Other than massive nuclear and wind and solar, I don't see what the energy source is going to be once oil goes into serious decline, and that does not address the transportation fuel issue unless we replace our transportation infrastructure.  And we have not started yet.  Using less energy is the only solution.  If we have 20 years, maybe we can do it, but if the top of that curve keeps tipping over....

But don't worry, because I heard on the radio this morning that the Saudis have been pumping like mad, and have produced so much oil that they expect to throttle back early next year, and the gas prices will go down further (back up to $2.29 this morning), and the economy will take off.  But there's no need to worry about inflation in spite of all the jobs that will be created. The FCC really needs to work on blocking those broadcasts from other dimensions....

Even the use of sustainable cellulose residue (instead of food crops) can only achieve 14.5 billion gallons (345 million barrels) of ethanol annually. The clear message here is that liquid fuels consumption has to go down. The clearest way to achieve that is migrating to electric transportation which can be supported by solar, wind, nuclear, and clean coal electric generating processes.

We can achieve a sustainable yet advanced technological civilization with what we know today. No, it won't look like what we have today but it's still better than the alternative of collapse. The only question is whether we will do so or not?

However what if sugar cane, coconut and date palms WORLD WIDE gets shunted into fuels.  This has already started in Indonesia and Brazil.  We already import gasoline and ethanol and we have a big appetite for transportation fuels.  I agree again with you that this still won't replace a very large percentage of petroleum.  But it could mask declines for awhile in the reports.

Do you have numbers for Canola or Mustard seed?
Soy beans is the worst example to give and in my mind, are a net-energy loss or close to it.
The numbers that I have seen (from coastal areas) say both canola and mustard yield close to 100 gallons per acre.  And they also are a great rotation crop for wheat to replenish the soil, so farmers must grow these (or something else) anyway.

There is no way the USA can ever supply even 10% our liquid fuel with ethanol & biodiesel.

This is a very bold statement.  We haven't even begun to tap ethanol from wood yet and it is an energy gain and can be processed from existing paper mills, but a cheaper method must be worked out.  The average car also get 21 MPG, if this number ever got to 42 (and it will with price) 10% would be more like 6-7% currently.