The Expanding Universe of Trash

It is not surprising that the humble garbage can, essential for Earth-borne civilization, is likewise essential for space station. Unlike the kitchen wastebasket, an omnivore that will eat just about any trashy thing, on space station our wastebaskets are picky eaters.  We sort our trash into a number of different categories different from the standard earthly recycle bins of paper, plastic, and glass.  The main categories are: dry trash (paper towels, food packaging, empty drink bags, paper items, etc.), wet trash (pouches and wrappers with food residue), spent batteries, life support systems expendables (fluid sample bags, toilet hoses, connectors, etc.), experimental expendables (used medical supplies, containers filled with leftover nasty things, etc.), and toilet waste (sealed buckets of you know what).  Some of our trash items have bar codes and serial numbers and require bookkeeping paperwork at the time of disposal.  Like happens at home, sometimes an item is tossed that is later discovered essential so we go orbital dumpster diving for its recovery.  Like passing through a miniature asteroid belt, in weightlessness such an operation can create a cloud of floating debris that is challenging to put back into its container.

One characteristic of an orbital trashcan is that it is always full.  When I change out a trash bag, within a short time it is once again full.  Like a gas expanding into a vacuum, items placed inside expand into the available volume thus giving the appearance of a full bag.  Unlike an ideal gas expanding into a vacuum, here the change in entropy is not zero.  Placing new items into such a bag is really an act of compression.  The trash is squeezed and compressed until the placing of one more item requires greater strength than your arms can supply.  At that point the bag is sealed with duct tape.  The final disposal is via Progress, the spent Russian cargo vehicle (and now we also can use ATV and HTV, the European and Japanese cargo vehicles).  The ultimate disposal of our garbage is thus via deorbital cremation.