If you need more propane, you can have the tank refilled or exchanged at a local retailer. A propane tank exchange is less expensive than buying a new one.
It is also possible to recycle your empty propane tank. Some retailers will accept unused or partially used propane tanks and will recycle them.
If you are unable to take it to a retail location, Waste Management Division will accept completely empty propane tanks at the metal recycling area.
For more recycling options, here are some helpful resources: