Plastic Bans Reports & Studies

Which Are Natural Polymers in the Sense of the Single-Use Plastic Ban?

Open Letter to DG Environment by the Nova-institut.

After a relatively short negotiation period, the new rules on single-use plastics to tackle marine litter were adopted and published in June 2019, in brief commonly known as the “single-use plastic ban” (European Parliament and Council 2019).

Items that fall under this ban include single-use products made of plastic to which alternatives exist on the market, such as cotton bud sticks, cutlery, plates, straws, stirrers, sticks for balloons, as well as cups, food and beverage containers made of expanded polystyrene and all products made of oxo-degradable plastic.

For the purpose of the Directive and its measures, a plastic is defined as a material consisting of a polymer to which additives or other substances may have been added, and which can function as a main structural component of final products, with the exception of natural polymers that have not been chemically modified (Annex 3.1 Definition – Plastic).

This means that all previously named items made of plastics defined as such (Annex 3.1 Definition – Plastic) fall under the ban except those made from ‘natural polymers that have not been chemically modified’, in the sense of the REACH definition of a not chemically modified substance (Annex 3.3 Definition – Not chemically modified substance).

However, within the Directive, it is not specified which polymers fall into the group of “natural polymers”. Also, the term “natural polymers” as such is not further defined within the proposal of the Directive.

For the definition of a polymer as a component of a plastic, the Directive refers to the REACH regulation (European Parliament and Council 2007) (Annex 3.1 Definition – Plastic), here the terms polymer (Annex 3.2 Definition – Polymer) and the term substances which occur in nature are defined (Annex 3.4 Definition – Substances which occur in nature).

By considering, delineating and interpreting these two definitions, the European Chemicals Agency (ECHA) implemented a definition for natural polymers in which they are explained ‘as polymers which are a result of a polymerisation process that has taken place in nature, independently of the extraction process with which they have been extracted’ (ECHA 2012) (Annex 3.5 Definition – Natural polymer).

Furthermore, it is emphasised that natural polymers are not necessarily substances which occur in nature when extracted and assessed according to the substances which occur in nature definition (Annex 3.4 Definition – Substances which occur in nature).

Based on this definition of a natural polymer, the following shows an exemplary list of polymers that should be considered as natural and examples of those that should not. It is emphasised that this list makes no claim of being complete.

1 Polymers to be considered as natural polymers

Polymerisation processes that take place in nature are those relying on the metabolism and biosynthesis of organisms and microorganisms such as animals, plants and algae, fungi and bacteria.

The majority of these natural polymers are polysaccharides or proteins, but also other forms are possible as it is the case for lignin and polyhydroxyalkanoates (PHAs).

In general, these natural polymers fulfil different functions within the organisms and/or microorganism as a texture-forming component (e.g. chitin), cellular interaction component (e.g. glycoproteins) or as energy storage material (e.g. polyhydroxyalkanoates (PHAs)).

The biosynthesis either takes place in nature itself or is deliberately induced in artificial cultivation and fermentation processes.

The following examples of chemically unmodified polymers and polymer classes are clustered according to their natural origin. They are produced via the explained biosynthesis and should be considered as natural polymers:

  • Natural polymers produced via biosynthesis in animals such as:
    • Polysaccharides and polymers based thereon: chitin, hyaluronic acid
    • − Proteins and based thereon: casein, collagen, gelatine, hair, keratin, silk
    • − Others: polyphosphates
  • Natural polymers produced via biosynthesis in plants and algae such as:
    • Polysaccharides and polymers based thereon: agar agar, alginate, cellulose1, hemicellulose, inulin, levan, pectins, starch (amylopectin, amylose), xanthan
    • Others: cutin, unmodified lignin, polyphosphates, suberin
    • Mixtures of natural polymers and other natural compounds: cotton, gluten, latex
  • Natural polymers produced via biosynthesis in fungi such as:
    • Polysaccharides and polymers based thereon: α-1,3-glucan, chitin, chitosan
    • Proteins and polymers based thereon: glycoproteins
    • Others: polymalat (PMLA), polyphosphates
  • Natural polymers produced via biosynthesis in bacteria such as:
    • Polysaccharides and polymers based thereon: alginate, bacterial cellulose, curdlan, dextran, pullulan, xanthan
    • Others: ε-poly-L-lysine, hyaluronic acid, poly-γ-glutamic acid, polyhydroxyalkanoates (PHAs), polyphosphates

Based on the definition of polymers in the REACH regulation (European Parliament and Council 2007) (Annex 3.2 Definition – Polymer), also so-called oligomers (if the number of monomers > 2) fall under this definition and natural varieties of these have to be considered here. In principle, oligomers are intermediates between monomers and polymers, they are lower molecular weight variants of polymers and are systematically named according to the number of monomers involved: dimer (2), trimer (3), tetramer (4) etc.

