What Are Biodegradable Plastic Bags Made Of?

November 11, 2026 10 min read

Biodegradable plastic bags are made from a handful of polymers: polylactic acid (PLA), starch blends, cellulose, polyhydroxyalkanoates (PHAs) and biodegradable polyesters such as PBAT. Some come from plants like corn, potato or sugarcane. Others are partly or fully petroleum-based. The material alone doesn’t tell you where a bag will break down, so the label and your local waste rules matter as much as the ingredient list.

If you’ve stood in a store aisle comparing “biodegradable,” “compostable” and “eco” bags, you know how quickly the wording gets confusing. This guide walks through what the bags are made of, how each material behaves, what the claims really mean, and how to dispose of them without guessing.

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TL;DR

Most biodegradable bags are made from PLA (from fermented plant starch or sugars), starch blends, cellulose, PHAs, or a PBAT polyester blended with one of these.
“Bio-based” describes where the material comes from. “Biodegradable” describes how it breaks down. A bag can be one without being the other.
All compostable bags are biodegradable, but not all biodegradable bags are compostable. Compostable is the narrower, better-defined claim.
Look for a named standard such as ASTM D6400 or EN 13432, and check your local composting program before you toss a bag in the green bin.
Never treat a biodegradable bag as litter-friendly, and keep compostable bags out of regular plastic recycling.

The main materials in biodegradable plastic bags
Bio-based is not the same as biodegradable
Biodegradable versus compostable bags
How biodegradable bags actually break down
Labels and standards that mean something
How to dispose of biodegradable and compostable bags
Choosing bags for a home or business
Keep your bags and wraps organized with bamboo
FAQ
Sources

The main materials in biodegradable plastic bags

The German Environment Agency lists the typical ingredients as thermoplastic starch, cellulose, degradable polyesters and PLA, or mixtures such as PLA with degradable polyesters. A peer-reviewed review of the field names PLA, starch, cellulose pulp and PHAs as the major biopolymers used in single-use bags and similar items. Here is what each one is in plain terms.

PLA (polylactic acid)

PLA is the one most articles mean when they say “corn-based.” It is made from lactic acid, which comes from fermenting plant starch or cellulose. Corn is a common feedstock, though sugarcane and other crops are used too. PLA is clear and fairly stiff, so it shows up in produce bags, liners and the film of many compostable bags. On its own it tends to be brittle, which is why it is often blended.

Starch blends

Thermoplastic starch is starch from corn, rice or potato that has been processed so it can be formed into film. A Québec government technical notice explains that many starch-based bags combine starch with a polyester, and that microorganisms such as actinomycetes, fungi and bacteria drive the biodegradation. The polyester gives the film the stretch and tear strength a bag needs to carry a load.

PBAT and other biodegradable polyesters

PBAT is a flexible co-polyester that is designed to biodegrade. It is the stretchy partner that makes PLA or starch film behave like a familiar shopping bag. BASF describes its ecovio bag polymer as a blend of PBAT and PLA, with some grades also containing other biodegradable polymers and inorganic fillers. Some degradable polyesters are petroleum-based, which is why “made from plants” is not guaranteed for every biodegradable bag.

PHAs

Polyhydroxyalkanoates, including polyhydroxybutyrate, are polyesters that microorganisms produce by fermenting sugars or oils. They are the least common of the group in everyday bags but appear in some specialty products. A 2025 study tested commercial products made from PLA, PBAT/starch and PHA, including waste bags and food bags, which shows how varied the shelf really is.

Cellulose

Cellulose comes from wood pulp or other plant fibers. It is used in films and in some paper-like bags and liners. Like the others, it can be used alone or blended.

Quick comparison

Material	Typical source	Common use in bags	Good to know
PLA	Fermented plant starch or sugars	Produce bags, liners, film layers	Often blended to add flexibility
Thermoplastic starch	Corn, rice or potato	Film blended with polyesters	Usually paired with a polyester
PBAT	Can be fossil-based	Flexible film, blended with PLA or starch	Biodegradable, but not necessarily plant-derived
PHA	Microbial fermentation	Specialty bags and films	Less common in everyday bags
Cellulose	Wood pulp or plant fibers	Films, paper-like bags	Used alone or in blends

Bio-based is not the same as biodegradable

This is the point that trips up most shoppers. The German Environment Agency separates the two ideas: bio-based refers to the origin of the raw material, while biodegradable refers to breakdown under particular conditions. Bio-based PET, for example, may not biodegrade at all, and some biodegradable plastics are fossil-based.

