on 3/28/2002 5:14 PM, Louis JOURDAN at [EMAIL PROTECTED] wrote: > ... a bad process (I mean ethanol production)
in reply to this comment in a previous message: >> ... the energy cost of producing ethanol >> exceeds the energy in the ethanol. Of course the energy is less. That's a natural consequence of the second law of thermodynamics. That does not necessarily mean it is a bad process. Surely we should be concerned about such a process in a world running low on energy, but there are other aspects of energy use that are also important, in addition to the amount of the energy alone. Take for example a pile of coal which may be burned to produce electricity. The electrical energy produced is invariably less than the chemical energy in the original coal (usually a max of about 33%). If that electricity is used to heat a home, one could argue that it would be more efficient (3 times as efficient) just to burn the coal in the home producing heat in the home directly from the burning process*. But what if that electricity is used to operate a television set? There is no way that the television set can be operated on the chemical energy in the coal or the heat generated simply by burning it. The conversion to electricity was necessary even though it resulted in a smaller amount of energy than the energy that was in the coal to begin with. Of course, all such situations need to be analyzed more thoroughly to decide if the net value of the energy is worth the loss in the conversion process. I'm not suggesting that the example of ethanol production is good. I am just saying that the decision as to whether or not the ethanol process (or any other example) is good or bad cannot be determined quite so simply as just checking the energy out compared to the energy in. There are always two sides to an issue ... maybe three ... or more. Regards, Bill Hooper college physics teacher (retired), USA (Florida) * Even that example (burning coal to produce heat which is used to produce electricity which is then used to produce heat in the home) can be justified by such factors as the danger of burning coal in the home (fire, carbon monoxide, etc.), the dirty smoke from home type coal burning, the energy cost of transporting heavy coal to the home as opposed to tranporting weightless electrical energy to the home, etc. +-+-+-+-+-+-+-+-+-+-+-+ Do It Easy, Do It Metric! +-+-+-+-+-+-+-+-+-+-+-+
