http://sitemaker.umich.edu/section4group6/introduction
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It is important to note that the NEB of Ethanol or any other fuel that is burned cannot be positive (Patzek 2006). The Second Law Of Thermodynamics implies that any energy conversion, solid to liquid to gas for ethanol, results in a negative net energy balance.[2] The same applies for gasoline (liquid to gas).
But then this same paper concludes:
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While there is a lot more “work†when converting ethanol into energy relative to fossil fuels, there is still a positive Net Energy Balance (Energy Output – Energy Inputted + Energy Credits).
www.mathproinc.com/pdf/2.1.6_Ethanol_NEV_Comparison.pdf
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The net energy value (NEV) of ethanol is the difference between the energy content of ethanol and the energy used in producing and distributing it.
Despite the advent of a national ethanol mandate, ethanol’s “real†NEV remains a controversial and, from an analytical standpoint, unresolved issue. Ethanol proponents, most notably the U.S. Department of Agriculture, assert that corn ethanol has a positive NEV (i.e., ethanol provides more energy than is used to produce it). Others, most notably Professors David Pimentel and Tad Patzek, assert that corn ethanol has a negative NEV (i.e., ethanol provides less energy than is used to produce it).
http://www.ethanol-gec.org/netenergy/net-energy-yield.htm
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these benefits to the American public from ethanol are all dependent on the simple fact that a typical gallon of ethanol produced in America today contains more energy than the fossil fuel inputs required to produce it. Said differently, all of the benefits are dependent on the fact that ethanol has a positive “net energy yield.†This positive net energy yield is made possible by renewable energy — the energy of the sun that is captured by corn or other plants and converted into ethanol in an ethanol facility. The solar energy that is captured by the plant and then converted to ethanol is greater than the amount of fossil fuel inputs required to achieve that conversion. In attempts to discredit ethanol, however, ethanol opponents frequently make unsubstantiated attacks on the net energy yield of ethanol.
http://www.ethanol-gec.org/netenergy/neypimentel.pdf
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The forgoing analysis, for which all major energy
inputs required in ethanol production were assessed,
confirms that ethanol production produces a
29% negative energy balance. Ethanol is not a net
additional energy source, is an uneconomical fuel,
and its overall production system causes serious environmental
degradation.
http://gristmill.grist.org/story/2007/1/14/133338/207
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The common response to Pimentel's heresy is summarized over on the greenie site Journey to Forever: Pimentel is a crackpot who gets his results by relying on out-of-date input numbers.
Interestingly, Pimentel's work got an endorsement from an unexpected source: the recent MIT study, which as Steenblik's post shows has to perform rather tortured gymnastics to find value in corn-based ethanol.
The MIT press release summarizes researcher Tiffany Groode's research thusly:
Based on her "most likely" outcomes, she concluded that traveling a kilometer using ethanol does indeed consume more energy than traveling the same distance using gasoline.
Nor does Groode parrot the Pimentel-relies-on-ancient-data line. Here's how the the press release quotes her:
The results show that everybody [including Pimentel, mentioned by name] is basically correct ... The energy balance is so close that the outcome depends on exactly how you define the problem. [my emphasis]
This is precisely what Pimentel has long argued: that most ethanol energy-balance studies omit key factors like the energy required to manufacture farm equipment.
...
So if Pimentel is essentially right about corn-based ethanol's negative energy balance, how does Groode wind up tepidly supporting it?
She says what's known as the "co-product credit" -- the energy-saving value of distillers grains, an ethanol by product that can be fed to livestock -- pushes ethanol's energy balance into positive territory.
Incidentally, Pimentel told me he does account for distillers grains, but finds that other researchers tend to overestimate the energy they save.
Again, I'm not competent to comment on this point, but I can say this: The MIT study is telling us that the entire case for corn-ethanol as a net saver of fossil fuel rests on a product -- distillers grains -- whose only market is industrial meat producers.
That group operates under a kind of bizarro triple bottom line: it profits by generating social, environmental and animal-welfare horror.
And last but not least the MIT report:
http://web.mit.edu/newsoffice/2007/ethanol.html
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A caution with allocating co-product credits is that it assumes, regardless of the allocation method, that the co-product is displacing a good that is already in the market place and therefore displacing the amount of fossil fuel consumed and GHG emissions released during its production. This is a bold assumption, as it is often not known what effect a new replacement product may have on the market it enters. It may replace current production or it may over saturate the market and drive prices down and thus not displace fossil fuel consumption or greenhouse gas emissions.
Someone once spoke of the politicization of science? The plot thickens.
