"Peeing in the sink is actually the green way to go, so you’re welcome. Instead of wasting 1.6 gallons of water on a flush, you pee in the sink. You then wash your hands in that very same sink, simultaneously washing down the urine and preserving nature’s most precious resource. Efficiency. A yellow-green solution, if you will."

Quoted by Neil deGrasse Tyson, when I asked him why was he in my house at 3 am.