Selecting a biodegradable plastic bag manufacturer starts with one question: where does the bag go at end of life? PBAT and PLA blends compost in industrial facilities, starch-based films behave differently, and oxo-degradable additives are restricted in the EU and several other markets. A serious biodegradable plastic bag manufacturer will ask about the disposal route, the destination market's certification rules and the sealing equipment on the line before quoting a price. This page explains the material families, how compostable bags are produced, and the documentation that separates a genuine producer from a converter reselling generic film.
Material Families and What They Actually Do
- PBAT/PLA blends — the mainstream compostable film family. PBAT supplies flexibility and toughness, PLA supplies stiffness and modulus; blends typically run from 60/40 to 30/70 depending on the bag's duty.
- Starch-based films — lower cost per tonne but humidity-sensitive, with a narrower sealing window. Common for niche uses rather than retail packaging.
- Oxo-degradable additives — conventional polyolefin plus a pro-oxidant package. Not compostable, excluded from EU composting standards, and a buyer specifying them risks market rejection.
How Compostable Bags Are Produced
The film is blown on a conventional extruder with a modified screw and tighter temperature control, because PLA is shear-sensitive and PBAT is hygroscopic — both resins need proper drying and a stable melt. Conversion is familiar: flexographic printing, bottom or side sealing, and perforation where the design calls for it. The difference from polyethene production sits in process discipline: narrow temperature bands, controlled dwell time, and sealing parameters validated per resin lot, since compostable films have a narrower sealing window than LDPE.
Certification and Market Rules
- EN 13432 — the EU packaging composting standard: disintegration, biodegradation, ecotoxicity and heavy-metal limits.
- ASTM D6400 — the US equivalent specification for compostable plastics.
- AS 4736 and AS 5810 — the Australian standards, including a home-composting variant for films.
- Seedling logo — the EU conformity mark tied to EN 13432 certification of the finished film, not the resin alone.
Buyers should insist that certification applies to the converted bag, not only to the resin pellet, because additives, inks and coatings can all affect the compostability result.
What to Confirm Before Ordering
- The destination market's accepted standard, and whether the certificate covers the exact film structure being supplied.
- Sealing compatibility with the packing line, validated on a sample run rather than assumed.
- Ink and additive compliance, since food-contact and home-compostable claims impose different limits.
- Shelf life and storage: compostable films age faster than polyethene, so delivery dates and warehouse conditions matter.
For the wider material picture, our overview of biodegradable plastics in the film segment compares growth routes and limitations, and the plastic recycling grades guide explains why compostable and recycled streams must stay separate. Producers are listed under plastic products, and factory-level checks are described in the supplier directory.
