Is “Biodegradable” Just a Buzz Word? Here’s What is Really Means.

by | Read time: 5 minutes

If you believe you’re doing the planet a favor by using biodegradable or compostable plastic, you probably aren’t. Frustrating to hear, I know.

Biodegradable Plastic Cup Thrown Out Onto Grass |

I bought compostable (or was it biodegradable? bio-based?) plastic cups and utensils for a party in 2013, thinking I was doing good. I didn’t contemplate the difference among the aforementioned descriptors nor did I consider the emissions, resources or potential chemicals (yes, chemicals) involved in making them — or what would happen to them and the environment when they ended up wherever they ended up. I just saw the pat-on-your-back label and you’re-awesome-if-you-buy this marketing and got on board.

Biodegradable plastic won’t decompose the way, for example, “a banana peel does in a backyard composter,” says Eve Fox, digital director of Beyond Plastics, an education and advocacy organization based at Bennington College’s Center for the Advancement of Public Action. “It will just sit there.”


To help, let’s consider that at its most basic, “biodegradable” means something is capable of being broken down, especially into innocuous parts, by the action of living things, according to Merriam-Webster, the holy grail of dictionaries, or at least it’s what book publishers for whom I’ve copyedited demand I use.

Technically, lots of things biodegrade. Eventually. And not always into the “innocuous” parts that our by-the-book definition would like, which we’ll read more about shortly.

For perspective, here are some estimates from bona fide sources on how long it takes common items to break down on land:

It’s worth noting that I came across several wildly divergent time estimates yet didn’t include them all.

That said, one thing is clear in the biodegradable sphere: Plastic is the biggest problem. It’s omnipresent, adversely affects health in many ways and has lots of sustainability and recycling demerits, especially when compared with superstars like cardboard and aluminum.

Given that, let’s zero in on plastic, its related terms and what we can do:


All plastic degrades, including the normal stuff. But even if it breaks down into bits or powder, that doesn’t make it useful for nature or healthful for humans or animals (in fact, the opposite, especially when it comes to traditional plastic).

biodegradable plastic

We hit on this a few paragraphs ago, but, again, biodegradable plastic should get broken down by microorganisms into okay components such as water — under the right conditions.

Unfortunately, there’s not usually enough oxygen flow in a landfill for proper decomposition, which means not only that the plastic doesn’t break down as hoped but also that methane, a no-good greenhouse gas, releases.

According to the Biodegradable Products Institute, the term “biodegradable” isn’t wedded to a specific timeframe. U.S. federal agencies, though, say it’s misleading to market something as “biodegradable” if it takes longer than a year for it to completely decompose. Meanwhile, an oft-cited Columbia University piece says “biodegradable” implies that decomposition happens in weeks to months.

Also: Everything that is compostable is biodegradable. But not everything that is biodegradable is compostable.

compostable plastic

Compostable plastic will biodegrade in a compost site — a commercial compost site, not the one in your yard, and few exist. Right now there aren’t standard test methods to evaluate whether plastic can be composted in a home environment, though Moonshot Compost says biodegradation in a residential setting takes at least a decade.

“Industrial compost is a whole different beast that gets the piles heated up to very high temps using one of a few different methods — some of which also require a decent amount of fossil fuel and water — that you can’t achieve in a regular composter,” Fox says. “That’s why you can usually throw things in there you would never compost in your yard, like tree branches and bones and meat scraps and fabric.”

Microorganisms, heat and humidity break the plastic down into carbon dioxide, water, inorganic compounds and biomass, at the same rate (within 6 months) as other organic materials in the compost, without leaving any toxic residue that would harm the finished compost’s ability to support plant growth, according to the U.S. Environmental Protection Agency.

ASTM International is in charge of defining and setting standards for biodegradable and compostable plastic, by the way, though for the life of me I couldn’t find a clear timeline for either on its website and have yet to hear back on my query regarding as much.

bio-based plastic

Bio-based plastics are made of plant materials instead of oil or natural gas — but that doesn’t automatically confer sustainability. Yes, some are designed to biodegrade or be compostable. But bio-based plastic also can be engineered as structurally identical to petroleum-based plastic, and if that happens it’ll lurk in the environment just as long as petroleum-based plastic.


Okay, another point of confusion: In practice, you’ll find “bioplastic” refers to plastic that is bio-based, biodegradable or compostable — and might even include fossil-fuel based plastic. I know, I know. I’m as frustrated as you are.


Here’s what you can do to lessen frustration: Avoid single-use or poorly built products altogether so that you don’t have to think about whether they are biodegradable or compostable or how long they take to decompose. Think: family heirlooms, stuff with heft and quality, from tableware to socks.

If that sounds overwhelming, start simply: Get your to-go drink in your own reusable mug, buy a glass straw (I was gifted one years ago and still use it), take your own food storage containers to restaurants for leftovers (been doing this for ages, and it sometimes invites curious questions from strangers).

If you must use plastic, opt for resin codes 1 and 2, the most commonly recycled plastic — “though in truth, it’s down-cycled,” Fox says. “But clearly, best of all would be to not use plastic of any kind.

“Part of the problem with bioplastics is that they don’t get composted by and large, end up in landfills or incinerators where they add even more climate change emissions, and are insidious in that they make consumers and companies believe the problem is solved — when it’s just allowing the underlying upstream problem of plastic production and consumption to go unchecked and become even more disastrous.”

Journalist Mitra Malek buried several bio-something-or-other utensils near her compost pile years ago and now isn’t sure that was the best idea. She acquired them after forgetting to put her bamboo to-go utensils in her purse.