As part of this standard, we perform radiocarbon analyses to determine the carbon content biobased of the products.

Please note, the content biobased does not in any way define the environmental impact or the sustainability of a product. To measure this impact, a life cycle assessment (LCA) must be carried out, according to defined sustainability criteria.

Radiocarbon analysis of biobased products

Radiocarbon analysis of products must imperatively comply with standard NF EN 16640. It is based on one of the three regulatory methods provided for by this standard. CIRAM laboratories present here how carbon-14 analysis by AMS works.

What is a biobased product?

The term biobased means "derived from biomass." A product can therefore be entirely or partially derived from biomass. Thanks to our laboratory analyses, we can characterize its biobased carbon content (paints, polymers, solvents…).

This measurement is of interest at various stages of a product's life. It can be applied as early as the R&D phase, but also on a finished product. This is particularly the case for biogenic carbon in biofuels, biogas, and flue gases. It also concerns cosmetic and agri-food products. Finally, it allows for checking the composition of raw materials provided by a supplier.

Carbon-14 measurement quantifies the content of biogenic carbon and synthetic (petro-sourced) carbon.

Carbon-14, an element present in all living organisms

Carbon-14 (¹⁴C) is a radioactive isotope of carbon produced by the interaction between nitrogen-14 atoms in the atmosphere and cosmic radiation. Naturally unstable, it gradually decays back into nitrogen-14. Its half-life, estimated at 5,568 years, means that its concentration decreases by half over this period and that it disappears almost completely after about 60,000 years.

Due to its continuous regeneration by solar activity, the concentration of carbon-14 is considered to be virtually constant in the atmosphere. It is therefore present in all living organisms, where it is assimilated through photosynthesis and respiration. Current biomass (cereals, algae, wood, residues, and organic waste) therefore has a fully active reservoir of "modern" carbon-14.

Conversely, fossil resources such as oil, gas, or coal, resulting from the transformation of organic matter over millions of years, no longer contain carbon-14. They contain exclusively ancient or petrogenic carbon, which makes it possible to clearly distinguish them from biobased sources.

By measuring the isotopic ratio between ¹⁴C, ¹³C, and ¹²C, scientists at CIRAM laboratories precisely determine the modern carbon (biobased) and fossil (petro-sourced) carbon content of a sample. This approach forms the foundation of radiocarbon analysis, used for the characterization of biobased products, raw material control, and the verification of environmental claims.

AMS radiocarbon analysis

The NF EN 16640 standard provides three methods for measuring the carbon-14 content of products biobased. CIRAM laboratories exclusively use accelerator mass spectrometry (AMS), a reference technique recognized for its high precision and sensitivity in radiocarbon analysis.

Before AMS measurement, we transform the sample into pure carbon, in the form of graphite, and then we compact it into a sample-holder cathode. This preparation step is essential to ensure the reliability of the results and the reproducibility of the measurements.

The carbon-14 content is then expressed either as a mass fraction of the sample or as a fraction of the total carbon content. The percentage of modern carbon, known as pMC (percent Modern Carbon), corresponds to a normalized and standardized value of the measured carbon-14. This value is compared to that of a reference material (REF), representing 100% biobased carbon.

Since 2003, the University of Groningen has published the official reference values used within the framework of the NF EN 16640 standard, thereby ensuring international consistency in the interpretation of carbon-14 analysis results.

To illustrate the evolution of these references, we can recall that:

• In 2022, the reference value for 100% carbon biobased was 100 pMC,
• In 2010, the reference value for certifying 100% content was 104 pMC,
• In 1964, this value reached 190 pMC, due to the effects of atmospheric nuclear testing on carbon-14 concentrations.

The calculation method for biobased products

The NF EN 16640 standard indicates that in addition to measuring the pMC, we must indicate:

• XTC the total carbon content of the sample,
• Xb the biobased carbon content as a fraction of the sample mass.

From the reference value REF, it is possible to calculate XTCB, which is the carbon content biobased as a fraction of the total carbon content. It is this value that is decisive. Please note, the NF EN 16640 standard indicates that the measurement of the carbon content biobased using the AMS radiocarbon technique has an uncertainty of ± 2%. This implies that the carbon content biobased can vary by ± 2%. In other words, an XTCB value of 98% could be considered 100% carbon biobased relative to total carbon, within the margin of uncertainty.

The NF EN 16640 standard does not recommend any particular treatment for materials containing inorganic carbonates. However, calcium carbonates contain "old carbon" and risk artificially lowering the XTCB value.

This particularity constitutes an important difference from the ASTM D6866 standard. Indeed, NF EN 16640 defines the percentage of carbon biobased relative to total carbon, while ASTM D6866 can consider the percentage of carbon biobased relative to total organic carbon. To learn more about this second standard and its industrial applications, consult our article dedicated to the ASTM D6866 standard.