ASTM D6691: Plastic Marine Biodegradation Consortium Testing Services
Accredited ASTM D6691 plastic marine biodegradation consortium testing from Infinita Lab, performed to the exact standard requirements - accurate, reproducible results with full documentation for compliance, R&D, and quality control programs.
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- Overview
- Scope, Applications, and Benefits
- Test Process
- Specifications
- Instrumentation
- Results and Deliverables
What Is ASTM D6691 Plastic Marine Biodegradation Consortium?
ASTM D6691, Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum, is the standardised respirometric method used to determine the extent and rate of plastic biodegradation when exposed to marine microorganisms. The method was developed to give manufacturers, regulators, and researchers a reproducible, laboratory-based way to evaluate how plastics behave in seawater, rather than relying on uncontrolled field observations of marine debris.
At a high level, the test method works by placing test material specimens in sealed reactor vessels along with either a pre-grown population of recognised aerobic marine microorganisms or a natural seawater inoculum, under controlled laboratory conditions maintained at a defined incubation temperature. As the microbial consortium metabolises the plastic as its sole or primary carbon source, it respires and releases carbon dioxide. This evolved CO2 is measured periodically throughout the exposure period and compared against the theoretical amount of CO2 that would be produced if all of the carbon in the test material were fully converted, yielding a per cent biodegradation value over time. Every test run also includes a positive control, typically a well-characterised biodegradable material such as cellulose, and a blank (inoculum only, no test material), so that microbial activity and background respiration can be verified and subtracted from the test results.
ASTM D6691 matters because it provides the scientific basis for substantiating marine-biodegradability claims on plastic products and packaging. As regulatory bodies, brand owners, and consumers pay closer attention to marine plastic pollution, manufacturers developing biodegradable or compostable plastic formulations need defensible, standardized data showing how their materials actually perform in a marine setting. Infinita Lab’s accredited laboratory network performs ASTM D6691 testing to support product development, environmental claims substantiation, and marine debris mitigation research.
Applications and Benefits of ASTM D6691 Plastic Marine Biodegradation Consortium Testing
Scope
- ASTM D6691 quantifies the per cent aerobic biodegradation of a plastic material in a marine environment based on the amount of carbon dioxide evolved during microbial metabolism.
- The test principle relies on exposing plastic test specimens to a defined microbial consortium of recognized marine microorganisms or to a natural seawater inoculum under controlled laboratory conditions.
- Biodegradation is calculated by comparing the cumulative CO2 evolved from the test material against the theoretical CO2 (ThCO2) that would result if all of the material’s carbon were converted to carbon dioxide.
- A positive control, such as cellulose or another well-defined biodegradable reference material, is run alongside the test material to confirm that the inoculum is biologically active.
- A blank control containing inoculum only, with no test material, is run in parallel to establish and correct for background respiration.
- Testing is conducted at a controlled incubation temperature representative of marine conditions and continues until CO2 evolution plateaus or a suitable endpoint is reached.
- The method applies to plastic materials, films, and formulations that contain sufficient organic carbon content and are not inhibitory to the marine microorganisms used in the test.
- ASTM D6691 is used across the polymers and plastics, packaging, consumer goods, and environmental testing industries to evaluate marine biodegradability of new and existing formulations.
- Typical use cases include screening candidate biodegradable resins, comparing polymer blends, and generating data to support environmental marketing and regulatory claims.
- Results from this test method support decisions on material selection, formulation adjustment, and communication of marine-biodegradability performance to regulators and customers.
Applications
- Development and screening of biodegradable and compostable plastic resins, films, and product formulations intended for marine or coastal use.
- Substantiation of marine-biodegradable and eco-friendly packaging claims made to regulators, retailers, and consumers.
- Comparative evaluation of competing polymer formulations to identify which biodegrade most effectively in seawater.
- Research supporting marine plastic pollution mitigation and debris reduction initiatives.
- Quality control and batch verification for manufacturers producing marine-biodegradable plastic products.
- Regulatory and compliance documentation for jurisdictions with emerging marine biodegradability requirements.
- Academic and environmental research into polymer fate and behaviour in ocean and coastal ecosystems.
Benefits
- Provides standardised, reproducible data on the rate and extent of plastic biodegradation in a marine environment.
- Generates defensible evidence to support marine-biodegradability and environmental marketing claims.
