Fully Compostable Packaging Bag with OK Compost Industrial and Home Certified Multi-Layer Bio-Polymer Film Structure

Achieving compostability in a multi-layer flexible package requires solving a materials compatibility challenge that conventional packaging avoids entirely. In a standard composite pouch (PET/foil/PE), each layer serves a single function and the layers are bonded permanently — the PET provides print surface and stiffness, the foil provides barrier, the PE provides sealability. In a compostable pouch, every layer must also degrade under the same biological conditions within the same time window, and the degradation products of each layer must not inhibit the degradation of the other layers. The EN 13432 standard requires that the complete package disintegrates (fragments <2mm after 12 weeks), biodegrades (>90% conversion to CO₂ within 6 months), and passes ecotoxicity testing (no adverse effects on plant germination and growth at 100% compost concentration).

Our structure achieves this through a carefully selected combination of certified compostable polymers: the outer layer is a blend of PBAT (polybutylene adipate terephthalate) and PLA that provides the flexibility and toughness that pure PLA lacks — PBAT is an aliphatic-aromatic copolyester that is fully biodegradable through enzymatic hydrolysis of the ester bonds, and its elastomeric properties compensate for PLA’s inherent brittleness. The middle barrier layer uses a PVOH (polyvinyl alcohol) coating applied at 2-3 gsm — PVOH is water-soluble and completely biodegradable, and when applied as a continuous coating it reduces oxygen transmission by 50-100x compared to uncoated biopolymer film. The inner sealant is a low-melting-point PBAT grade with a seal initiation temperature of 80-90°C, enabling energy-efficient heat sealing without degrading the heat-sensitive PLA in the outer layer.

The distinction between Industrial and HOME composting is critical and often misunderstood. Industrial composting under EN 13432 requires sustained temperatures of 58°C ± 2°C, which accelerates both hydrolysis and microbial metabolism. HOME composting under OK Compost HOME (TÜV Austria) requires biodegradation at ambient temperatures (20-30°C), which is a far more demanding standard — the polymer must hydrolyze and biodegrade without the thermal acceleration that industrial conditions provide. Our HOME-certified variant achieves this through a higher PBAT content in the formulation, because PBAT’s aliphatic ester bonds are more susceptible to enzymatic hydrolysis at ambient temperature than PLA’s more crystalline structure. The trade-off is that higher PBAT content reduces stiffness and increases cost, so the HOME variant is specified for brands whose customers have access to home composting and for whom the ambient-temperature degradation claim carries premium marketing value.