Are Compostable Plastics Actually Compostable? — This Green Lifestyle

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:

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.