Don’t: Just toss it to the curb for the trash guys.

Do:
Haul it to the nearest recycling location, operated by the Southern Nevada Christmas Tree Recycling Committee. Springs Preserve is one spot, for instance, and with more than 30 drop-off points, you should be able to find a convenient one. The trees will be mulched for use in parks and so on. Also, it's free.

Wait, they’re
 still doing that? Yes — but only through Saturday.

Why bother?
“When we recycle trees, we’re diverting waste from landfills, conserving water, and beautifying our local communities,” a committee spokeswoman told the Review-Journal.

I suppose you have some interesting contextual facts?
Yes! The committee has recycled more than 300,000 trees since starting the program in 2001. That's a lotta mulch.