- Enables direct, apples-to-apples comparison between different polymer formulations and additive packages.
- Supports informed material selection and formulation decisions earlier in product development.
- Helps manufacturers respond to growing regulatory and consumer scrutiny of ocean plastic pollution.
- Delivers quantifiable results that can be tracked over time and referenced across multiple product generations.
Our ASTM D6691 Testing Procedure
Sample Selection & Preparation
A representative plastic sample is selected, its carbon content is determined, and the specimen is accurately weighed.
1Inoculum Preparation & Exposure Setup
The marine inoculum is prepared, and the samples are exposed in sealed test bottles.
2Incubation & Biogas Measurement
Samples are incubated at 30 ± 2°C, and CO₂ evolution is monitored.
3Data Collection & Analysis
Biogas production is recorded, and polymer carbon conversion is calculated.
4ASTM D6691 Test Parameters and Requirements
| Parameter | Details |
|---|---|
| Applicable Materials | Plastics with ≥20% carbon |
| Temperature | 30 ± 2°C |
| Measurement Method | Closed respirometry |
| Output Units | SI units |
| Measured Outputs | CO₂ generation, biodegradation rate |
- Respirometer / CO2 measurement system – Tracks and quantifies the carbon dioxide evolved from each test vessel throughout the incubation period.
- Controlled-temperature incubator – Maintains sealed test vessels at the consistent marine incubation temperature required by the standard.
- Sealed test vessels/bioreactors – House the test material, positive control, and blank specimens together with the microbial inoculum during exposure.
- Marine inoculum preparation and collection equipment – Used to collect, prepare, and maintain the defined microbial consortium or natural seawater inoculum.
- Analytical balance – Provides precise weighing of test material, positive control, and reference specimens before testing.
- Infrared or titration-based CO2 analysis equipment – Quantifies evolved carbon dioxide from each vessel for calculating per cent biodegradation.
- Data logging system – Records CO2 evolution readings and temperature data across the full test duration for reporting and analysis.
Equipment and Instrumentation Used for ASTM D6691 Testing
What You Receive: Test Report, Data, and Certification
- Per cent biodegradation of the test material over time, calculated from evolved CO2 versus theoretical CO2.
- Cumulative CO2 evolution data for the test material, positive control, and blank.
- Biodegradation curves illustrating the rate and progression of biodegradation throughout the exposure period.
- Comparative performance data referencing the positive control to confirm inoculum viability and contextualise test material results.
- A comprehensive test report suitable for supporting marine-biodegradability claims, regulatory submissions, and internal R&D documentation.
- Guidance on interpreting results for formulation development, material comparison, and environmental claims substantiation.
ASTM D6691 Plastic Marine Biodegradation Consortium FAQs
ASTM D6691 is an aqueous aerobic biodegradability test that determines the degree and rate of aerobic biodegradation of plastic materials in seawater.
The content of CO2 in biogas measurement aids in assessing the intensity and biodegradation rate of plastics in the marine environment based on the extent of degradation, which is a determinant of the resultant biodegradable impact.
The apparatus comprises a biogas production monitoring system, sample bottles, a gas-volume measuring and collection system, a water bath or a controlled environment shaker/incubator, and an analytical balance for weighing the test materials.
ASTM D6691 reports the degree and rate of aerobic biodegradation of polymeric materials by biogas (CO2) evolution and represents the amount of carbon in polymer converted to carbon in biogas.
The results of ASTM D6691 can guide the design and formulation of more biodegradable plastic materials, assisting manufacturers in producing products with lower environmental impact, particularly in marine applications.
ASTM D6691-24 is the Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum. It determines the rate and degree of aerobic biodegradation of plastic materials under controlled laboratory conditions by measuring biological conversion of the material into biogas, primarily carbon dioxide.
Why Choose Infinita Lab for Plastic Marine Biodegradation Consortium Testing
When your Plastic Marine Biodegradation Consortium results have to hold up - for compliance, a customer audit, or an engineering decision - ASTM D6691 accuracy and an unbiased third-party report matter more than price. Infinita Lab routes your ASTM D6691 plastic marine biodegradation consortium testing to ISO/IEC 17025-accredited U.S. partner labs with hands-on method experience, so you get defensible data, transparent reporting, and turnaround times built around your project deadline - not ours.
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