Biodegradable plastic

Biodegradable plastics or biodegradable plastics consist of polymers that can be decomposed by microorganisms such as fungi or bacteria , using enzymes under certain conditions. More details are defined in various standards. The degradation takes place mainly through oxidation and hydrolysis processes to the decomposition products water, carbon dioxide or methane and biomass . Biodegradable plastics are not to be confused with bio-based plastics .

Mulch film made from biodegradable PLA blend ...

... at the beginning of use

... partially dismantled

Differentiation from other terms

Bio-based plastics

Sometimes biodegradable plastics are referred to as bioplastics or bioplastics . However, these terms are misleading and - depending on the definition - also or only denote plastics made from renewable raw materials (including bio-based plastics).

→ Main article : Bio-based plastic

Due to the ambiguity, the terms bioplastic and bioplastic should not be used.

Biodegradability is a property that both bio-based plastics (e.g. PLA ) and plastics of petrochemical origin (e.g. PCL ) can have. In return, there are also bio-based plastics that are not biodegradable (e.g. CA ).

Oxo-degradable / oxo-biodegradable plastics

The term “biodegradable” must be clearly distinguished from polyolefin films (especially PE ) used in the packaging industry , which are declared as “oxo-biodegradable” or “oxo-degradable”. " Oxo-degradable " additives usually consist of metal ions ( cobalt , manganese , iron , zinc ) which accelerate the oxidation and chain breakdown in plastics, especially when exposed to heat, air and oxygen. The results of this chain breakdown are very small, barely visible chain fragments that are not biodegraded (none of the additive manufacturers has yet been able to provide data), but migrate through the food chain. Manufacturers of these additives occasionally refer to an ASTM test guideline, which does not contain any limit values, nor does it enable a certificate to be achieved.

Materials that are degradable in the body

In the narrower sense (especially in the field of biomedicine ), materials are called biodegradable which are broken down in the body by macrophages, enzymes or hydrolysis within days to a few years. This includes biogenic polymers such as collagen , fibrin or hyaluronic acid , but also polylactic acid (polylactide) , polyhydroxyacetic acid and polycaprolactone .

Applications

Disposable tableware made from biodegradable plastic

Biodegradable plastics can be used in many everyday and special areas. They are often used in packaging and in the catering sector, for example in the form of disposable cutlery instead of conventional plastic, and are then often advertised as supposedly environmentally friendly.

In the medical field, biodegradable plastics can be used, for example, for the controlled release of drugs or vaccines in the body. They are also used as scaffolding for tissue engineering and for absorbable threads in operations. In the health sector (medicine and pharmacy) there are also numerous other applications.

Mulch films made of biodegradable plastics are offered in the agricultural sector. The advantage is that these can be plowed under and then decomposed in the ground.

Legal regulations

European regulations

Compostability mark of DIN CERTCO and European Bioplastics according to EN 13432

Garbage bag made from biodegradable PLA - in Germany only a few municipalities are allowed to put organic waste

Cups made of biodegradable plastic - are not allowed in the organic waste in Germany

At the European level, the guidelines for biodegradable plastics are regulated in the European standard EN 13432. The standard requires the following standards so that a plastic is considered completely compostable:

• Chemical analysis: Presentation of all ingredients and verification of the limit values ​​for heavy metals .
• Degradability in aqueous media: 90% of the organic material must be converted into CO ₂ in 6 months .
• Composting : After 12 weeks of composting, no more than 10% residues based on the original mass may remain in a 2 mm sieve.
• Practical test of technical compostability: There must be no negative effects on the composting process.
• Ecotoxicity : Investigation of the effects of compost on plants (growth and ecotoxicity).

In particular, it should be noted that only industrial compostability is required. Self-composting means that even products labeled as 100 percent compostable , such as some shopping bags, are not necessarily completely degraded. In addition, because of their biodegradability, they are not necessarily composted, but may also be sorted out in industrial plants.

