The outer casing is used to rebuild the cartridge. They split the cartridge and replace the insides such a drum, cleaning blade, charge roller, and seals. Then sell it as a compatible cartridge. There is nothing inside that is recyclable just replaced. Some companies will pay for empty OEM cartridges. Using compatible cartridges is ok. I worked in the copier/printer industry for 32 years and I use them. The key is where you get them from. Anyway, hope this answered your question.