Monday 19 July 2021

Biopolymers – Difference Between Bio-Based Content vs. Bio-Based Carbon Content

Hello and welcome to a new post. With the arrival of new legislation to better protect the environment in Europe and other parts of the world, polymer manufacturers are extending their portfolio on bio-based polymers. In this post we investigate the question of what exactly the bio-content means of biopolymers.

In general, a bio-based product is made from biomass (plants, trees, algae, marine organisms, microorganisms) and there are two different concepts used in the plastics industry:

1.    Bio-based content: refers to the amount of biomass in a product; it considers four key elements: carbon, hydrogen, oxygen and nitrogen; expressed as percentage of overall weight of product;

2.    Bio-based carbon content: focus is on the carbon; expressed as percentage of the carbon the product contains;  

Most of the bio-based polyamide polymers use monomers from the sebacic acid chain which in turn is derived from non-food competing castor oil.

EN 16785-1 – bio-based content                 

Determination of the bio-based content is done over the EN 16785-1 standard which includes the measurement of the bio-based carbon (C14).

ASTM D6866 and EN 16640 – bio-based carbon content

For determination of the bio-based carbon content of polymers, ASTM D6866 standard was established with the working principle of radiocarbon analysis. With this method, determination of the carbon fraction including the bio-based percentage therein (C14 measurement) is done.

Illustrating the difference with an example

We want to access the bio content of a PLA (plant-origin, containing 50% carbon) and polypropylene (fossil-origin, containing 86% carbon) which are blended in a ratio of 30/70%. According to EN 16785-1, the bio-based content of this composition is in total 30%, whereas according to ASTM D6866 and EN 16640, the bio-based carbon content is 20% (Figure 1).

Figure 1: Difference between bio-based content (EN 16785-1) and bio-based carbon content (ASTM 6866 / EN 16640) estimation for biopolymers

I hope that this post helped to better understand bio-polymers and how to read the amount of bio content. 

Thanks for reading and #findoutaboutplastics

Herwig Juster

#biopolymers #herwigjuster

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[1] T. Garrison Bio-Based Polymers with Potential for Biodegradability, Polymers, 2016
[2] TÜV - Information Document 536 (EN) – 19.10

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