Well, that's the funny part--it's not pollution. Pollution is something like CO (Carbon Monoxide, which is going to find an extra oxygen atom somewhere and convert to CO2 anyhow), NOx (oxides of nitrogen, which also aren't much of a true pollutant seeing as how lightning makes a bunch of it), or some VOCs (Volatile Organic Compounds), especially nasty ones.
Carbon Dioxide is just an intermediate compound in the organic life cycle on the planet. What most folks don't know (and many scientists, for that matter) is that once upon a time, we had a hyperbaric atmosphere compared to today. In actuality, Jurassic Park couldn't in fact happen because the large dinosaurs cannot respire in this relatively rarefied atmosphere. There's just not enough oxygen partial pressure to keep them alive because we've lost alot. If Kirk, Scotty and the Enterprise could go back in time, beam up a Brachiosaurus, hop through time in a heartbeat and beam the gigantic animal back down to anywhere on Earth, it would die of hypoxia within minutes.
We started with a lot more and are now suffering some loss due to solar wind and more due to the same problems at the
Biosphere experiments.
I've been working on a green, renewable, home-energy strategy and as an engineer with an eye to project costs, it's been a real pain. Conversion and storage efficiencies are the worst part although peak load capacity versus system turndown is a nightmare as well--that is, if you've got a budget. If money is no object then Katie bar the door!