re: "Good" CO2 and "bad" CO2
This is also why burning methane and emitting CO2 is "good"... Our livestock manure and landfills emit large amounts of methane. If you burn the methane you create one CO2 molecule for ever methane molecule, but since 1 pound methane is the GHG equivalent of 25 pounds of CO2 the result is a net reduction of global warming potential.
(Note: It is not clear that this figure takes into account the difference in lifetime of the CO2 and methane molecules in the atmosphere)