These alternative energies are really not going to fill the gap left by petroleum unless some breakthroughs are made. Petroleum is just so much more effective, mainly due to two things. First, the energy required to go into the process has already been accomplished, and it's pretty hard to beat millions of years with a season's corn crop. Second, it costs nothing to actually produce because all the work has been done already. Drilling it is the only cost besides the manufacturing process and delivery system.

With something like ethanol, seeds must be bought, the soil prepared, the crops fed, harvested, and then manufactured and delivered. A latent dysfunction of this ethanol/grown fuel process is that for every piece of corn (or sugar, or whatever the flavor of the month is) grown for fuel, that's one piece of land that cannot be used to grow food. The opportunity cost could become fairly high if this becomes a worldwide trend.

Basically, the laws of thermodynamics are not on our side.