For many communities, recycling costs are simply astronomical.  But at the International Space Station which hovers far above the planet, recycling is simply a matter of necessity.  This is because nothing can go to waste in a place where resources are scarce.  The plumbing, for example, is laid out in a complex network of tubes, pipes and ducts between the station’s outer skin and inner walls. So like veins in the human body, it circulates the vital liquids and gases that keep the crew in good health.  Indeed, even the urine of the crew and animals is recycled and returned safely processed into drinking water.  With even the air in the cabin shuttled to carbon scrubbers and back, this is one eco-topia that’s simply out of this world.