Updated: 9 September 2026
Quick Answer
There is no single decomposition time for biodegradable plastic.
Certified industrially compostable plastics are designed and tested to biodegrade under controlled commercial or municipal composting conditions. Under these conditions, decomposition and disintegration are typically measured in months according to the applicable compostability standard.
Outside controlled composting conditions—such as ordinary soil, home compost, landfill or marine environments—the same material may degrade much more slowly or may not fully biodegrade within a practical timeframe.
The actual decomposition rate depends on:
- polymer type and formulation
- product thickness and structure
- temperature
- moisture
- oxygen
- microbial activity
- the disposal environment
The most important question is therefore not simply “How long does biodegradable plastic take to decompose?” but what material is being tested and under what conditions?
Biodegradable Plastic Decomposition Time at a Glance
| Material / Environment | Practical Expectation |
|---|---|
| Certified industrially compostable plastic | Designed to biodegrade under controlled commercial or municipal composting conditions |
| PLA-based compostable products | Most effectively biodegrade under elevated-temperature industrial composting conditions |
| Home-compostable products | Designed for lower-temperature composting only when specifically certified for home composting |
| Biodegradable plastic in soil | Highly dependent on polymer, temperature, moisture and microbial activity |
| Compostable plastic in landfill | Not an appropriate composting environment; degradation can be very slow |
| Conventional PE or PET plastic | Not designed to biodegrade or compost under normal composting conditions |
These are practical categories rather than universal decomposition times. Two products made from similar polymers may behave differently because of thickness, formulation, additives and disposal conditions.
How Long Does Biodegradable Plastic Take to Decompose in Different Environments?
The disposal environment has a major effect on biodegradation.
Industrial Composting
Industrial composting provides controlled heat, moisture, oxygen and microbial activity.
Certified commercially compostable plastics are designed and tested for these conditions. In the United States, ASTM D6400-26 covers plastics and plastic products designed to be aerobically composted in municipal or industrial composting facilities where thermophilic conditions are achieved.
The certification or testing timeframe should not be interpreted as a guarantee that every product will disappear in exactly the same number of days in every composting facility.
Home Composting
Home compost systems generally operate at lower and more variable temperatures than industrial composting facilities.
A product certified only for industrial composting should not automatically be assumed to biodegrade effectively in a backyard compost system.
Products intended for home composting should be evaluated against an appropriate home-compostability certification or standard.
Soil
Biodegradation in soil varies widely.
Temperature, moisture, soil microorganisms, product thickness and polymer chemistry can all affect the rate. A material that performs well in industrial composting may remain present much longer in ordinary soil.
For this reason, an industrial-compostability claim should not be converted into a fixed “soil decomposition time.”
Marine Environments
Marine environments are generally colder and have different microbial conditions from industrial composting systems.
Research into plastic and biodegradable-material behaviour in marine environments shows why degradation claims should be evaluated against the actual environment rather than assumed from a compostability label. The University of Plymouth research on biodegradable plastics in natural environments provides useful background on how plastic materials behave outside controlled composting systems.
Products designed for industrial composting should not be disposed of in the ocean, and industrial-compostability certification should not be interpreted as evidence of marine biodegradability.
Landfill
Landfills are not composting systems.
They generally do not provide the controlled temperature, oxygen, moisture and microbial conditions used for industrial composting.
The FTC Green Guides on degradable and biodegradable claims also caution against unqualified degradable claims for products that are normally disposed of in landfills, incinerators or recycling facilities, because these environments generally do not support complete decomposition within a short period.
A product certified for industrial composting should therefore not be expected to biodegrade on the same timeline when disposed of in landfill.
What Is Biodegradable Plastic?
Biodegradable plastic is plastic that can be broken down by microorganisms under specified environmental conditions.
However, biodegradable, compostable and bio-based do not mean the same thing. According to the U.S. EPA guidance on biodegradable and compostable plastics, compostable plastic is biodegradable, but not every biodegradable plastic is compostable.
A compostable plastic must meet defined requirements under specified composting conditions, while a bio-based plastic describes the source of the raw material and may or may not be biodegradable.
How Does Biodegradation Work?
Biodegradation occurs when microorganisms and their enzymes act on a material under suitable environmental conditions.
Depending on the polymer and disposal environment, larger polymer chains are progressively converted into smaller compounds that microorganisms can metabolize.
For compostable plastics, successful biodegradation depends on factors such as heat, moisture, oxygen, microbial activity and sufficient processing time.
This is why disposal conditions are central to any biodegradation claim.
Why There Is No Single Decomposition Time
The same biodegradable polymer can behave very differently in different environments.
Six factors are especially important:
Polymer Chemistry
PLA, PHA, PBAT and other biodegradable polymers have different chemical structures and degradation pathways.
Temperature
Higher temperatures can significantly accelerate some biodegradation processes. PLA is a good example because hydrolysis and subsequent biodegradation are much more effective under elevated composting temperatures than under ordinary ambient conditions.
Moisture
Water availability can affect hydrolysis, microbial activity and the overall biodegradation process.
Oxygen
Industrial composting is normally an aerobic process. Oxygen availability can therefore affect how organic materials and compostable products are processed.
Microbial Activity
Different environments contain different microorganisms. A polymer that biodegrades under one set of microbial conditions may perform very differently elsewhere.
