But back to fuels of today. Without modification of present automobile engines, up to 15% alcohol can be added to gasoline. As pointed out earlier, the energy balance is negative: More man-made energy goes into growing corn or wheat and distilling it than is contained in the resulting product.
This is sometimes disputed (usually by companies and congressmen from Iowa and Nebraska, and of course, by wonderchild Amory), but here are the figures, taken from a report commissioned by the DoE (see below):
Per ton of corn grain and residue, the energy inputs are 1.31 million BTU of petroleum, .02 MBTU of electricity, and .82 MBTU of fertilizer and pesticides for a total of 2.1 MBTU per ton of corn production; to which must be added 5.1 MBTU of heat for the distillation process (even if the energy contained in the corn stover is utilized). The ethanol produced from the ton of corn and residue then has a heat content of 4.1 MBTU, resulting in a net energy loss of 3.1 MBTU/ton.
For sugar cane (which takes less energy both to grow and to distill), there is a net energy gain of 2.3 MBTU/ton; great for Cuba and Brazil, but not very interesting for the US.
There are nevertheless reasons why the idea of gasohol is not hopeless. First, in a pinch, one might be willing to take some losses if oil energy can be replaced by coal energy. That is, if the distillation energy is simply not counted when it comes from non-petroleum sources, then the "net petroleum gain" amounts to 2.0 MBTU/ton of corn. The trouble with that kind of slanted calculation is that if mere substitution of non-petroleum energy is enough, then there are better ways of doing it¾and without premiums in either BTU's or dollars. The most blatant¾indeed, insane¾case right now is that of nuclear plants kept idle for political reasons; just the seven plants that will be denied license by the utterly unjustifiable moratorium would be the equivalent of 200,000 barrels of oil per day¾about 2/3 of the former imports from Iran.
But there are also technological reasons, untainted by political fraud, why gasohol is not hopeless. As the figures above show, most of the energy input is that needed for distillation, i.e., for separating the alcohol from the water after fermentation. Distillation makes use of the differing boiling points of the two liquids.
But there are other differences¾chemical behavior, for example. Alcohol dissolves in a number of liquids that do not mix with water; it can then be separated by solvent extraction. Then there are methods based on differing densities, and also methods still essentially amounting to distillation, but with a far higher energy efficiency than Snuffy-Smith type booze making. Among them is adding gasoline as an alcohol-entraining agent to the mix to be distilled; there is no need to separate the gasoline from the alcohol after distillation, since it is gasohol that is the desired product anyway.
The most elegant solution, of course, would be to pass the mix through a membrane acting as a molecular sieve in much the same way as used for the desalination of brine (AtE Oct.78). The process would need very little energy, and membranes of this type already exist on a laboratory scale, but they could not withstand the pressures needed in a large-scale process. Experts speculate that this type of separation on an industrial scale is still a decade away.
[More: DoE Rep. HCP/T4101-03, Biomass-based alcohol fuels, Aug 1978, $6 from Govt. Printing Off., Wash., DC 20402; stock no. 061-000-00151-4); R.S.Chambers et al., "Gasohol: Does it or doesn't it produce positive net energy?" Science, 16 Nov. 79, pp.789-795; "Lowering the cost of alcohol," Science, 5 Oct. 79.]
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Vol. 7, No. 5
Newsletter: Access to Energy Newsletter Archive Volume: Volume 7 Issue/No.: Vol. 7, No. 5 Date: January 01, 1980 03:04 PM Title: Huxley, not Orwell
Copyright © 2004 - Access to Energy Newsletter Archive
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