ASTM D6691 Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment

    ASTM D6691 Introduction

    ASTM D6691 (Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment) provides a controlled process to evaluate the marine aerobic biodegradation of plastics. This test assists industries in addressing the emerging issue of plastic waste in the sea. Aerobic biodegradation can be defined as the degradation of materials by the presence of microorganisms in the presence of oxygen, to give out carbon dioxide. Thus, ASTM D6691 evaluates the CO2 evolution to determine the degradation. The approach assists in the selection of material to be used in an environmentally responsible way. It is also useful for estimating the persistence of plastics in marine ecosystems, such as coastal and open-ocean environments. The users should, however, exercise caution when generalizing laboratory results to real-life environments.

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    Get Certified ASTM D6691 Testing for Marine Biodegradable Plastics

    Big data on biodegradation enables industries to process eco-friendly plastic materials. Furthermore, certification helps in assuring that the products comply with the environmental expectations. Proper testing helps to comply with regulations and minimize environmental risks. 

    Scope of ASTM D6691 Test Standard

    • Identifies the rate and level of plastics aerobic biodegradation.
    • Inoculates with marine microorganisms or natural seawater.
    • Applies to polymers that contain carbon at least 20%.
    • Eliminates harmful materials to marine organisms. 

    Equipment and Sample Preparation

    Biodegradation ReactorMaintains controlled aerobic marine conditions for microbial activity.
    Specimen DetailsASTM D6691 involves selecting and characterizing plastic materials for testing, as well as preparing a uniform inoculum of marine microorganisms or obtaining a natural seawater sample.
    Specimen SizeThe ASTM D6691 test sample should be weighed to the nearest 0.1 mg and contain enough carbon (at least 20%) to allow the respirometer to detect carbon dioxide levels.

    Use of ASTM D6691

    • Assesses marine biodegradable plastics.
    • Promotes the creation of environmentally-friendly materials.
    • Helps with compliance regulations and the environment.
    • Helps estimate the survival of plastics in the marine environment. 

    How Does ASTM D6691 Measure Biodegradation in Marine Conditions?

    ASTM D6691 is a test that determines the degradation of biodegradation by carbon dioxide evolution. The microorganisms decompose plastic substances in aerobic conditions. As a result, the amount of CO2  that is emitted in the process of metabolism indicates the degradation level. Increased CO2  formation is a pointer to increased biodegradation. 

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    Why Is Microbial Inoculum Important in ASTM D6691?

    Microbial inoculum supplies active organisms that degrade materials biologically. A specified consortium guarantees regulated and replicable circumstances for the process. In other cases, natural seawater is a reflection of the real environmental variety. Thus, the choice of inoculum influences the accuracy of tests and their relevance directly. 

    Common Challenges and Troubleshooting 

    Testing can have variation because of the differences in microbial activity. Further, certain plastics can suppress the growth of microbes, which can interfere with the findings. CO2  measurements may also be changed due to inconsistent environmental conditions. Also, short-term tests can not be referenced to the long-term behavior of the marine environment. To resolve these problems, the laboratories should be kept in stable conditions, choose the right inoculum, and be careful with the interpretation of the results. Controlled testing provides strong testing of biodegradation. 

    Testing Technique Process, and Data Collection

    The initial stages of testing include sample preparation and selection of inoculum. Then, the technicians insert samples into the controlled marine environment, where oxygen is provided. The material gets broken down by microorganisms and emits carbon dioxide. Then, they are continuously measured by instruments, which measure the evolution of CO2 . Lastly, the data obtained are used to determine the biodegradation rate and level. 

    ASTM D6691 Testing Procedure and Requirements

    ASTM D6691 uses carbon dioxide to measure biodegradation through the use of microbial activity. The first step involves placing plastic samples in a known inoculum of microbial consortium or natural seawater provided. Next, technicians sustain moderate aerobic conditions during the test. Lastly, they quantify the CO2 evolution rate and the degree of degradation. 

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    Characterization of the MaterialASTM D6691 involves selecting and characterizing plastic materials based on their carbon content and molecular weight.
    Exposure to the inoculumMarine microorganisms are introduced to the test material. A respirometer tracks the release of carbon dioxide (CO2) gas over time as the material breaks down.
    Measurement of BiodegradabilityThe amount of polymer carbon converted into biogas carbon, which determines biodegradability 
    Theoretical Carbon Content MeasurementAs time passes, the test provides the percentage of gas produced compared to the carbon content of the material.
    Image shows a respirometer system used to measure the aerobic biodegradation of plastic materials in marine environments by tracking the evolution of carbon dioxide over time, as discussed in ASTM D6691.
    Respirometer System

    ASTM D6691 Analysis Results and Interpretation 

    ASTM D6691 presents the results in SI units as a standard. Biodegradation is given as a percentage (%) with respect to the theoretical carbon conversion. The amount of carbon dioxide evolved is measured to determine the amount of degradation taking place. An increase in the percentage values results in increased biodegradability. These results help engineers to compare materials and determine environmental suitability. 

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    Link to ASTM D6691 Standard

    FAQ

    Where can I get the astm d6691 tested?
    You can share your astm d6691 testing requirements with MaTestLab. MaTestLab has a vast network of material testing laboratories, spread across the USA and Canada. We support your all material testing needs ranging from specific astm d6691 test to various testing techniques.
    Please contact us for a detailed quote for your astm d6691 testing needs. Cost incurred to carry out different astm d6691 testing methodology depends on the type of raw material; number of samples, coupons, or specimens; test conditions, turn around time etc. Costs of some ASTM testing methods start from $100 and the final value depends upon the factors listed above. Please contact us for the best and latest prices.
    The required number of samples or specimens should comply with the procedure given in the astm d6691 standard. However, the MaTestLab operations team can assist you for your special requirements once you share your testing details with us.
    MaTestLab has a vast testing laboratory network, hence we bring you the best testing facilities in a cost-effective way. We offer considerable discounts (15-20%) to our returning customers based on test volume and frequency.
    The turnaround time for astm d6691 test methodology depends upon the test procedure mentioned in the standard test document. However, we at MaTestLab understand your research requirements and hence try to get your test completed within the least possible time.
    Suyog Kamble
    About Author
    Suyog Kamble
    Suyog Kamble is an Operations Associate at MaTestLab Inc. and holds a postgraduate degree in Organic Chemistry.
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