Yes and no. Paper mills require clean paper for recycling. If you remove the insert of have a pizza box without grease on it, then it can be recycled. If the box has cheese or grease residue on it, then it cannot be recycled. It would be considered a contaminant and must be put in the trash. If you have a pizza box that is greasy on the bottom, but the lid is free of grease, then you can separate the two sections, placing the clean lid in the recycling container and the greasy bottom in the trash.