Compostable vs Biodegradable: What Those Words Actually Mean

The Key Difference

Compostable means a product breaks down under specific composting conditions (typically industrial facilities with 140-160°F sustained heat) within a defined timeframe, leaving nutrient-rich compost.

Biodegradable means a material breaks down through biological processes in various natural environments. When paired with a specific test standard and timeframe (e.g., "biodegradable per ASTM D6691 in marine environments within 6 months"), this provides clear, verifiable performance expectations.

The critical question: Does your community have industrial composting facilities? If not, biodegradable materials tested for soil, marine, or landfill conditions may be more practical than "compostable" materials that require infrastructure you don't have access to.

Composting field

What "Compostable" Really Means (And Its Limitations)

The Industrial Composting Requirement

"Compostable" typically refers to industrial composting standards like ASTM D6400 or EN 13432, which require:

• High sustained temperatures: 140-160°F for weeks
• Controlled conditions: Specific moisture, oxygen, and microbial activity
• 180-day timeframe: ≥90% of material must biodegrade
• Commercial facilities: These conditions rarely exist outside industrial operations

The Infrastructure Problem

Here's the challenge: Most communities lack industrial composting facilities. According to industry data:

• Only ~25-30% of Americans have access to commercial composting
• Many facilities don't accept compostable packaging (only food waste)
• Without proper infrastructure, "compostable" products end up in landfills
• In landfills, compostable materials don't break down as intended

Important reality: A product being "compostable" only provides environmental benefit if it actually reaches an industrial composting facility and is accepted there.

Laboratory Testing vs. Certification

Products can meet compostability standards through:

• Laboratory test reports: Accredited labs test products to ASTM D6400/EN 13432 and provide documentation
• Third-party certification: Organizations like BPI or TÜV Austria review lab reports and issue certifications (adds cost, takes time)

Both paths require the same rigorous lab testing. Lab-verified products meet the same performance standards as certified products - certification is an additional verification layer that some businesses pursue for marketing purposes.

What "Biodegradable" Really Means

The Good: Biodegradable with Test Standards

Properly tested biodegradable materials specify exactly how, where, and when they break down. Examples:

• ASTM D5511: Anaerobic biodegradation in landfill conditions (what actually happens to most waste)
• ASTM D6691: Marine biodegradation - breaks down in ocean water if accidentally littered
• ISO 17556: Soil biodegradation - breaks down when buried in soil
• ASTM D5338: Aerobic biodegradation - breaks down in composting-like conditions

Why this matters: These standards test biodegradation in environments that actually exist and are accessible. You don't need special industrial facilities - the materials work where waste naturally ends up.

The Bad: Vague "Biodegradable" Claims

Without a specific test standard and timeframe, "biodegradable" is meaningless. Watch out for:

• No test standard mentioned - How do they know it biodegrades?
• No timeframe specified - Could take 1 year or 100 years
• No environmental conditions stated - In what conditions does it break down?
• "Oxo-degradable" plastics - These just fragment into microplastics (banned in EU)

Always ask: "What test standard proves this claim, and what's the timeframe?" Legitimate suppliers will have lab reports ready to share.

Biodegradation in soil

Comparing the Standards

Understanding Different Biodegradation Standards

ASTM D5511: Anaerobic Landfill Biodegradation

• Environment: Anaerobic (no oxygen) conditions like actual landfills
• Why it matters: This is where most waste actually ends up
• Practical benefit: Materials break down even if commercial composting isn't available
• Typical timeframe: Varies by material, measured over months to years

ASTM D6691: Marine Biodegradation

• Environment: Ocean water conditions
• Why it matters: If waste accidentally reaches waterways, it breaks down rather than persisting
• Practical benefit: Environmental safety net for coastal areas
• Materials: PHA is marine biodegradable; PLA is not

ISO 17556: Soil Biodegradation

• Environment: Soil conditions (buried in ground)
• Why it matters: Works in agricultural settings or land applications
• Practical benefit: Accessible for farms, gardens, and rural areas
• Typical timeframe: 6-24 months depending on material and soil type

ASTM D6400: Industrial Composting

• Environment: Industrial composting facilities (140-160°F)
• Why it matters: Fastest breakdown, creates usable compost
• Limitation: Requires access to commercial composting facility
• Typical timeframe: 180 days

Real-World Examples

Lab-Verified Biodegradable Materials (Look for test reports)

• PLA straws - Lab-tested to ASTM D6400 (compostable) + ASTM D5511 (landfill biodegradable)
• PHA straws - Lab-tested to ASTM D6400, D5511, D6691 (marine), ISO 17556 (soil)
• Quality paper products - Natural biodegradation with predictable breakdown

Avoid: Vague "Biodegradable" Without Documentation

• "Oxo-degradable" plastics - Fragment into microplastics, banned in EU
• "Biodegradable" without test standard - No proof of actual breakdown
• Petroleum plastic with vague claims - May not truly biodegrade
• "Eco-friendly" without specifics - Marketing language, not verified performance

Why This Matters for Your Business

Match Materials to Your Infrastructure Reality

If your community has industrial composting: Compostable products (ASTM D6400) are ideal - they'll actually be composted as intended.

