or the drop in CO2 from that used by a car and its single occupant (even if he doesn't smoke).

And the CO2 emitted making the car v the bike? e.g. there are those that think that manufacturing CO2 is significant relative to "scrapping & buying new eco-better cars"

if you want precision, think of all the aspects.

Of course, on a sample of millions, the cyclist is going to live longer and thus exhale more lifetime CO2 but on the plus side we exhale Oxygen as well, our lungs are not as efficient as the infernal combustion engine.

Simple answers? Life ain'ta like that.