Are Compostable Plastics Actually Compostable?

With plastic pollution as one of the biggest concerns facing the environment today, it’s no surprise that more sustainable alternatives are being sought after. Biodegradable and compostable plastics are touted as an alternative to their conventional counterparts – but how sustainable are they, really?

Compostable plastics are a type of biodegradable plastic made from renewable resources and designed to break down in a compost system. Unfortunately, compostable plastics are not as good as they may seem at first glance. Compostable plastics still have a significant carbon footprint and they often end up in the landfill, where they fail to break down as intended.

While compostable plastics seem like a cure-all to plastic pollution, the truth is actually quite complicated.

Photo by Brian Yurasits

What are compostable plastics?

In the words of the Big Compost Experiment, compostable plastics are:

“...a subset of biodegradable plastics that are designed to break down under controlled environmental conditions into water, biomass, and gasses such as carbon dioxide and methane.”

Whereas most conventional plastics are made from the byproducts of crude oil, compostable plastics are made from renewable resources such as corn, potato, cellulose, or beet. Currently, the most common raw material for compostable plastic is corn, a resource-intensive monocrop that has significant environmental and health consequences.

Ultimately, compostable plastics are still energy- and resource-intensive to produce. Moreover, because they’re designed to be compostable in industrial composting facilities, they don’t necessarily break down at home or elsewhere in the environment – including the ocean.

This means that compostable plastics are sadly a good example of greenwashing; using them makes you feel good, but their environmental impact is still significant.

A brief history of plastics

The term plastic originally comes from plasticity, or the “capacity for being molded or altered.” While the term is not new, it now more commonly refers to a type of material known as a polymer. Polymers are commonly found in nature, including in cellulose. Plastic, however, is a type of synthetic polymer made from petroleum and other fossil fuels.

The first plastic was invented in 1869 in an effort to substitute ivory. Thanks to its pliability and strength, plastic was quickly praised throughout society. Over the next century, inventors and scientists alike developed all kinds of plastics that replaced otherwise nonrenewable resources, and they became ubiquitous, proving not only useful but also cheap and durable.

Unfortunately, conventional plastics don’t biodegrade; in other words, even though they break into smaller and smaller pieces over time, those microplastics can remain in the environment for hundreds or thousands of years, posing a significant health and environmental risk.

That’s where the rise of bioplastics and compostable plastics comes in. While these types of plastics have yet to solve the plastic problem, more research continues to provide hope.

For more on the history (and future) of plastic, click here.

Compostable vs. biodegradable plastics

Compostable plastic isn’t exactly the same as biodegradable plastic. That is, while all compostable plastic is biodegradable, not all biodegradable plastic is compostable. Confused yet? Don’t worry, us too.

Biodegradable plastics are made of a combination of petroleum and plant-based resins. These hybrid plastics aren’t truly compostable, although they’re supposed to be able to break down, at least under certain conditions. Unfortunately, nature doesn’t always experience lab-perfect conditions, so it’s never guaranteed that biodegradable plastic actually biodegrades.

Advancements have led to what we now refer to as compostable plastics; a subset of biodegradable plastics that are supposed to biodegrade into compost. Again, these plastics are engineered under particular conditions in a lab, so it’s important to understand that compostable plastics don’t decompose in the same way as, say, a banana peel would.

That said, in order for a plastic to be labeled “compostable,” it has to be able to break down at an industrial composting facility with the help of mechanics, microorganisms, heat, and humidity. Furthermore, it has to decompose at a reasonable rate of 6 months or less and leave no toxic residue in the end product.

How to tell if a plastic is compostable

With all of the greenwashing going on, it can be difficult to tell if a plastic labeled as “100% natural,” “biodegradable,” or “compostable” is actually compostable. Luckily, there are some standards and regulations that manufacturers must follow in order to truly label something as compostable.

To see if a plastic is compostable, look for these signs:

• The word “compostable.”

• A certification from the Biodegradable Products Institute (BPI).

• The plastic recycling symbol with the number 7 and the letters PLA underneath it.

In most cases, manufacturers want you to know that their product is compostable. But without a BPI certification, you may want to do some research to find out whether or not their claim is true.

How to dispose of compostable plastics

Now that you have a somewhat better understanding of what compostable plastics are, you may be wondering: “But how do I get rid of them?”

Part of the issue with compostable plastics is that there’s no straightforward way to make sure that they actually turn into their intended end product: compost.

Can you put compostable plastic in the compost bin?

Compostable plastics require specific conditions (heat, water, and air) in order to break down into a material that can be described as a soil amendment. While those conditions can be replicated in an industrial composting facility, most home compost piles or bins don’t get nearly hot enough for nearly enough time to degrade the plastic.

Some materials labeled as compostable or home compostable, such as packaging made from paper, are fine to put in the home compost pile. Compostable plastic, however, is best kept out.

Are compostable plastics considered green waste?

If your city has a green waste program, they may or may not accept compostable plastics. Even if your area has a home compost pick-up program, it may not accept compostable plastics if it doesn’t have the right equipment to deal with them.

For example, compostable plastics can be difficult to tell apart from conventional plastics, and not all compost collection programs have the resources to properly sort their waste. If they suspect contamination, it may mean sending the whole batch to the landfill, where it anaerobically breaks down and releases methane, a greenhouse gas 80 times more potent than carbon dioxide.

So, before you add compostable plastics to your green waste pickup, double check with your local recycling company to see if they’ll accept them in the first place.

Can you recycle compostable plastics?

If your local composting facility doesn’t accept compostable plastics, your next thought may be whether compostable plastics are recyclable. After all, there’s often a recycling symbol imprinted on the plastic, right?

Don’t be fooled, however. Compostable plastics are not intended to be recycled with conventional petroleum-based plastics, so if they end up with regular recycling they may be considered a contaminant. If there’s too many contaminants in a batch of recycling, it may result in all of it being sent to the landfill, or burned.

Sustainable alternatives to compostable plastics

Compostable plastics may not yet be the cure-all we’re looking for, but there are other alternatives that can help to reduce our plastic-dependency.

The most sustainable option is to replace single-use plastics with durable, reusable products. For example, in an effort to become zero-waste, Live Nation is shifting to reusable cups instead of single-use compostable plastic cups, which just end up in landfills most of the time anyway. The reusable TURN cups, which are still made of plastic, are supposed to “break even” on their environmental impact in as little as 3 uses.

Additionally, there are packaging options other than biodegradable or compostable plastic that can easily be recycled, including materials made from paper, cardboard, and aluminum (or no packaging at all). Other things you can do include bringing your own reusable containers, dishware, and cutlery when shopping, buying coffee, or getting takeout.

Do you encounter compostable plastics in your daily life? How do you dispose of them? Comment below if you have any other questions!