Urea
I have used Urea in the past. It is a nitrogen fertilizer. It burned the lawns along the edges of the sidewalks badly. I don't know if it was "overspray" when it was applied, or run off from the melt. Hard to say when it was applied to walks by up to 15 men at times.I can say it melted A LOT slower than salt does. This was at a school, and melting ice fast was a priority. I think it ended up that it was applied heavily to walkways in an attept to speed up the melting process. It didn't help it melt any faster. They went back to salt when the supply of Urea ran out, in fact, they had other schools in town "donate" more rock salt, and ended up throwing away quite a bit of the Urea (to help "run out" faster). One of the guys brought some home, since it is also a fertilizer. He applied it very lightly to his lawn in the spring, and it killed it completely.
Also, you really shouldn't use a walk behind spreader to apply de icer to walks without a "shield" on it to limit the spread width. Even then I recommend applying by hand, unless the walks are WIDE.
The Urea came in paper bags with a plastic liner like concrete and mortar come in. Not something you'd want to leave out in the back of your truck while it's snowing.
I'm with JCurtis, and John Parker, I recommend Magic, though it may not be available locally. Then again, John will ship anywhere in the continental US.
You can find out more about it at:
http://www.magicsalt.com
~Chuck