ASTM D7475-20

Standard Test Method for Determining the Aerobic Degradation and Anaerobic Biodegradation of Plastic Materials under Accelerated Bioreactor Landfill Conditions

SIGNIFICANCE AND USE
5.1 Decomposition of a plastic within a landfill involves processes in aerobic and anaerobic environmental conditions that can affect the decomposition of other materials enclosed by or in close proximity to the plastic. The rate of change from aerobic to anaerobic conditions is probably a characteristic of the particular landfill site, its garbage and the filling technique and is therefore difficult to assess with any degree of accuracy. Different sources indicate days to months (Refs (8) and (9)) for this change with the spread dependent on the perspective of what is aerobic or anaerobic and how fast the environment changes, 30 days is chosen in this method as a compromise time period. (Note, even very low levels of oxygen, far below normal atmospheric concentration can promote oxidative degradation). Obviously, there will be pockets of protected (in bags, cans, etc.) aerobic activity enclosed in any landfill. There is currently no evidence or data to support claims that rapid degradation of the plastic (when compared to conventional non-degradable plastic) can increase the economic feasibility of landfill-gas recovery, minimize the duration of after-care of the landfill, and make possible the recovery of the volume reduction of the waste due to degradation and biodegradation during the active life of the landfill. Additionally, it is possible that the rapid degradation and biodegradation of plastics can create hazardous conditions in landfills, such as the shifting of cells and overall stability. This standard method has been developed to permit determination of the aerobic degradation and anaerobic biodegradation of plastic products when placed in biologically active environments simulating some landfill conditions.  
5.2 The decomposition of plastic materials in a landfill is of importance, as most landfills are biologically active and are an increasingly significant source of renewable energy. As degradation occurs in a landfill, it is of immediate concern th...
SCOPE
1.1 This test method is used to determine the degree and rate of aerobic degradation (as indicated by loss of tensile strength, molecular weight, possibly resulting in disintegration and fragmentation) and anaerobic biodegradation of plastic materials in an accelerated aerobic-anaerobic bioreactor landfill test environment. It can simulate the change from aerobic to anaerobic environments over time as landfill depth increases. In Tier 1, the test plastic material is mixed with household waste, then pretreated and stabilized aerobically in the presence of air, in a sealed vessel in a temperature range that is consistent with the average temperature range of those recorded for landfills. The tier is an accelerated simulation of degradation with concomitant oxygen consumption and depletion with time as if oxidative degradation proceeds. In Tier 2 samples of the plastic materials pretreated aerobically as described in Tier 1, are exposed to a methanogenic inoculum derived from anaerobic digesters operating only on pretreated household waste. The anaerobic decomposition and biodegradation occur under dry (more than 30 % total solids) and static non-mixed conditions.  
1.2 This test method generates comparative data for several materials and must not be used to make claims regarding benefits of placing degradable or biodegradable plastics in landfills. Claims must be limited to and dependent on the results obtained from each tier.  
1.2.1 If only Tier 1 is run, then the claims must state: Will modify the performance/physical properties (for example, mechanical properties will degrade), up to a measured percent, X%, in a given time period, Y days using Test Methods D3593 (Molecular weight change) and Test Method D3826 (tensile strength change) in a biologically active “bioreactor” landfill. Report measured percent property changes and standards used to measure the test results which are, for example, changes in tensile streng...

General Information

• Status: Published
• Publication Date: 31-Jan-2020
• ICS: 13.030.40 - Installations and equipment for waste disposal and treatment
• Technical Committee: D20 - Plastics
• Drafting Committee: D20.96 - Environmentally Degradable Plastics and Biobased Products

