What Is Compostable? (Official Definition)
What Does “Compostable” Mean?
Compostable means that a material or finished product is designed to break down through biological activity under defined composting conditions, within a specified timeframe, without leaving harmful residues that would prevent the resulting compost from meeting applicable requirements.
In practical terms, “compostable” does not mean that a product will simply disappear wherever it is discarded. Composting requires suitable conditions such as moisture, oxygen, microbial activity and, depending on the composting system, controlled temperature.
This is why compostability is a defined and verifiable property rather than a general environmental marketing term.
Unlike vague environmental claims, compostability is a verifiable property that can be assessed against recognized standards and certification requirements. To be considered compostable, a material must:
Decompose under controlled composting conditions (temperature, humidity, oxygen, and microbial activity)
Fully disintegrate within a specified period, typically 90–180 days in industrial composting
Leave no harmful residues and support healthy soil quality
In packaging and waste management systems, compostability claims may be assessed against recognized standards such as EN 13432, ASTM D6400 and AS 4736, while certification schemes such as OK compost INDUSTRIAL and OK compost HOME by TÜV AUSTRIA provide third-party certification within their applicable certificate scope.
Materials that do not meet these certification requirements may still be biodegradable in theory, but they do not qualify as compostable in regulated composting or waste collection systems.
Compostable Is a Controlled Claim — Not a Promise of Natural Breakdown
A common misunderstanding is that a compostable product will break down quickly in any natural environment.
In reality, compostability depends on the conditions for which the product has been designed and assessed. Industrial composting, home composting, soil, landfill and marine environments are not interchangeable.
A product described as compostable should therefore be evaluated against the applicable composting route, standard, certification requirements and actual waste-management system.
Composting Conditions Required
Compostable materials do not break down in normal soil, oceans, or landfills.
They require a managed composting environment with:
Sustained elevated temperatures
Controlled humidity
Oxygen circulation
Active microbial populations
Without these conditions, compostable materials may remain intact for long periods and should not be assumed to decompose naturally.
Key Criteria That Define Compostable Materials
To be genuinely compostable, a material must meet all of the following conditions:
- Biological decomposition by microorganisms
- Time-bound breakdown, typically within 90–180 days under industrial composting
- Complete disintegration, not fragmentation into microplastics
- No toxic residue, proven through plant growth and ecotoxicity testing
- Certification under established standards, not self-declared claims
Materials that merely “break down over time” without these controls do not qualify as compostable in regulated systems.
Compostable vs Biodegradable vs Recyclable
These terms are often confused, but they are not interchangeable.
| Term | What It Means | Key Limitation |
|---|---|---|
| Compostable | Fully breaks down into harmless organic matter under certified composting conditions | Requires correct composting system |
| Biodegradable | May break down eventually, with no defined timeframe or residue guarantee | Microplastics risk |
| Recyclable | Can be reprocessed into new products | Contamination if mis-sorted |
All compostable materials are biodegradable, but not all biodegradable materials are compostable.
For a full comparison, see: Biodegradable vs Compostable: Key Differences Explained
Is Compostable the Same as Biodegradable?
Compostable materials are biodegradable, but most biodegradable materials are not compostable.
Biodegradable claims do not guarantee complete breakdown, safe residues, or compatibility with composting systems.
Compostable products should meet applicable compostability standards, performance requirements and certification requirements for the intended market.
What Conditions Are Required for Composting?
Most compostable materials — especially compostable plastics — are designed for industrial composting, not natural soil or landfills.
To understand why these materials behave differently in backyard systems, see the differences between home composting and industrial composting.
Typical industrial composting conditions include:
- Sustained temperatures above 55 °C
- Controlled humidity
- Adequate oxygen flow
- High microbial activity
Without these conditions, compostable materials will not decompose as intended.
Does Compostable Mean Home Compostable?
No. A product described as compostable should not automatically be assumed to be suitable for home composting.
Industrial and home composting operate under different conditions. Home-compostable claims should be supported by requirements applicable to the finished product. For example, AS 5810 is an Australian home-compostability standard, while OK compost HOME is a TÜV AUSTRIA certification scheme and conformity mark.
For a detailed comparison, see our Home Composting vs Industrial Composting guide.
Home-compostable claims should be supported by requirements applicable to the finished product. AS 5810 is an Australian home-compostability standard, while OK compost HOME is a certification scheme and conformity mark operated by TÜV AUSTRIA.
This distinction exists because home and industrial composting systems are not interchangeable.