So when you read “made from corn,” you’ve learned about the feedstock. You haven’t learned whether the bag will break down in a compost pile, in soil or anywhere else. That depends on the finished material and the conditions.

Biodegradable versus compostable bags

The European Environment Agency explains that biodegradable is a broad claim tied to a specific environment, such as soil, water or compost, and it should state the conditions and the timeframe. Compostable is narrower: it requires demonstrated disintegration and biodegradation in a defined composting process, with controls for residues and compost quality. The U.S. EPA puts it simply: every compostable plastic is biodegradable, but not every biodegradable plastic is compostable.

The UK waste charity WRAP adds that “biodegradable” with no environment or timeframe is vague and potentially misleading. That is a good rule of thumb at the shelf: a claim without conditions tells you very little.

Two more terms are worth knowing:

Industrially compostable: designed for an industrial composting facility, or industrial anaerobic digestion followed by composting. The EPA notes that “commercially compostable” normally means managed industrial or municipal composting, not automatically a home bin.
Home compostable: designed for a well-managed home composter, which runs at lower temperatures. The EEA describes both categories in its review of the field.

A related term, oxo-degradable, is different again. The Canadian Council of Ministers of the Environment describes oxo-degradable plastics as using additives that promote oxidation so the plastic fragments into smaller plastic pieces, which is not the same as biological breakdown. For more on that distinction, see our guide to biodegradable versus degradable.

How biodegradable bags actually break down

Biodegradation is the work of microorganisms. Under suitable conditions they convert the polymer into water, carbon dioxide, mineral salts and new biomass. Temperature, moisture, oxygen, microbial activity, nutrients and time all set the pace. When conditions are wrong, the same bag can break down slowly or only fragment.

Biodegradation outputs and conditions affecting the process

That is why testing matters. In a 2025 study that simulated industrial composting at 58°C and 55% moisture for 90 days, ten commercial biodegradable products disintegrated by 75% to 100%, five of them completely. Microplastics were detected in the compost undersieves for two products. Same conditions, different results: the product matters, and so does the certification behind it.

Outside a compost facility the picture is slower. A long-term experiment reported by BBC News found biodegradable bags still intact after more than three years in soil or sea, and compostable bags were still present in soil after 27 months. The takeaway is practical: a compostable bag is built for a managed composting system, not for the roadside or the garden bed.

The EPA also warns that unqualified degradable claims are deceptive for products normally sent to landfills, incinerators or recycling facilities, because those places don’t provide conditions for complete decomposition within a defined timeframe. If you’d like a plainer walk-through, our post on what biodegradable bags are really made of covers the basics, and what really differs between biodegradable and compostable goes deeper on the labels.

Labels and standards that mean something

The EEA’s advice is to look for a certification showing conformity with an established standard, and to check that the claim names the environment and conditions. In practice, these are the ones you will meet:

ASTM D6400 and D6868 (United States): the EPA states these provide the specifications for labeling plastic as commercially compostable. The Washington State Department of Ecology summarizes the D6400 criteria as no more than 10% of the original dry weight remaining after 84 days, at least 90% of organic carbon converted to carbon dioxide within 180 days, and limits on plant toxicity and regulated heavy metals.
ISO 17088: the international specification, which covers biodegradation, disintegration, effects on the composting process and facility, and effects on compost quality.
EN 13432 (Europe): the European packaging standard for industrial composting. The Compost Foundation lists it alongside AS 4736 in Australia and CAN/BNQ 0017-088 in Canada as national counterparts.
Home-compost schemes: the European Bioplastics guide notes that EN 13432 concerns industrial composting, while home-compostability schemes test lower temperatures and longer residence times. TÜV AUSTRIA’s home certification is one example.

The 2025 study shows why this matters. Among nine products marketed as compostable, six were certified to EN 13432, two held a TÜV Austria OK compost home certification and one was uncertified. A product labeled “100% biodegradable” had no certification and did not state its biodegradation environment. A certification mark plus a stated environment is the combination to look for.

For a deeper look at standards and what counts, see our explainers on compostable packaging and compostable materials.

