ISO 16620-2, for dedicated radiocarbon analysis of plastics
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In the plastics and polymers industry, manufacturers use fossil raw materials or renewable resources. To determine the share of carbon derived from biomass in these materials, carbon-14 analysis constitutes a reference method.
The ISO 16620-2 standard governs this measurement and defines a method for determining the carbon content biobased of plastics. Manufacturers can thus characterize their materials and document their bio-based carbon content.
In summary:
- ISO 16620-2 standard defines a method for determining the carbon content biobased of plastics, polymers, monomers, and additives.
- Radiocarbon measurement allows for the calculation of the proportion of carbon biobased relative to total carbon or total organic carbon.
- Biopolymers can be derived from plant, animal, or microorganism resources. They are not necessarily all biodegradable.
ISO 16620-2 standard: a reference method for plastics biobased
ISO 16620-2, entitled "Plastics – Biobased content biobased – Part 2: Determination of biobased carbon content biobased", describes a calculation method based on the measurement of carbon 14.
It applies to plastics, plastic materials, polymer resins, as well as certain monomers and additives derived from biobased and/or fossil raw materials. Furthermore, manufacturers can rely on voluntary declarations based on mass balance, life cycle analysis, or traceability approaches such as the ISCC method. However, these approaches must be supplemented by objective measures so that the carbon share biobased of the materials can be qualified and quantified.
Radiocarbon analysis of plastics: the carbon 14 method
Carbon-14 analysis allows for the determination of the proportion of carbon biobased in polymers. It thus distinguishes carbon derived from recent biomass from carbon of fossil origin. It is based on the measurement of carbon isotope ratios, notably those of carbon 14, 13, and 12. These measurements make it possible to determine the percentage of modern carbon.
According to the ISO 16620-2 standard, the result of the radiocarbon measurement is expressed as a percentage of modern carbon, or pMC (percent Modern Carbon). The carbon content biobased can then be related to total carbon (TC) or total organic carbon (TOC), depending on the calculation method used.
The standard also defines a reference value, called REF, corresponding to a carbon content biobased of 100%. This reference changes according to the year in question. In the 2019 edition of the standard, it is notably 102 pMC for 2015 and 100 pMC for 2019.
The carbon content biobased is calculated by relating the measured pMC to the corresponding REF value. This operation makes it possible to determine the proportion of carbon of biological origin in the sample.
Why is this standard crucial for manufacturers?
Analyses carried out according to the ISO 16620-2 standard allow industry professionals to quantify the renewable carbon content of their products and to have objective data for their certification processes. This characterization can, in particular, help to verify manufacturers' claims and document the compliance of products with the requirements of applicable standards.
In France, certain categories of single-use plastic bags are subject to minimum content thresholds biobased: 50% since 2020 and 60% since 2025. These requirements concern products covered by the Environment Code and do not apply to all plastics biobased.
Measuring carbon content biobased thus constitutes a justification element for companies wishing to document the composition of their materials and meet the requirements of their market.
Certification and quantification of biomass in plastics
The ISO 16620-2 standard is involved in product certification processes biobased, particularly for standards such as OK biobased® from TÜV AUSTRIA or those from DIN CERTCO.
It specifies the data required for the determination and expression of the carbon content biobased. Analysis results may notably reveal:
- χTC : the total carbon content of the sample ;
- χB : the carbon content biobased, expressed as a fraction of the sample mass;
- χTCB : the carbon content biobased relative to the total carbon content.
This latter value makes it possible to determine the proportion of bio-based carbon in the total carbon of the sample. It constitutes an essential indicator for characterizing the carbon content biobased of the material. This measurement must be distinguished from the total mass content of the material biobased. To determine the latter, a complementary method may be necessary, in particular the one described in the ISO 16620-4:2024 standard, which combines radiocarbon analysis with elemental analysis.
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You may be asking yourself these questions about the ISO 16620-2 standard?
The ISO 16620-2 standard applies to various plastic materials, polymer resins, monomers, and additives, whether they are derived from fossil resources, biobased or a mixture of both. The analysis makes it possible to determine the share of bio-based carbon present in these materials.
The analysis begins with the preparation of the sample in order to isolate the carbon to be measured. This is then transformed into a form suitable for measurement by accelerator mass spectrometry (AMS). This technique allows for the measurement of the quantity of carbon 14 present in the sample and for the calculation of its carbon content biobased. The result is notably expressed in pMC, in accordance with the chosen method.
The pMC (percent Modern Carbon) indicates the amount of modern carbon measured in a sample relative to a conventional reference. To determine the biobased carbon content, this value is compared to the reference value (REF) defined by the ISO 16620-2 standard for the period in question. The result thus makes it possible to estimate the proportion of bio-based carbon in the total carbon of the sample.
The two standards concern the content characterization biobased of plastics, but they do not determine the same indicator. The ISO 16620-2 standard defines a method for determining carbon content biobased based on the measurement of carbon 14. The ISO 16620-4:2024 standard, for its part, allows for the determination of the bio-based content biobased by combining radiocarbon analysis and elemental analysis.
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