A carboy cannot handle pressure.
I recycle my CO2 two ways: first, I have a gadget that lets me connect a keg to the water line. When I pull the empty soda water keg out of the kegger, it has 30 psi of CO2 in it. This gets absorbed as the main pressure forces water into the empty keg.
Second, I use floaters to force cleaning solution through tubing, faucets, etc. I have a short hose with two gas connectors & connect the floater to a keg of solution.
Ain't being cheap, it's 40 miles to the welding shop and they aren't open on weekends.
Remember one unassailable statistic, as explained by the late, great George Carlin: "Just think of how stupid the average person is, and then realize half of them are even stupider!"
"I would like to die on Mars, just not on impact." Elon Musk