Learning is easy. Getting it right is harder. Expunging falsehoods is hardest, but most rewarding.
There is a “meme” (using the definition of a meme as something most people in a certain community think whether it is true or not) that to produce one gallon of Ethanol for fuel you have to use some larger number (I’ve heard two, and I’ve heard five) gallons of gasoline.
In an ideal world there would be farms with giant solar collectors and wind generators. These devices would produce electricity to run distilling machines and hybrid tractors and such. On the farm would be grown GMO plants designed specifically to maximize ethanol output per acre of crop, with minimal energy input, and producing as a byproduct a carbon-trapping substance that could be spread on the fields where the GMO crop was grown, though a portion of it might be eaten by the workers on the farm some of whom might be cyborgs. Ethanol produced on this farm would thus be entirely solar, in a sense. Some of the ethanol would be used to run the farm, but there would always be a surplus. The surplus would be shipped in tanker trucks … hybrid tanker trucks charged from the farm’s solar and wind generators and using biofuels produced on the farm … to nearby distribution centers so people could fill up their flex-fuel hybrids. Oh, and the fields are covered with glass (or, better, invisible aluminum, like the clear material covering your smart phone or tablet), so water is recycled within the farm rather than lost as vapor to the atmosphere, and the growing season would be lengthened. The farm would be like a giant alga-endocrine cell chimera, with most of the energy trapping and using processes involved in the cell’s life cycle, but a reliable and abundant secretion of liquid humans can burn. There would probably be some biodiesel production as a sideline.
In that case, there would be zero “gasoline” (or whatever) used in the process of turing sunlight into human transport.
But even without that ideal cell-farm, the “meme” is wrong. It is wrong for two reasons.
First, as is the case with so much thoughtless critique of “alternative” energy forms, the comparison is unfair. If it takes X gallons of fuel (such as gasoline) to produce one gallon of ethanol, how many gallons of fuel does it take to produce one gallon of gasoline? In other words, the meme seems to assume that ethanol production is an energy-consuming process while gasoline appears spontaneously, with no energy input at all, at the point where you buy it and pump it into your car. This, of course, is not how it happens.
Anyway, all along I’ve wondered if someone should do a study that looks at the energy inputs and outputs of corn-based ethanol production, and it turns out a friend of mine did exactly this study a few years ago and never even mentioned it to me! (Well, I never asked him either, to be fair). And today, he, John Abraham, put up a blog post about this at The Guardian.
This is the blog post: Global warming, ethanol, and will-o-wisp solutions. Go and read this to find out how many gallons of gasoline it takes to produce a gallon of ethanol! (And other important things.) The abstract of the peer reviewed study done by John and his student, Fushcia-Ann Hoover is here.
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The post to which you link does not actually say how many gallons of gasoline are used to produce a gallon of ethanol; it only says that the quantity is less than one gallon. It says the ratio of energy returned to energy invested is 5.5 to 1 for perennial ethanol – but corn isn’t a perennial, so he’s talking about something else there. The post does provide a link to the published study, but the study costs $44, so I’m limiting my reading to the abstract, which says explicitly: “[I]t is apparent that corn ethanol is not viable for replacing petroleum fuels.” Nevertheless, if you have the full study and would be willing to post their estimate of the EROEI, that would be of interest.
Jane, the paper does not provide an easily cited number, but shows a rather more complicated picture. You should put a comment on john’s post asking him about this.
I went back to check again, because “complicated picture” made it sound like I might have missed a figure. Nope. The essay only indicates that with the investment of one gallon of gasoline, you get out more than one gallon of ethanol – presumably enough more to exceed the energy in a gallon of gasoline – so the EROEI is greater than 1. However, it doesn’t say whether to expect an EROEI of 3 or 1.2. Either way, it really does not supply an effective energy source for a high-energy society. Petroleum’s EROEI used to be as much as 100 in the easy fields – spend a barrel to get 100 barrels – and until recently was at least 20. It has been suggested by some that an EROEI of 5 is the minimum necessary to run a society like ours – if you have to start pouring more than 20% of your energy production just into producing energy, the amount that’s left to do other things with will plummet intolerably. You could maybe get away with that if you could increase gross energy production at will indefinitely, without causing a pollution crisis, but it doesn’t appear that either of those conditions holds true.