Why ‘Biodegradable Plastics’ Is a Dangerous Oxymoron

Did you know researchers have dug a perfectly readable newspaper out of a landfill decades after it was thrown away?¹ That means you can get your driver's license, graduate high school, change your degree 11 times, backpack through Europe, fall in love in a hostel in Berlin, move back home, start a company, sell the company, have two kids, move out to the burbs, and STILL dig up the newspaper from the day you were born and read what was happening in the world. I mean… c'mon. That's not biodegrading.

So where's the disconnect? Why are words like "biodegradable" and "compostable" thrown around with so much conviction if we're still left with unanswered questions? Or worse, what if we're just accepting them as true?

If adulthood has taught us anything, it's to apply a cynical eye. Why are we 100x harder on a blind date than on the labels deciding the fate of our planet? Let's recalibrate and get some answers.

Biodegradable vs. compostable: not the same thing

These days the two words get used like they mean the same thing. They don't.

• Biodegradable means microorganisms can eventually break a material down. There's no set timeframe and no set conditions, so on its own the word promises very little.
• Compostable is stricter. The material has to break down into carbon dioxide, water and humus within a set timeframe under composting conditions. (Humus: no, we didn't misspell hummus. It's the dark organic part of soil.)

Putting either word on a package is a surefire way to drive up sales, which is why it pays to look closer.

The catch with "compostable" plastics like PLA

PLA (polylactic acid) is the most common plant-based plastic, made from renewable resources like corn starch. It's what a lot of "compostable" cups and cutlery are made of. The problem? Its breakdown rate in home compost and in soil is low.² In most cases it needs the sustained high heat of an industrial composting facility, not your backyard bin.

That distinction is rarely made clear on the package, so people reasonably assume their cup will disappear in a home compost pile. Telling people a plastic is "compostable" without telling them where and how isn't just withholding, it's misleading.

Even if you carry that cup around all day and bring it home, most backyard piles don't get hot enough, for long enough, to break down PLA. Bummer.

What happens in a landfill

Landfills are built to seal waste in, away from air, moisture and sunlight. That's the opposite of what breakdown needs, so even "biodegradable" products don't break down the way you'd hope.

And when organic material does break down in there, it happens without oxygen, and bacteria produce methane. Landfills are the third-largest source of human-related methane emissions in the US.³ Methane traps roughly 27 to 30 times more heat than CO2 over 100 years.⁴ Yikes.

So there isn't much difference between throwing a regular cup in the trash and throwing a biodegradable cup in the trash. At least not nearly as much as the label leads you to believe.

Industrial composting isn't a sure thing either

A "compostable" plastic only lives up to its name if it actually reaches a facility that takes it. Many don't. PLA has to stay in high-heat conditions for a long time and breaks down more slowly than food scraps and yard waste, which has made some industrial composters reluctant to accept it.⁵ This wouldn't be as big a deal if we had solid composting infrastructure everywhere. We don't.

And some "biodegradable" plastics just break into smaller plastic

Not every product marketed as biodegradable is plant-based. Some are conventional plastics with additives that make them crumble faster. A UN report found these "oxo-degradable" plastics can take years to fragment at sea, and the microplastics they leave behind should be assumed to stay in the ocean.⁶ The same report found that plastics labeled biodegradable mostly don't break down in the ocean at all, because the conditions they need are rarely met there.⁶

Smaller pieces. Still plastic. Still harmful.

So how do we move forward?

It's the small things. Lots of people making small changes means BIG changes for the world.

• Skip the paper and plastic plates at home, even the ones marked "made with recycled materials" or "totally biodegradable." Take the extra .000000021 seconds to wash a plate. The world will thank you.
• Carry a reusable bottle, cup and bag.
• If something says "compostable," check whether your city's composting program actually accepts it before you count on it.
• Choose brands that cut plastic out of their packaging in the first place. Here's how we're cutting plastic from our protein powder.

"Reduce, Reduce, Reduce, Reduce, Reduce, and Then Try to Reuse" is the new "Reduce, Reuse, Recycle."

Stay green, my friends.