A year ago, Click & Clack (a syndicated automotive radio show) took on ethanol from a somewhat uninformed (their words) and objective (mine) view point. What they say is very important to consider when you are comparing, well, anything. LOOK AT THE BIG PICTURE.
Q: ...The report on this site says that 131,000 BTUs are needed to make one gallon of ethanol, but each gallon of ethanol produces only 77,000 BTUs. That means we're losing 54,000 BTUs for every gallon we produce...
RAY: From what we can tell, the basic issue is this: When you calculate how much energy it takes to produce a gallon of ethanol, you have to make certain decisions. Everybody agrees that you need to include the energy needed to plant the corn, water it, harvest it and convert the starch to alcohol. But, for instance, do you include the energy needed to manufacture the tractors that plow the fields? Scientists disagree about that.
TOM: They also disagree about the other side of the equation. The guy whose study you refer to, David Pimentel of Cornell University, is well regarded and has been studying this issue for years. He adds up his calculation of the amount of energy needed to grow the corn, subtracts the amount of energy you get from a gallon of ethanol, and gets a negative number.
RAY: But there are other credible researchers, such as David Lorenz and David Morris of the Institute for Local Self-Reliance, who take Pimentel's research and say yes, but , a gallon of ethanol isn't the only thing you get from that corn. You also get stuff such as corn oil and gluten feed. So some of the energy that goes into growing the corn has to be assigned to those other byproducts. When they do the numbers, the energy ratio of ethanol comes out positive.
TOM: The answer is not clear. What everybody does agree on is that ethanol made from plants with more cellulose, such as switchgrass or sugar cane, will produce more ethanol per acre than corn will. And that will improve the case for ethanol -- no matter what your starting point.
As it stands, I'm not a huge proponent of ethanol. I don't think it is going to be viable, plain and simple. The fuel you get is not all that great and the way you get it now sucks. I don't see a huge area of improvement with ethanol. I also believe we should not completely choose or completely eliminate any alternative to petroleum unless it proves to be a complete bust. Is ethanol a complete bust? Not in my opinion...
FYI, Pimentel's output to input energy ratio is calculated to be 0.78 (i.e. 78% of the energy put into ethanol production is realized during use). This sucks ("sucking" defined as "not currently preferable or sustainable"). An earlier study by Wang (1999) came up with 0.96; still crappy ("crappy" being generally synonymous with "sucking"). A more recent report (long source... Ethanol as Fuel: Energy, Carbon Dioxide Balances, and Ecological Footprint., By: Dias De Oliveira, Marcelo E., Vaughan, Burton E., Rykiel Jr., Edward J., Bioscience, 00063568, Jul2005, Vol. 55, Issue 7) gives a 1.1 ratio for corn grown in America and a 3.7 ratio for sugarcane grown in Brazil (which is why ethanol works in that country and not here). The report is technical but if you want some true information about it, search it out. It should be free for anyone (search through a university library; that's the easiest way to find it).