Is Your Masterbatch Invalidating Your Bioplastic Certification?

Is Your Masterbatch Invalidating Your Bioplastic Certification?

Yes. A masterbatch with a conventional PE or PP carrier resin introduced into a PLA or PBAT formulation can incorporate non-biodegradable fractions that prevent the material from meeting the biodegradation thresholds required by EN 13432, ASTM D6400, and OK Compost, resulting in the loss or non-renewal of the certification.

The silent problem behind the 'compostable' label

In our technical experience working with bioplastics producers, we have identified one of the most costly and least visible errors in the industry: the selection of a masterbatch that is incompatible with the compostable polymer system. The result is not an aesthetic or process failure. It is the invalidation of the compostability certification of the final product, with direct consequences for commercialization, regulatory compliance, and brand reputation.

In this article we analyze the technical mechanism of the problem, the standards that determine non-conformity, and the actions we have developed to help our clients protect their certification.

How does masterbatch work and why is the carrier the key?

A masterbatch is a concentrated mixture of pigments or additives dispersed in a carrier resin, presented in pellet form. It is used to color plastics or give them functional properties (UV stabilization, antiblocking, lubrication) in a metered, clean, and reproducible way. Typical dosages range from 1% to 5% over the base resin.

The carrier is the majority component of the masterbatch. In conventional formulations, the most commonly used carriers are polyethylene (PE) and polypropylene (PP) — fossil-based polymers with biodegradation times of hundreds of years under natural conditions. When this type of masterbatch is incorporated into a bioplastic formulation (for example, PLA or PBAT), the conventional carrier is distributed homogeneously throughout the mass of the product.

The result is a mixture in which a fraction of the material is fundamentally non-biodegradable. And it is precisely that fraction that can compromise the compostability certification.

The standards that determine non-conformity

EN 13432 / ISO 14855: The 90% threshold

The European standard EN 13432 (equivalent to ISO 14855 in its test methods) establishes that 90% of the tested material must biodegrade within a maximum of 180 days under controlled industrial composting conditions (temperature 58°C ± 2°C, controlled microbial activity). This threshold is measured on the total organic carbon of the material, including all its components: base resin and masterbatch.

A masterbatch with 2% PE carrier may seem like a marginal percentage. However, the test methodology evaluates the complete formulation as a single unit. If the non-biodegradable carrier accounts for more than 10% of the non-compostable organic materials in the system, the material fails the threshold and the certification is not granted or renewed.

ASTM D6400 and OK Compost: The same principle, different markets

The American standard ASTM D6400, basis of the BPI (Biodegradable Products Institute) seal, and the OK Compost standard from TÜV Austria (issued in Belgium and recognized globally) apply equivalent criteria: biodegradation exceeding 90% in 180 days for industrial composting, and exceeding 90% in 365 days for home composting (OK Compost Home). In both cases, all components of the formulation — including the masterbatch and its carrier — form part of the evaluated system.

We have observed that many manufacturers obtain certification for the pure base resin (virgin PLA or PBAT), but not for the composite material including the additives and colorants incorporated in actual production. This gap between the certified material and the actual manufactured product is the root of the problem.

Main risk vectors identified

• PE or PP carrier in color masterbatch: the most frequent use, with dosages of 2–4%, introduces non-biodegradable fractions into the system.
• Synthetic stabilizing additives: UV stabilizers of HALS type (Hindered Amine Light Stabilizers) or high-molecular-weight phenolic antioxidants with conventional carrier.
• White masterbatch with high TiO2 content and PE carrier: titanium dioxide itself is inert and does not affect compostability, but its carrier can.
• Masterbatch supplier change without re-verification: replacing an approved supplier with another using a different carrier formulation, without re-testing, is one of the most common non-compliance scenarios.
• Multi-component formulations: when several masterbatches are combined (color + stabilizer + antiblocking), the accumulated conventional carriers may exceed the tolerance threshold.

