Most curbside recycling programs accept two types of plastic reliably: Type 1 (PET) and Type 2 (HDPE). Types 4 and 5 are increasingly accepted depending on where you live, while Types 3, 6, and 7 are rarely recyclable through standard programs. The number stamped on the bottom of a plastic item tells you what kind of resin it’s made from, but it does not mean the item is recyclable.
What the Numbers on Plastic Actually Mean
Every rigid plastic product carries a small number, 1 through 7, inside a triangle. This is a resin identification code, not a recycling symbol. The system was created in 1988 by the plastics industry to help sorting facilities identify what type of plastic they’re handling. Originally, the number sat inside a triangle made of “chasing arrows,” which understandably led people to assume it meant “recyclable.” In 2010, the standard was updated to use a solid triangle instead, specifically to reduce that confusion. But many products still use the old arrow design, and at least 36 U.S. states have their own laws governing which version manufacturers must use. The bottom line: the number identifies the plastic type. Whether your local program accepts it is a separate question entirely.
Type 1 (PET): The Most Recyclable Plastic
PET is the clear plastic used for water bottles, soda bottles, and many food containers. It’s the most widely recycled plastic in the world and is accepted by virtually every curbside program. Recycling PET saves roughly 75% of the energy needed to make it from scratch, which is one reason it’s so economically attractive to recyclers.
PET can be recycled back into new bottles through a “bottle-to-bottle” process that produces material pure enough to meet food-contact safety standards. This closed-loop recycling is the gold standard because it keeps the material at its highest value instead of turning it into a lower-grade product. Recycled PET also ends up in polyester clothing, carpet fiber, and food packaging.
To recycle PET properly, empty the container, give it a quick rinse, and put the cap back on. Most programs now ask you to leave caps attached rather than removing them.
Type 2 (HDPE): Nearly as Widely Accepted
HDPE is the slightly opaque, sturdier plastic used for milk jugs, detergent bottles, and shampoo containers. It’s the second most commonly recycled plastic and is accepted by nearly all curbside programs. Recycling HDPE saves 50 to 60% of the energy compared to producing it new.
Unlike PET, recycled HDPE is more often “downcycled” into products like plastic lumber, drainage pipes, and new detergent bottles rather than going back into food-grade containers. It’s still a strong market, and HDPE bales consistently hold their value at sorting facilities.
Types 4 and 5: Accepted in Some Areas
Type 4 (LDPE) is the softer, flexible plastic found in squeezable bottles, some food wraps, and the lids of takeout containers. Type 5 (polypropylene) shows up in yogurt cups, medicine bottles, bottle caps, and microwave-safe food containers. Both are technically recyclable, and a growing number of municipal programs now accept them, particularly Type 5.
The catch is that acceptance varies widely by location. If your program doesn’t list these numbers, putting them in the bin does more harm than good. They become contaminants that sorting facilities have to pull out by hand, slowing down the process and sometimes degrading entire batches of otherwise clean material.
LDPE film, like grocery bags and plastic wrap, is almost never accepted curbside because it tangles in sorting machinery. Many grocery stores have drop-off bins specifically for plastic film, which gets collected and recycled separately.
Types 3, 6, and 7: Rarely Recyclable
These three categories cause the most problems in the recycling stream, and most curbside programs reject them outright.
- Type 3 (PVC) is used in plastic pipes, blister packaging, and some cling wraps. PVC releases hydrochloric acid gas when heated to the temperatures needed to process other plastics. Even a small amount of PVC mixed into a batch of PET will degrade the entire load. Making matters worse, PVC and PET have overlapping densities, so the standard water-based separation method used at sorting facilities can’t reliably tell them apart.
- Type 6 (polystyrene) includes foam takeout containers, disposable cups, and packing peanuts. It’s lightweight, breaks apart easily, and is, in the words of one published assessment, “extremely difficult to cost-effectively separate from co-mingled collection.” Dedicated collection of industrial polystyrene foam can work, but household polystyrene almost always ends up in landfill.
- Type 7 (other) is a catch-all for everything else, including multi-layer plastics, bioplastics, and polycarbonate. Because this category lumps together incompatible materials, there’s no single way to process it. Most facilities reject it entirely.
Why Color Matters More Than You’d Think
Even if a plastic is the right type, its color can make it unrecyclable. Sorting facilities use near-infrared sensors to identify plastics on a fast-moving conveyor belt. Black plastic absorbs infrared light instead of reflecting it, making it essentially invisible to these sensors. The culprit is carbon black, a pigment added to give plastic its dark color. Because the sensors can’t read it, black plastic items often sail past the sorting equipment and end up in the trash. This applies to black takeout trays, plant pots, and many electronics casings, even when they’re made from otherwise recyclable resins like PET or polypropylene.
Items That Should Never Go in the Bin
Some of the most common recycling mistakes involve items that look like they should be recyclable but aren’t. Plastic bags and flexible film packaging jam sorting equipment and can shut down a facility’s conveyor line. Candy wrappers, chip bags, and cereal bag liners are made from multiple fused layers of plastic and metal that can’t be separated. Putting these in your recycling bin doesn’t give them a second chance. It contaminates the clean, sortable plastics around them, lowering the quality of the whole bale and sometimes sending otherwise recyclable material to landfill.
A good rule of thumb: if the item isn’t a rigid container, bottle, or jug, it probably doesn’t belong in your curbside bin unless your program specifically says otherwise.
Chemical Recycling and Hard-to-Recycle Plastics
Traditional recycling is mechanical. Plastics are washed, shredded, melted, and reformed into pellets. This works well for clean, sorted PET and HDPE, but each time plastic goes through the process, the polymer chains degrade slightly, and impurities accumulate. That’s why mechanically recycled plastic often ends up in lower-value products over successive cycles.
Chemical recycling takes a different approach, breaking plastic down into its basic chemical building blocks. The resulting material is identical in quality to virgin plastic, with no accumulated degradation or impurities. This process can handle mixed and contaminated plastics that mechanical recycling can’t touch. The tradeoff is energy: chemical recycling requires significantly more energy than mechanical methods. For PET and polystyrene, lifecycle analyses show mechanical recycling is clearly better for carbon emissions. For polyethylene and polypropylene, chemical recycling that recovers the original building blocks can actually match or slightly outperform mechanical methods on environmental impact, depending on the specific process.
Chemical recycling is not yet widely available at a consumer level, but it’s expanding as a solution for plastics that would otherwise have no path back into the supply chain.
How to Check What Your Program Accepts
Recycling rules are set locally, not nationally, so the only reliable guide is your own municipality’s website or waste hauler. Look for the specific resin numbers they accept and any restrictions on container types. Most programs accept Types 1 and 2 without question. Many now accept Type 5. Beyond that, it depends entirely on your local sorting infrastructure and the markets available for recycled material in your region. When in doubt, leaving something out of the recycling bin is better than tossing it in and hoping for the best.