If you pee in the toilet, you gotta flush, or else it stinks (smelly pee sitting in a bowl). That “wastes” gallons of water, when/if you flush. (Water is everywhere, so is it really " a waste"?) But if you pee in the sink, you don’t need to flush. Maybe spigot “a spritzer” to wash it down, saving water. So, thus: is it more environmentally friendly to pee in the sink
Yes.
Hence, waterless urinal.
And, there is no reason to put waste in quotes. Water may be everywhere, but clean, drinkable water isn’t, and is an increasingly valuable resource.
We have those at many of our buildings in the state. They have signs over them saying 40,000 gallons of fresh water saved a year, and it’s easy to believe that they save quite a bit. Not sure why, especially here in the south west, everyone doesn’t go to these things. There must be a reason, but I’m not seeing it. It saves water AND must save money too, so why not adopt them or put them in when the old ones go bad?
Huh. I’ve been in mensrooms where someone was peeing in the sink. I never realized they were environmental warriors.
Keep in mind that if you pee in the sink, urine mist will be deposited all around the sink area. It’s one thing to discuss this from a theoretical standpoint, but in practice it would end up with urine in lots of places that people typically wouldn’t want it.
In my experience they clog up more easily. Or at least, in places that have them I often see one or more of the urinals full of pee. I think they are more sensitive to what goes down them than traditional urinals, if you get my drift.
Sounds so much better than “line jumper” at halftime of an NFL game; I’ll need to remember that. 
In some places the water is coming out of wells that are depleting the aquifer (see Ogallala Aquifer for example; most of the usage is agricultural, but toilet-flushing doesn’t help).
In any municipal water supply, the water has been processed and treated to ensure it’s potable, and then distributed through a piping network. Any increase in demand increases the required capacity of that system, and therefore adds cost. If the usage is deemed necessary (e.g. to keep people from peeing in the sink), then it’s not really a waste. But if there’s a way to accomplish the same task (i.e. human waste removal) using less water than the old way, then yes, the old way can be deemed wasteful.
One of the office buildings near us had the waterless urinals. They eventually took them all out, not sure why. However, one thing I heard from a plumber was that urine crystals can eventually build up and clog a drain (often a problem for those old washrooms where the urinal flusher failed and the stuff never fully flushed). Proper flushing prevents this - no standing water, so to speak. So the most environmentally sensible system is the sensor-based flush systems.
How many remember the regularly timed flushes in the good old days - happened right on schedule, even if you were standing there - and probably went on all night long when nobody was using them? Plus flush on demand reduces the amount of time urine sits in the drain before it is flushed.
How can a waterless urinal NOT smell?
They don’t have a nose, as far as I know…
A patented vertical eco trap, of course!
The bathtub is a lot easier. Fill a pitcher with water while your shower is warming up and use that for flushing. Every few days add a little bleach to the pitcher of water.
Well, I know of one building that’s had them over 10 years. Now, I don’t go to that building that often, but I’ve never seen them clogged. Also, there isn’t really any smell…well, none worse than any other male bathroom I’ve been in. 
I can see them getting clogged more easily though, sure. I don’t think people in these buildings are going to toss other, um, things in them, but if they did they would certainly clog (there is a screen thing that seems hydrophobic…when you pee it doesn’t stick to the bottom or sides but definitely goes down the drain, but if you put other things in there it would certainly clog that screen).
Still, seems like a great way to save water, and I’ve noticed a lot of other buildings in the same organization going that way and replacing even the automated flush style ones with these kind.
Be sure you’ve finished your bath first. 
The waterless urinals I saw had a sort of pop-up cover on the drain; it seemed to pop up enough to drain the stream so to speak; then popped backdown. The things still smelled but not as bad as you’d think.
Brillant!
I was kinda desperate once, while on a volunteer thing. Female restroom was locked up for some reason, so me and friend planned for me to go into an empty Male restroom, and her guard the door. As I had no choice I went in. Oh, my freakin’ kidney pain, those waterless urinals smelled so gross. I passed about 20 in a row to get to the stall. It was as gross as well. I’ll pee my pants next time. Mens, y’all be nasty.
ETA, the floor was also sticky, why was that?
Some modern toilets have two half-buttons that you press for flushing. One has a single drop design on it while the other will have two/multiple water drop design in the metal. Pressing the single drop gives you a reduced water flow flush & is adequate for urine while you use the “two for two”.
You don’t wanna know. Men’s rooms are disgusting filthy places whether or not the urinals flush. And unless they flush automatically they usually aren’t getting flushed anyway.
You probably didn’t notice or look, but my guess is it wasn’t the waterless urinals that smelled bad, but what was under them. There are always…and I do mean always…puddles UNDER the urinals. And this goes for the water kind or the waterless. It’s why you need to have cleaning staffs going in constantly.
And that answers your question about the sticky floor. Public men’s rooms are disgusting. Even the best ones in the cleanest buildings.