The holodeck biofilter was a filtration device incorporated into Federation holodecks that collected organic material deposited by the users. On California-class starships, removing waste from the biofilter was considered one of the worst jobs on the ship, along with carbon filter maintenance and turbolift lubing.
In 2380, Captain Carol Freeman and Commander Jack Ransom of the USS Cerritos plotted to make Ensign Beckett Mariner request a transfer by giving her all the worst assignments, including holodeck waste removal. When that failed, Freeman demanded that Ransom give her worse jobs, to which he complained, "I've got her emptying *bleep* out of the holodeck's *bleep* filter!" (LD: "Moist Vessel")