How much oil does ethanol replace?

Dr. Bruce Dale, a distinguished professor at Michigan State University, had an interesting post on the Huffington Post yesterday. Check it out here.

In his post, Dale notes that from a national security perspective, the most relevant question involving ethanol is, "How much oil does ethanol replace?"

Here is his answer:

The answer might surprise you. Very little oil - mostly diesel fuel for planting, tilling and harvesting crops - is required to produce ethanol. A recent publication in the journal Science shows that only about 0.04 MJ (mega joule, a measure of energy content) of petroleum is required to produce one MJ of ethanol. That is a 25:1 advantage in favor of ethanol production. Because ethanol has less energy per gallon than gasoline, we get more than 30 gallons of ethanol for every gallon of oil we "invest" to make the ethanol, versus eight-tenths of a gallon of gasoline per gallon of oil. When ethanol is used as E85 fuel in a flex-fuel vehicle, we are effectively getting around 800 miles per gallon of oil consumed.

Thus, overall domestic fuel supplies are stretched far into the future when we take our own oil and use it to produce ethanol from our domestic agricultural and forest materials. Ethanol from corn and the much larger amounts of grassoline that are on the way are the only near-term petroleum alternatives we have that significantly enhance national security by replacing lots and lots of oil.