Skip to main content
King County logo

Resin codes

Resin codes are indicated by the small number enclosed by the “chasing arrows” symbol on the bottom of many plastics. These codes were developed by the Society of the Plastics Industry (SPI) in 1988 to provide an industry-wide standard that would make it easier to identify and sort recyclable plastic.

Resin codes are often misleading to the consumer because they were not intended to indicate if the plastic is actually recyclable. Rather they indicate what general type of chemical compound is used to make the products. The codes are not a guarantee to consumers that a given item would be accepted for recycling in their community.

Although there are only seven resin codes Download PDF , external link there are actually thousands of different types of plastic. Different combinations of dyes and additives can be added to the basic resin to produce a desired color, shape and texture in the final product. These variations in the manufacturing process lead to different melting points and other properties within the same resin code.

To be made into another product, plastic must be carefully sorted by type, and therefore not necessarily by resin code. Combining different types of plastic, even of the same resin code, may decrease the value of the plastic recyclers or make it more difficult to manufacture.

Recycling different plastic types in king county

The technology exists to recycle most types of plastic, but a lack of markets prevents all but the most common kinds of plastic from being recycled. Only a few kinds of plastic have the supply and market conditions that make recycling possible. Collection is expensive because plastic bottles are light yet bulky, making it hard to efficiently gather significant amounts. In King County, plastics collected at curbside are those that consumers generate in the largest amount (bottles and jugs) and for which there are markets. For more information about King County curbside recycling the Residential Quick Guide to Recycling.

To make it easier for the consumer to understand which plastics can be recycled, King County removed the resin code categories from What do I do with…? and arranged the plastics by categories of plastic materials that are recyclable:

  • Bottles, jugs and tubs
    These are valuable in the recycling market and include plastic jugs with a neck (milk, juice, and pop bottles), plastic bottles with a neck (beverage, fabric softener, detergent, and window, bathroom and kitchen cleaners), and round plastic dairy tubs (yogurt, dairy, and butter or margarine). These materials are accepted in your King County curbside recycling bin, at some transfer stations and by plastics recyclers. All materials should be rinsed and should not include caps or lids. This category does not include “clam shells” or other food take-out plastic containers. Plastic recyclers will also accept large quantities of these plastics.
  • Plastic film and grocery bags
    Plastic film includes dry cleaning bags, bread bags, newspaper bags, pallet wrap, and shrink wrap as well as plastic grocery bags. Plastic grocery bags may or may not be accepted in King County curbside recycling collection programs. Contact your local hauler to find out what is accepted in your King County curbside recycling bin. Clean plastic bags taken back to participating retail and grocery stores for recycling have a higher value than those collected at the curb. The bags are baled with other packaging plastics and may be sold for remanufacture into plastic lumber. Some stores may give a small rebate for reusing them during your shopping trip. When dropping bags or film off at a plastics recycler, shake them clean, place all types of plastic bags or film into one plastic bag, and use the bag handles to tie it shut. See below for more information about biodegradable and compostable plastic bags.
  • Packing peanuts and polystyrene
    Packing materials include packing peanuts and expanded polystyrene (EPS) blocks. These materials are not accepted in your King County curbside recycling bin. Packing peanuts are the small Styrofoam™ “peanuts” found in many packages shipped through the mail. Packing peanuts are not recyclable, but they are reusable. Many gift stores or shipping centers will accept clean packing peanuts free of charge to reuse in packaging or shipping. EPS blocks are commonly used in the packing of electronics and may be recyclable – visit the What Do I Do With…? website for recycling options. This category does not include clam shells or other food take-out containers.
  • Nursery pots
    Nursery pots include round or square pots made from low grade plastic. They are not accepted in your King County curbside recycling bin. Some nurseries and plastic recyclers will accept nursery pots for reuse or recycling. When recycling nursery pots, shake out loose dirt and stack according to size.
  • Plastic office supplies
    This category includes transparencies (such as overhead transparencies used in classrooms) and Tyvek® Envelopes (thin, water/rip resistant plastic envelopes). These types of plastics are not accepted in your King County curbside recycling bin. A few businesses may accept these for recycling through mail-in programs.
  • Agricultural plastic
    Agricultural plastic includes empty plastic pesticide containers, plastic twine, irrigation pipe, bale wrap, mulch film and other plastic films. They are not accepted in your King County curbside recycling bin. Some plastic recyclers will accept these plastics. For better recycling, keep like items together, as dry and clean as possible and out of the sunlight.
  • Mixed plastics and other types of plastics
    Many other types of plastic, such as vinyl banners, disposable Tyvek® clothing (shoe and boot covers, coveralls, hoods, lab coats, aprons, sleeves and pants), and large quantities of other plastics may be recyclable. These types of plastics are not accepted in your King County curbside recycling bin. Vinyl banners and Tyvek® clothing are accepted by only a few businesses.  Large quantities of mixed plastics may be accepted by local plastic recyclers on case-by-case basis. Call in advance to see if they will accept your material.

What about biodegradable and compostable plastics?

There are other types of plastic that may be labeled biodegradable, compostable, or degradable. It is important to know the difference between these plastics when choosing how to use and dispose of them:

  • Degradable (or “oxo-degradable”) plastic is an oil-based plastic containing a chemical additive that causes the plastic to break down into smaller pieces. The residues of oxo-degradable plastics are not food matter for microorganisms and are not biodegradable or compostable by local standards. Currently, there are no recycling providers in King County that accept oxo-degradable plastics in any form. These plastics, including degradable bags, belong in your garbage.
  • Biodegradable and compostable plastics, also called “greenplastics” or “bioplastics”, are often made from products like cornstarch. Biodegradable and compostable plastics biologically degrade or break down during the composting process. During this process carbon dioxide, water, inorganic compounds, and biomass are produced. At the end of the process, these plastics leave no visual or toxic residues. These plastics cannot be recycled and do not belong in your King County curbside recycling bin. Biodegradable or compostable bags should be labeled either “Biodegradable” or “Compostable”, or have the Biodegradable Products Institute external link logo:
    Biodegradeable Products Institute logo

For King County residents, biodegradable and compostable bags are the only form of “bioplastic” currently accepted in curbside yard waste bins. These bags can be filled with yard waste and food scraps and placed in your yard waste bin. Check the Cedar Grove Composting website external link to view a list approved biodegradable/compostable bags that can go in your curbside yard waste container.

All other “bioplastics” should go in your in your garbage. However, if you are planning a large event, such as a wedding, contact Cedar Grove Composting external link on a case-by-case basis to find out how to use and properly dispose of other “bioplastics” such as plates, cups, and eating utensils.

Contact Us

 Call: 206-477-4466

TTY Relay: 711

Fax: 206-296-0197

King County Solid Waste Division mission: Waste Prevention, Resource Recovery, Waste Disposal