Product Thickness and Structure
Film thickness, surface area, coatings, additives and product geometry can affect disintegration and biodegradation.
Thin films may disintegrate more readily than thick molded products under the same conditions, but thickness alone does not determine the final biodegradation rate.
How Long Does PLA Take to Decompose?
PLA, or polylactic acid, is most effectively biodegraded under controlled industrial composting conditions with elevated temperatures, moisture and active microorganisms.
There is no universal rule that every PLA product decomposes in exactly 90, 120 or 180 days.
The actual result depends on the PLA grade, product thickness, formulation and composting conditions.
At lower temperatures—such as ordinary soil, many backyard compost systems and landfill environments—PLA degradation can be substantially slower.
A PLA product certified for industrial composting should therefore not automatically be treated as home compostable.
How Long Does PHA Take to Decompose?
PHA is a family of biodegradable polyesters rather than one single material.
Different PHA grades can have different biodegradation characteristics, and some have demonstrated biodegradation under a broader range of environments than PLA.
However, decomposition time still depends on the specific PHA grade, product structure, temperature, moisture and microbial environment.
A general claim that “PHA decomposes in X months” should therefore be treated as an approximation unless it is supported by product-specific testing.
How Long Do Compostable and Biodegradable Bags Take to Decompose?
“Biodegradable bag” and “compostable bag” should not automatically be treated as equivalent.
A certified compostable bag is evaluated against a defined compostability standard and a specified disposal environment.
A generic biodegradable claim, on the other hand, does not by itself tell you:
- where the bag should be disposed of
- how quickly it will biodegrade
- whether it is suitable for industrial composting
- whether it is suitable for home composting
Compostable bags may use materials such as PBAT, PLA and starch-containing formulations.
For certified products, decomposition claims should be based on the actual finished bag, applicable certification scope and intended composting environment rather than the raw material alone.
How Does Conventional Plastic Compare?
Conventional plastics such as polyethylene (PE) and PET are not designed to biodegrade under composting conditions.
Environmental exposure can cause conventional plastics to weather, weaken and fragment, but fragmentation is not the same as complete biodegradation.
This page focuses on biodegradable and compostable plastics.
For a detailed guide to conventional plastic bags, bottles and other products, see How Long Does It Take for Plastic to Biodegrade?
How ORIZON Evaluates Compostable Bag Claims
ORIZON manufactures compostable bags for B2B applications and works with product specifications and certification requirements including ASTM D6400, EN 13432, AS 4736 and TÜV compostability schemes.
A decomposition or compostability claim should always be matched to:
- the actual finished-product specification
- material formulation
- thickness
- printing and additives
- applicable certificate scope
- intended disposal environment
A raw-material claim should not automatically be treated as proof that every finished bag specification carries the same certification or decomposition performance.
For company and certificate evidence, see Verify ORIZON Certifications.
FAQ
How long does biodegradable plastic take to decompose?
There is no universal decomposition time. Certified industrially compostable plastics are designed to biodegrade under controlled composting conditions, while the same or similar materials can degrade much more slowly in soil, landfill, home compost or marine environments.
How long does compostable plastic take to decompose?
Commercially compostable plastic is tested against defined compostability requirements under controlled industrial or municipal composting conditions. The exact processing time depends on the product, standard and composting facility.
How long does PLA take to decompose?
PLA biodegrades most effectively under elevated-temperature industrial composting conditions. At ordinary ambient temperatures, including many soil and backyard-compost environments, degradation can be much slower.
How long do compostable bags take to decompose?
Certified compostable bags are designed to meet the decomposition and disintegration requirements of their applicable compostability standard. The actual time depends on the bag specification and composting conditions.
How long does a biodegradable bag take to decompose?
The term “biodegradable bag” alone does not provide a reliable decomposition time. The polymer, product thickness, test method and disposal environment must be known before a meaningful timeframe can be given.
Does biodegradable plastic decompose in landfill?
It may degrade very slowly, but landfill is not the controlled environment used for compostability testing. Industrially compostable products should not be expected to compost in landfill on the same timeline as they would in a suitable composting facility.
Does PLA decompose in home compost?
Not necessarily. PLA products designed only for industrial composting generally require higher temperatures than many backyard compost systems achieve. Only products with an appropriate home-compostability claim should be treated as home compostable.
Do bioplastics decompose?
Some do and some do not. “Bioplastic” can describe a bio-based material, a biodegradable material or both. The actual biodegradability depends on the polymer and its intended disposal environment.
What affects biodegradable plastic decomposition time?
Important factors include polymer chemistry, temperature, moisture, oxygen, microbial activity, film thickness, additives and product structure.
Is biodegradable plastic the same as compostable plastic?
No. Compostable plastic is a category of biodegradable plastic that must meet defined compostability requirements under specified conditions. Not every biodegradable plastic is compostable.
Conclusion
How long does biodegradable plastic take to decompose? There is no single number.
Certified compostable plastics can biodegrade within the timeframe required by the applicable compostability standard when processed under the correct controlled conditions. Outside those conditions, decomposition may be substantially slower.
The most reliable way to evaluate a claim is to identify the polymer, finished-product specification, certification and intended disposal environment rather than relying on a generic “biodegradable” label.
For more detail, see Biodegradable vs Compostable Bags or review ORIZON’s Certification & Verification Center.
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