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.

Definition

Compostable refers to materials that are scientifically proven and independently certified to biodegrade completely in defined composting environments, breaking down into water, carbon dioxide, and biomass without leaving harmful residues. Unlike the general term “biodegradable,” compostability is a precise, measurable property with standardized testing requirements and certification processes.

Compostability is fundamentally a standards-based definition: a material is only “compostable” if it meets specific criteria verified through rigorous laboratory testing and third-party certification. Without certification, claims of compostability are essentially unverifiable and potentially misleading.

Key Requirements for Certification

Biodegradation Rate:

• Minimum 90% biodegradation must occur within 180 days
• Testing conducted at 58°C (±2°C) in controlled industrial composting conditions
• Biodegradation measured as CO2 evolution (gas chromatography) or mass loss

Disintegration:

• Material must physically break apart into fragments smaller than 2mm
• Typically requires 90% fragmentation within 180 days
• Small fragments must not be visible in final compost
• Tests conducted on actual compost samples (not just laboratory measurements)

Ecotoxicity Assessment:

• Compost produced from the material must not harm plant growth or aquatic organisms
• Tested using standard ecotoxicity protocols (plant germination tests, earthworm viability)
• Must demonstrate no hazardous substances leach into soil or water
• Heavy metal content must comply with standards

Material Composition:

• Certifiers may restrict additives, dyes, and processing aids
• Certain substances banned entirely (heavy metals, persistent organics)
• Material identification and traceability required
• Formulation consistency over time mandatory

Types of Compostable Certification

Industrial Composting (Most Common):

• Designed for high-temperature, controlled facilities (55-60°C)
• Requires active management (aeration, moisture control, temperature monitoring)
• Fastest biodegradation rates (90-180 days)
• Suitable for: packaging films, food service items, agricultural applications
• Standards: EN 13432, ASTM D6400 (industrial only), OK Compost
• Represents 95%+ of commercially available compostable products

Home Composting:

• Designed for backyard or smaller-scale composting piles (40-50°C typical)
• More variable conditions (less active management)
• Slower degradation than industrial (up to 12 months or more)
• More stringent requirements (must work in realistic home conditions)
• Standards: ASTM D6868, DIN EN 14995 (limited home compostable certifications)
• Relatively rare due to stringent requirements and unpredictable home composting conditions

Marine Biodegradable:

• Separate certification for ocean/saltwater environments
• Different from traditional compostability standards
• Degradation timeframes: 1-3 years
• Standards: ASTM D6691, OK Biodegradable Marine, Vinçotte Marine
• Applications: fishing gear, marine coatings, aquaculture equipment

Composting Infrastructure and Processes

Industrial Composting Facility Operation:

1. Feedstock Preparation: Organic waste (food scraps, yard waste, compostable packaging) collected and prepared for composting

2. Process Control: Facilities manage:

   • Temperature maintenance (55-60°C optimal, often rising to 65-70°C)
   • Moisture level (40-60% ideal)
   • Carbon-to-nitrogen ratio (20-30:1)
   • Aeration through turning or forced air

3. Degradation Phase: Over 3-6 weeks, compostable materials and organic waste break down under microbial action

4. Curing and Screening: Remaining compost allowed to cure, then screened to remove fragments above 2mm

   • Oversized fragments (including incompletely degraded material) removed
   • This screening step essential for certification compliance
   • Undigested material recycled back to process

5. Quality Control: Final compost tested for:

   • Contamination rates
   • Heavy metals
   • Plant growth performance
   • Stability and maturity

6. End Product: Finished compost used for:

   • Soil amendment in agriculture and landscaping
   • Potting soil components
   • Top dressing for gardens and parks
   • Erosion control and land remediation

Geographic Variation: Composting infrastructure differs significantly by region:

