Air is awash in N2 but has darned little carbon, e.g., parts per million for CO2 and that has the O2 and not just the C and each O weighs 16 or so and each C about 12. There ain't much C in air.
There's so little C in air that it's astounding that some plants can get the C they need to grow just from air.
For C, we have much better sources than air. And if want C from air, then go to, say, any electric power plant burning fossil fuels, any plant making cement (heat calcium carbonate and let the CO2 escape), etc.
We know the prices of oil and gasoline, and oil prices are due to fall due to the Arctic, ANWAR, Venezuela coming back on-line, pipelines to make better use of the Alberta tar sands, US offshore drilling, much more in fracking, e.g., what the USGS reported about west TX, etc. more fuel efficient cars, etc.
As expensive as gasoline is, it is still much easier to fill up a 20 gallon tank of gasoline than to get the same energy that fast from electric power. Gasoline just ain't that easy to compete with, fundamentally and from existing well engineered infrastructure.
In a car, super tough to compete with a 20 gallon take of gasoline. Yes, it takes an internal combustion engine to use the gasoline to turn the wheels, but we're really good at making those -- 300,000 miles with minimal maintenance. Typically the body, fuel lines, brake lines, gas tank, radiator, parts of the frame, even the oil pan are rusted out before the engine wears out. We're GOOD at making the engines. Yes a battery in every way as good as a 20 gallon tank of gasoline would be terrific because the motor is much simpler and don't need a transmission, but batteries are a long way from such a tank of gas. And, again, as shocking as it is, now the piston engines are really good.
If we really care about the waste from the oil patch, then demote Jane Fonda from our de facto Secretary of Energy at large and get back to good nuclear fission power and also breeding, fissionable elements other than uranium and plutonium, really safe reactor designs, etc. Then make gasoline like South Africa and Hitler did -- start with coal and add water and electric energy. Besides can use the same nukes to make really good drinking water, maybe cheap enough for a lot of farming, and get down electric bills and permit electric home heating, etc. "too cheap to meter".
If solar power were so cheap, then the US SW would be covered with solar panels, importing water and coal, and filling pipelines with gasoline whenever the sun was shining. Same for lots of places with lots of sun. But they aren't -- net, solar power is not as cheap as it is cracked up to be.