ASTM D8646-26

1.1 This test method applies to non-floating biodegradable plastics intended for use in aerobic aquatic environments, specifically in marine, brackish, or fresh water ecosystems. The plastics covered under this test method are designed to not persist in the environment by converting into carbon dioxide through microbial metabolism within the defined aerobic aquatic environments under specified temperature conditions.

1.2 The test method establishes detailed requirements for reporting on non-floating plastics intended to biodegrade in a specified aerobic aquatic environment at three or more temperatures. Biodegradation is defined as the conversion of total polymer carbon into carbon dioxide. The estimated time required for full biodegradation (expressed in days, months, or years) shall be derived from experimental test data and calculated using non-linear regression analysis based on the global kinetic rate law, incorporating the Arrhenius equation. The polymer carbon conversion constant (k) and the estimated time (t) for biodegradation shall be reported. Experimental data shall be obtained through ASTM D6691 or ISO 14852 standard test methods to ensure consistency and reliability.

1.3 This test method defines the necessary criteria to determine whether non-floating plastics intended for use in aerobic aquatic environments will not persist or accumulate. This standard requires a minimum of 90 % of the total polymer carbon to be converted into carbon dioxide, either absolutely or relative to chromatography-grade cellulose. This test method also estimates the time required for carbon dioxide conversion (non-persistence) in the aquatic environment at a specific temperature applying fundamental kinetic rate laws. Additionally, this test method establishes criteria for evaluating whether plastics intended for use in aquatic environments will affect those ecosystems and the health of organisms.

1.4 This test method does not support or condone the intentional disposal, loss, or leakage of biodegradable plastics into aquatic environments. Instead, this standard focuses on demonstrating that biodegradable plastics conforming to these requirements will not persist or accumulate in aquatic environments. The time for complete removal of the plastic is estimated using experimentally derived data and kinetic modeling. Comparative testing of non-biodegradable persistent hydrocarbonbased plastics, such as polyethylene (PE) or polypropylene (PP), is required to validate the test's methodology and demonstrate the persistence of such materials in aquatic environments, using recognized ASTM biodegradation test methods.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.