The CO2 in naturally-brewed beer is produced from its ingredients (barley, hops, and yeast) which got their carbon mainly from the CO2 in the atmosphere, and is therefore by definition renewable (just like firewood). Brewers may brew beers that need no additional CO2, or they may produce the carbonation fizz by finishing (adding sugars during bottling, sometimes with added yeast), or they may capture the natural CO2 emissions of the brewing process and inject them back in during bottling, or they may just add bottled CO2 obtained from industrial suppliers.
The amount of "evil" in industrial CO2 depends on its source. It can be made as a sideproduct of atmospheric distillation whose intended products are nitrogen, oxygen, and argon, or captured from the combustion of fossil fuels (increasingly common now because of emissions regulations), or by simple chemical processes (typically involving acids and carbonic rocks like limestone).
