The fate of old notes is a critical issue for central banks that oversee their disposal. These notes cannot be thrown away like ordinary rubbish. Instead, central banks have developed standards to ensure the disposal is safe and secure.
This often involves a type of shredding that slices each note into hundreds of tiny pieces, each typically smaller than about thirty square millimeters. The shredded paper, or increasingly plastic, can then be disposed of, or recycled, off site.