[oddeyed]

Not necessarily comparable for purposes of global heating effect (not sure if that's what you're doing or not).

The CO2 that a human exhales is from the carbon in the food they consume. That carbon ultimately comes (whether indirectly via animals or not) from plants, which drew that CO2 out of the air directly, typically at most a few years prior. The net change in CO2 concentration is zero.

Contrast this to burning fossil fuels which moves carbon from places where it is not enhancing the greenhouse effect (e.g. it's in coal, gas wells or crude oil) into the atmosphere where it will cause global heating - a net increase in CO2 concentration.

As a side note, methane produced by livestock or food waste does still have a global heating effect as CH4 is a more "potent" greenhouse gas than CO2, so there is a net increase in heating potential due to this conversion.