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Frequently Asked Questions: Plastic Recycling

Q: What type of plastic containers can be recycled at the Stanford Recycling Drop Off Center?

A: The Stanford Recycling Drop Off Center accepts all plastic containers in three categories: #1 PETE, #2 HDPE clear plastic containers, and #2 HDPE colored plastic containers. We do not accept #3-7 plastics nor #6 expanded polystyrene (also known as Styrofoam). Look for the number inside three chasing arrows on the bottom of the container and lids. The number inside the chasing arrows just identifies the type of plastic the container is made of, not necessarily its recyclability. If it is not a plastic container or it doesn't have a number inside of the chasing arrows on it, then we do not accept it.

Please remember to separate caps and lids and place both in the recycling bin. If possible, rinse and flatten container before putting in the recycling bin.

Q: Is the cap of a recyclable plastic bottle also recyclable?

A: Yes, the cap recyclable, but it is usually made of a different type of plastic than the bottle which is why it is important to separate the cap from the bottle and place both in the recycling bin. It is important to separate the plastic bottle from the lid because if left together the two types of plastics would contaminate each other. The different types of plastics must be separated before the recycling process begins because the seven different types of plastics are incompatible with each other.

Q: What steps should I take to recycle my plastic bottles?

A: Empty the bottle, seperate caps and lids and place in plastics, metal, and glass recycling bin on campus or in the correct recycling bin at the drop-off center.

Q: What happens to plastic bottles once I place it in the recycle bin?

A: Collectors empty all of the recycling bins and bring the material back to the Stanford Recycling Center. The center separates the different materials and ships them to processing plants. After we ship them to the market, the plastic bottles are chipped into small flakes, washed, melted and turned into pellets which are sold the plastic bottle manufacturers who make new bottles or other plastic products.

Q: Can I recycle plastic bags, bubble wrap, air pillows, and dry cleaning bags?

A: Yes, plastic grocery or merchandise bags, bubble wrap, air pillows, and dry cleaning bags can be recycled at the Stanford Recycling Drop-Off Center. To be sure this is a successful program, please place only the types of bags requested and remove all receipts, other packaging material, and any food residue. It does not matter if the recycling symbol is not on the bag or if a certain number is inside the chasing arrows on the bag. They can all be placed in the plastic bag bin.  These items can also be placed in the paper recycling bins on campusPlastic bags that contained packaged food or prepared food (i.e. salad bags, cereal bags, chopped vegetables) or resealable bags (i.e. nuts, laundry detergent) are not recyclable.  These must be landfilled.

Plastic bags cannot be recycled with rigid containers because they have a different melting point. The plastic bags melt very quickly compared to rigid containers and therefore cannot be used in the same process.

Plastic bags can be reused and most grocery stores have recycling bins near the front door for plastic bags as well. Instead of using a plastic bag, try using durable canvas bags on your next shopping trip!

Q: Can I recycle old photographs and negatives?
A: No, we cannot recycle these materials.

Q: Can I recycle Styrofoam?

A: Reuse them if you can! Polystyrene (also known as Styrofoam or #6 plastic) packaging materials (peanuts or large blocks) are not accepted in Stanford’s recycling programs. Call 1-800-828-2214 to find the location of the nearest packaging store or business that accepts packing peanuts for reuse. If you decide to throw them away, please put the material in a bag so they do not fly around and litter the ground when the garbage can is being emptied. As of January 2009, the Palo Alto Recycling Center no longer accepts Styrofoam for recycling.

Q: Can lab plastics be recycled?

A: Yes, all plastic containers from labs on campus can be recycled in the Plastics, Metals, and Glass recycling bins.  We also recycle plastic bags, air pillows and bubblewrap - but you must put that material in the paper recycling bin.

Before you recycle your lab containers, please be sure that your bottles are truely empty by following the Empty Container Tree found on the EHS website:

Q: Can pipette trays be recycled? 
A: The best way to handle pipette trays is for the manufacturer to take them back for recycling.  There are three companies that we are aware of that do take back their trays: 1) VWR, 2) E&K Scientific, and 3) Rainin. They will only pick up their own product. If that is not an option, you can place them in the Plastics, Metals, and Glass recycling bins.

Q: Can aseptic and carton containers be recycled?

A: Yes, aseptic and carton containers including juice and milk cartons and soy milk containers along with other containers in the plastics, metals, and glass recycling bin.

Aseptic containers also known as a carton hold primarily beverages such as milk, fruit juice and wine. These containers are made of high quality paper and polyethylene. Some of the drink boxes have a small percentage of aluminum.

Once collected, aseptic boxes are hydropulped to separate paper fibers from plastic and aluminum foil. Mills value the fiber recovered from aseptic packaging because of its strength, length, and brightness. Depending on the markets, the plastic/foil residual can also be recycled into high-end plastic lumber products.
Source: Carton Council

Q: Why does one community recycle one type of plastics while another community doesn't?

A: Not all plastics are the same nor can they all be recycled or recycled easily. Something is only recyclable if there is a company out there who is willing to use it to make a new product. If there is no one who will accept the material and make a new product out of it, then it is not recyclable. There may be a company that uses the material to make a new product somewhere in the world (say Southern CA), but the transport costs to get the material to that factory would cost prohibitive therefore the material would be deemed unrecyclable in our area (but not in Southern CA, in this example). With plastics in particular, how the plastics are put together (molded or extruded) changes their chemical make up and make them non recyclable in certain applications.

Q:How many water bottles are recycled and why should we recycle them?

