Pick up almost any piece of plastic packaging and you’ll find a small triangle of arrows with a number from 1 to 7 inside it, usually molded into the bottom of a bottle or stamped on the underside of a container. Most people assume the triangle means “recyclable.” It doesn’t. It means “this plastic is made of resin type X” — and only a couple of those resin types actually get recycled in most American curbside programs.
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The numbers are properly called Resin Identification Codes, and they were developed in 1988 by the Society of the Plastics Industry (now the Plastics Industry Association) to help recyclers sort material — not to tell consumers what to put in the bin. The triangle of arrows around the number was deliberately chosen to look like the universal recycling symbol, which has caused a generation of confusion about what gets recycled and what just looks like it should be.
This guide explains what each number means, what gets recycled in practice, and where compostable plastics fit into the picture (spoiler: they don’t fit inside the triangle system at all).
A quick history of the codes
In the late 1980s, plastic packaging was growing fast, recycling programs were rolling out across the US, and material recovery facilities (MRFs) needed a fast way to identify what plastic they were looking at. Different plastics melt at different temperatures, have different chemical properties, and can’t be mixed in recycling streams without ruining the output material.
The Society of the Plastics Industry proposed the seven-code system. Each number identified one major resin type. The triangle was meant as a visual cue for sorters — and, the industry hoped, as a public-relations win that would associate plastic packaging with recyclability.
In practice, it produced widespread confusion. By the 2000s, the EPA and ASTM took over the code system (now ASTM D7611), removed the chasing-arrow triangle in favor of a solid triangle in the official version, and tried to clarify that the codes identify material — not recyclability. Most plastic packaging still uses the older arrow design.
The seven codes, plain English
1 — PET or PETE (Polyethylene Terephthalate)
Clear, lightweight, common in beverage bottles, salad dressing bottles, peanut butter jars, and clear deli containers. The most widely recycled plastic in the US. Sells well as bales to fiber and bottle-grade reprocessors.
Where it goes: back into bottles, into polyester fiber for clothing and carpeting, into food trays.
What to watch: PET bottle caps are usually a different plastic (often PP, #5) and may need to be separated depending on local rules. Most modern MRFs now want caps left on, but check your municipality.
Used by: Coca-Cola bottles, Aquafina, Dasani, most clear food packaging.
2 — HDPE (High-Density Polyethylene)
Opaque, sturdy, common in milk jugs, detergent bottles, shampoo bottles, motor oil bottles, some grocery bags. Second-most recycled plastic in the US.
Where it goes: into pipes, plastic lumber, new bottles, drainage products, some toys.
What to watch: HDPE in pigmented form (colored detergent bottles) is sometimes processed separately from natural HDPE (translucent milk jugs). Both are recyclable but they sell into different markets.
Used by: Clorox bottles, Tide jugs, most milk jugs.
3 — PVC (Polyvinyl Chloride)
Used in some food packaging, blister packs, cling wraps, plumbing pipes, vinyl siding, shower curtains. Almost never recycled in curbside programs because it releases chlorine and harmful compounds during processing, and contaminates other recycling streams.
Where it goes: usually landfill or incineration from consumer waste.
What to watch: avoid putting #3 plastics in curbside recycling. They contaminate the bale.
Used by: some shrink wraps, vinyl flooring, some bottled water bottles.
4 — LDPE (Low-Density Polyethylene)
Flexible films and bags. Plastic grocery bags, bread bags, dry cleaning bags, squeezable bottles, flexible lids. Common but problematic for curbside recycling because films tangle MRF sorting equipment.
Where it goes: store drop-off programs at large grocery chains take clean #4 film and aggregate it for recycling into plastic lumber, composite decking, and trash bag resin. Curbside programs almost never accept it.
What to watch: don’t put plastic bags in curbside bins — they jam sorting machines. The yellow “wrap recycling” bins at Target, Whole Foods, and many Kroger and Safeway stores are the right channel.
Used by: plastic grocery bags, Saran Wrap, bread bags.
5 — PP (Polypropylene)
Yogurt cups, margarine tubs, prescription bottles, bottle caps, straws, takeout containers, microwaveable food trays. Increasingly recyclable as more MRFs install PP sorting.
Where it goes: into auto parts, garden furniture, paint buckets, some new packaging. The Polypropylene Recycling Coalition (an industry group) has been pushing US recycling capacity for PP since 2020 and acceptance is growing.
What to watch: many curbside programs now accept #5; some still don’t. Check locally. Rigid clean PP is much more likely to be recycled than soft or contaminated PP.
Used by: Yoplait yogurt cups, Tide pods containers, most takeout deli cups.
6 — PS (Polystyrene)
Two forms: rigid (clear plastic cutlery, CD cases, some clear deli cups) and expanded (Styrofoam — coffee cups, packing peanuts, foam takeout boxes). Rarely recycled curbside in any form. Expanded polystyrene has been banned for food service in many US cities (Berkeley, San Francisco, Seattle, NYC, DC, Maine, Maryland) precisely because of poor recyclability and litter problems.
Where it goes: mostly landfill. Some specialty drop-off programs recycle clean EPS through densifier equipment, but volume is small.
What to watch: #6 is the worst-fit for curbside recycling. Don’t include it.
Used by: Styrofoam cups, foam takeout, plastic cutlery, CD cases.
7 — Other / All Other Resins
The catch-all bin. Includes polycarbonate (some water bottles), nylon, ABS plastics, layered multi-material packaging, and — critically for this site — compostable bioplastics like PLA. Almost never accepted in curbside recycling because the category is too heterogeneous to sort.
