ASTM D7991-22

Standard Test Method for Determining Aerobic Biodegradation of Plastics Buried in Sandy Marine Sediment under Controlled Laboratory Conditions

SIGNIFICANCE AND USE
5.1 Plastic is sometimes carried by rivers or accidentally discharged by ships into the sea; this plastic can then reach different parts of the marine environment. Tides and waves also frequently deliver plastic marine debris into the sandy tidal zones.  
5.2 This test method simulates the environmental conditions found in the tidal zone. Plastic debris that reaches the sandy tidal zone can settle there and become partially or totally buried by sand and kept wet by waves or tides. It is of interest to assess the biodegradation behavior of plastic materials under these conditions to predict the removal time of this waste in the environment.  
5.3 This test method is applied to determine the extent of biodegradation of a plastic exposed in the laboratory to a sandy sediment kept wet with seawater. Both sediment and seawater are collected from a sandy beach in the tidal zone. If the natural microbial population present in the sediment is able to biodegrade the plastic, there will be an evolution of CO2 as a consequence of the aerobic microbial respiration. The level of biodegradation at any given time is the ratio between the cumulative amount of the evolved net carbon dioxide and the theoretical amount produced in the case of total conversion of the organic carbon present in the plastic into carbon dioxide.  
5.4 This test method does not measure the amount of organic carbon that is converted into biomass, but only the biodegradation that leads to mineralization (that is, the formation of CO2).
SCOPE
1.1 This test method determines the biodegradation level of plastic materials exposed to laboratory conditions that simulate the environment found in the sandy tidal zone.  
1.2 The tidal zone, that is, the part of the coast affected by the tides and movement of the waves, is the borderline between sea and land, frequently a sandy area that is kept constantly damp by the lapping of the waves. Stony and rocky shorelines also exist.  
1.3 Plastic marine debris is frequently washed up in this habitat where it must be removed in order to restore the original landscape.  
1.4 It is of interest to know the biodegradation behavior of plastics when exposed to conditions simulating this habitat, because this information can help in predicting the time needed for the biodegradation of the litter.  
1.5 Biodegradation is determined by measuring the CO2 evolved by the plastic material when exposed to a sediment kept wet with salt-water in a reactor, to simulate the tidal zone.  
1.6 Marine fresh-water habitats (for example, those found in brackish waters and estuaries) are not considered by this standard.  
1.7 Reports shall clearly state the percentage of net CO2 generation for both the test and reference samples at the completion of the test. Furthermore, in the laboratory reports, the results shall not be extrapolated beyond the actual duration of the test.  
Note 1: There is no known ISO equivalent to this standard.  
1.8 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.9 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.  
1.10 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.

General Information

• Status: Published
• Publication Date: 30-Apr-2022
• ICS: 83.080.01 - Plastics in general
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.96 - Environmentally Degradable Plastics and Biobased Products

Standards Content (Sample)

