Right next to the bay where they sell new tubes, HD have a cover in plastic with one removable end cap. Its slightly bigger in diameter than the tube. You take off the removable end, slide the old tube in, replace the removable cap, put it over a garbage bin, hit the cover with a hammer, the tube shatters, take off the removable end, and finally pour the (by now tiny) shards of class into the bin. There seems to be a little smoke or maybe dust. You could put on a hazmat suit and a respirator if you're a real wuss. The garbage bin empties into a black bag which is compacted by the garbage truck together with hundreds of other peoples' garbage and goes (guess) to a landfill in some flyover state.