A: An on-the-go society combined with masses of health conscious consumers has turned the single serve bottle of water into a national icon. Now, according to a report released by the CalRecycle, billions of these empty “icons” are causing serious environmental problems.

According to the report, more than 1 billion water bottles are winding up in the trash in California each year. That translates into nearly 3 million empty water bottles going to the trash EVERY day and an estimated $26 million in unclaimed California Refund Value (CRV) deposits annually. If recycled, the raw material from those bottles could be used to make 74 million square feet of carpet, 74 million extra large T-shirts, or 16 million sweaters, among other things.

So, what can we do to increase bottle and can recycling? Look for recycling bins at the places you visit. More and more parks, amusement parks, concert halls, gyms, and other places where beverages are consumed away from home have recycling bins for bottles and cans. If you can’t find one, ask about it. The more these places hear from their customers the desire to recycle, the more likely they are to place recycling bins. If all else fails, bring the bottle home and place it in your curbside recycling bin or redeem it yourself at a redemption center.  For more information, please visit

Q: What do the numbers on the bottom of the container mean?

A: There are seven types of consumer plastic or resin. Each has different qualities that a company might want to package its product.  The number you see on the bottom is an identification code not a recyclability code.  The code is used to sort the different plastics so they can be used to make a new product. 

Q: What are the seven types of plastic?

A: There are seven types of consumer plastic or resin. They are identified by a number inside three chasing arrows.

#1 PETE: Polyethylene Terephthalate. 
Commonly used in soft drinks, juice, and cough syrup containers and microwave trays.

#2 HDPE: High Density Polyethylene. 
Commonly used in milk jugs, detergent and shampoo bottles.

#3 V: Polyvinyl Chloride. 
Commonly used in film for meat packaging and some rigid plastic containers.

#4 LDPE: Low Density Polyethylene. 
Commonly used in newspaper and grocery bags and butter cups lids.

#5 PP: Polypropylene. 
Commonly used in yogurt containers and deli trays.

#6 PS: Polystyrene. 
Commonly used in plastic cups and plates and to-go containers.

#7 OTHER: Other mixed resins. 
Commonly used in mixed plastic containers or plastic products.

The Stanford Recycling Drop Off Center accepts all plastic containers in three categories: #1 PETE, #2 HDPE clear plastic containers, and #2 HDPE colored plastic containers. We do not accept #3-7 plastics nor #6 expanded polystyrene (also known as Styrofoam). Try not to accept polystyrene or take it back to the place that you got it and ask them to take it back.

Q: What is PETE Plastic?

A: Confused about recycling plastics? You are not the only one! There are seven types of consumer plastics. Each has certain qualities that manufacturers desire to package their products in. Most plastic containers are identified by a number inside three chasing arrows located on the bottom of the container. Because each plastic has certain characteristics, they must be identified and recycled separately. PETE stands for Polyethylene Terephthalate and is also known as #1 plastic.

PETE is a commonly recycled household plastic material. It represents approximately 30 percent of the plastic bottle market and is used to package a wide variety of food and beverage products such as soft drinks, juices, edible oils, liquor, and peanut butter.  PETE is valued for its clarity, toughness, and ability to resist permeation by carbon dioxide. Products made from recycled PETE included carpets, insulating material in garments and sleeping bags (fiberfill), strapping, bottles, containers, scouring pads, auto parts, paint brushes, and geotextiles, such as landfill liners.

Q: What are some of things that #1 PETE Plastic can be made into?

A: Thirty-five percent of the polyester carpet made and sold in the United States contains PETE plastic. It takes five two-liter PETE bottles to make one square foot of polyester carpet. Recycled PETE is used to make T-shirts too. Just five of these bottles yield enough recycled PETE to make an extra large T-Shirt. Your bottle and help keep you warm too! It could be the fiberfill in your ski jacket or sleeping bag. PETE containers can also be made into tennis ball felt, combs, cassette tapes, car bumpers, sails for boats, parts for cars, furniture, and even other bottles. All we have to do now is create a demand for these products!

Q: What types of products are packaged in PETE containers?

A: More and more products are being packaged in plastic containers instead of steel or glass. It is important to pick the product that is packaged in a recyclable container. The following are the types of products that are being packaged in PETE plastic or recycled PETE plastic. Since more and more new products are being packaged in recycled content PETE, this list is changing constantly. Sports Drinks Bottled Water

  • Soft Drinks Liquor
  • Fruit Drinks Tonic Water
  • Cough Syrup Mouthwash
  • Liquid Cleaners Dishwashing Liquid
  • Cooking Oils Salad Dressing
  • Salsa Spices
  • Instant Coffee Popcorn
  • Mustard Ketchup
  • BBQ Sauce Mayonnaise
  • Peanut Butter Tennis Balls

Shop smart, look for these products in the grocery store and check for the identification code (a one inside three chasing arrows). Once you are done with it you will be able to recycle it instead of throwing it in the garbage.

Q: PETE bottles can be recycled back into food and beverage containers. True or False?

A: True, PET bottles can be recycled into food and beverage containers using technologies reviewed by the Food and Drug Administration.

Q: What is the difference between blow molded and injection molded plastic and why does it matter?

A:  Plastic bottles are "blow molded." This means the shape is made by blowing air into a mold, similar to blowing air into a balloon. The tub- or cup-shaped plastic and other plastic packaging are "injection molded," whereby the plastic is "stamped" into its shape. These plastics cool and melt at different temperatures, and therefore are not compatible in the reprocessing stage. We collect both types in the same bin.