[mchannon]

Good point, but it does end up depending on the vehicle. A 6 m^2 15% efficient array parked outside in a desert climate could generate 5.4kWh a day and over 37kWh a week. GM's EV-1 had efficiencies of over 6mi/kWh. As such, a vehicle could be built that could go 32 miles a day off sunlight alone, using ho-hum $1/W solar cells and without any tracking.

Of course, at that point, you don't need to futz with bacteria and internal combustion, when batteries store and release that energy much more efficiently.

[ScottBurson]

32 miles a day... in Arizona... in a car 80% of whose upper surface area is solar cells, leaving little room to see out. I can imagine some enthusiast building one, but I don't think it's a mass-market product.

None of this, I hasten to add, is to impugn the idea of using bacteria to fix CO2. It's just that the idea of doing it in your car, driven by solar cells on the roof, is silly. The numbers just don't pencil out.

(And as you point out, it's doubly silly since you would use batteries anyway.)