Where it goes: landfill, except for some niche programs.
What to watch: #7 is informational only — it doesn’t tell a recycler whether the item is bio-based, compostable, or just a weird plastic blend. PLA cups marked #7 have caused real contamination problems at MRFs because well-meaning consumers put them in recycling thinking compostable means recyclable.
Used by: PLA cups, some baby bottles, multi-layer pouches, some 5-gallon water jugs.
What actually gets recycled
The reality of US curbside recycling in 2026:
- #1 PET — recycled at 28 to 31% national rate (NAPCOR)
- #2 HDPE — recycled at 28 to 33% national rate
- #3 PVC — under 1% recycled curbside
- #4 LDPE — under 6% recycled curbside; higher through store drop-off
- #5 PP — 7 to 12% recycled, growing
- #6 PS — under 1% recycled curbside
- #7 Other — under 1% recycled curbside
In other words: if it’s not a #1 PET bottle or a #2 HDPE jug, the odds of any given consumer item actually being recycled drop sharply. This is why “wishcycling” (tossing things in hoping they’re recyclable) is harmful — it contaminates the bales of the things that actually do get recycled.
Where compostable plastics fit in
Compostable plastics — PLA cups, PHA straws, bagasse food containers — are not recyclable through the same system. They are designed to break down in industrial composting environments under heat, moisture, and microbial activity over 60 to 180 days.
Many compostable plastic products are labeled with a #7 because there is no dedicated resin code for them. This is one of the most-cited problems with the resin code system. ASTM has discussed adding new codes for bio-based and compostable resins, but as of early 2026, there is no widely-adopted code addition.
For compostable plastics:
- Look for the BPI logo (Biodegradable Products Institute) — verifies industrial compostability under ASTM D6400.
- Look for TÜV OK Compost INDUSTRIAL — European certification.
- Look for TÜV OK Compost HOME — distinct certification for backyard compost conditions.
- The #7 in a triangle on a compostable product is not informative — rely on the cert logo, not the resin code.
For more on the resin and certification side, see related deep-dives on compostable cups and straws, compostable plates, and our compostable food containers category.
Common confusion points
The triangle does not mean “recyclable.” It means “made of resin type X.” Whether your local program accepts that resin is a separate question, answered by your municipality, not the symbol.
A #1 in California is not the same as a #1 in West Virginia. Local recycling capabilities vary enormously. San Francisco’s Recology accepts many more resin types than a rural North Carolina county hauler. Earth911’s recycling locator (earth911.com) is the best tool for checking local acceptance.
Caps on or caps off? Modern MRFs prefer caps on (so they don’t fly into the wrong sort line as small contaminants). A decade ago the answer was caps off. Things change.
Black plastic is often not recycled. Black pigment confuses near-infrared sorting equipment at MRFs, so black takeout trays and meat trays often get rejected even when the underlying resin would otherwise be recyclable. Some MRFs now have black-plastic capable optical sorters but most don’t.
The arrow triangle vs the solid triangle. ASTM updated the codes to use a solid triangle to break the visual association with the “chasing arrows” recycling symbol. Most plastic still uses the older arrow version. Both mean the same thing — resin identification, not recycling guarantee.
What buyers and operators should do
For procurement, marketing, and ops teams:
- Stop quoting “recyclable” on packaging without verification. If the resin code is on the package, that does not make a recyclability claim defensible under FTC Green Guides.
- For compostable claims, cite the cert. “BPI-certified compostable” is a specific, defensible claim. “Eco-friendly” is not.
- Help customers route correctly. If you sell PLA cups in a market without industrial composting, the cups will go to landfill. Be honest about it in your packaging copy.
- For internal operations, sort your back-of-house waste into actual streams: PET bottles in one, HDPE jugs in another, food scraps + BPI-certified compostables in a third. Mixed streams contaminate downstream processing.
A realistic mental model
Treat the resin codes as a chemistry label, not a recycling instruction. Treat the chasing-arrows triangle as marketing legacy, not a recyclability guarantee. Treat compostable certifications (BPI, TÜV) as separate from the resin code system.
When in doubt, check local acceptance. Earth911, your municipal website, and the hauler’s contact line are the authoritative sources. The symbol on the package is informational at best, misleading at worst.
A few honest takeaways from the system as it stands:
- The triangle codes are largely artifacts of a 1988 industry initiative that didn’t age well.
- US recycling rates for plastic are far lower than most consumers assume — 5 to 6% overall by EPA’s most recent estimates.
- Compostable plastics need industrial composting infrastructure to actually compost; they shouldn’t be in recycling streams.
- The cleanest path forward is to reduce single-use plastic generally, use #1 and #2 plastics where they’re appropriate, choose certified compostables where industrial composting exists, and stop pretending the triangle means more than it does.
The numbers inside recycling triangles are a chemistry shortcut. They’re useful for sorting equipment and procurement specs. They are not a license to put any plastic in the blue bin and hope for the best. Once you know that, the symbol stops feeling reassuring and starts feeling like what it is — a small, dated, occasionally-helpful piece of plastic packaging trivia.
For B2B sourcing, see our compostable skewers & picks catalog.
Background on the underlying standards: ASTM D6400 defines the U.S. industrial-compost performance bar, EN 13432 harmonises the EU equivalent, and the FTC Green Guides govern how “compostable” can be marketed on packaging in the United States.