ASTM D6691-24 PDF

Overview

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, issued by ASTM International. This standard supports efforts to address the environmental challenges posed by plastics in marine environments. With the increased use of plastics on ships and restrictions on ocean-based waste disposal, ASTM D6691-24 provides a robust, laboratory-based method to evaluate how plastics biodegrade aerobically when exposed to marine microorganisms.

The method measures the rate and extent of biodegradation by quantifying carbon dioxide produced as plastics are broken down, offering valuable data on potential biodegradability and persistence of plastics in marine settings such as seashores and open oceans. This test gives stakeholders a standardized way to assess new materials marketed as “biodegradable” in marine environments.

Key Topics

• Aerobic Biodegradation Testing The standard details procedures for exposing plastic materials to either a consortium of pre-grown marine microorganisms or indigenous populations in natural sea water under controlled laboratory conditions.

• Carbon Dioxide Measurement Biodegradation is determined by tracking the amount of CO₂ generated as plastics decompose, using sensitive respirometric equipment.

• Material Applicability ASTM D6691-24 applies to all polymer materials with at least 20% carbon content that are not toxic to marine microorganisms. Testing can accommodate powders, films, fragments, or formed articles.

• Reference Materials and Comparisons A positive control (such as cellulose or chitin) must be included to ensure the microbial inoculum is active. Results are measured relative to these reference materials.

• Interpretation and Limitations While the test gives insight into potential marine biodegradability, users are cautioned against over-extrapolation of laboratory results to long-term real-world environmental fate.

• Safety and Good Laboratory Practice The standard emphasizes proper handling of microorganisms, safe chemical use, and adherence to health and environmental regulations.

Applications

ASTM D6691-24 is a critical tool for:

• Biodegradable Plastics Assessment Manufacturers use this standard to verify claims of marine biodegradability for plastic materials, facilitating environmentally conscious product development.

• Comparative Material Testing Researchers and quality assurance professionals compare different polymers or blends for their biodegradation rates in marine environments.

• Regulatory and Environmental Compliance The test method assists regulatory bodies and eco-labeling programs in evaluating and certifying biodegradable materials intended for marine use.

• Reducing Marine Plastic Pollution By enabling rigorous, standardized testing, ASTM D6691-24 helps industries develop materials that may reduce the persistence of plastic waste in oceans.

Related Standards

• ASTM D883 - Terminology Relating to Plastics
• ASTM D618 - Practice for Conditioning Plastics for Testing
• ASTM D1193 - Specification for Reagent Water
• ASTM D4129 - Test Method for Total and Organic Carbon in Water by High Temperature Oxidation and by Coulometric Detection
• ASTM D2593 - Test Method for Butadiene Purity and Hydrocarbon Impurities by Gas Chromatography

Note: There is currently no ISO equivalent to ASTM D6691-24.

By adhering to ASTM D6691-24, stakeholders gain reliable, reproducible data for materials science, marine protection, and sustainability initiatives, promoting responsible use of plastics in environments where their impact is most critical.