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Compostable

Term Also known as: Certified Compostable, Industrially Compostable, Home Compostable

Quick Overview

Compostable materials meet strict international standards requiring complete biodegradation and disintegration within 180 days in industrial composting facilities. Certification ensures environmental safety and compatibility with composting systems.

Related terms: Biodegradable PLA PBAT Starch-based Bioplastic EN 13432 Composting Infrastructure

What Does “Compostable” Mean?

A material is compostable when it has been independently certified to biodegrade completely under defined composting conditions — breaking down into water, carbon dioxide, and biomass without leaving harmful residues. Unlike the vague term “biodegradable”, compostability is a precise, standards-backed claim.

The key distinction: All compostable materials are biodegradable, but not all biodegradable materials are compostable. Compostability requires certification against specific standards with strict timeframes and conditions.

Composting Certification Requirements

To earn compostable certification, a material must pass four tests:

1. Biodegradation

  • ≥90% biodegradation within 180 days under industrial composting conditions (58°C ± 2°C)
  • Measured as CO₂ evolution using respirometry or gas chromatography
  • Must demonstrate complete organic carbon conversion

2. Disintegration

  • Material must physically fragment to pieces smaller than 2mm within 180 days
  • No visible fragments remaining after screening
  • Tested on actual compost samples, not just laboratory media

3. Ecotoxicity

  • Compost produced from the material must not harm plant growth or soil organisms
  • Plant germination tests (cress, radish) must show no significant inhibition
  • Earthworm viability testing required under some standards
  • Heavy metal content must comply with limits

4. Material Composition

  • Restrictions on certain additives, dyes, and processing aids
  • Heavy metals and persistent organic pollutants prohibited
  • Formulation consistency required for certification maintenance

Types of Compostable Certification

CertificationStandardTemperatureTimeframeCommon Products
Industrial compostingEN 1343255–68°C180 daysPackaging, food service, bags
Industrial compostingASTM D640055–60°C180 daysNorth American market
Home compostingOK Compost HOME20–30°C365 daysLimited products
Home compostingASTM D686820–30°C365 daysVery few certified products
Marine biodegradableASTM D6691Variable seawater1–3 yearsFishing gear, marine applications

Important: Most commercially compostable products are certified for industrial composting only. Home compostable certification is significantly harder to achieve, and very few materials qualify.

Certified Compostable Bioplastics

Not every bioplastic is compostable. Here’s how the major materials perform:

MaterialCompostable?CertificationNotes
PLA (blended)Yes (with PBAT)EN 13432, ASTM D6400Pure PLA degrades too slowly alone
PBATYesEN 13432, ASTM D6400Typically used as blending component
PHAYesEN 13432, ASTM D6400Also marine biodegradable
Starch/PBAT blendsYesEN 13432, ASTM D6400Most cost-effective compostable option
PBSYesEN 13432, ASTM D6400Better heat resistance than PLA
PCLYesASTM D6400Medical and specialty applications
Bio-PENoNot compostableIdentical to conventional PE — recyclable only
Bio-PETNoNot compostableIdentical to conventional PET — recyclable only

Critical Distinctions

Compostable ≠ Biodegradable

Biodegradable has no defined timeframe. A material could take 50 years to biodegrade and still be “biodegradable.” Compostable requires 90% degradation in 180 days at certified conditions.

Compostable ≠ Home Compostable

Most compostable products require industrial facilities operating at 55–68°C. Backyard compost bins rarely exceed 40°C, meaning industrially compostable PLA will not reliably degrade in home compost.

Compostable ≠ Landfill-friendly

Compostable materials in landfill conditions (anaerobic, low temperature, limited microbial activity) degrade extremely slowly — sometimes no faster than conventional plastic. Composting infrastructure is essential.

Compostable ≠ Bio-based

PBAT is petroleum-derived but compostable. Bio-PE is plant-based but not compostable. These are independent properties.

Recognised Certification Marks

Look for these logos on compostable products:

  • Seedling logo (European Bioplastics) — EN 13432 certified
  • OK Compost (TÜV Austria) — Industrial and home composting
  • BPI (Biodegradable Products Institute) — North America (ASTM D6400)
  • DIN CERTCO — European certification body

Composting Infrastructure Dependency

Compostable materials deliver their environmental benefit only when they reach appropriate composting facilities. A compostable bag in a landfill provides no advantage.

The composting chain requires:

  1. Consumer awareness — knowing compostable materials go in organic waste bins, not recycling
  2. Separate collection — dedicated organic waste collection systems
  3. Processing facilities — industrial composting plants operating at 55–68°C
  4. End markets — demand for finished compost from agriculture and landscaping

Without all four elements, compostable materials cannot fulfill their environmental promise.

Frequently Asked Questions

Is compostable better than recyclable? It depends on the application. For food-contaminated packaging, compostable is often better (recycling degrades with food residue). For clean bottles, recycling typically recovers more value.

Can I compost certified products at home? Only if the product specifically carries home composting certification (OK Compost HOME or equivalent). Most industrially compostable products will not degrade in a home compost bin.

Do compostable plastics contaminate recycling? Yes. Compostable plastics in recycling streams can compromise recyclate quality. They should be directed to composting, not recycling.

How can I tell if something is truly compostable? Look for recognised certification marks (Seedling logo, OK Compost, BPI) rather than just “biodegradable” or “eco-friendly” claims.

Are compostable plastics more expensive? Generally yes — typically 30–200% more than equivalent conventional plastics, depending on material and application. Prices are decreasing as production scales up.

What happens to compostable packaging in landfill? Very little. Landfill conditions (anaerobic, low temperature) do not support the microbial activity needed for composting. Compostable materials in landfill may persist for years.

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