ASTM D6691 – Aerobic Biodegradation of Plastic Materials in the Marine Environment

ASTM D6691: Determining Aerobic Biodegradation of Plastic Materials in the Marine Environment by a Defined Microbial Consortium or Natural Sea Water Inoculum

With the widespread use of plastics abroad ships, marine water pollution remains a pressing issue. Biodegradable plastics can enable a safe disposal of such materials at sea. The aim of the ASTM D6691 test is to evaluate the rate and degree of aerobic biodegradability of plastic materials for a safe disposal of plastics in sea and ocean waters.

This biodegradability test is intended to assess the degree and rate of aerobic biodegradation of plastic products that have been exposed to aerobic microorganisms in natural seawater. Aerobic biodegradation is evaluated by calculating the amount of carbon dioxide emitted over the course of the test.

The purpose of the ASTM D6691 method is to identify potentially biodegradable polymer materials, relative to a positive reference, in an aerobic environment. This biodegradability test is applicable for polymeric materials containing at least 20% carbon and non-inhibiting to microorganisms found in the aquatic environment.

This ASTM method is a unique test that is not harmonized nor equivalent to any ISO methods. The test is conducted under standardized laboratory conditions and is meant to estimate the persistence of plastic materials in biologically active aquatic environments. As with any short-term exposure test intended to predict long-term environmental fate, caution shell be exercised when evaluating the experimental results in terms of the effects in the natural environment it is meant to reflect on.

For anaerobic biodegradability evaluation of plastics and similar materials, ASTM D5511 is commonly requested. In this anaerobic biodegradation assessment, a high-solids anaerobic microbial inoculum derived from functioning anaerobic digestor is utilized.

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