How to Dispose of Empty CO2 Gas TanksRecycle Them. The best way to dispose of empty CO2 tanks and cylinders is to recycle them with other scrap metal. Dispose of Them in a Landfill. If you don't wish to recycle your CO2 tank, you can also choose to send it to a landfill. Return Them to Their Owner. Refill or Resell Them.