-XV-EPA.pdf
http://www.mda.state.mn.us/news/publications/renewable/ethanol/e20drivab...
Again, a Hershy Bar has a thousand btus, or so; but you can't burn it in an ICE. BTUs, without considering Octane, is a worthless metric. In the "Real" world you can do as much work with ethanol as with gasoline.
Octane number, and therefore compression ratio, certainly affects thermodynamic efficiency, but if you aren't putting the energy in you aren't going to get it out. So ethanol is starting off at a disadvantage.
(Idle speculation) I bet you could dissolve Hershey Bars in fuel oil and run 'em through a Wartsila-Sulzer RTA-96. Which the manufacturer claims to be the most efficient non-combined-cycle prime mover ever made (almost 50%). Would probably need a total rebuild afterwards though. And it wouldn't fit in a car - 1820 litres per cylinder, up to 14 cylinders.
PUD.
PUD,
To support your argument, I have said elsewhere on this post that the compression ratio/efficiency curve is pretty flat by the time 10:1 is reached. At 10:1 its about 60%, at 14:1 its about 65%. The additional load on the piston rings and the shearing loss in the oil film of the crankshaft bearings, imposed by the the additional load, mean some of this thermal efficiency gain is lost through increased friction. No amount of compression ratio increase will make up for the reduced calorific value of ethanol, period.