I know that the main current fuel is diesel but what can the future fuel be? Between bio diesel, propane, natural gas, hydrogen, ethanol, electricity, etc. which is the number 1 best for the benefits of this world?

(may be broke/outdated!)
I know that the main current fuel is diesel but what can the future fuel be? Between bio diesel, propane, natural gas, hydrogen, ethanol, electricity, etc. which is the number 1 best for the benefits of this world?