The solution: Masterbatch with certified biodegradable carrier

Our technical solution to this problem is specific and verifiable: the exclusive use of masterbatches whose carrier resin is formulated based on PLA, PBAT, or blends of both, and where the complete masterbatch holds an independent biodegradability certification according to ISO 14855 and applicable compostability standards.

This requires an audit of the formulation chain that includes:

• Documentary verification of the masterbatch carrier (technical data sheet and supplier certificate).
• Request for biodegradation tests of the masterbatch as an individual component, not just the base resin.
• Testing of the complete formulation (resin + masterbatch + other additives) under EN 13432 or ASTM D6400 before applying for or renewing the certification.
• Incorporation of technical compliance clauses in contracts with masterbatch suppliers.

Regulatory impact 2025–2026: The context accelerating the risk

The European Packaging Regulation PPWR (Regulation 2025/40, published in the EU Official Journal on 22 January 2025) establishes that, from 12 August 2026, certain packaging must be compostable to guarantee biodegradability. France already prohibits bioplastics similar to plastic without EN 13432 certification. California requires ASTM D6400 + BPI for legal use of the term 'compostable'.

In this context, masterbatch non-conformity is not just a technical problem: it is a market risk with immediate commercial, legal, and reputational consequences.

Conclusion

Together with our clients, we have developed a selection and verification protocol for masterbatches used in bioplastic formulations that eliminates this risk at the root. Compostability certification is a strategic asset. Protecting it requires extending technical rigor to every component of the formulation, including the masterbatch.

If you currently have no certainty about the compatibility of your masterbatch with your bioplastic's certification, the right time to act is before renewal — not during the testing process.

Frequently Asked Questions (FAQ)

What percentage of conventional masterbatch invalidates compostability certification?

There is no single percentage established in the standard. EN 13432 and ASTM D6400 require that 90% of all material (including the masterbatch) biodegrades in 180 days. Any fraction of non-biodegradable carrier that causes the system to exceed 10% non-degraded material can result in non-conformity. The risk increases with masterbatch dosages above 1.5% with a PE or PP carrier.

Are all masterbatches for bioplastics compostable?

No. Many commercial masterbatches for PLA or PBAT use polyethylene or polypropylene carriers because they offer better processability and lower cost. Only masterbatches formulated with biodegradable carrier (PLA, PBAT) and with independent biodegradability certification guarantee no interference with the final product's certification.

What standard applies to verify that a masterbatch is compatible with a compostable bioplastic?

The reference test is ISO 14855 (aerobic biodegradation in compost). The complete formulation (resin + masterbatch + additives) must exceed the 90% biodegradation threshold in 180 days. For TÜV Austria's OK Compost Home seal, the period extends to 365 days at ambient temperature. For EN 13432 certification, the certifying body may be DIN CERTCO or TÜV Austria.

Can I use the same masterbatch I use in PP or PE for my PLA products?

Not recommended. A masterbatch formulated for PP or PE uses a carrier of the same nature and has not been evaluated for compostability. Introducing it into a PLA or PBAT formulation can compromise the compostability certification of the product. Always ask the supplier for the biodegradability certificate for the masterbatch in question.

How does the new European PPWR Regulation (2025) affect masterbatch selection?

The PPWR (Regulation 2025/40, in force from February 2025, application August 2026) requires certain packaging to be certifiably compostable. This makes masterbatch compatibility a legal requirement, not just a technical one. Manufacturers who cannot demonstrate that their complete formulation (including the masterbatch) passes EN 13432 will not be able to market their packaging as compostable in the European Union.

What should I ask my masterbatch supplier to guarantee compatibility?

Require: (1) Technical data sheet specifying the carrier resin and its percentage. (2) Biodegradability certificate for the masterbatch according to ISO 14855. (3) Declaration of absence of non-biodegradable synthetic additives (HALS stabilizers, high-MW phenolic antioxidants with conventional carrier). (4) Test report of the complete formulation (base resin + masterbatch) under EN 13432 or ASTM D6400.