Waste and Space Toilets on the International Space Station, Contributed by @candyman

On the International Space Station, all things are recycled to the extent possible. This includes human waste. In fact, toilets on the International Space Station are part of an elaborate system of re-collecting drinking water and oxygen. Not all waste can be recycled for re-use, so other waste is kept in minimal quantities until it can be sent out for disposal.

One way to collect water is to draw humidity from the air. Sweat, breath, and urine are all potential sources of moisture. While filtering urine sounds gross, the drinking water made from it is far more pure than most peoples’ terrestrial drinking water.

Here is a space toilet that has been used by the Russians in the past. This model is on display at the Chabot Space & Science Center. The International Space Station’s system is similar. Look at how many stages there are after the toilet itself.

The current toilet system on the International Space Station uses forced air to direct the flow of waste. Vacuum pressure is used to kill bacteria, including any potential pathogens. The air is then filtered and returned to the cabin. Solid waste is collected in bags, while there is a separate urine receptacle. In 2008, a pump on the urine receptacle failed on one of the International Space Station’s toilets. Astronauts had to collect urine manually until a new pump was brought up by the Space Shuttle Discovery. And much of the water they drink is recycled from urine - yummy!

In 2016, NASA announced its Space Poop Challenge, a contest for inventors to create a space suit system that addresses human waste needs for up to 144 hours at a time. In the meantime, on those spacewalks, they use diapers like the ones shown in the top photograph above.

Garbage on the International Space Station includes dirty clothes and food containers. Obviously, these are minimized, but they also are a fact of life. There is not much water to allow for rehydrated meals, so bulkier cans and other containers are needed. And there is no laundry washing on the Space Station either, also mostly due to lack of water, so most dirty clothes are thrown away once they cannot be re-used (although someone used a pair of dirty underwear to grow some plants once).

Solid waste generally ends up in a Progress module that is sent back down towards earth. These are the same modules which bring supplies up to the station, so when they are used again, they go down with waste. However, this waste does not reach earth, since it burns up in the atmosphere.

Here is a short video from the ESA about laundry in space:

Next time you see a meteor in the night sky, it might be a package of dirty clothes burning up! Or it could be simply a space gorilla.

Photo credits: NASA and Chabot Space Center (public domain).

Resources:
https://www.nasa.gov/vision/space/livinginspace/Astronaut_Laundry.html
http://time.com/4581854/nasa-space-poop-challenge/
Chabot Space & Science Center Exhibits, chabotspace.org
https://en.wikipedia.org/wiki/Space_toilet