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ISO 23977-1: Aerobic Biodegradability of Plastics in Seawater - CO2 Evolution (ISO/IEC 17025:2017 Accredited)

ISO 23977-1 is an aqueous aerobic biodegradability test that determines the aerobic biodegradability of plastic materials in seawater by measuring CO2 evolution during biodegradation in a closed system. This test relies on the microorganisms originally present in seawater without the addition of a specific inoculum. The conditions in this study might not always correspond to the optimum conditions for the maximum degree of biodegradation. However, this test method is designed to give an indication of the potential biodegradability of plastic materials.

The test normally lasts for up to 1 year, but can be extended to a maximum of 2 years.


ISO 23977-1 describes two variations of a test method for determining the biodegradability of plastic materials by the indigenous population of microorganisms in natural seawater using a static aqueous test system.

The test is performed under mesophilic test conditions for up to two years by incubating plastic materials with either seawater only ("pelagic seawater test") or with seawater to which low amount of sediment has been added (''suspended sediment seawater test"), coming from the same site as that from which the seawater was taken.

Biodegradation is followed by measuring the evolution of CO2 using a suitable, analytical method. The level of biodegradation is determined by comparing the amount of CO2 evolved with the theoretical amount of evolved CO2 (ThCO2) and expressed in percentage. The test result is the maximum level of biodegradation, determined from the plateau phase of the biodegradation curve. 

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ISO 23977-1

ISO 23977-1 Key Summary

▶ Materials that can be tested:
     ➢ Plastic materials.
▶ Test substance requirement:
     ➢ The total organic carbon (C%) needs to be known in order to calculate the ThCO2;
     ➢ Preferably in powder form with a maximum diameter size of 250 um;
     ➢ Similar shapes of different substances should be used if they are to be compared.
▶ Temperature: 15-25°C.
▶ Reference: a well-defined biodegradable polymer (e.g., microcrystalline cellulose powder or ashless cellulose filters).
▶ Test substance dosage: 150-300 mg of test substance per liter of seawater.
▶ Reactor example: 300 mL of volume with 90 mL of natural seawater only, or natural seawater with 0.1-1 g/L sediment.
▶ CO2 absorber solution: 10 mL Ba(OH)2 at 0.0125M, 3 mL KOH at 0.5 M, or 4 mL NaOH at 1 M. 
▶ Number of reactors: 3 for blank control, 3 for reference control, and 3 for test substance.
▶ Duration: normally up to 1 year; prolong the test up to 2 years if significant biodegradation is still observed after 1 year.

ISO 23977-1 Requirement and Applicability

Different testing methods are applicable for materials with different properties. Below is a summary of the applicability of ISO 23977-1. Please check our Method Selection Guide to select the most appropriate method for your materials. You can also find the applicability for many other methods on Aropha Resource Center

TestAnalytical methodSample info required *Poorly solubleVolatileAdsorbing
ISO 23977-1CO2 evolution in headspaceOrganic carbon content *+++

*"Sample info required" is the information needed to calculate the biodegradation percentages. This must be available for a selected method.
*"Organic carbon content" is the ratio of the organic carbon weight to the weight of the sample. It can be calculated by the sample formula (e.g., acetic acid C2H4O2, carbon content is 12*2/(12*2+1*4+16*2)=40%). Try our Online C% Calculator. If the formula is unknown, we can send the sample out to a third party lab for you for analysis (normally $110 with a 10-day turnaround time).

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To learn more about different types of biodegradation tests, their applicability, biodegradation mechanisms, and many other information such as case studies, publications, and blogs, please check our Aropha Resource Center

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