Did you know? Recycling contamination can be defined as the introduction of “incorrect items/materials into the system” or the introduction of the correct items/materials in “the wrong way (e.g., food residue in containers, recyclables in plastic bags).”
Here are a few examples of curbside recycling contaminants:
Plastic bags are the “worst recycling [contaminants] of all.” They may get snagged in recycling facility machinery, thus causing damage to the equipment.
Freezer-food boxes have a glossy finish for the purpose of withstanding life in the freezer. Other items like this (e.g. paper coffee cups with an interior lining of plastic to contain the beverage) are also recycling contaminants.
Paper that is brightly colored all of the way through – paper that is only brightly colored on its exterior layers is acceptable; tear your brightly colored paper to check if the interior is white.
Loose plastic bottle caps (they must be kept with their containers1) 
Containers of hazardous waste (e.g. paint cans) – whether they are accepted at your local recycling program will vary based on your location. Check with your recycling facility!
Metal caps that match glass bottle must be disposed of separately; do not recycle the top and bottle as a unit.
Flattened containers (such as crushed aluminum cans) – single-stream sorting equipment separates flat material from round material, and may mistakenly send flattened containers through the paper-recycling process, contaminating the current batch of paper product.
Excessive food waste – rinse containers to make the lives of sorters less messy, as well as improve the recyclability of the item.
If contamination in a load of recycling becomes too great, all of the items will be sent to a landfill. Reduce and prevent recycling contamination by communicating with your local recycling service regarding recyclable and non-recyclable materials. If you’re unsure whether you can recycle a certain material in Ann Arbor, check here.