What biodegradable actually means
Biodegradable and compostable are not interchangeable. Biodegradable means a material breaks down through microbial action, but it says nothing about how long that takes or what is left behind. Compostable means it meets a defined standard, such as EN 13432 or ASTM D6400, and disintegrates within a set time under industrial composting conditions. Buyers should ask which standard applies and which disposal route the material was tested for.
Most flexible packaging is a laminate of several polymers, and mixed structures rarely break down cleanly. That is why compostable formats tend to use fewer layers. A mono-material PE or PP recyclable structure is a different route: it stays a plastic but fits existing recycling streams. Neither option is automatically better. The right choice depends on where your customer actually disposes of the pack.
Materials and barrier performance
PLA and PBS are common compostable options, often blended with starch-based films to balance stiffness, seal strength and cost. PHA offers better moisture resistance but is produced in smaller volumes and usually costs more. Each has limits. PLA softens at moderate temperatures, so it suits ambient or chilled goods rather than hot filling. Starch films can be sensitive to humidity.
Barrier is the harder problem. Compostable films generally let through more oxygen and moisture than PET/AL/PE or PET/NY/PE laminates. For coffee, nuts or dried fruit, that shortens shelf life unless you add a high-barrier compostable layer or accept a shorter date code. Test oxygen transmission rate and water vapour transmission rate on the actual structure, not the resin data sheet.
Filling, sealing and line speed
Compostable films behave differently on existing form-fill-seal equipment. They can be more brittle, more prone to blocking on the roll, and less forgiving in the seal jaw. Seal initiation temperature is often lower, and the sealing window is narrower. Run a trial on your line before committing to a full order, and check that your filler can handle the reduced tensile strength.
Add-ons matter too. A one-way degassing valve, zipper or spout must be compatible with the compostable substrate and with the disposal route. A compostable pouch with a conventional plastic valve may fail certification. Specify every component, including the cap and any window film, and confirm they meet the same standard as the pouch body.
What drives the cost
Compostable and biodegradable resins cost more per kilogram than standard PE or PET. The gap narrows at volume, but it rarely disappears. Print method is the second lever. Digital printing suits short runs and low minimums, while rotogravure becomes cheaper per pouch once quantities are high. A simpler structure with fewer layers also reduces material cost and improves end-of-life options.
Freight and storage add to the total. Some bio-based films need cooler, drier storage and have a shorter shelf life before conversion. If you are comparing quotes, compare landed cost per filled pack, not price per kilogram of film. Include the cost of any line trial, slower running speeds and potential rework. Those items often decide whether a compostable format is viable.
Compliance and labelling
Food-contact compliance is separate from compostability. A film can be certified compostable and still need documentation for food contact under EU 10/2011, FDA requirements or local rules. Ask for the declaration of compliance, migration test data and the exact grade reference. Keep these on file. Retailers increasingly request them during supplier approval.
Labelling is where brands get into trouble. Terms like eco-friendly, green or biodegradable without a standard behind them invite complaints. If the pack is certified compostable, state the standard and the disposal route, for example home or industrial composting. If it is recyclable, say which stream. Do not imply a pack will break down in a home compost heap unless it has been tested for that specific environment.
Questions to ask before you specify
Before committing, work through a short checklist with your supplier: - Which standard does the finished structure meet, and for which disposal route? - What are the OTR and WVTR figures for the full laminate, not the resin? - How does the film run on my filler, and at what seal temperature? - Are the valve, zipper, spout and cap compliant with the same standard? - What is the storage life of the film before conversion?
Answers to these five points usually separate a workable project from an expensive experiment. If a supplier cannot provide the test data, treat the claim as unproven. Compostable packaging can work well for dry goods, short shelf-life items and brands with a clear disposal story. It is a poor fit for long-life products that need a high oxygen barrier unless the structure is designed for it from the start.