How to determine the bio-based content of materials
Oona Korhonen - Tohtori, biotuotetekniikka
4. elokuuta 2022
Article originally published on European Bioplastics website.
As fossil-based materials are becoming less attractive and politics are restricting the use of fossil-based raw materials, it is increasingly important to know the real composition of the raw materials you use. At the same time, bio-based materials can be chemically identical to their petroleum-based counterparts, and identifying the origin of the chemicals is thus essential.
How is the amount of bio-based components measured?
One of the most accurate ways to study a material’s bio-based vs. petroleum-based composition is to analyze the carbon in the product. Bio-based carbon originating from plants is radioactive, whereas carbon originating from fossils no longer is. The amount of radioactive carbon in the sample can thus be used to determine the amount of bio-based content in the material.
The radio-activeness of the bio-based carbon originates from the atmosphere and photosynthesis. The content of radiocarbon in the atmosphere is relatively stable, and thus living plants have the same radioactive carbon content as air. When the plant is alive, it continuously absorbs carbon from the air during photosynthesis. Once the plant dies, the radioactive carbon it has absorbed starts to deteriorate at a known rate, called “half-life”. This way, the age of biomass-based components can be evaluated based on their content of radioactive carbon.
The content of radioactive carbon in the organic material can be determined using accelerator mass spectrometry (AMS) by measuring the different carbon isotopes in the sample. This method is commonly used for evaluation of the age of the organic material, but it can also be used to evaluate how much of the carbon in the material is originating from renewable biomass and how much from fossil origin.
Understand the analysis results and avoid misinterpretation
There are standardized methods for the determination of biobased carbon, and the amount can be expressed as a fraction of the total organic carbon or total carbon in the sample. If the sample contains a high amount of inorganic carbon (which is neither biomass- nor petroleum-based), it will impact how bio-based the material seems.
Let’s take an example: If all organic carbon in a material is biomass-based, the amount of bio-based carbons of the total organic carbons will be 100%. However, if the material also includes inorganic carbons, the amount of bio-based carbons of the total carbons will be less than 100%.
The different measurements may result in misinterpretations of the materials' origin, which is why it is important to specify how the biobased carbon content was determined.
The main standard methods used for determining the biobased carbon content in a material are ASTM D6866 in which the biobased carbon content is determined from total organic carbon, and CEN 16137 and ISO 16620, which express the biobased carbon content of total carbon. Most commonly the bio-based carbon content is determined from the total organic carbon since it gives the most accurate information when the goal is to determine how much of the material’s carbon originates from renewable resources and how much is petroleum-based.
Evaluating how bio-based the final product is
It is important to note that the bio-based carbon content refers only to the fraction of carbon originating from renewable sources, not to the degree of bio-basedness of the product as a whole. It is thus only an indirect measure of how bio-based the final product is.
To get information about how bio-based the product is, the total amount of carbons in the product needs to be identified. When the percentage of biomass-based carbons of the total carbons is calculated against the carbon-content of the end product, information can be obtained about how much of the product is originating from renewable sources.
These measurements are important tools that help in evaluating potential subcontractors, controlling product quality, and building transparency and trustworthiness towards customers and stakeholders. Having reliable data about the origin of your products is essential for many aspects of the business and should not be overlooked in any case.
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