ASTM D7991-22 PDF

Full title and description

Standard Test Method for Determining Aerobic Biodegradation of Plastics Buried in Sandy Marine Sediment under Controlled Laboratory Conditions — an ASTM test method (designation D7991-22) that defines a laboratory procedure to measure aerobic biodegradation (CO2 evolution) of non‑floating plastic materials buried in sandy tidal sediment kept wet with seawater under controlled conditions.

Abstract

This test method describes how to assess the degree of aerobic biodegradation of plastics that become buried in sandy tidal zones by measuring cumulative net carbon dioxide evolved from test specimens incubated in natural sandy sediment wetted with seawater. Results are reported as percentage of organic carbon converted to CO2 over the test duration and are intended for laboratory comparison and environmental persistence estimation under the simulated tidal‑sand conditions.

General information

• Status: Active standard.
• Publication date: 2022 (D7991‑22; edition published May 1, 2022 / recorded as 2022 edition).
• Publisher: ASTM International (ASTM).
• ICS / categories: 83.080.01 (Plastics — general).
• Edition / version: D7991‑22 (current revision 2022).
• Number of pages: 5 pages (concise test method document).

Key bibliographic details above are recorded in standard catalogs and the ASTM publication listing.

Scope

The scope covers determination of the biodegradation level of plastic materials exposed in the laboratory to conditions that simulate the sandy tidal zone (sandy sediment kept wet with seawater). The method applies to non‑floating plastics that may become buried in the foreshore and intertidal sand; it measures mineralization to CO2 by the indigenous microbial population in the collected sediment and seawater. The method does not address brackish or freshwater habitats and does not measure conversion to biomass (only CO2 formation). Reports shall state percentage net CO2 generation for test and reference materials and must not extrapolate results beyond the actual test duration.

Key topics and requirements

• Test concept: incubation of test specimens in natural sandy marine sediment wetted with seawater and measurement of evolved CO2 (respirometric approach).
• Performance metric: percentage of organic carbon in the plastic converted to CO2 (cumulative net CO2) over the test period.
• Specimen handling: use of representative sediment and seawater collected from a sandy tidal beach (natural inoculum) and controlled laboratory conditions (temperature, aeration, reactors/respirometers).
• Reference materials: inclusion of positive reference material(s) and appropriate blanks/controls to account for background CO2 from sediment and seawater.
• Units and reporting: SI units required; clear statement of test duration; do not extrapolate beyond measured data.
• Limitations: not applicable to floating plastics, not a measurement of biomass formation, and results represent simulation of tidal sandy conditions rather than in situ long‑term fate.

These procedural and reporting requirements follow the method text and explanatory notes in the D7991‑22 standard.

Typical use and users

Used by environmental testing laboratories, polymer and additives manufacturers, research institutions, regulatory bodies, and eco‑label/certification organizations to evaluate and compare the aerobic biodegradation behavior of non‑floating plastics under simulated sandy tidal conditions. Typical applications include material screening, comparative biodegradability studies, and providing data for environmental fate assessments and labeling considerations.

Related standards

Closely related/neighboring standards and methods include ASTM D6691 (marine biodegradation by defined consortium or natural seawater inoculum), ASTM D5988 (biodegradation in soil), ISO standards for marine biodegradation and seawater/sediment interface testing (for example ISO 18830 and ISO 19679 among others), and OECD methods for biodegradation in aquatic systems. These standards are often referenced for complementary test designs or to address other aquatic habitats or measurement techniques.

Keywords

aerobic biodegradation; plastics; sandy marine sediment; tidal zone; respirometric CO2 measurement; environmental fate; ASTM D7991‑22; seawater; natural inoculum; laboratory simulation.

FAQ

Q: What is this standard?

A: ASTM D7991‑22 is a standardized laboratory test method for determining aerobic biodegradation (measured as CO2 evolution) of plastics buried in sandy marine sediment under controlled conditions.

Q: What does it cover?

A: It covers preparation, incubation, CO2 measurement, controls, and reporting for plastics placed in natural sandy tidal sediment kept wet with seawater to simulate the intertidal/sandy foreshore environment; it quantifies mineralization to CO2 but does not measure biomass formation.

Q: Who typically uses it?

A: Environmental and materials testing laboratories, polymer manufacturers, researchers, regulators, and certification bodies use this method to compare biodegradation behavior of non‑floating plastic materials in simulated sandy marine conditions.

Q: Is it current or superseded?

A: The active revision is D7991‑22 (2022). It updates the earlier D7991‑15 edition; users should consult the D7991‑22 text for the official, current requirements.

Q: Is it part of a series?

A: It is one of several ASTM/ISO/OECD methods addressing marine and aquatic biodegradation (for example ASTM D6691, ISO 18830, ISO 19679, OECD aquatic biodegradation methods) and is used alongside those standards when different habitats, inocula, or measurement techniques are required.

Q: What are the key keywords?

A: Aerobic biodegradation, plastics, sandy sediment, tidal zone, seawater, CO2 evolution, respirometry, ASTM D7991‑22.