You can build or buy a filament recycling machine. The issue is that it costs more than a 3D printer, and often times the filament is not as good later, so you

You can build or buy a filament recycling machine. The issue is that it costs more than a 3D printer, and often times the filament is not as good later, so you end up spending time and energy recycling when it would be less time and energy to create new filament. It would probably be better to put that time and money into insulating your house and growing flowers for local birds and bees.