The best energy source to replace fossil fuels this century is nuclear. The technology improvements over the last 50 years have made nuclear the obvious choice. But environmentalists have fearmongered against it pointing to the three "accidents" that occurred over 50 years with minimal global impact as somehow a threat to human existence. Far fewer people have died in nuclear accidents than have died fighting over fossil fuels.

Renewable energy sources including man made carbon fuel will eventually displace fossil fuels for "peak" energy demand, once the technology drives down the cost below that of fossil fuels. While the earth continues to have abundant fossil fuel supplies, those supplies are increasingly in less hospitable environments and thus more expensive to extract.

So, we will soon be producing man made carbon fuels in quantities needed to support the range of uses for carbon fuels that are not easily replaces by electricity, until then we will need fossil fuels.

Interestingly, man-made carbon fuels do not require resource extraction from the ground. Some of those technologies use algae or artificial photosynthesis to convert CO2, water, and sunlight into carbon fuel just like plants do. The cool thing is the water does not have to drinkable, the CO2 is abundantly available in the air, and sunlight is free. It does not need a surface area to capture the sunlight, but someday that will likely be relatively low value land in areas with adequate sunlight.

Carbon remains the best and safest way to store energy. Batteries have environmental issues; carbon fuel dissipates into harmless CO2 and water. Our problem is not too much CO2, but rather our failure to harness it to for productive use. Worst case we could simply extract CO2 convert it to organic material and pump it into the ground for future use.