"It does the job clean".
One of the wonders of automation is the freedom it gives us, allowing us space gods not to deal with the things we don't want yo deal with. Poop is one of those things.
Introducing, the Auto Excreter, a scientific wonder that will allow you to put the poop from the humans straight into the burner... or wherever it is you want to put it.
Connect it with a conveyer belt to access the humans; and output all that brown nastiness with a pipe straight to where you want it.
Live humans will continue their bodily functions as normal on the conveyer belt, so keep that in mind.