If you don't have access to composting: Materials with broader biodegradation testing (ASTM D5511 landfill, ISO 17556 soil, D6691 marine) ensure environmental benefits even without specialized facilities.

Customer Communication

Be honest about end-of-life options:

• "Lab-tested biodegradable" with specific standards builds credibility
• Don't overpromise on composting if infrastructure doesn't exist locally
• Show test reports when customers ask about environmental claims
• Multiple pathways (compostable + landfill biodegradable) show genuine commitment

Regulatory Compliance

Some jurisdictions have specific requirements:

• California requires compostable certification for certain product claims
• European Union bans oxo-degradable "biodegradable" plastics
• Many cities specify materials for single-use foodware bans
• Always have lab documentation ready to prove your claims

How to Verify Biodegradability Claims

Ask for Lab Test Reports

Legitimate suppliers will provide:

• Accredited lab reports showing specific test standards (ASTM D5511, D6691, ISO 17556, etc.)
• Timeframes and conditions clearly stated in the test results
• Percentage of biodegradation achieved in testing
• Product specifications matching what you're actually buying

Understand What Matters to Your Business

Ask yourself:

• Does my community have industrial composting? (If yes, prioritize ASTM D6400)
• Will this waste go to landfills? (Look for ASTM D5511 testing)
• Do we operate near water? (Consider ASTM D6691 marine biodegradation)
• Do customers have compost bins at home? (Look for home compostable or soil biodegradable)

Red Flags to Watch For

• "Biodegradable" without naming a test standard
• "Eco-friendly" or "green" without specifics
• "Breaks down naturally" without timeframe or conditions
• "Degrades in landfills" without ASTM D5511 test report

Different End-of-Life Pathways

Industrial Composting (Best Case - If Available)

• Conditions: 140-160°F sustained heat, controlled moisture and microbes
• Timeframe: Typically 180 days for ASTM D6400 materials
• Result: Nutrient-rich compost for agriculture/landscaping
• Availability: Limited - only 25-30% of US has access
• Acceptance: Many facilities only take food waste, not packaging

Home Composting (Rare but Growing)

• Conditions: Lower temperatures (ambient to 100°F), backyard conditions
• Timeframe: 12-24 months typically
• Materials: Limited - only PHA and some paper products work reliably
• Look for: TÜV Austria OK compost HOME or equivalent testing

Landfill Biodegradation (Most Common Reality)

• Conditions: Anaerobic (no oxygen), variable temperature/moisture
• Timeframe: Varies by material - test standard ASTM D5511 measures this
• Materials: PHA and composites can biodegrade here if properly formulated
• Reality check: Where most waste actually ends up

Soil Biodegradation

• Conditions: Buried in soil, natural microbes
• Timeframe: 6-24 months typical per ISO 17556
• Practical for: Agricultural operations, rural areas, gardens
• Materials: PHA and composites excel here

Marine Environment

• Conditions: Ocean water, natural marine microbes
• Timeframe: Varies - test standard ASTM D6691
• Materials: PHA biodegrades in marine conditions; PLA does not
• Importance: Safety net if waste accidentally reaches waterways

Frequently Asked Questions

Can I throw compostable products in my trash?

You can, but they need the right conditions to biodegrade. If your waste goes to a landfill, look for products that have been tested to ASTM D5511 (anaerobic landfill biodegradation) to ensure they'll actually break down there.

Are "biodegradable" or "compostable" plastics recyclable?

No - these materials contaminate traditional plastic recycling and must be sorted out. They're designed for composting or biodegradation, not recycling.

What if my city doesn't have commercial composting?

This is the reality for most places. In this case, materials like PHA with multiple biodegradation pathways (tested to ASTM D5511 for landfills, ISO 17556 for soil, etc.) provide more practical environmental benefits than compostable-only materials.

How do I know if a supplier's claims are real?

Ask for lab test reports. Legitimate suppliers will provide test reports or documentation showing specific test standards (ASTM D6400, D5511, D6691, ISO 17556, etc.) with results and timeframes. If they can't provide test reports, be skeptical.

Is "home compostable" better than "industrial compostable"?

It's more accessible since anyone with a compost bin can use it, but fewer materials qualify. Industrial compostable works faster and for more material types, but requires facility access. Ideally, choose materials tested to multiple standards.

Do compostable products break down in landfills?

It depends. Landfills lack the oxygen and microbial activity of composting facilities, so breakdown is much slower. Materials tested to ASTM D5511 are designed to biodegrade in landfill conditions; materials only tested to ASTM D6400 may not.

What about PLA vs PHA for biodegradation?

PLA: Works in industrial composting (D6400) and can biodegrade in landfills (D5511) if properly formulated. Does not biodegrade in marine environments.

PHA: Works in industrial composting, landfills, soil (ISO 17556), and marine environments (D6691). More biodegradation pathways but typically higher cost.

Should I trust certification logos or lab reports?

Both are valuable. Certifications (BPI, TÜV Austria) mean an organization has reviewed the lab reports and verified claims - adds credibility but also cost and time. Lab reports alone (from accredited labs) show the same test performance; you're just reviewing the data directly rather than through a third party. Either way, the underlying lab testing is what proves biodegradation.