• Europe: Most developed infrastructure; EN 13432 standard widely adopted; strong municipal programs
• North America: Growing but variable; ASTM D6400 standard; municipal programs expanding
• Asia: Rapidly developing; mixed standards; investment in infrastructure increasing
• Developing nations: Minimal infrastructure; manual composting more common than mechanized facilities

International Certification Standards

EN 13432 (European Standard): Developed by CEN (European Committee for Standardization); most rigorous and recognized globally:

• 90% biodegradation in 180 days at 58°C
• Disintegration to <2mm fragments
• Plant ecotoxicity testing (germination index)
• Heavy metal content limits
• Recognized in Europe, increasingly internationally
• Third-party testing and annual audits required

ASTM D6400 (North American Standard): Developed by American Society for Testing and Materials; major standard in USA/Canada:

• 90% biodegradation in 180 days (industrial) or 360 days (home)
• Disintegration requirements
• Ecotoxicity testing
• Slightly less stringent than EN 13432 in some parameters
• Growing alignment with EN 13432 for international compatibility

ASTM D6868 (Home Compostable): Specific standard for home composting applications:

• 90% biodegradation in one year at 20-30°C (ambient temperature)
• Stringent requirements reflecting unpredictability of home composting
• Very few materials certified to this standard
• More demanding than industrial standards

ISO 14855 Series (Test Methods): International standardized test protocols:

• ISO 14855-1: Aerobic biodegradation (measurement of CO2 evolution)
• ISO 14855-2: Anaerobic biodegradation
• Not a certification standard itself but establishes testing methodology
• Used to verify compliance with EN 13432, ASTM D6400, and other standards

OK Compost Certification: European certification program administered by TÜV Austria:

• Verifies EN 13432 compliance
• Covers both industrial and home compostable products
• Third-party testing and annual follow-up audits
• Recognized certification mark on products

DIN EN 14995 (Plastic Materials): German/European standard for plastic product design for composting:

• Specifies design requirements (not just material properties)
• Addresses contaminants, additives, lamination, pigments
• Supplements material-level standards with product-level requirements

Certified Compostable Materials

PLA (Polylactic Acid):

• Requires blending with PBAT or other polymers to meet EN 13432
• Pure PLA does NOT meet standards (too slow to degrade)
• PLA/PBAT blends (typically 70/30 to 80/20) are EN 13432 certified
• Most widely used compostable plastic material

PBAT (Polybutylene Adipate Terephthalate):

• Readily compostable when formulated correctly
• Excellent film flexibility enables bag and film applications
• Often used as blending component rather than standalone
• EN 13432 certified formulations widely available

PBS (Polybutylene Succinate):

• Fully compostable to EN 13432 standards
• Better heat resistance than PLA enables hot-fill applications
• Excellent mechanical properties for durable compostable products
• Less widely used than PLA/PBAT but growing market

PHA (Polyhydroxyalkanoates):

• Most formulations readily compostable in industrial conditions
• Many PHA types also marine biodegradable (bonus environmental property)
• Available from multiple suppliers (Danimer, Kaneka, etc.)
• Higher cost limits mass-market adoption

Starch-based Blends:

• Starch/PBAT blends (40-70% starch) are EN 13432 certified
• Lower cost than polymer-only options
• Excellent for bags and flexible applications
• Moisture sensitivity requires controlled storage

Critical Distinctions

Compostable ≠ Biodegradable:

• Compostable is a specific, certified claim
• A material may eventually biodegrade but not meet composting standards
• Example: A plastic that takes 10 years to degrade in soil is biodegradable but NOT compostable

Compostable ≠ Home Compostable:

• Most certified compostable materials require 58°C industrial conditions
• Home compost typically only reaches 40-50°C
• Home compostable materials are rare and harder to find
• Labeling distinction critical for consumer understanding

Compostable ≠ Biodegradable in Landfills:

• Industrial composting provides optimal conditions: oxygen, temperature, microbial diversity
• Landfills are anaerobic (oxygen-depleted), cold, and inhospitable
• Materials that readily compost may persist for years in landfills
• Composting infrastructure dependence is critical distinction

