[NortySpock]

All trash (food wrappers, paper, packaging, some medical waste I presume, old experiment gear, etc), and dehydrated sewage, currently only leaves the space station via visiting vessels. It requires an astronaut's time to pack trash, disconnect and seal dehydrated sewage containers, and load them into a visiting spacecraft prior to departure.

Imagine having trash and sewage picked up only twice a month or once a month. That's about how often new vehicles visit the space station.

Some uncrewed vehicles (Russia's Roscosmos Progress vehicle, Japan's JAXA HTV, USA's Northrop Grumman Cygnus) are designed to burn up on reentry. SpaceX Dragon is designed to make it to the ground and thus would need to be unpacked after splashdown.

Nanoracks' Bishop airlock is supposed to offer trash disposal-to-orbit, but has not been used in orbit yet.