Here’s another method of turning CO2 to CO:
http://www.wired.com/science/discoveries/news/2008/01/S2P

I also found this on wikipedia:
http://en.wikipedia.org/wiki/Bosch_reaction

Also worth noting: the cost estimates for the “artificial trees” assume current electricity costs. Really cheap power would make it even better. I don’t know how much of the cost is energy, but if we assume half we’re talking fifty cents for a gallon of gas.

This article says that 250,000 artificial trees could absorb all current emissions.
http://news.bbc.co.uk/2/hi/science/nature/2784227.stm

Transportation accounts for less than half of CO2 emissions, so 100,000 artificial trees would be about the right ballpark for supplying all vehicle fuel. That compares pretty favorably to the number of windmills people are talking about building. According to a paper I read, one of these artificial trees would reduce net emissions about as much as 500 similar-size windmills.

In short, combining this technology with focus fusion would obsolete the entire fossil fuel industry pretty quickly. We’d still need the pipelines and gas stations, and probably refineries, but that’s it.