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.
Designation: D7991 − 22
Standard Test Method for
Determining Aerobic Biodegradation of Plastics Buried in
Sandy Marine Sediment under Controlled Laboratory
1
Conditions
This standard is issued under the fixed designation D7991; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 1.9 This standard does not purport to address all of the
safety concerns, if any, associated with its use. It is the
1.1 This test method determines the biodegradation level of
responsibility of the user of this standard to establish appro-
plastic materials exposed to laboratory conditions that simulate
priate safety, health, and environmental practices and deter-
the environment found in the sandy tidal zone.
mine the applicability of regulatory limitations prior to use.
1.2 The tidal zone, that is, the part of the coast affected by
1.10 This international standard was developed in accor-
thetidesandmovementofthewaves,istheborderlinebetween
dance with internationally recognized principles on standard-
sea and land, frequently a sandy area that is kept constantly
ization established in the Decision on Principles for the
damp by the lapping of the waves. Stony and rocky shorelines
Development of International Standards, Guides and Recom-
also exist.
mendations issued by the World Trade Organization Technical
Barriers to Trade (TBT) Committee.
1.3 Plastic marine debris is frequently washed up in this
habitat where it must be removed in order to restore the
2. Referenced Documents
original landscape.
2
2.1 ASTM Standards:
1.4 It is of interest to know the biodegradation behavior of
D5988 Test Method for Determining Aerobic Biodegrada-
plastics when exposed to conditions simulating this habitat,
tion of Plastic Materials in Soil
becausethisinformationcanhelpinpredictingthetimeneeded
3
2.2 ISO Standards:
for the biodegradation of the litter.
ISO 8245 Water quality Guidelines for the determination of
1.5 Biodegradation is determined by measuring the CO
2
total organic carbon (TOC) and dissolved organic carbon
evolved by the plastic material when exposed to a sediment
(DOC)
kept wet with salt-water in a reactor, to simulate the tidal zone.
3. Terminology
1.6 Marinefresh-waterhabitats(forexample,thosefoundin
brackish waters and estuaries) are not considered by this 3.1 Definitions:
3.1.1 tidal zone, n—the part of the marine environment that
standard.
extends from the high tide line, which is rarely inundated with
1.7 Reports shall clearly state the percentage of net CO
2
water, to the low tide line, which is typically always covered
generation for both the test and reference samples at the
with water.
completion of the test. Furthermore, in the laboratory reports,
3.1.1.1 Discussion—Synonyms are: eulittoral zone, midlit-
the results shall not be extrapolated beyond the actual duration
toral zone, mediolittoral zone, intertidal zone, foreshore.
of the test.
4. Summary of Test Method
NOTE 1—There is no known ISO equivalent to this standard.
1.8 Units—The values stated in SI units are to be regarded 4.1 This test method consists of the following:
4.1.1 Selection of plastic material for the determination of
as standard. No other units of measurement are included in this
standard. aerobic biodegradation in a controlled laboratory system.
4.1.2 Obtaining sediment and seawater from the shoreline.
1 2
This test method is under the jurisdiction ofASTM Committee D20 on Plastics For referenced ASTM standards, visit the ASTM website, www.astm.org, or
and is the direct responsibility of Subcommittee D20.96 on Environmentally contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Degradable Plastics and Biobased Products. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved May 1, 2022. Published May 2022. Originally the ASTM website.
3
approved in 2015. Last previous edition approved in 2015 as D7991 - 15. DOI: Available fromAmerican National Standards Institute (ANSI), 25 W. 43rd St.,
10.1520/D7991–22. 4th Floor, New York, NY 10036, http://www.ansi.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7991 − 22
be 12:12 day/night. Details on the lighting regime, light intensity, wave
4.1.3 Exposing the plastic material to the wet sediment
length, incubator type, etc. shall be provided in t
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: D7991 − 15 D7991 − 22
Standard Test Method for
Determining Aerobic Biodegradation of Plastics Buried in
Sandy Marine Sediment under Controlled Laboratory
1
Conditions
This standard is issued under the fixed designation D7991; the number immediately following the designation indicates the year of
original adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A
superscript epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This test method determines the biodegradation level of plastic materials exposed to laboratory conditions that simulate the
environment found in the sandy tidal zone.
1.2 The tidal zone, that is, the part of the coast affected by the tides and movement of the waves, is the borderline between sea
and land, frequently a sandy area that is kept constantly damp by the lapping of the waves. Stony and rocky shorelines also exist.
1.3 Plastic marine debris is frequently washed up in this habitat where it must be removed in order to restore the original
landscape.
1.4 It is of interest to know the biodegradation behavior of plastics when exposed to conditions simulating this habitat, because
this information can help in predicting the time needed for the biodegradation of the litter.
1.5 Biodegradation is determined by measuring the CO evolved by the plastic material when exposed to a sediment kept wet with
2
salt-water in a reactor, to simulate the tidal zone.
1.6 Marine fresh-water habitats (for example, those found in brackish waters and estuaries) are not considered by this standard.
1.7 Reports shall clearly state the percentage of net CO generation for both the test and reference samples at the completion of
2
the test. Furthermore, in the laboratory reports, the results shall not be extrapolated beyond the actual duration of the test.
NOTE 1—There is no known ISO equivalent to this standard.
1.8 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this
standard.
1.9 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 safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use.
1
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.96 on Environmentally Degradable
Plastics and Biobased Products.
Current edition approved Sept. 1, 2015May 1, 2022. Published September 2015May 2022. Originally approved in 2015. Last previous edition approved in 2015 as
D7991 - 15. DOI: 10.1520/D7991–15.10.1520/D7991–22.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
1

---------------------- Page: 1 ----------------------
D7991 − 22
1.10 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.
2. Referenced Documents
2
2.1 ASTM Standards:
D5988 Test Method for Determining Aerobic Biodegradation of Plastic Materials in Soil
3
2.2 ISO Standards:
ISO 8245 Water quality Guidelines for the determination of total organic carbon (TOC) and dissolved organic carbon (DOC)
3. Terminology
3.1 Definitions:
3.1.1 tidal zone, n—the part of the marine environment that extends from the high tide line, which is rarely inundated with water,
to the low tide line, which is typically always covered with water.
3.1.1.1 Discussion—
Synonyms are: eulittoral zone, midlittoral zone, mediolittoral zone, intertidal zone, foreshore.
4. Summary of Test Method
4.1 This test method consists of the following:
4.1.1 Selection of plastic material for the determination of aerobic biodegradation in a controlled laboratory system.
4.1.2 Obtaining sediment and seawater from the shoreline.
4.1.3 Exposing the plastic material to the wet sediment under controlled conditions.
4.1.4 Measuring CO evolved as a function of time.
2
4.1.5 Assessing the degree of biodegradation by determining the percentage of organic carbon in the plastic material that is
converted to CO during the duration of the test. This percentage represents the percentage
...