17 July 2006

Soy A Better Fuel Than Corn.

The natural foods press is big on more soy for healthful living. And, while it has waned a little, the war on carbs, corn included, continues. But, who would have thought that similar advice applies to biofuels for your car. It turns out that soy biodiesel is a better deal on a net energy basis than ethanol from corn according to a recent article in the proceedings from the National Academy of Science:

Ethanol yields 25% more energy than the energy invested in its production, whereas biodiesel yields 93% more. Compared with ethanol, biodiesel releases just 1.0%, 8.3%, and 13% of the agricultural nitrogen, phosphorus, and pesticide pollutants, respectively, per net energy gain. Relative to the fossil fuels they displace, greenhouse gas emissions are reduced 12% by the production and combustion of ethanol and 41% by biodiesel. Biodiesel also releases less air pollutants per net energy gain than ethanol. These advantages of biodiesel over ethanol come from lower agricultural inputs and more efficient conversion of feedstocks to fuel. Neither biofuel can replace much petroleum without impacting food supplies. Even dedicating all U.S. corn and soybean production to biofuels would meet only 12% of gasoline demand and 6% of diesel demand.


In English, soy is better primarily because, as a legume, it is on the soil enriching side of the nitrogen cycle, rather than the soil depleting side. This is important because when we really need biofuels, oil based fertilizers may even more expensive than they are now.

Hat Tip to Science News.

5 comments:

Jon W. said...

I can't get to the linked article, but I wonder if it considers ethanol from sources other than corn? I have read (and perhaps you've mentioned it in the past) that ethanol from sugar cane is more efficient, and would be more cost effective, if not for the import tariffs. If legislators are serious about alternative energy, perhaps they'll reconsider.

These same tariffs are responsible for the widespread use of high-fructose corn syrup. Back when I drank soda, I lamented Coca Cola's change to "new Coke," and then to the corn syrup-based "classic." (A friend and I did a taste test, and we could tell the difference between old and classic Coke.) It was a treat to find a store that sold bottles imported from Mexico, where sugar is still used.

Andrew Oh-Willeke said...

The article this post is based on considers only soy and corn.

I suspect that soy would still come out ahead of sugar cane, but sugar cane depletes soils greatly, and thus, would require fertilizer, which is the factor that also hurts corn.

But, since the demand for biofuels far exceeds the supply of corn, soy and sugar cane combined, it may not matter much.

Kyle said...

Nice post. Not long ago I did some research into biodiesel at the urging of a friend. It was fascinating stuff. The production process is surprisingly simple, and as you point out, the payoff is really quite good.

Here in AL there's a push for biodiesel, of course because we have a huge soybean industry - or at least potential. It won't require much of an increase from current gas levels before biodiesel starts looking really attractive.

Kyle said...

Also, about exceeding the supply, this is undoubtedly true. There are efforts to produce biodiesel from tall grasses and unusued plant parts. They are less attractive from an economic standpoint, but once again, being economical is just a matter of how pricey oil gets. This plant matter could make a significant dent in oil use.

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