Alternative fuel: methanol/ethanol, biogas, Hydrogen
Ethanol (alcohol) can be made in large amounts, for example from fermenting sugar cane.
biogas is a mixture of gases (with relative lots of methane) that is formed in the bacterial fermentation of shitty products.
Hydrogen can be made in a process of electrolysis. Unfortunately this costs rather some energy, so what's the nett effect? If you must first make energy out of natural gas to make Hydrogen for energy, why is that?
But nevertheless, lots of research is needed to resolve the problems and to find the best ways for Hydrogen production.
there are ideas. We could learn something from plants and their photosynthesis. In this process, under influence of sun light, water is split into Hydrogen and Oxygen. Wouldn't that be a beautiful mixture to create energy without any production of carbon dioxyde?
Alternative, non chemical sources for energy: nuclear energy, water plant energy, wind energy, solar energy.