Compostability Certifications for Molded Pulp Packaging: A Technical Reference Guide

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Quick Reference: Certification Standards at a Glance

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EN 13432 vs. ASTM D6400: The Technical Differences

Both standards demand the same four pillars — biodegradation, disintegration, eco-toxicity, and heavy metals — but they differ in testing methodology and assessment approach.

Biodegradation Requirements

| Parameter | EN 13432 | ASTM D6400 |

|:--|:--|:--|

| Test method | ISO 14855-1 (controlled composting) | ASTM D5338 (controlled composting) |

| Temperature | 58°C ± 2°C | 58°C ± 2°C |

| Duration | Maximum 180 days (typically 45-90 for cellulose) | Same as EN 13432 for homopolymer materials |

| Threshold | ≥90% absolute biodegradation OR ≥90% relative to cellulose reference | ≥90% absolute biodegradation |

| Individual constituents | Each organic constituent >1% mass must achieve ≥90% | Product assessed as whole |

Practical implication: EN 13432's "per-constituent" requirement means any coating, pigment, or additive used in molded pulp above 1% by mass must independently meet the 90% biodegradation threshold. This is why water-based barrier coatings (starches, plant waxes, acrylic emulsions) must be individually tested — not just assumed to biodegrade as part of the pulp matrix.

Disintegration Requirements

| Parameter | EN 13432 | ASTM D6400 |

|:--|:--|:--|

| Test method | ISO 16929 (pilot-scale composting) | ASTM D5929 |

| Duration | 12 weeks | 84 days (12 weeks) |

| Threshold | ≥90% passes through 2mm sieve | ≥90% passes through 2mm sieve |

Molded pulp consistently achieves 100% disintegration within 4-6 weeks — far below the 12-week threshold. The fiber structure absorbs moisture and fragments rapidly in the thermophilic composting phase.

Heavy Metal Limits (Identical Across Both Standards)

| Element | Limit (mg/kg dry substance) |

|:--|:--|

| Zinc (Zn) | 150 |

| Copper (Cu) | 50 |

| Nickel (Ni) | 25 |

| Cadmium (Cd) | 0.5 |

| Lead (Pb) | 50 |

| Mercury (Hg) | 0.5 |

| Chromium (Cr) | 50 |

| Molybdenum (Mo) | 1 |

| Selenium (Se) | 0.75 |

| Arsenic (As) | 5 |

| Fluorine (F) | 100 |

Uncoated virgin kraft pulp typically measures below 20% of all thresholds. The critical checkpoint for coated molded pulp is the coating chemistry — PFAS, certain pigments, and some synthetic binders can push individual elements near or above limits.

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OK Compost HOME: When Industrial Composting Isn't Enough

The distinction between OK Compost INDUSTRIAL and OK Compost HOME is technically significant:

| Parameter | OK Compost INDUSTRIAL (EN 13432) | OK Compost HOME |

|:--|:--|:--|

| Temperature | 58°C ± 2°C (thermophilic) | 20-30°C (ambient) |

| Duration for biodegradation | 180 days max | 365 days max |

| Test method | ISO 14855-1 | ISO 14855-1 modified (ambient temp) |

| Disintegration method | ISO 16929 | ISO 16929 modified |

| Practical availability | Requires industrial composting facility | Backyard compost heap |

For molded pulp: Uncoated molded pulp achieves OK Compost HOME certification. Coated molded pulp with water-based barriers at <5% weight may pass, but this must be confirmed through specific testing — the lower temperature slows barrier degradation significantly. PLA-coated molded pulp generally does not pass HOME certification because PLA requires temperatures above 55°C for hydrolysis — conditions only found in industrial composting.

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Buyer's Certification Checklist

When sourcing certified compostable molded pulp packaging, request:

✅ Valid certificate from a recognized body (TÜV Austria, DIN CERTCO, or BPI) — check expiration date and scope (does it cover your specific product configuration?)

✅ Certificate number for independent verification on the certifier's public database

✅ Lot traceability system — each production batch should be traceable to the certified production site and product specification

✅ Coating/additive disclosure — full list of all coating components with individual biodegradation data if any exceed 1% mass

✅ Heavy metal test report — third-party lab, not supplier self-declaration, testing all 11 elements at the thresholds above

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*This technical reference covers major compostability certifications relevant to molded pulp packaging. Certification requirements may vary by end-market jurisdiction. Always verify current certificate validity with the issuing body.*