No significant technical reason to prohibit recycling of used pizza boxes:
> The general conclusion of this work is that the strength loss of the resulting product made with recovered fiber that incorporates post-consumer pizza boxes should be minimal at typical levels of grease expected to be received in a recycling facility (<2%) and when included in the recovered fiber at expected levels of <3% of furnish. The addition of small amounts of cheese will not impact the fiber bonding in a negative way. It is expected that the larger chunks of cheese will be screened out of the process. Therefore, there is no significant technical reason to prohibit post-consumer pizza boxes from the recycle stream.
Impacts of Grease and Cheese on the Recyclability of Pizza Boxes · HackerTrans
> The general conclusion of this work is that the strength loss of the resulting product made with recovered fiber that incorporates post-consumer pizza boxes should be minimal at typical levels of grease expected to be received in a recycling facility (<2%) and when included in the recovered fiber at expected levels of <3% of furnish. The addition of small amounts of cheese will not impact the fiber bonding in a negative way. It is expected that the larger chunks of cheese will be screened out of the process. Therefore, there is no significant technical reason to prohibit post-consumer pizza boxes from the recycle stream.