[deff]

If I were to guess, the metabolism generates waste during activity that gets processed and exhaled as CO2 during sleep.

[robbiep]

Bad guess, I am not sure what OP really intends (perhaps you don’t consume whilst you sleep?!) because as you probably are starting to remember from primary school your body maintains homeostasis by continually respiring. It doesn’t suddenly decide to take a dump.

Ok, it does, but even when it does that, in order to do that it has been continually maintaining homeostasis

[NAHWheatCracker]

Doesn't the CO2 get exhaled during activity rather than sleep?