Relations

• Replaces: ASTM D7475-11 - Standard Test Method for Determining the Aerobic Degradation and Anaerobic Biodegradation of Plastic Materials under Accelerated Bioreactor Landfill Conditions
• Effective Date: 01-Feb-2020
• Refers: ASTM D2908-91(2024) - Standard Practice for Measuring Volatile Organic Matter in Water by Aqueous-Injection Gas Chromatography
• Effective Date: 01-Apr-2024
• Refers: ASTM D883-24 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2024
• Refers: ASTM D6954-24 - Standard Guide for Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation
• Effective Date: 01-Jan-2024
• Refers: ASTM D883-23 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2023
• Refers: ASTM D883-20 - Standard Terminology Relating to Plastics
• Effective Date: 01-Jan-2020
• Refers: ASTM D4129-05(2020) - Standard Test Method for Total and Organic Carbon in Water by High Temperature Oxidation and by Coulometric Detection
• Effective Date: 01-Jan-2020
• Refers: ASTM E260-96(2019) - Standard Practice for Packed Column Gas Chromatography
• Effective Date: 01-Sep-2019
• Refers: ASTM D883-19c - Standard Terminology Relating to Plastics
• Effective Date: 01-Aug-2019
• Refers: ASTM D883-19a - Standard Terminology Relating to Plastics
• Effective Date: 15-Apr-2019
• Refers: ASTM D883-19 - Standard Terminology Relating to Plastics
• Effective Date: 01-Feb-2019
• Refers: ASTM D883-18a - Standard Terminology Relating to Plastics
• Effective Date: 01-Dec-2018
• Refers: ASTM D3826-18 - Standard Practice for Determining Degradation End Point in Degradable Polyethylene and Polypropylene Using a Tensile Test
• Effective Date: 01-Nov-2018
• Refers: ASTM D883-18 - Standard Terminology Relating to Plastics
• Effective Date: 01-Nov-2018
• Refers: ASTM D5526-18 - Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions
• Effective Date: 15-Sep-2018

Overview

ASTM D7475-20 is the Standard Test Method for Determining the Aerobic Degradation and Anaerobic Biodegradation of Plastic Materials under Accelerated Bioreactor Landfill Conditions. Developed by ASTM International, this standard provides an effective laboratory method for evaluating the degree and rate of both aerobic degradation and anaerobic biodegradation of plastics in simulated landfill environments. With the increasing environmental focus on plastics in waste management, ASTM D7475-20 is a vital tool for comparing degradation behaviors and environmental impact of various plastic materials intended for disposal.

Key Topics

• Simulation of Bioreactor Landfill Conditions: The standard provides a two-tiered approach to test plastics.

  • Tier 1 (Aerobic Degradation): Simulates initial aerobic conditions found in landfills, evaluating changes in properties such as tensile strength and molecular weight.
  • Tier 2 (Anaerobic Biodegradation): Follows the transition to oxygen-deprived conditions, assessing biogas (methane and carbon dioxide) produced as plastics break down.

• Comparative Benchmarking: Enables comparison and ranking of different plastic types for their decomposition behaviors under biologically active landfill conditions.

• Test Procedures: Specifies sample preparation, control use, environmental simulation (e.g., temperature, solids content), and analytical methods for measuring degradation and biodegradation.

• Reporting Requirements: Emphasizes comprehensive reporting, including environmental conditions, degradation metrics, and, if performed, ecotoxicity results. Claims must be limited to test results, avoiding unsupported generalizations about landfill benefits.

• Limitations and Safety: Acknowledges that results are specific to laboratory settings and bioreactor landfills, with real-world applicability subject to interpretation. Identifies hazards associated with handling waste, chemicals, and biogas production.

Applications

ASTM D7475-20 has practical applications in several key areas:

• R&D for Plastics Manufacturers: Supports the development and evaluation of biodegradable and environmentally degradable plastics, enabling comparative studies under simulated landfill conditions.
• Environmental Impact Assessment: Assists waste management professionals and regulators in understanding how different plastics will behave in active landfill settings, especially where gas recovery is considered.
• Product Certification and Labeling: Provides a framework for substantiating claims about the aerobic and anaerobic degradation properties of plastics, although claims must reference specific test conditions and outcomes.
• Landfill Operation and Policy Development: Informs policy makers and landfill operators about the degradation processes of disposed plastics, supporting strategies for biogas recovery and environmental risk assessments related to plastics in landfills.