How to dispose of biodegradable and compostable bags

Follow the label and your local waste authority. Here is the short version:

Industrially compostable bags: send them only to a facility or collection program that accepts them. The EPA advises confirming acceptance with your local composting program.
Home-compostable bags: use them only in a suitable, well-managed home system. The EPA says compostable plastics generally shouldn’t go into a home bin unless explicitly labeled for home composting.
Recycling bin: keep them out. The EPA warns that compostable plastics can contaminate and disrupt conventional plastic recycling.
No local composting? Check your municipality’s rules. The German Environment Agency notes that even biodegradable packaging can interfere with composting, and that local rules may direct it to packaging or residual-waste collection rather than biowaste. Rules differ by country and city, so the local page is the final word.
Never litter them: open soil and water are not managed composting.

Our post on checking local composting first covers this from a buyer’s side.

Choosing bags for a home or business

Start with where the bags will end up. If your city has a compost collection that accepts certified compostable bags, a bag certified to ASTM D6400 is the straightforward match. If it doesn’t, a compostable bag may offer little advantage over your regular trash route, and you’re better off asking what your hauler accepts.

Businesses have one more layer: staff and cleaners need to know which bin is which. A clear office waste segregation plan with labeled bins keeps compostable liners from ending up in the recycling stream, and it makes any compostable bag purchase worth the money. For restaurants, cafes, schools and senior living centers, put the certified bags where food waste is created and post a simple sign above the bin.

A few buying checks for any bag:

A named standard on the package, not just a leaf icon or a green color.
The environment stated: industrial compost, home compost or both.
A timeframe, so you know what “breaks down” means.
Avoid vague words like “eco” or “degradable” with no explanation.

If you want more ideas for waste-reducing household swaps, see our list of compostable household products.

Our perspective

We make handcrafted bamboo products, so we spend a lot of time thinking about what “sustainable” should mean in a kitchen. Our view is simple: the material is only half the story. What matters is how a product is used, how long it lasts and where it goes next.

That is why we like a plain-spoken approach to bags. Read the standard, match it to your local composting, and then build habits that cut down on single-use items in the first place. Our designs are made from natural bamboo and built to be easy to install, so everyday kitchen tasks, like pulling a bag or a sheet of wrap, stay tidy and organized for years.

Biodegradable and compostable bags have a real place in a thoughtful home or business. Pair them with good storage and clear bins, and you’ll waste less of everything.

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Keep your bags and wraps organized with bamboo

Whether you’re stocking compostable liners, zip bags or kitchen wrap, a tidy drawer makes it easier to use only what you need. Our bamboo bag organizer with wrap dispenser is designed to keep bags and wrap in one easy-to-reach place, and you can browse the full range of bamboo bag organizers, trash bag dispensers and drawer organizers. Free shipping applies within the contiguous U.S., and every order is backed by our money-back guarantee.

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For more kitchen ideas, our guide to food bag storage for eco-friendly kitchens is a good next stop.

FAQ

What is a compostable bag?

A compostable bag is designed to biodegrade and disintegrate in a defined composting system at a rate comparable to other compostable organic material, leaving no unacceptable toxic residues. The EPA notes that commercially compostable normally means managed industrial or municipal composting. Check the label for a standard such as ASTM D6400.

Are biodegradable bags made of corn?

Many are made with PLA, which comes from fermented plant starch such as corn, but others use potato or rice starch, cellulose, PHAs or PBAT. Some of those polyesters are petroleum-based. The bag’s raw material and its ability to biodegrade are two separate questions.

Are biodegradable plastic bags really biodegradable?

They are designed to biodegrade in a specific medium under specific conditions. In other conditions they may break down slowly, not at all, or fragment. The EEA says conditions such as temperature, moisture and oxygen set the rate, so look for a stated environment and a certification.

Can I put compostable bags in my recycling bin?

No. The EPA warns that compostable plastics can contaminate conventional plastic recycling. Use a compost collection that accepts them, or follow your local waste authority’s instructions.

Can I put biodegradable bags in my home compost?

Only if the bag is explicitly labeled home compostable. The EPA advises that compostable plastics generally don’t belong in a home bin otherwise, and that you confirm acceptance with your local composting program.

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What Are Biodegradable Plastic Bags Made Of?

TL;DR

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