  • Natural oligomers produced via biosynthesis plants and algae such as:
    • Secondary metabolites: ellagitannins, gallotannins, oligomeric proanthocyanidins
  • Natural oligomers produced via biosynthesis in fungi such as:
    • Fatty acid-based oligomers: exophilin A

2 Polymers not to be considered as natural polymers

Besides these natural polymers that can be and are used as such without any further modifications, also natural polymers exist that are chemically modified prior to use to obtain specific properties.

The following examples of polymers and polymer classes should therefore not be considered as natural polymers.

Also this list does not make any claim of being complete:

  • Examples of natural polymers that are chemically modified
    • Cellulose: cellulose acetate, cellulose butyrate and other cellulose derivatives
    • Lignin: ligninsulfonate
    • Starch: starch acetates and other starch derivatives

As defined in Annex 3.2 Definition – Polymer, polymers in general are always consisting of the same or different monomers, also called building blocks.

These building blocks can be produced by plants and algae, as well as fungi and bacteria from renewable feedstocks and are therefore from natural, bio-based origin.

Bio-based polymers that are made from these bio-based monomers are always synthesised by a polymerisation reaction outside the plant or microbial cell, which is a chemical modification.

The following examples of bio-based polymers should therefore also not be considered as natural polymers:

  • Examples of bio-based monomers used for bio-based polymer production such as:
    • Bio-based monomers from plants and algae: bioethanol for bio-based polyethylene
    • Bio-based monomers from fungi and bacteria: lactic acid for polylactic acid (PLA), sebacic acid for polyamides (PA), succinic acid and 1,4-butanediol for polybutylene succinate (PBS)

Based on these scientific facts and the clear guidance given by REACH (European Parliament and Council 2007) and ECHA (ECHA 2012), we request the European Commission to exempt the above named “natural polymers” from the measures outlined in Directive 2019/904 (European Parliament and Council 2019).

Experts supporting this proposal: Cologne, September 2019

• Prof. Dr. Lars M. Blank, Rheinisch-Westfälische Technische Hochschule Aachen (RWTH Aachen University), Institute of Applied Microbiology (iAMB), Germany

• Prof. Dr. Christian Bonten, Stuttgart University, Institut für Kunststofftechnik (IKT), Germany

• Prof. Dr. George Guo-Qiang Chen, Tsinghua University, Center for Synthetic & Systems Biology, China

• Prof. Dr. Craig Criddle, Stanford University, Environmental Biotechnology Group, United States

• Prof. Dr. Bruce E. Dale, Michigan State University (MSU), Michigan Biotechnology Institute, East Lansing, United States

• Prof. Dr. Stefaan De Wildeman, KULeuven, Center for Sustainable Catalysis and Engineering (CSCE), Leuven, Belgium

• Prof. Dr. Ludo Diels, Flemish Institute for Technological Research (VITO), Mol and Antwerp University, Institute of Environment & Sustainable Development, Belgium

• Prof. Dr. María Auxiliadora Prieto Jiménez, Biological Research Center-Spanish National Research Council (CIB-CSIC), Polymer Biotechnology Group, Madrid, Spain

• Ass.-Prof. Dr. Marina Kalyuzhnaya, San Diego State University (SDSU), Cell & Molecular Biology Faculty, United States

• Prof. Dr. Klaus Kümmerer, Leuphana University Lüneburg, Chair for Sustainable Chemistry and Physical Resources, Germany

• Prof. Dr. Mikael Lindström, Research Institutes of Sweden, RISE Bioeconomy, Biobased materials, Stockholm, Sweden

• Prof. Dr. Katja Loos, University of Groningen, Macromolecular Chemistry and New Polymeric Materials, The Netherlands

• Prof. Dr. Kevin O’Connor, University College Dublin (UCD), BEACON SFI Bioeconomy Research Centre and School of Biomolecular and Biomedical Science, Ireland

• Prof. Dr. Antje Potthast, University of Natural Resources and Life Sciences, Institute of Chemistry of Renewables, Vienna, Austria

• Prof. Dr. Juliana Ramsay, Queen’s University, Department of Chemical Engineering, Kingston, Canada

• Prof. Dr. Stefan Spirk, Graz University of Technology Institute of Paper, Pulp and Fiber Technology, Austria

• Prof. Dr. Alexander Steinbüchel, Westfälische Wilhelms-Universität Münster, Institute for Molecular Microbiology and Biotechnology, Germany

• Prof. Dr. Manfred Zinn, University of Applied Sciences and Arts Western Switzerland – Valais (HES-SO Valais-Wallis), Institute of Life Technologies, Sion 2, Switzerland

• and the nova team: Michael Carus, Dr. Pia Skoczinski, Lara Dammer and Achim Raschka

REFS

Published by nova-Institute, Hürth, Germany, 18 September 2019; Updated version 08 October 2019

19-10-08-Which-polymers-are-natural-polymers

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