>Looking at efficiency alone is not enough. In general I would say I actually agree with this. It can be perfectly feasible to use an energy source that's terr

>Looking at efficiency alone is not enough. In general I would say I actually agree with this. It can be perfectly feasible to use an energy source that's terribly inefficient in some intuitive sense, but as long as it's economical to do so, poses no environmental harm, and you're getting significantly more energy out than you're putting in, you can be as inefficient as you want. Now that said, I don't think that this kind of general truism is terribly responsive in this particular case, because it's nevertheless going to be true that inefficiency, and whatever sense you construe it, can indeed be a deal breaker and I think that's what GP is intending to communicate with respect to h2, biofuels, etc.