Thanks to the laws of physics and some good old ingenuity, there's no need to use water to get rid of liquid waste any more. Even though it sounds gross, flushless/waterless urinals received a 2006 Award for Design Excellence and have been endorsed by the U.S. Green Building Council. Best of all, if just 10% of conventional urinals could be converted to waterless, 200 billion gallons of water could be saved each year.
How does it work? The flushless urinal contains a liquid consisting of alcohol and mineral oils, which are lighter than the urine which flows through the liquid and down the drain. There's a special cartridge that replaces the conventional drain that makes this possible. It wouldn't be much fun to be the poor soul who has to change those cartridges, though.
No Flush: Let the Yellow Mellow [Wired News]