First, however, the global demand for non-transportation energy is also huge. Suppling it is not technically difficult. Our failsafe and most reliable source will be simply tapping the heat of the earth and pumping that energy to the surface and putting it through a converter. It has not been cheap enough as yet, or more precisely, there have been plenty of cheaper sources to use such as dams, coal fired power plants and the like. Accessing that energy is simply a matter of drilling deep enough almost anywhere which the oil industry has plenty of experience doing.
In other words., as long as we are not demanding portability, we have absolutely nothing to worry about.
That is not true for the petroleum regime.We have burned one trillion barrels of oil and we may have three to four times that ultimately recoverable at great expense. In other words. unlike geothermal energy, the resource is truly finite and finite inside a human lifespan, now that all the human race is modernizing as fast as possible.
One third the global population is comfortably middle class, another third will be there in the next twenty years and the rest can be there in the next twenty depending on their political masters. And they all need some access to personal transportation at some level.
A huge amount of effort has gone into developing other energy storage technology with marginal success to date. We cannot today depend on a breakthrough to help us.
The best available energy storage device is still the hydrocarbon molecule. It is compact, fairly safe and very portable. That is why we use it. The next best alternative is the ethanol molecule which is alcohol from fermented sugar. And the cheapest source of that sugar is corn.
The point that I am making is that a global corn culture combined with carbon sequestration of the waste is capable of supplying the maximum bio available fuel. I do not know if that could be enough to exactly satisfy our actual needs.
On the other hand, it is trivial to re engineer our life ways to minimize the demand on transportation fuels. Simply ensure that personal use of a car is not the first or only option. Over time, price alone will largely do that with the application of a little common sense by the planners.
It would not be surprising to discover that we can easily live within our ethanol fuel budget even with a global population over ten billion.