[jjotto]

Slideshow at the link and wiki (direct-ethanol fuel cell) have basic explanations.

[exDemMom]

Okay, I see what is going on now. The ethanol is basically being used in a battery for a redox reaction. Instead of recharging the battery using an external power source, the ethanol is replaced. So the battery "charging" step takes place remotely, at the point where plants convert CO₂ into sugar using solar energy, and yeast ferments the sugar into EtOH.

This actually is not the same as hydrogen "fuel cell" technology, since it takes an energy input from some artificial source to "break" water into hydrogen and oxygen, in order to get a lesser amount of energy back from burning the hydrogen to reform water. Hydrogen fuel cells do not depend on redox reactions and are not batteries.