Certification is regulated at national level in cooperation with the European Bioplastics industry association .

German regulations

Important German regulations that affect biodegradable plastics are the Packaging Act and the Biowaste Ordinance .

In general, biodegradable plastics must not be disposed of in organic waste, but must be disposed of in the yellow bin. Only collection bags that are biodegradable in accordance with the EN 14995 or EN 13432 standard and are predominantly bio-based may be disposed of there, unless the local waste disposal company prohibits this. In many cases, however, the disposal companies forbid this, as composting takes too long for them.

In Germany, biodegradable plastics can one of the certification DIN CERTO , allocated Compostability are marked.

American regulations

In the USA , biodegradable plastics are regulated primarily via ASTM standard 6400. In order to label products as compostable , 60% of the plastic must be degraded within 180 days.

Certification is carried out by the Biodegradable Products Institute.

Test procedure

The OECD test procedures , which are also used for the approval of chemicals, are generally recognized . For the classification as biodegradable plastic, the compostability is also examined.

Readily biodegradable (OECD 301)

The tests of the OECD test series 301 (A – F) demonstrate rapid and complete biodegradation.

Ease of biodegradability a rapid and reasonably complete degradation of a test substance in an aquatic environment under aerobic conditions. Different test methods are available for readily or poorly soluble as well as for volatile substances.

• Carbon dioxide development test (OECD 301 B) : The carbon dioxide produced by the biological degradation of the test substance is analyzed regularly over 28 days and is an indicator of the biological degradation. This so-called Sturm test is used to examine chemicals that are poorly soluble in water .
• Closed bottle test (OECD 301 D) : The biodegradability of the test substance is determined by determining the consumption of dissolved oxygen at regular intervals over a period of 28 days. This test is used for volatile chemicals.
• Modified OECD screening test (OECD 301 E) : The biodegradability of the test substance is determined by measuring the Dissolved Organic Carbon (= dissolved organic carbon ) over a period of 28 days. This test is used when chemicals are sufficiently soluble in water.

Inherent degradability (OECD 302)

The tests of the OECD test series 302 (A – C) show that the chemical being examined is biodegradable to a limited extent, but it is fundamentally possible. Substances that pass such tests are generally or inherently biodegradable.

• The Zahn-Wellens EMPA test (OECD 302 B) examines the aerobic biodegradability of the test substance and gives the result of the decrease in chemical oxygen demand or the dissolved organic carbon. It is the most widely used test to study inherent degradability. It also provides information about the adsorption behavior of the examined substance.

criticism

The German Federal Environment Agency (UBA) is completely opposed to biodegradable plastics from fossil sources and is reluctant to hostile to bio-based biodegradable plastics. It believes that there are no proven environmental benefits from biodegradable plastics and that such plastics should not be promoted as environmentally friendly until there is evidence. It is also stated that the multiple use and recycling of more stable products has ecological advantages over degradable plastics. The suitability for food contact is also viewed critically, since it is feared that the degrading microorganisms lead to contamination of the food.

Since only compostability is tested and certified under special conditions, it is questioned to what extent biodegradable plastics make sense in relation to the litter problem - especially in the oceans .

Another point of criticism is that when composting is sought, the chemical energy in the materials is not used sensibly, in contrast to, for example, waste incineration .

It is feared that the biodegradability of plastics will lead to consumers handling them less responsibly and more likely to throw them away. The assumption was confirmed in an investigation.

literature

• Hans-Josef Endres, Andrea Siebert-Raths: Technical biopolymers . Hanser-Verlag, Munich 2009, ISBN 978-3-446-41683-3 .
• G. Maier: Polymer materials, 1. Introduction . In: Erich Wintermantel, Suk-Woo Ha: Medical technology with biocompatible materials and processes. 2nd Edition. Springer-Verlag, Berlin, Heidelberg, New York 2002, ISBN 3-540-41261-1 .
• Erich Wintermantel, Suk-Woo Ha: Biocompatible materials and construction methods . 2nd Edition. Springer-Verlag, Berlin, Heidelberg, New York 1998, ISBN 3-540-64656-6 .

