Biodegradability Testing for Synthetic Polymers: Developing Structures Exempt from the EU Microplastics Legislation

The EU has had growing concerns around microplastic creation for years, resulting in new legislation continually being developed. From proposing measures to reduce the discharge of macro- and micro-sized plastic debris in marine environments to proposing a ban on polymers in cosmetics, personal care products, and detergents, microplastics have become cause for concern for all industries. 

EU legislation has restrictions on the microplastics found in numerous applications, including the encapsulation of fragrances, microbeads used to exfoliate or polish, nail products, agricultural products, and more. This legislation has been put in place in an effort to prevent microplastics from making their way into the environment. Preventing introduction to the environment is important because microplastics resist biodegradation and once they are in the environment, they can accumulate in animals and make their way into humans as well through multiple pathways. 

There are some synthetic materials which do not result in microplastics, the EU has incorporated several exemptions into the legislation, one of which being proof of biodegradation. There are several groups of biodegradability tests for polymers that you can use on your products to act as evidence for exemption from the EU microplastics legislation. Below, we explore the test offered at Aropha; however, if you would like a complete overview, feel free to contact our team. 

Biodegradability Test for Polymers

Group 1

OECD 301B

This biodegradability test determines the ready biodegradability of a material in an aqueous, aerobic environment. The production of CO₂ is measured as biodegradation occurs in continuously aerated bottles. OECD 301B testing takes place over a period of 28 days and is used to determine if a chemical is potentially readily biodegradable, rather than predicting the actual rate of biodegradation. 

A polymer is considered readily biodegradable if 60% of degradation is reached within a 10-day window; however, for exemption from the EU microplastics legislation, the 10-day window does not apply. The beginning of this window is defined as when 10% of degradation is reached. This testing method is very popular because if the chemical reaches the 60% threshold, it does not need to undergo other testing to make it exempt from the EU microplastics legislation.  

OECD 301D

Like OECD 301B,  OECD 301D determines the biodegradability of a material in an aqueous, aerobic environment. However, this test measures the dissolved oxygen consumption that takes place in closed bottles. 

This test is very similar to OECD 301B test, taking place over 28 days. The passing considerations are also the same, with polymers being considered readily biodegradable if 60% of degradation is reached within a 10-day window.

OECD 301F

This test has the same conditions and passing considerations as the other OECD 301 tests discussed above. However, to determine the ready biodegradability of a substance, the oxygen consumption in closed reactors is measured. 

Group 2

OECD 306

In addition to the OECD 301 tests, Group 2 permits the use of the OECD 306 test. The OECD 306 is an aerobic biodegradation test that determines the biodegradability of an organic material in seawater by relying on the microorganisms originally present in the seawater. There are two specified methods for this test: the Shake Flask Method and the Closed Bottle Method. 

For the Shake Flask Method, the dissolved organic carbon removed in the biodegradation process is measured. This test takes place over 60 days and a positive result is >70% organic carbon removal.  Alternatively, for the Closed Bottle Method, the dissolved oxygen consumption is measured. This test takes 28 days and a positive result is >60% dissolved oxygen consumption. 

It is important to note that for either method of the OECD 306 test, no inoculum outside of marine water is added. This test relies on the microorganisms already present in the seawater. 

Group 4

ISO 14851

ISO 14851 tests the ultimate aerobic biodegradability of plastic materials in aqueous medium. In order to determine the biodegradability of the polymer, the oxygen demand during biodegradation in a closed respirometer is measured. This test typically lasts for 2 months, however, it can be extended up to 6 months. Like ISO 14852, this test is suitable for various polymers, including natural, synthetic, copolymers, mixtures, and plastics that contain additives like plasticizers, colorants, and compounds. 

ISO 14852

This biodegradability test for polymers determines the ultimate aerobic biodegradability of plastic materials in aqueous medium. To determine the biodegradability of these plastics, the CO₂ evolution is measured through respirometry in continuously aerated bottles. 

ISO 14852 can last up to 6 months and is used to test various polymers, including those with the following properties: 

• Highly soluble, poorly soluble, insoluble, and/or absorbing 
• Natural and synthetic polymers, or a mixture of the two
• Plastics that contain additives, such as plasticizers, colorants, and compounds

ISO 17556

This tests for the ultimate biodegradability of organic polymers/plastics in soil, relying only on the microorganisms originally present in that soil. There are two methods to this test — the oxygen demand method and the CO₂ evolution method. 

In the oxygen demand method, the level of biodegradation is measured through the percentage of oxygen consumption that occurs during biodegradation. Conversely, the CO₂ evolution method measures the level of biodegradation through CO₂ evolution. 

Both methods of the ISO 17556 can be used to test natural, synthetic, copolymers, or mixtures. This testing method is also appropriate for use on plastics that contain additives like plasticizers, colorants, and more. 

OECD 120 

Rather than testing for biodegradability, the OECD 120 tests for polymer solubility. This test is used to analyze the solution and extraction behaviors of polymers in water. The test polymer and water are added to vessels that are fitted with glass stoppers. The mixture is then agitated at 20ºC over a 24 hour period. Once complete, the content is centrifuged or filtered and the concentration of the polymer present in the clear aqueous phase is determined. While this test can be used on many polymers, it is not appropriate for liquid polymers or polymers that react adversely with water. 

Interested in a Biodegradability Test for Polymers? Aropha is Here to Help

At Aropha, we are dedicated to providing efficient, cost-effective biodegradability testing for all who need it. Not only do we offer traditional lab biodegradability testing, but we also offer biodegradability predictions through our machine learning program, ArophaAI. 

If you are interested in seeing what our services can do for you, contact us today.