From original cartridges, after they run out of inks, users may either send them back or deliver it directly to many recycling facilities. Then, returned cartridges undergo sorting and cleaning, by removing any harmful metals and non-plastic materials from each container. We're talking about recyling plastic-made materials, thus any other components aside from plastic must be separated. Afterwards, here goes the famous grinding process where it harshly chopped and cut all those cartridges into tiny little pieces.
After grinding and shredding, extra ingredients were added into the mixture such as shredded PET bottles and the likes, to make them more sturdy and pliable just like a new cartridge made from virgin materials. The mixture is then toss into an enormous V-shaped blending machine to grind the materials again and let all the components blend well. The raw mixture will be extruded from the machine, which then be used for manufacturing new replacement cartridges.
Indeed, it's more likely easy to refill a small container with inks or toners, but considering the ecological impacts of doing such thing, I'd gladly reject the option. Choosing eco-friendly toner cartridges and ink cartridges for all printing needs is still way better than any other options available. Instead of manufacturing new printer cartridges using virgin materials from our natural resources, why not invest on establishing more recycling plants. Quality control plays a key-role in the recycling process. It may seem too complicated right now but economically and environmentally speaking, printer cartridges recycling has a lot of good points.