Related Standards

ASTM D7475-20 references and aligns with several important ASTM and related standards, including:

• ASTM D5526 - Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions
• ASTM D3593 - Test Method for Molecular Weight Averages/Distribution of Certain Polymers by Liquid Size-Exclusion Chromatography
• ASTM D3826 - Practice for Determining Degradation End Point in Degradable Polyethylene and Polypropylene Using a Tensile Test
• ASTM D6954 - Guide for Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and Biodegradation
• APHA Standard Methods 2540D/2540E - Methods for solids analysis in waste

Conclusion

ASTM D7475-20 is an essential standard for assessing how plastics degrade in the complex environments of bioreactor landfill conditions. By providing a clear, reproducible method to evaluate both aerobic and anaerobic degradation, this standard supports innovation, environmental responsibility, and regulatory compliance in the lifecycle management of plastic materials. Proper adherence and reporting following ASTM D7475-20 enable accurate, meaningful comparisons and help stakeholders make informed decisions regarding plastics in waste streams.

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:D7475 −20
Standard Test Method for
Determining the Aerobic Degradation and Anaerobic
Biodegradation of Plastic Materials under Accelerated
Bioreactor Landfill Conditions
This standard is issued under the fixed designation D7475; 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 tensilestrength,massandmolecularweight,aswellasresidual
particle size ranges in Section 14 to support the extent of such
1.1 Thistestmethodisusedtodeterminethedegreeandrate
claims.
of aerobic degradation (as indicated by loss of tensile strength,
1.2.2 If both Tier 1 and Tier 2 are run, then claims shall
molecular weight, possibly resulting in disintegration and
state: Will biodegrade in a biologically active “bioreactor”
fragmentation) and anaerobic biodegradation of plastic mate-
landfill to a degree, X%, in Y days established by the test
rials in an accelerated aerobic-anaerobic bioreactor landfill test
results based on the extent to which the plastic sample is
environment. It can simulate the change from aerobic to
converted to gaseous carbon in the form of carbon dioxide and
anaerobic environments over time as landfill depth increases.
methane and this shall be made available according to Section
In Tier 1, the test plastic material is mixed with household
14 to support the extent of such claims. It should be noted that
waste, then pretreated and stabilized aerobically in the pres-
biodegradation testing is very dependent on conditions chosen
ence of air, in a sealed vessel in a temperature range that is
in this laboratory test and may well vary widely when the test
consistent with the average temperature range of those re-
isrunwithdifferentinoculum,Theresultsreportedpertainonly
corded for landfills. The tier is an accelerated simulation of
to the test conditions run and do not rule out potential
degradation with concomitant oxygen consumption and deple-
biodegradation under other conditions and real world environ-
tion with time as if oxidative degradation proceeds. In Tier 2
ments.
samples of the plastic materials pretreated aerobically as
described in Tier 1, are exposed to a methanogenic inoculum 1.3 Tier 1 of this test method is designed to estimate the
derived from anaerobic digesters operating only on pretreated aerobic degradation of plastics, that is disintegration and
household waste. The anaerobic decomposition and biodegra- fragmentation, only, by measuring the loss of physical and
dation occur under dry (more than 30 % total solids) and static chemical properties of said plastics. The test environment is
non-mixed conditions. then changed to that of Tier 2, an anaerobic condition, and
biodegradation is measured by a combination of evolved
1.2 This test method generates comparative data for several
carbon dioxide and methane gases as a percentage of the
materials and must not be used to make claims regarding
conversion of carbon in the plastic sample to carbon in the
benefits of placing degradable or biodegradable plastics in
gaseous form under conditions that resemble landfill condi-
landfills. Claims must be limited to and dependent on the
tions. This test method does not simulate all conditions found
results obtained from each tier.
