Energy: Ethanol and Genetically Modified Crops
Jim Blair

Recent threads have debated the issue of fuel additives, and the replacement of MTBE with ethanol, and whether or not ethanol is an energy source (converting sunlight into a motor fuel) or an energy sink (taking more petroleum to produce than it returns as a fuel).

If you want some facts about ethanol, Look at "How Much Energy Does it Take to Make a Gallon of Ethanol?" at:

This article concludes that each unit of energy (BTU or Kcal) invested in corn to ethanol production can produce 1.24 units of energy as output. But one of the studies cited estimate a return of 0.42 (that is, getting back only 42% of the energy invested.)

The article suggests that the earlier 1970's estimates of ethanol from corn to be an energy sink were because of the lower bushels per acre yields for corn then.

A recent Madison newspaper article featured a local farmer who grows several hundred bushels of corn per acre using relatively low energy input as the result of his use of Monsanto's genetically modified corn. Until this past decade, ethanol from corn consumed more energy than it contained. But recently because of higher yields, ethanol from corn can become an energy source.

Notice that by far the largest energy cost for fertilizer is for nitrogen. A genetically modified corn that self fertilized (as legumes do) could reduce this energy input considerably

This should pose a conflict for the environmentalists that favor ethanol but oppose genetically modified crops. Because the higher corn yields that make ethanol an energy source use genetically modified corn. And a corn which provides its own nitrogen fixation (which is likely only by gene splicing) could really make ethanol a practical replacement for petroleum.

So would that be GOOD because it would be a sustainable energy source and reduce greenhouse emissions? Or would it be BAD because it would expand the use of GM crops?

Note on nitrogen fixing

Postgate, J. (1989)
Fixing Nitrogen
Biological Sciences Review, 1(4), 2-6
Philip Allan Publishers, Market Place, Deddington, Oxfordshire, OX5 4SE. ISSN 0953-5365

Fixing atmospheric nitrogen into ammonia and nitrates, forms usable to plants, is essential for plant growth. Nitrogen is fixed in three ways - spontaneously by lightning, combustion and photochemical reactions, industrially using the Haber process to make N-fertilizers, and biologically by nitrogen-fixing bacteria. The industrial process, which produces 25% fixed nitrogen, is extremely important, especially in the third world where population growth is high. The new high yielding varieties of rice have a high nitrogen demand. However, the special conditions and high energy demand of the Haber process make any fertiliser very expensive.

Microbial fixation accounts for 60% of the nitrogen fixed. Most of these nitrogen-fixing bacteria form symbiotic relationships with plants such as legumes, fungi, liverworts, or Azolla. The plants provide the carbon source and in return the diazotrophs provide nitrogenous compounds. Two nitrogenases catalyse the first step of nitrogen fixation; the first binds to the nitrogen and the second reduces it to ammonia. Both contain iron and another metal, usually molybdenum. The process is slow, requires much energy and the enzyme is destroyed by oxygen. Plants use various strategies for producing a low oxygen environment for the bacteria.

Recent genetic research has revealed a group of genes, called nif genes, which code for nitrogenase. Also, other nitrogen-fixing enzymes, containing vanadium or iron instead of molybdenum, have been discovered. It seems the metal atom gets the nitrogen into a position to be more easily converted to ammonia. Scientists are now developing a less expensive substitute for the Haber process, investigating new symbiotic relationships for use as fertilizers, and studying the possibility of inserting nif genes into plants to produce a nitrogen- fixing cereal.

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