Many people seem unaware that empty laser printer toners and cartridges can still pose a small health risk, especially if found by children or chewed on by pets. The best way to deal with them is, of course, to take them to a recycling center directly, and, if you work in an office that prints often, you should make sure that an adequate recycling program is in place.
Another option is to place the empty cartridge in a tight container or a Ziploc bag, until you find the time or the opportunity to dispose of it properly. Sadly, millions of empty cartridges end up every year in landfills, even if we’re now so careful about recycling everything else. Most producers provide information about collection centers on the package, so you might want to keep that around, or just make a note of the information and use it at the right time. Even if you don’t print too much, and it’s just your home printer cartridge, you should still take the appropriate measure to dispose of used laser toners in a safe way.