Wrong, and wrong. Pure ethanol is 77,000 BTU/gal. Pure gasoline us 114,000 BTU/gal, although most gasoline sold at the pumps have additives that that bring it down to 110-112k BTU/gal. Gasoline does have a weight advantage however, weighing in around 6.0lb/gal versus 6.75lb/gal for ethanol. Per gallon, ethanol has about 66% as much energy content. Per pound, it's still 60% as energy dense. Fuel pumps sell by the gallon and pipeline costs are by the gallon, but trucking/shipping costs are by the pound. Either way, it's more than half the energy content.

As for real world fuel economy, engines tuned for E85 or for pure ethanol are able to take advantage of it's very high octane properties and run more timing / higher compression ratios, both of which increase volumetric efficiency of the engine. Well, compression ratio much more so, but you can't be a "flex fuel" engine if you raise the compression ratio to 14:1, it would have to be E85-E100, for example. Like Wayne said though, fully tuned, you can get about 80% of the efficiency.

As for the comments about the US having a sustainable population of 40-100 million, that would be based on current technology. I'm sure 500 years ago they said the sustainable population was 1 million, and at the time it was probably true. If you want an example though, look at Japan and many European countries that are already declining in population. The only reason the US isn't in decline is our massive influx of immigrants. Our population will level off and decline some day too, especially as living costs increase due to the fact renewable resources will drive up the cost of living and make it less affordable to have kids.