What are the potential alternative energy solution that we can use to replace gasoline in the long run?

This may sound ridiculous at this moment but we may need to face it sometime in the future , so what kind of alternative energy sources that we can tap into before we run out of gasoline? Do you think the oil companies or some other major corporations should really invest in such energy development since this is essential for the survival of our civilization.

Tagged as: alternative energy sources, civilization, corporations, energy development, gasoline, oil companies, survival