Bill: Yes there is a fermentation mash left over after the ethanol is removed - called distiller's grain. This product is comparatively high in protein but is depleted of starch and is used as an animal feed supplement - about the maximum amount that can be mixed in with other animal feed is 25-30% by weight - more than this and the feed becomes toxic to the animal - probably burns out the liver.
The energy embodied in this distillers grain is one of the energy credits attributed to the production of ethanol from corn and is the main reason why the energy returned over energy invested for corn-to-ethanol is slightly greater than one (about 1.3/1 as the most optimistic projections seem to suggest). Without the energy credit associated with this animal feed by-product the total energy embodied in the liquid ethanol produced from corn might be less than the fossil fuel energy that went into making it.
On the question of using stalks and crop residues as a fuel to help operate the corn-to-ethanol fermentation plant, a paper published from the U of Minn. a year or two ago suggested that perhaps 30% of the crop residues might be able to be removed from the field without significantly degrading the soil of necessary carbon and other nutrient inputs.
By all these criteria the corn-to-ethanol venture is not ever going to be an avenue by which we can expect to significantly reduce our reliance on fossil fuels.
Whether or not ethanol-from-cellulose (grasses, woody plants) can ever play a more significant role in our energy picture remains to be seen. Some estimates are encouraging - fossil fuel inputs are expected to be lower (perennial grasses, less fertilizer, perhaps less irrigation) but the process of converting cellulose into useable ethanol still has technical challenges that need to be overcome, such as finding enzymes that are affordable and robust enough to convert both cellulose and hemi-cellulose into ethanol on a commercial scale. Currently capital costs for construction of a cellulose to ethanol plant are estimated to be about double those of corn-to-ethanol fermentation and the cost of bio-engineered enzymes to trigger the fermentation is prohibitively high. Perhaps these costs will come down as research and development proceeds
Still any biofuels project that is successful and that depends on arable land for growing its raw material is likely eventually to scale up to a level that it will begin competing for land currently being used for growing food crops, which again creates the moral issue of land for food or land for fuel. That is an issue where, it seems to me, Christians should be making a clear testimony.
ken
Ken Piers
"We are by nature creatures of faith, as perhaps all creatures are; we live by counting on things that cannot be proved. As creatures of faith, we must choose either to be religious or superstitious, to believe in things that cannot be proved or to believe in things that can be disproved."
Wendell Berry
>>> Bill Hamilton <williamehamiltonjr@yahoo.com> 5/19/2008 1:01 PM >>>
Dave Siemens wrote
As an additional problem, there is talk of using corn stalks, straw
and other crop residue to produce ethanol. But this reduces the humus in the
soil, with a negative effect on fertility and conservation.
Bill responds:
I read the other day that pointed out that after corn kernels have been fermented to produce ethanol, the residue is used to make an animal feed, so the corn used to make ethanol is not entirely lost to feed. I suspect something similar is true of using crop residue: the byproduct can probably be plowed into the soil to add to the humus. I'm not trying to say that nothing is lost in making ethanol, but the situation may not be as bad as it has been painted.
Dave continues:
I suspect that every
optimistic prediction can be countered by a pessimistic report.
Bill:
Agreed.
William E. (Bill) Hamilton, Ph.D.
248.652.4148 (home) 248.821.8156 (mobile)
"...If God is for us, who is against us?" Rom 8:31
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Received on Mon May 19 13:55:28 2008
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