I was told some months ago that paper and cardboard recycling processes need clean raw material. In particular, paper stained with oil may be inappropriate to recycle, and should rather be thrown away.
Where I live we separate our waste between:
- paper, cardboard, recyclable plastic containers, metal cans
- garbage, that is, everything else
When I happen to have a used pizza box, it is often stained with oil.
As I am not aware of the chemistry that is at stake for paper/cardboard recycling, I don't know if I should throw the oily pizza cardboard in the recycling or the trash. More finely, how oily can the cardboard be and still be a good candidate for recycling?