I was thinking, and those little plastic bags that hold the astronauts' food have to go somewhere. Where do they go? Are they compacted into a big cube like on WALL-E, and sent out into space, or are they sent back down to earth on the next mission?
This paper shows how trash and waste were planned to be handled on the ISS in the year 2000.
The ISS Program shall provide accommodations and capabilities for the preflight, flight, on-orbit and return to earth of trash, waste, and non-recoverable materials in order to ensure the safety and health of both flight crew and ground operations personnel.
If we look lower down at the Waste section of the paper we can see that waste consists of:
chemicals, radioactive materials, batteries, sharps, and biologically/biomedically active products and consumables of no further use
So this definitely covers the waste of which you specifically speak.
This waste is handled by storing it onboard safely (away from public living areas) and then returning it to Earth at earliest convenience or by jettisoning it in orbit.
Standard stowage devices shall be made available for on-orbit and return based upon manifest approval of systems and payloads. A pantry of standard trash/waste stowage devices is maintained by JSC-OC/Logistics and Maintenance. The pantry of standard trash/waste stowage devices shall accommodate both planned and off-nominal operations.
So as we can see from this, even if they aren't able to send it back to Earth they have the facilities on board to presumably chuck it into space to ensure the health of the crew.