Biofuel's Water Problem

A better idea is to use crops that don't require any more water than what local rains provide

Yes, true. But why stop at just water? It seems that the real goal of this whole energy dilemma is to use less energy than the Sun provides daily, right? I mean, in the end, when all the oil is depleted (whenever that may be) and humans will be completely reliant on 'natural' energies, we will at max be able to use the amount of energy the Sun provides our planet with per day, everyday.

the other disadvantage of bio fuel is that for every acre/hectare grown for fuel, that is less food production. Plus, it takes more fuel to produce the crops than the crops produce.

I agree that diversion of cultivation space for biofuel is paramount to sin, but must disagree in relation to your comment that it takes more fuel to produce the crops than the crops produce.

Current fuel usage per Ha of canola, or peanuts or sugar cane is measured in liters (because that's the relevant scale) while the output from the same area is measured in tonnes (because that's the relevant scale).

We were leant a tractor once that ran on peanut oil (for demonstration purposes) and the fuel consumption was comparable to conventional diesel tractor. The paddock involved yielded 2.5t/Ha of sunflower seed at 65% oil content. We didn't use more than 2000L of fuel to prepare, plant and harvest 150Ha. I'm sure there would have been a little left over.

(By the way, no fertilizer was used. Some "purists" use the energy production of fertilizer in their calculations.)

I suppose the ultimate biofuel is grass.

Dad used to talk of their farm where the horses were used. (Yes, real ones) Each horse could allow them to produce enough fodder to feed itself for a year and then still provide fodder for cattle and sheep. Farmers would not have moved to use those animals if there wasn't benefit. Tractors and other farm machinery introduce additional economies, like you don't have to feed/fuel them all 365 days of the year, only when you are using them.

I nominate algae as the ultimate potential Biofuel feedstock

Sugar beets ain't too shabby either, the extraction of food grade sugar runs into diminishing returns after the 1st 50%. The bagasse can be converted to ethanol...

Water is not the only problem. It takes about 200 hectares of agricultural land to produce 1 MW of energy from biofuels. This same 200 hectares can feed about 1700 people, maybe a little more, if we restrict calorie intake to world averages rather than first world standards...