Biotechnological carbon fixation.

Carbon fixation is accomplished almost entirely through fotosynthesis right now. We rely on plants to turn carbon dioxide into carbon hydrates such as suger and starch. The advent of synthetic fuels will require a large supply of these, but already enviromentalist groups and human rights activists are crying about the huge amount of staple foods required to provide with the wee amount of bio ethanol we're currently using. If we ever hope to synthesise kerosene and plastic from ethanol, we'll need a better way of producing these staples.

I don't think it's impossible to do this biotechnologically. We've managed to get bacteria to synthesise insulin, why not sugar? Set up a huge broth filled tank that houses these bacteria, and pump carbon dioxide through the tank. They'd need a supply of light as well, but that could be engeneered easely enough. Maybe large shallow tanks with lights strung over them, stacked on top of eachother. We've been using other microorganisms (yeasts) to turn sugars into alcohol for thousands of years, and we've got the chemical knowledge to use this alcohol to synthesise fuels.

This technology could also help us deal with world hunger, and it would allow small communities to generate a lot of food/energy themselves. It would also turn the agricultural world upside down. Imagine the price of starch plummeting, while fuel for harvestors and combines becomes prohibitively expensive. High density food production will also benefit areas with high population densities if transporting food became more expensive than producing it.

As for something that's happening now: algae oil.
Not exactly micro-organisms, but they get the job done, and the oil they produce is supposed to be great for making biodiesel.

If you've got kids: get them an education in biotechnology or process engeneering, for they will be the farmers of the future.