I'm not sure we'll ever be totally free of them. We have to get energy from someplace, and even though we're tentatively dabbling in some alternatives, we're nowhere near being able to switch to them. And even those alternatives have negative impacts. Electric cars? Very good idea. How do we recharge them? Solar might work, but that technology is nowhere near as advanced as current battery-driven cars. And those that get a driving range comparable to gasoline engines are prohibitively expensive for all but a handful of people.

Synthetic oil is another good idea. I use it in my own car. But we still need to create the stuff, and that--again--requires a huge input of energy that right now is dependent on fossil fuels. Kind of like MC Escher's "Drawing Hands."

Vegetable energy sources? Another good idea. What farmlands are we going to switch from food production to fuel production? Which is more important to us?

So I wouldn't look for a total transition in the near future. We got started on this way too late.