Compostable ≠ Natural or Necessarily Renewable:

• Some compostable plastics are petroleum-derived (PBAT)
• Bio-based content and compostability are independent properties
• A fossil-derived material can be compostable; a bio-based material may not be

Compostable ≠ Best Environmental Option for All Scenarios:

• Benefits only realized if industrial composting infrastructure exists and material actually reaches facility
• In regions without composting infrastructure, compostable materials in landfills offer no advantage over conventional plastics
• For applications with efficient recycling (bottles), recycled options may be preferable to compostable

Composting Infrastructure Challenges

Geographic Variability:

• Facilities concentrated in developed countries
• Rural areas often lack infrastructure
• Inconsistent facility capabilities and standards
• Infrastructure development lags market growth

Collection Systems:

• Requires separate collection from standard recycling
• Consumer confusion between compostable and recyclable
• Many municipalities lack organic waste collection programs
• Contamination of recycling streams when compostable placed in recycling bins

Facility Contamination:

• Compostable items mixed with non-compostable contaminate batches
• Some facilities cannot process certain compostable materials
• Certification verification required for facility acceptance
• Labeling clarity essential for sorting

Economic Feasibility:

• Municipal programs require adequate feedstock volumes
• Economics depend on tipping fees and compost market value
• Many facilities focus on yard waste and food scraps, not packaging
• Infrastructure investment barriers in developing regions

Consumer Education Gap:

• Many consumers unfamiliar with composting requirements
• Confusion about what goes in composting vs. recycling
• “Green” appearance misleading (suggests environmental solution regardless of infrastructure)
• Marketing sometimes overstates environmental benefits

Environmental and Performance Considerations

Water Usage:

• Industrial composting requires adequate moisture
• Can increase water consumption in water-stressed regions
• Infrastructure design critical for water efficiency

Emissions Profile:

• Proper composting produces CO2 and H2O (beneficial)
• Poorly managed facilities may produce methane (potent greenhouse gas)
• Carbon footprint depends on facility efficiency and compost end-use

Infrastructure Development:

• Compostable materials drive infrastructure investment
• Composting programs create jobs and local economic benefits
• Nutrient recycling in compost returns value to soil
• Supports circular economy and soil health

Contamination Risks:

• Compostable bags/packaging in recycling contaminate plastic batches
• Non-compostable items in compost reduce quality
• Clear labeling and consumer education essential
• Facility must screen out over-sized fragments

Future Outlook

Infrastructure Expansion: Expected growth in composting facilities driven by:

• Regulatory mandates for organic waste collection (EU, some US states, Asia)
• Corporate commitments to compostable packaging
• Recognition of compost value for soil health
• Carbon sequestration benefits in soil

Material Development:

• Advanced blends optimizing cost and performance
• Temperature-triggered degradation (degradation only in industrial settings)
• Improved home composting formulations
• Marine compostable materials for aquatic applications

Standards Evolution:

• Harmonization of EN 13432 and ASTM D6400 for global trade
• Expanded marine biodegradable standards
• Product-level design standards (ISO 14995 expansion)
• Verification and tracking systems for certified materials

Market Growth:

• Compostable plastics production estimated to grow 10-15% annually through 2030
• Driven by single-use plastic bans and organic waste regulations
• Expected capacity expansion in developing regions
• Material price expected to decrease as scale increases

Compostability represents a scientifically rigorous, certified approach to end-of-life management for single-use materials. Unlike vague “biodegradable” claims, compostability guarantees are backed by international standards, third-party testing, and facility-level validation. However, these guarantees only deliver environmental benefits if industrial composting infrastructure exists where end-of-life products are managed. As composting infrastructure expands globally and consumer awareness improves, compostable materials are positioned to become a cornerstone of circular economy systems for single-use items and packaging.