What do the numbers on plastic mean? And 3 other trashy questions, answered.

Master the art of the blue bin.
A blue recycling bin with a recycling symbol on it.

There are a lot of feel-good terms related to recycling, but it can be hard to know what they actually mean. Sigmund / Unsplash

Plastic is everywhere. We wear it, sleep on it, drive around in it, and even eat it. But because much of it is made from natural gas and the byproducts of both the natural gas and crude oil refining processes, no amount of reuse or recycling can “make up” for the environmental harm caused by plastic production. The damage has already been done.

The plastic recycling process is a complex and energy-intensive endeavor popularized by the plastics industry itself. In many cases, it is unclear whether “recyclable” products even have a lesser environmental toll than non-recyclable plastic. However, reducing the amount of plastic waste can still help prevent wildlife deaths, modestly reduce the size of landfills, and prevent harmful chemicals and microplastic particles from entering the environment. For these reasons, it’s worthwhile to recycle the plastic items that you’re able to, rather than just tossing them in the trash.

So, what do the numbers mean?

Most plastic products bear a familiar symbol: three arrows chasing one another along a triangular path. This symbol has come to represent the very concept of recycling, but be aware: it only means that a product is made from plastic resin, not that it’s necessarily recyclable. What’s more important is the number inside this symbol, which indicates the specific type of plastic involved.

Plastics bearing the numbers 1 or 2 are often recyclable, while those numbered 3 through 7 are less likely to be. There are various guides that can help give you a better sense of what different types of plastic look like and where they may end up, but there are unfortunately no universal rules for which numbers represent recyclable plastics. This is because different towns, cities, and regions are home to different recycling facilities with different types of machinery. 

[Related: Inside the machine that separates your recyclables]

Some recycling facilities are run by local governments, while many are operated by private companies that collect recyclable materials for profit. Some locations have state-of-the-art equipment, while others can only handle a few types of plastic. Because these details vary so much depending on where you live, your best bet is to research the recycling rules in your area before tossing any plastic items in the blue bin. 

What are bioplastics?

“Bioplastic,” “plant-based,” “made from corn”—all these terms feel like a breath of fresh air to the well-intentioned consumer. After a lifetime of using petroleum-based materials, the lure of “planet-friendly” plastics is hard to dispute. But be careful around these labels: many of them offer incomplete information about the product’s actual impact on the environment.

“Bioplastic” is a recent development from the world of materials chemistry that uses plant material rather than fossil fuels to create the complex polymer chains that make up plastic. Many folks assume that because plants are involved, the end result must be biodegradable. But that’s not the case: many bioplastics are chemically identical to traditional plastic, meaning they can stay in the environment for just as long. 

While some bioplastics can be recycled, they often have to be separated from petroleum-based plastics so they can be processed in a different way. The only way to know for sure how to properly dispose of bioplastic items is to carefully read the labels on their packaging and research your local recycling policies. If you’ve been handed a piece of bioplastic, such as a to-go drink cup or a single-use bag, this level of diligence may not be possible. So while bioplastics have the distinct benefit of decreasing our reliance on fossil fuels, they often don’t spare the planet from harmful plastic waste.

How do biodegradable and compostable plastics work?

“Biodegradable” plastic does just that: it degrades over time. While seeing this label may call to mind a gently rotting compost pile, degrading plastic items can be problematic: depending on their specific makeup, they may simply break down into microplastics, which end up in our soil, water, and food supply. Moreover, “biodegradable” plastics often require special recycling facilities. This means that you can’t just toss this type of plastic into a recycling bin or a compost pile and wait for it to dissolve. You’ll need to do more research to determine where and how to dispose of it.

“Compostable” plastics make an even bolder claim: that not only will they degrade over time, but that they will break down into a few simple component parts: the biomass that we recognize as compost, along with water, carbon dioxide, and some inorganic compounds. It’s a common misconception that “compostable” plastic items can be tossed onto your home compost pile along with carrot tops, eggshells, and banana peels. Instead, these plastics need to be collected and treated at special composting facilities that have the right combination of heat, microorganisms, and chemicals to carry out the recycling process. While scientists are working on compostable plastics that can break down in your own backyard, this material is not yet available for public use.

[Related: Adding enzymes to bioplastics can make them disappear]

Unless your area has special facilities that can properly process biodegradable and compostable plastics, you may have to throw these items in the trash to avoid contaminating the traditional recycling stream. Check your local guidelines to see what your recycling provider recommends. It’s also important to educate those around you about what these labels really mean. Widespread understanding of these plastics’ limitations will help pressure governments and manufacturers alike to offer better alternatives.

What can we do if we can’t recycle?

Creating plastic takes fossil fuels, recycling it produces greenhouse gasses, and throwing it away creates harmful waste. No matter what you do with it, plastic hurts our planet’s ecosystems, atmosphere, and natural resources. The key to reducing that harm is avoiding plastic as much as you can—especially plastics designed to be disposable. Cloth bags, glass jars, cardboard boxes, and ceramic dishware are all examples of items we can use to replace plastic in our lives. 

It’s also worth noting that individual consumers’ plastic consumption accounts for only a fraction of the waste across the globe: far more to blame are the corporations that make this material and use it wastefully for packaging, shipping, and manufacturing. If you’re able, consider supporting companies that minimize this environmental harm, as well as legislation that regulates plastic use. Until a truly sustainable plastic can be developed, reducing its role in our society will be far more impactful than any amount of recycling.