Web links

• European Bioplastics eV

Individual evidence

1. ↑ ^{a b} Christian Bonten: Plastics Technology: Introduction and basics . 2nd updated edition. Hanse Verlag, 2016, ISBN 978-3-446-44917-6 , p. 465-477 .
2. ↑ Hans-Josef Endres & Andrea Siebert-Raths: Technical biopolymers - framework conditions, market situation, production, structure and properties . Hanser Verlag, Munich 2009, ISBN 978-3-446-41683-3 , chap. 3 , p. 49-89 .
3. ↑ Hans-Josef Endres & Andrea Siebert-Raths: Technical biopolymers - framework conditions, market situation, production, structure and properties . Hanser Verlag, Munich 2009, ISBN 978-3-446-41683-3 , p. 6 .
4. ↑ European Bioplastics: What are bioplastics? Retrieved September 23, 2019 . 
5. ↑ Michael Thielen: Bioplastics. Fachagentur nachwachsende Rohstoffe eV (FNR), 2019, accessed on 23 September 2019 . 
6. ↑ Keyword bioplastics in: Brockhaus Enzyklopädie online, accessed on August 8, 2008.
7. ↑ Fachagentur Nachwachsende Rohstoffe eV (FNR): 10 points on bio-based plastics. 2018, accessed September 23, 2019 . 
8. ^ Hans-Josef Endres, Andrea Siebert-Raths: Technical Biopolymers . Hanser-Verlag, Munich 2009; ISBN 978-3-446-41683-3 , pp. 28-29.
9. ↑ European Bioplastics: Position paper: Oxo-biodegradable Plastics ( Memento of the original from October 22, 2015 in the Internet Archive ) Info: The archive link has been inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , 2009, accessed September 24, 2009. 
10. ^ NN Position Paper on Oxo-degradable Plastics FKuR Kunststoff GmbH, 2008.
11. ↑ ^{a b c} Wolfgang Baier: Biodegradable plastics. Federal Environment Agency, 2009, accessed on November 12, 2019 . 
12. ↑ Checking “organic” disposable tableware: Doubtful ecological arguments. Consumer advice center NRW, October 2, 2018, accessed on November 12, 2019 . 
13. ↑ Tejas V. Shah & Dilip V. Vasava: A glimpse of biodegradable polymers and their biomedical applications . In: e-Polymers . tape 19 , no. 1 , 2019, p. 385-410 , doi : 10.1515 / epoly-2019-0041 .
14. ↑ EN-13432 Proof of compostability. European Bioplastics Association, accessed on September 24, 2019 . 
15. ↑ Frankfurter Rundschau: But not compostable? The swindle with the organic bags , from April 11, 2012, accessed on June 11, 2013.
16. ↑ Bio-based and biodegradable plastics (3.2). Federal Environment Agency, April 22, 2019, accessed on September 24, 2019 . 
17. ↑ Oliver Türk: Material use of renewable raw materials . 1st edition. Springer Vieweg, Wiesbaden 2014, ISBN 978-3-8348-1763-1 , p. 61-66 .
18. ↑ Bio-based and biodegradable plastics (3.9). Federal Environment Agency, April 22, 2019, accessed on October 22, 2019 . 
19. ↑ ^{a b} Arno Behr & Thomas Seidensticker: Introduction to the chemistry of renewable raw materials - occurrence, conversion, use . Springer Spectrum, 2018, ISBN 978-3-662-55254-4 , p. 317-335 .
20. ↑ Tobias P. Haider, Carolin Völker, Johanna Kramm, Katharina Landfester & Frederik R. Wurm: Plastics of the future? The impact of biodegradable polymers on the environment and society . In: Angewandte Chemie . tape 131 , 2018, p. 50-63 , doi : 10.1002 / anie.201805766 .