FAQ: Contamination & Recycling

Help us make mixed recycling a success on campus by recycling properly and avoiding contamination.

Q: Where does our waste go?

A. Our recycling goes to All County Recycling in Trenton, NJ. Our landfill waste is sent to the Tullytown Landfill in Tullytown, PA. In the dining halls and Frist Campus Center, all food scraps from the kitchen as well as plate scrapings and napkins are sent to AgriArk, based in Hopewell, NJ where they are processed into biological soil amendments.

Q: What is contamination?

A: One of the challenges to mixed recycling is the increased potential for contamination. Too much contamination is the reason manufacturers reject tons of recyclables. Contamination happens when non-recyclable items are put in with recyclables or when recyclables are soiled with food or oils. Paper products covered with food or grease cannot be processed with clean paper and can ruin a newly made product if it is not caught before it leaves the recycling center.

All County Recycling in Trenton, NJ

Q: Why can't I recycle ____?

A. The recyclability of plastics as well as metals, paper etc., depends on 1) available downstream markets 2) ability to properly sort and separate material at the designated material recovery facility, or MRF for short, and 3) willingness of the local material recovery facility to accept the material. 

“Over-recycling”,  or putting non-recyclable materials in a recycling bin, jeopardizes the success of the whole program. For example, wire hangers are often placed inside mixed recycling containers because they are metal. However, wire hangers can damage sorting machines and are therefore not accepted. Not all glass is created equal either. Sometimes lightbulbs or broken panes of window glass are mistakenly placed in single-stream recycling. These glass shards often wind up in cardboard or paper bales at the end of the recycling process, leading to the contamination and eventual rejection of the valuable paper or cardboard bales downstream. 

Q: Can I recycle plastic plates with a small amount of residual food?

A: Provided they are recyclable (#1-5), the best way to handle the plates is to rinse or wipe off the food residue before putting it in the bin.

Q: What should I do with slightly soiled paper food containers, paper towels, paper plates, paper napkins, or paper cups?

A: Although these items are paper, when they become soiled with food or other contaminants, they should be placed in the bins marked landfill, with the exception that napkins can be disposed of with food scraps in the dining halls and Frist. Additionally, many paper products have a thin plastic lining to provide strength and prevent leaking. This plastic lining is considered a contaminant in the pulping process. For example, pizza boxes and other to-go containers have these liners. Paperboard food containers such as cereal boxes, paper egg cartons, and cake mix boxes that are unsoiled are recyclable. Please be sure to remove the plastic liner and shake out extra food crumbs before recycling.

What do the numbers in the triangles mean?

A. The numbers found within triangles on plastic items designate resin type. These numbers were created by the plastics industry to identify the type of plastic resin the product was made from - not the recyclability of the product. Chasing arrow triangular symbols are often placed on items to show that an item was either made from some amount of recycled material or can be recycled after use. The symbol itself does not guarantee recyclability. The chasing arrow symbol is not regulated by any governing body since the symbol was never patented in the 1960's when it was created.

If you are unsure if an item is recyclable, please email sustain@princeton.edu or call 609-258-6085.

For more recycling information, visit our Recycling page.

Adapted from Stanford University.