Yesterday, my roommate approached me holding an empty plastic granola container from Whole Foods and asked if it could be put in our household recycling bin. My instinctive response was, “Yea, of course. Doesn’t it have the little arrows in a triangle with a number in the center? Then it is recyclable.” As she walked away to toss it, I thought, “Shoot. I better look that up…” I have been recycling plastics all my life but I don’t think I ever actually learned what the numbers mean in the center of the recycling symbol. Well, here is what I learned:

The number on plastics actually represents the type of plastic used in the manufacturing of that particular plastic product. Plastics are often called “resins” and the numbers are called “Resin ID Codes”. The numbers are also there to tell you which plastics are best for reusing and how to appropriately recycle them. There are seven Resin ID Codes used and they all differ in what they are made of, safety, how they should be recycled, whether they are reusable and what they can be made into after being recycled.

#1 : PET or PETE (polyethylene terephthalate)
Found in: soda, juice, water and beer bottles, mouthwash bottles, oven-ready meal trays, peanut butter containers, salad dressing containers and vegetable oil containers.
Warnings: it is a porous plastic that allows bacteria and flavor to accumulate, therefore they shouldn’t be reused or refilled for personal use.
Recycling: picked up by most curbside recycling programs
Recycled into: fiber, tote bags, furniture, carpet and polar fleece.

#2 : HDPE (high-density polyethylene)
Found in: milk jugs, detergent bottles, butter tubs, personal care product bottles, cereal box liners, and some trash and shopping bags (it is an opaque plastic).
Warnings: none
Recycling: picked up by most curbside recycling programs
Recycled into: laundry detergent bottles, oil bottles, fencing, pens, recycling containers, floor tile, and benches.

#3 : PVC (vinyl or polyvinyl chloride)
Found in: plastic cling wraps, many children’s toys, detergent and window cleaner bottles, cooking oil bottles, medical equipment, shower curtains, and fashion accessories.
Warnings: it contains chlorine and during manufacture it releases highly toxic dioxins, not safe to cook food with or near, contains phthalates which can interfere with hormonal development and should never be burned because toxic chemicals can be released.
Recycling: rarely accepted by recycling programs.
Recycled into: decks, mudflaps, roadway gutters, cables, speed bumps and mats.

#4 : LDPE (low-density polyethylene)
Found in: grocery bags, some food wraps, squeezable bottles, clothing, carpet, furniture, and bread, frozen food and dry cleaning bags.
Warnings: none
Recycling: recyclable but not often accepted by curbside recycling programs (but many stores will often take back shopping bags after use.)
Recycled into: trash can liners and cans, shipping envelopes, floor tiles, compost bins and paneling.

#5 : PP (polypropylene)
Found in: syrup bottles, ketchup bottles, some yogurt containers, caps, straws, medicine bottles, many reusable food and drink containers (think Tupperware and Rubbermaid), and some baby bottles.
Warnings: none
Recycling: recyclable through some curbside programs.
Recycled into: signal lights, brooms brushes, ice scrapers, battery cables, trays and bins.

#6 : PS (polystyrene) (Styrofoam)
Found in: disposable containers and packaging: foam trays for meat and fish, egg cartons, vending cups, plastic cutlery, protective packaging for electronic goods and toys.
Warnings: it has been found to leach styrene–a neurotoxin and possible human carcinogen, and should not be heated.
Recycling: difficult to recycle, often not accepted by curbside recycling programs.
Recycled into: insulation, light switch plates, rulers, foam packing and carry-out containers.

#7 : Other (miscellaneous plastics invented after 1987)
Found in: iPods, computer cases, baby bottles, food storage containers, three and five-gallon water bottles, “bullet-proof” materials, DVDs, and nylon.
Warnings: unsafe sometimes because some contain BPA, a hormone disruptor, and Polycarbonate or PC (found in old Nalgene bottles).
Recycling: difficult to recycle, often not accepted by curbside recycling programs.
Recycled into: custom-made products and plastic lumber.

Thanks to EcoVillageGreen, The Daily Green, and Planet Green, I learned a lot today!

Because recycling rules vary in each community, we are so glad there are great sites like Earth911.com that allow you to look up nearby recycling centers and programs in your area. We also encourage you to be green by supporting companies that use recycled products like Boston’s own, Preserve Products.