in landfills, especially those found in biologically inactive
1.2.1 If only Tier 1 is run, then the claims must state: Will
landfills. This test method more closely resembles those types
modify the performance/physical properties (for example,
of bioreactor landfills in which the gas generated is recovered
mechanical properties will degrade), up to a measured percent,
orevenactivelypromoted,orboth,forexample,byinoculation
X%, in a given time period,Ydays usingTest Methods D3593
(co-deposition of anaerobic sewage sludge and anaerobic
(Molecular weight change) and Test Method D3826 (tensile
leachate recirculation), moisture control in the landfill
strength change) in a biologically active “bioreactor” landfill.
(leachate recirculation), and temperature control (short-term
Report measured percent property changes and standards used
injection of oxygen and heating of re-circulated leachate)
to measure the test results which are, for example, changes in
(1-7).
1.4 This test method produces partially degraded mixtures
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
of municipal solid waste and plastics that, where required, are
and is the direct responsibility of Subcommittee D20.96 on Environmentally
Degradable Plastics and Biobased Products.
Current edition approved Feb. 1, 2020. Published February 2020. Originally
approved in 2011. Last previous edition approved in 2011 as D7475 – 11. The boldface numbers in parentheses refer to a list of references at the end of
DOI:10.1520/D7475-20. this standard.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7475−20
used to assess the ecotoxicological risks associated with the Chromatography (Gel Permeation Chromatography GPC)
degradation of plastics after various stages of aerobic degra- Using Universal Calibration (Withdrawn 1993)
dation and anaerobic biodegradation in a landfill. D3826 Practice for Determining Degradation End Point in
Degradable Polyethylene and Polypropylene Using aTen-
1.5 The intended use of this method is for a comparison and
sile Test
ranking of aerobic degradation and anaerobic biodegradation
D4129 Test Method for Total and Organic Carbon in Water
of plastics after disposal in a bioreactor landfill. It is not
by High Temperature Oxidation and by Coulometric
designed or intended to be used to support claims recommend-
Detection
ing the value of plastic degradation in full-scale landfills. This
D5526 Test Method for DeterminingAnaerobic Biodegrada-
simulation of an active landfill allows measurement of the
tion of Plastic Materials UnderAccelerated Landfill Con-
percentage of aerobic degradation and anaerobic biodegrada-
ditions
tion (biogas evolution) in specified time periods, only.
D5951 Practice for Preparing Residual Solids Obtained Af-
1.6 Though the test method is in two tiers, they are meant to
ter Biodegradability Standard Methods for Plastics in
simulate a real world cycle of degradation in a landfill and are
Solid Waste for Toxicity and Compost Quality Testing
most preferably run consecutively and not independently or 4
(Withdrawn 2011)
separately.
D6954 GuideforExposingandTestingPlasticsthatDegrade
1.7 It is cautioned that the results of any laboratory landfill in the Environment by a Combination of Oxidation and
Biodegradation
simulation cannot be directly extrapolated to actual disposal
environments: confirmation to real world exposure is ulti- E260 Practice for Packed Column Gas Chromatography
E355 Practice for Gas ChromatographyTerms and Relation-
mately required as with all ASTM Standards. This confirma-
tionisessentialforlandfillasthetypesoflandfillsvarywidely, ships
some are even heavily lined, tombs, and these will limit 2.2 APHA-AWWA-WPCF Standards:
degradation severely. 2540D Total Suspended Solids Dried at 103°–105°C
2540E Fixed and Volatile Solids Ignited at 550°C
1.8 The values stated in SI units are to be regarded as
212 Nitrogen Ammonia
standard. No other units of measurement are included in this
standard.
3. Terminology
1.9 This standard does not purport to address all of the
3.1 Definitions—For definitions of terms used in this test
safety concerns, if any, associated with its use. It is the
method see Terminology D883.
responsibility of the user of this standard to establish appro-
3.2 Definitions of Terms Specific to This Standard:
priate safety, health, and environmental practices and deter-
3.2.1 methanogenicinoculum——anaerobicallydigestedor-
mine the applicability of regulatory limitations prior to use.
