Contamination is everywhere when it comes to recycling. Sometimes people want to recycle as much as possible, and figure that anything tossed in a recycling bin will be recycled in some way.
Contamination is the quickest way that an entire batch of recyclables will end up in a landfill because of a few outsiders. This is especially true when it comes to paper, since you rarely find a paper product that is entirely made of paper.
1. Food Waste
Paper is recycled by mixing shredded fiber with water to make new pulp. Oil and water don’t mix well, so oil stains won’t simply dissolve in the water. Instead, you’ll get new paper that still has oil stains. Common Example: Pizza boxes
2. Hazardous Products
Anything that comes into contact with paint. When you’re painting the walls, you don’t want to get the floor dirty, so often people lay down newspaper. Well, if paint drips on the newsprint, it belongs in the trash.
3. Plastic/Wax Lining
Linings are added to many paper products for a number of reasons like, temperature control, leak control, and strength and durability. Plastic and wax lining is too difficult to separate during the recycling process. Common Example: Paper cups (use reusable mugs!)
4. Pressure-Sensitive Adhesives (Stickers)
Anything that you can peel and stick without moisture. They are difficult to filter out and don’t dissolve in water (although the adhesive does), meaning they could be lodged in equipment.Common Example: Sticky notes
5. Wet Paper
You may be wondering why wet paper is a contaminant if the paper will be drenched with water prior to recycling anyway. The answer is that exposure to water shortens paper fibers, making it less valuable. If your curbside program or local recycling center can’t sell the paper to a mill, there’s no point in collecting it for recycling.
this information is from the RecycleBank website