Why Compostable Plastics Aren't Eco-Friendly As You Think

When you see the words “compostable plastic” printed on a food container, shopping bag, or package, it feels like the perfect solution to plastic pollution.

Instead of throwing away another piece of traditional plastic that could remain in the environment for decades, you assume the compostable version will simply break down and return to nature. But here's the part almost no one talks about:

Compostable plastic doesn't automatically disappear just because you throw it in the trash. Many compostable plastics are designed to only break down under specific conditions found inside commercial or industrial composting facilities. If they end up in a landfill, recycling bin, or a backyard compost pile that isn't suitable for them, they won't break down.

Fun Fact: The terms “bio-based,” “biodegradable,” and “compostable” don’t mean the same thing. A plastic can be made from plants without being biodegradable, and compostable plastic can mean plastic that only breaks down under the right conditions.

So, are compostable plastics actually better for the environment?

In today's blog, I'll explain what compostable plastic actually is, why it doesn't always break down in your backyard or landfill, how these products can create problems for recycling and composting facilities, and what you can do to make more environmentally friendly choices.

What Exactly Is Compostable Plastic?

Unlike traditional plastic, many compostable plastics are made with polymers that microorganisms can eventually break down under the right environmental conditions. Some common materials used in compostable plastics include:

• PLA (Polylactic Acid): A plant-based polymer usually made from fermented plant sugars such as corn or sugarcane. It's frequently used for cups, containers, food packaging, and other disposable products.
• PHA (Polyhydroxyalkanoates): A family of biodegradable polymers produced by microorganisms. Depending on the specific material, PHAs can break down under a wider range of environmental conditions than some other bioplastics.
• PBAT (Polybutylene Adipate Terephthalate): A biodegradable polyester often blended with other materials to improve strength and performance. Despite being labeled a bioplastic in some products, it is commonly produced from fossil-derived feedstocks.
• Starch-Based Blends: Materials that combine starch with other polymers to create flexible bags, packaging, and food-service products.

This is where things start getting confusing. A product can be plant-based without being compostable, and it can also be compostable without being entirely plant-based. (In other words, the source of the plastic doesn't tell you what will happen to it after you throw it away!)

What conditions does this material actually need to break down?

Many products labeled as commercially compostable are designed to break down in municipal or industrial composting facilities, where temperature, moisture, oxygen, and other conditions are carefully managed.

That means you can't assume a compostable plastic product will break down just because you put it in your backyard compost bin or landfills. A compostable plastic is designed for a specific composting environment, not simply for disappearing anywhere it happens to be thrown away.

Summary: Compostable plastic is a type of biodegradable plastic designed to break down into compost under specific conditions such as the right temperature, moisture, oxygen, microorganisms, and composting conditions to break down properly. Some compostable plastics are made from plant-based materials such as corn, sugarcane, or starch, while others contain synthetic biodegradable polymers.

The Problem With Compostable Plastics In Your Home Compost

When people hear “compostable plastic,” they might picture something they can toss into their backyard compost pile and forget. After all, if it says “compostable,” shouldn't it break down just like food scraps, leaves, and other organic materials?

Unfortunately, unless a product is specifically designed and certified for home composting, you shouldn't assume it belongs in your backyard compost bin!

Many products labeled as commercially or industrially compostable are designed for the much more controlled conditions found at professional composting facilities. These facilities can manage important factors such as temperature, moisture, oxygen, and microbial activity to help compostable materials break down.

Your backyard compost pile usually doesn't have that same level of control. Temperatures may be lower, moisture levels can change, and the microorganisms needed to break down certain compostable plastics may not be present in the right amounts.

This distinction is incredibly important because the average consumer may see the word “compostable” and assume it means “put it anywhere and nature will take care of the rest.” That's simply not how these materials work.

Summary: A compostable plastic product can be a useful alternative when it is sent to the right composting facility. But putting a commercially compostable product into your backyard compost doesn't guarantee that it will completely break down. (It can do more harm than good!)

Why Compostable Plastic Doesn't Belong In Recycling Bin

At first glance, putting a compostable plastic container or bag into your recycling bin might seem like the responsible thing to do. After all, it's still plastic, right?

Unfortunately, it doesn't work that way.

Compostable plastics are made with different materials and are designed to break down through composting rather than being processed through traditional plastic recycling. When they end up in a recycling bin, they can become contamination and cause problems for recycling facilities.

The EPA has specifically warned that compostable plastics can create contamination problems in both recycling and composting systems. Some composting facilities don't even accept them at all, while others must use additional sorting and processing to separate different materials.

Even though it looks like plastic and the package says “compostable,” putting it into the wrong bin can actually make waste management more complicated. (Also, the word “compostable” shouldn't be treated as a synonym for “recyclable.”)

And don't even think “If it says compostable, it will eventually disappear in a landfill.”

If a product is thrown into the trash, there is no guarantee that it will ever reach the specialized composting environment it was designed for. As a result, a compostable plastic item that would break down under controlled industrial composting conditions may persist much longer when buried in a landfill.

Again, compostable plastics are primarily designed to break down under aerobic composting conditions, not every environment where waste can end up. Their behavior depends heavily on the specific material and environmental conditions.

Summary: Compostable plastic isn't automatically recyclable, and recyclable plastic isn't automatically compostable. Before throwing a product into your recycling or compost bin, check the label and your local waste-management guidelines to make sure you're using the right disposal method.

Quick Takeaway

Compostable plastics can sound like the perfect answer to our plastic pollution problem. However, “compostable” doesn't mean “throw it away and forget about it.”

Many commercially compostable plastics need specific conditions to break down properly, including the right temperature, moisture, oxygen, and microbial activity. Not every composting facility has those conditions, and some don't accept compostable plastics at all.

When these products end up in the wrong waste stream, they can also create problems for recycling, landfill, or composting facilities. (Just like normal plastic!)

That's why you shouldn't assume that a big green label automatically makes a product environmentally friendly. Before buying compostable plastic, ask yourself if the product is actually certified for the disposal method you're planning to use, or does your local composting program accept this product?

My Personal Take: I think compostable plastics are a good example of why being sustainable isn't always as simple as choosing the product with the biggest green label. The idea sounds great, but a material can only deliver its environmental benefits when the entire system around it works.

At the end of the day, I would rather see people focus on using fewer disposable products altogether than simply replacing traditional plastic with another single-use material and assuming the problem is solved.

Frequently Asked Questions About Compostable Plastics:

Question 1: Are compostable plastics actually plastic?

Answer: Yes. Compostable plastics are still plastics because they are made from polymers. The important difference is that they are specifically engineered to decompose under certain conditions rather than persist like many conventional plastics.

Question 2: Can I put compostable plastic in my backyard compost bin?

Answer: No. Many products labeled compostable are designed for commercial or industrial composting facilities, where temperature, moisture, oxygen, and other conditions are carefully controlled. Unless a product is specifically certified for home composting, you shouldn't assume it will break down properly in your backyard pile.

Question 3: Can compostable plastics go into the recycling bin?

Answer: Usually not. Compostable plastics can contaminate conventional plastic recycling streams because they are made from different materials. Always follow the disposal instructions from your local recycling and waste-management program.

Last Updated: August 28, 2026