Manufacturers are increasingly developing paints that incorporate renewable raw materials to limit their dependence on fossil resources. But how can the actual proportion of biobased in a paint be determined? And how can this content be justified within the framework of the "Bio-based Product" label?

Carbon-14 analysis provides an answer to these questions. It makes it possible to measure the proportion of carbon from recent biomass in a material and to distinguish this fraction from carbon of fossil origin.

What is a biobased painting?

A paint biobased contains components made from renewable raw materials of biological origin. These materials can notably come from plant or animal resources or organic residues. In industrial formulations, several components can incorporate a share biobased :

• Binders: certain resins can be produced from vegetable oils, such as those from flax, soybean, or castor.
• Solvents: some manufacturers use solvents derived from renewable resources.
• Additives: substances of plant origin can help modify certain properties of the formulation.

The presence of these components is not, however, sufficient to determine the overall biobased content of the paint. This depends on the proportion of renewable materials incorporated into the formulation and their carbon composition.

A paint biobased must also meet the technical requirements of its application: adhesion, mechanical and chemical resistance, durability over time, and compatibility with the substrates.

The "Bio-based Product" label: what are the criteria for industrial paints?

The "Bio-based Product" label helps promote products that incorporate a defined proportion of biological materials. It provides a reference framework for characterizing and communicating about their content biobased.

For industrial paint manufacturers, this approach can help differentiate their products and provide their clients with objective information about the composition of their formulations.

The label's standard defines the criteria to be met, in particular the content thresholds biobased applicable to the different product categories. The required percentage therefore depends on the category concerned: it is advisable to consult the requirements of the standard in force before communicating on the eligibility of a paint.

Determining this content requires a suitable characterization method. Two approaches in particular can be used:

• Radiocarbon analysis, governed by the NF EN 16640 standard, which measures the proportion of carbon of biogenic origin.
• The material balance, according to the EN 16785-2 standard, which allows for the determination of the content biobased based on the product's composition and data relating to its constituents.

How to measure the carbon content biobased of a paint?

The principle of carbon-14 dating

Carbon exists in different isotopic forms, including carbon 14. This radioactive isotope is naturally present in living organisms and materials derived from recent biomass.

Conversely, fossil resources, formed millions of years ago, contain practically no carbon-14. This difference makes it possible to distinguish biogenic carbon from fossil carbon in a material.

By measuring the proportion of carbon-14 present in a sample, the laboratory can determine the share of carbon derived from recent biomass.

This method applies to industrial paints and pigments containing carbon. It allows for the characterization of their biogenic fraction, even when biobased and fossil components are mixed.

Which standards govern radiocarbon analysis?

The NF EN 16640 standard describes a method for determining the carbon content biobased of products based on their carbon-14 content.

The ASTM D6866 standard also relies on carbon-14 measurement to distinguish modern carbon from fossil carbon.

These methods provide a result expressed as a proportion of carbon biobased. It is important not to confuse this value with the percentage of raw materials biobased in the formulation: switching from one to the other requires additional data on the product's composition.

Why analyze paintings and pigments?

Radiocarbon analysis offers several benefits for manufacturers:

• Characterize formulations: determine the proportion of biogenic carbon in a paint or pigment.
• Documenting claims biobased : having analytical results to support the information provided on the composition.
• Supporting a labeling process: providing data useful for evaluating the content biobased, according to the requirements of the relevant standard.
• Monitor formulation changes: compare the biogenic carbon content of different versions of a product.

The analysis must, however, be based on a representative sample and take into account the nature of the product as well as its composition.

Do paints biobased also have to meet performance requirements?

The integration of renewable raw materials does not exempt manufacturers from meeting the technical requirements specific to their industrial applications.

Paints must in particular retain properties adapted to their use: adhesion to the surface, resistance to friction, resistance to moisture or chemical products, and long-term stability.

Manufacturers must therefore separately assess the composition biobased of their products and their technical performance. Radiocarbon analysis provides information on the origin of the carbon, but it does not measure mechanical properties, resistance, or volatile organic compound (VOC) emissions.

Similarly, a high carbon content biobased does not by itself demonstrate a lower overall environmental impact. To evaluate this aspect, it is necessary to consider the entire life cycle of the product.