To understand what home composting systems can realistically handle, including temperature limits and material restrictions, see our guide on home composting basics.
Common Compostable Materials
Compostable products can be made from various bio-based or bio-derived materials, including:
PLA (Polylactic Acid) – widely used; industrial composting required
PBAT / PBS blends – flexible films and compostable bags
PHA – fully compostable and, in limited cases, marine-degradable
Plant fibers such as bagasse and paper-based composites
Material choice affects performance, cost, durability, and composting compatibility.
Compostability Standards and Certification Schemes
Compostability is not a marketing claim — it is a verified property.
Common compostability standards and certification schemes include:
- EN 13432 – European industrial compostability standard
- ASTM D6400 – U.S. industrial compostability standard
- AS 4736 – Australian industrial compostability standard
- AS 5810 – Australian home compostability standard
- OK compost INDUSTRIAL / OK compost HOME – TÜV AUSTRIA certification schemes and conformity marks
Compostability claims should be supported by the applicable standard, testing, documentation and certification requirements of the target market.
How to Identify Genuine Compostable Plastics
Because environmental claims are often misused, identifying genuine compostable plastics requires more than marketing language.
Examples of Compostability Standards and Certification Marks
BPI Certification Mark
A third-party certification mark used for eligible products meeting applicable ASTM compostability requirements.
Seedling Mark
A certification mark associated with industrial compostability requirements such as EN 13432. Certification may be issued by authorized certification bodies, including TÜV AUSTRIA and DIN CERTCO.
AS 4736
An Australian standard defining requirements for biodegradable plastics suitable for industrial composting. AS 4736 itself is a standard, not a certification mark.
OK compost INDUSTRIAL / OK compost HOME
TÜV AUSTRIA certification schemes and conformity marks. Their use is permitted only for products covered by the applicable certification scope.
Common Misunderstandings About “Compostable”
- Compostable does not mean it breaks down anywhere
- Compostable does not mean recyclable
- Compostable does not guarantee home compostability unless explicitly certified
- Compostable claims without certification increase compliance and contamination risks
What “Compostable” Does Not Mean
Compostable does not mean that a product:
Breaks down in landfills
Decomposes in oceans or natural environments
Can be recycled with conventional plastics
Will compost at home unless explicitly certified
Incorrect disposal can eliminate the environmental benefits of compostable materials and contaminate waste streams.
Where Should Compostable Products Be Disposed?
Compostable products should only be placed in a composting or organics collection system that accepts the specific product.
The correct disposal route depends on:
- whether the product is industrial or home compostable;
- the applicable certification and product labeling;
- local council or municipal rules;
- organics collection requirements; and
- acceptance rules of the composting facility.
Industrially compostable products should not automatically be placed in a home compost bin, and compostable plastics should generally not be mixed with conventional plastic recycling.
Local acceptance should always be checked because certification does not guarantee that every municipal organics program accepts every compostable product.
For practical disposal guidance, see How to Dispose of Compostable Plastics Correctly.
How Long Does Compostable Plastic Take to Decompose?
Decomposition time depends entirely on the composting environment:
Industrial composting: ~90–180 days
Home composting (certified products only): up to 12 months
Landfill or uncontrolled environments: unpredictable and often ineffective
Always follow local organics collection rules and product labeling.
Why the Definition of Compostable Matters for Businesses
For brands, packaging buyers, and municipalities, using the correct definition helps to:
Avoid greenwashing and compliance risk
Meet labeling and regulatory requirements
Prevent contamination of recycling systems
Support ESG and sustainability reporting
In regulated waste systems, misusing the term “compostable” can result in fines, rejected packaging, or loss of trust.
Frequently Asked Questions
No. Compostable materials should not be placed in plastic recycling streams.
No. Compostable materials require controlled composting conditions.
No. Home compostable products must meet stricter, separate certification requirements.
No. Compostable plastics must not be placed in plastic recycling streams.
In regulated waste systems, certified compostable materials provide clearer and more verifiable environmental outcomes.
Certified compostable materials should not — when processed under proper composting conditions.
Only when they are correctly certified, correctly disposed of, and supported by composting infrastructure.
Home composting is limited in temperature and consistency. To understand these limits in practice, review our home composting basics guide.
Related Knowledge Pages
Conclusion
Compostable is a scientifically and legally defined term that applies only to materials proven to break down safely under controlled composting conditions.
Understanding this definition helps buyers, brands, and waste systems make accurate, compliant, and responsible decisions — and avoid misleading environmental claims.
