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By Robert Rapier on May 25, 2006 with no responses

E85: Spinning Our Wheels


The following is an expanded version of an essay that I posted to The Oil Drum entitled: E85: Spinning Our Wheels. The essay was inspired by comments made by Odograph over at The Oil Drum and at Gristmill. I have added a section at the end of the essay explaining the mathematics in detail.

How Much E85 Can We Make?

If you listen to the news lately, you know that E85 is going to lead the U.S. to energy independence, just like it did in Brazil. Senator Hillary Clinton has announced that she is getting into the act: (1)

“President Bush and other elected officials have called for a greater expansion of E-85, a fuel made of 85 percent ethanol that can be used in vehicles built to run on both regular unleaded gasoline and E-85.

E-85 is currently available in less than one percent of the country’s gas stations, and Clinton wants to accelerate the spread of the fuel to half of the nation’s gas stations by 2015 by offering a 50 percent tax credit for station owners who install ethanol pumps.

`We’ve got to take action on this pump issue or we’re just spinning our wheels,’ she said.”

Just spinning our wheels. Indeed. But let’s do a reality check and see whose wheels are spinning. These claims deserve a mathematical analysis, which none of the E85 proponents appear to have done.

According to (2) (Warning: 1.9 meg file) the estimated corn harvest in 2005 was 10.35 billion bushels, and corn exports were 1.95 billion bushels. According to the 2002 USDA study The Energy Balance of Corn Ethanol: An Update, (3) you can get 2.7 gallons of ethanol from a bushel of corn. That means if we turned the entire corn crop into ethanol, we could make 27.9 billion gallons of ethanol. But as we all know, the BTU value of ethanol is around 67% that of gasoline, meaning that on a BTU basis this much ethanol is equivalent to 18.8 billion gallons of gasoline.

According to the Bureau of Transportation Statistics, our annual gasoline consumption is up to almost 140 billion gallons. (4) That means on a BTU equivalent basis, converting the entire corn crop into ethanol would amount to 13.4% of our annual gasoline demand. Putting all of that ethanol into the gasoline supply would mean ethanol could comprise 19% of the gasoline supply on a volumetric basis (while consuming all of our corn production). In other words, all of the gasoline in the country could be E19 if we wanted to use 100% of the corn crop. Of course if we only want to turn all of our current exports into ethanol (ignoring the many implications), that would amount to 2.5% of our annual gasoline demand. In that case, E10 could make up about a third of our gasoline supply on a volumetric basis. If we want to convert all of the corn exports into E85, it could make up 3.3% of our total gasoline pool.

But that’s the good news. According to the previously mentioned USDA study, it takes 77,228 BTUs of fossil fuel inputs to make 83,961 BTUs of “green, renewable” ethanol. Ignoring co-products for a moment, that means the created energy was a mere 8% in excess of the input energy. Given that the fossil fuels (primarily natural gas) that went into making the ethanol can usually serve as transportation fuels, the amount of transportation fuel that is displaced is only the 8% that was “created”. That means that in reality, using our entire corn crop would only displace 1% of our annual gasoline consumption. If we only decide to use our exports, the net displacement of gasoline would be 0.2% of our annual gasoline consumption.

Now, a word about co-products. Energy balance studies of grain ethanol almost always include a BTU credit for the co-products (mostly animal feed). I think this is appropriate, provided that a proper analysis is made of the energy inputs into the products that were displaced. Let’s ignore for a moment the fact that some estimates indicate that the “byproduct markets could saturate well short of 11 billion gallons of production”. (5) Let’s give full credit for the byproducts, just as if they are liquid fuels to be burned. This has no effect on the BTU equivalent calculation, but will affect the displacement calculation. With by-products included, the USDA report has 77,228 BTUs of fossil fuel inputs for 98,333 BTUs of total outputs. In this best case scenario, the ratio of energy out/energy in is 1.27. Converting 100% of the corn crop into ethanol, presuming we had a market for the byproducts, would then displace an incredible 2.0% of our annual gasoline consumption.

