Wow! It’s always great to hear when materials that were not accepted before now can be accepted for recycling! This is a very interesting study. As your article states though, only 21% of municipalities explicitly state that they accept pizza boxes. So, residents should still check with their local recycling program to see if they accept this item before just throwing it in the bin. Differences in machinery and recycling feed buyers in the area are two main contributors to why a facility would accept or deny any given item, so while your article does show hope that these will eventually be universally accepted, it does not mean residents should throw greasy pizza boxes in their bins because they hope they can be recycled. Always check your specific program first to avoid recycling contamination at your facility. We do recommend to remove the greasy part and recycle the clean part of the box at least if your facility doesn’t accept this item yet.

https://www.greenbiz.com/article/grease-and-cheese-study-proved-pizza-box-recyclability

Any recyclable container must be empty and clean. If it’s for plants, then I would suggest wiping the dirt out with a cloth. Be care though because many recycling programs do not accept black plastic. Check with your local program to see if that item is accepted.