So, why the big rush to get E85 pumps at 50% of the nation’s gas stations? We can’t possibly produce enough E85 to justify putting in all those pumps. Wouldn’t it be much better just to push for E10 at more locations? In that case, expensive new pumps are not required, and E10 can already be burned in most vehicles on the road. Or how about encouraging more natural gas vehicles, instead of inefficiently and expensively turning natural gas into ethanol? But I suppose those would be rational solutions, as opposed to feel-good solutions that promise energy independence.


There are a couple of things to conclude from this exercise. First, the “E85 everywhere” push is much ado about nothing. E85 can’t contribute enough to the gasoline pool to justify putting pumps everywhere. Second, it should be clear that ethanol is not going to make us energy independent. It is time to stop believing that Brazil is energy independent because of ethanol, and realize that it is because their energy consumption is 1/6th of ours in the U.S. If we reduced our energy consumption by that amount, we would be energy independent as well. Finally, it should be clear that we are going to have to take conservation seriously. Ethanol may make some sense in certain parts of the Corn Belt. It is an impractical solution nationwide, and won’t ever contribute more than a small fraction of our fuel needs (barring a breakthrough in cellulosic ethanol technology).

Mathematical Details and Notes

The estimated corn harvest in 2005 was 10.35 billion bushels and corn exports were 1.95 billion bushels.

According to the USDA, you can get 2.7 gallons of ethanol from a bushel of corn.

2.7*10.35 = 27.9 billion gallons of ethanol.

2.7*1.95 = 5.3 billion gallons of ethanol.

The higher heating value of gasoline is 125,000 BTUs/gallon, and for ethanol it is 83,961 BTUs/gal. This means that ethanol has 67% of the energy value of gasoline.

If we introduce ethanol into the fuel supply, we will need 1/(0.67), or 1.49 gallons of ethanol for every gallon of gasoline that is taken out of the gasoline pool.

U.S. fuel consumption is currently around 140 billion gallons. If we put the 27.9 billion gallons of ethanol (from the entire corn harvest) into the gasoline pool, it will only have the energy equivalent of 27.9*0.67, or 18.8 billion gallons of gasoline. This means the motor gasoline pool will have to increase to 140 – 18.8 + 27.9, or 149.1 gallons. Therefore, to maintain the same number of BTUs that we have today in the gasoline pool, and by converting 100% of the corn crop into ethanol, it could make up 27.9/149.1, or 18.7% of the gasoline pool on a volumetric basis. However, as was discussed above, ethanol only has the energy value of 67% of gasoline’s, so the net BTU contribution (the important piece) is 18.8 billion gallons of a 140 billion gallon gasoline pool. This is equivalent to 13.4%. Doing the same calculation for just our corn exports shows it could make up 3.5% on a volumetric basis, or 2.5% on a BTU equivalent basis of our current gasoline pool.

Regarding the displacement calculation, there is an excess of 8% energy created when a gallon of ethanol is produced (ignoring co-products for the moment). This is because fossil fuels had to be input into the process. When the input fossil fuels are natural gas, diesel, or gasoline, they can serve as transportation fuels themselves. In that case, the net to the gasoline pool per gallon of ethanol is only 8% of the ethanol produced. 8% of 18.8 is 1.5 billion gallons of net energy production. 1.5 billion gallons/140 gallon gasoline pool is a 1.1% net BTU contribution for turning the entire corn crop into ethanol.


1. “Senator Clinton Pitching Ethanol Energy Plan”, Yahoo News, May 23, 2006.

2. “Corn: Part of Our Daily Lives”, Corn Refiners Association Annual Report, 2005. (Warning: 1.9 meg file)

3. Shapouri, H., et al., “The Energy Balance of Corn Ethanol: An Update”, United States Department of Agriculture, AER/813, 2002.

4. “Estimated Consumption of Alternative and Replacement Fuels for Highway Vehicles”, Bureau of Transportation Statistics, 2005.

5. Lave, L., and Griffin, W. M., “The Green Bullet”, Foreign Policy, March 7, 2006.