ganic waste containing a high concentration of anaerobic
NOTE 1—There is no known ISO equivalent to this standard.
methane-producing microorganisms.
1.10 This international standard was developed in accor-
3.2.2 aerobic degradation of a plastic—degradation of
dance with internationally recognized principles on standard-
properties promoted by oxidation and is synonymous with
ization established in the Decision on Principles for the
defined oxidative degradation of plastics.
Development of International Standards, Guides and Recom-
mendations issued by the World Trade Organization Technical
4. Summary of Test Method
Barriers to Trade (TBT) Committee.
4.1 Combination Aerobic Degradation and Anaerobic
Biodegradation—This two-tiered test method described herein
2. Referenced Documents
consists of the following: Tier 1 (aerobic degradation): (1)
2.1 ASTM Standards:
selecting and analyzing material for testing; (2) exposing the
D618 Practice for Conditioning Plastics for Testing
test plastic material for degradation in a sealed aerobic envi-
D883 Terminology Relating to Plastics
ronment together with municipal solid waste during pretreat-
D1293 Test Methods for pH of Water
ment and stabilizing (3) measuring oxidative degradations
D1888 MethodsOfTestforParticulateandDissolvedMatter
occurringintheplasticmaterialbypropertychangesovertime.
in Water (Withdrawn 1989)
Tier 2 (anaerobic biodegradation): (1) either utilizing the
D2908 Practice for Measuring Volatile Organic Matter in
degradedstabilizedpretreatedmixtureofmunicipalsolidwaste
Water by Aqueous-Injection Gas Chromatography
and the plastic aerobically degraded (products from Tier 1) or
D3590 Test Methods for Total Kjeldahl Nitrogen in Water
combining a previously pretreated and stabilized solid munici-
D3593 Test Method for Molecular Weight Averages/ Distri-
pal waste (in the absence of test plastic material) and new
bution of Certain Polymers by Liquid Size-Exclusion
added plastic material with a concentrated anaerobic inoculum
from an anaerobic digester; (2) exposing the mix to an
anaerobic static batch fermentation at more than 30 % solids;
For referenced ASTM standards, visit the ASTM website, www.astm.org, or
contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Standards volume information, refer to the standard’s Document Summary page on
the ASTM website. Standard Methods for the Examination of Water and Wastewater, 17th ed.,
The last approved version of this historical standard is referenced on 1989, available from American Public Health Association, 1740 Broadway, New
www.astm.org. York, NY 10018.
D7475−20
(3) measuring total carbon in the gas (CO and CH ) evolved developed to permit determination of the aerobic degradation
2 4
as a function of time; (4) removing the specimens for cleaning and anaerobic biodegradation of plastic products when placed
(optional), conditioning, testing, and reporting; (5) assessing in biologically active environments simulating some landfill
the degree of degradability and/or biodegradability under less conditions.
than optimum conditions.
5.2 The decomposition of plastic materials in a landfill is of
4.2 The rate of aerobic degradation in Tier 1 is obtained by importance, as most landfills are biologically active and are an
determining chemical and physical property changes, such as increasingly significant source of renewable energy. As degra-
tensile strength, friability, molecular weight, or other selected dation occurs in a landfill, it is of immediate concern that the
characteristic with time, relative to the initial material. plastic materials do not produce toxic metabolites or end
products under the various conditions that occur in a landfill.
4.3 The rate of environment conversion from aerobic to
The mixtures remaining after completion of the test method,
anaerobic is followed by the head space gas sampling and
containing fully or partially degraded plastic materials or
analysis of the reactor over time. Any increase in carbon
extracts can be, when appropriate, submitted subsequently to
dioxide or methane production indicates some biodegradation
ecotoxicity testing, see Practice
D5951 and Guide D6954 for
is occurring.
details, in order to assess the environmental hazards posed by
NOTE 2—Test Methods D3593 and D3826 are key standards that must
the breakdown of plastics to varying degrees in landfills,
be used for molecular weight and tensile strength measurements, though
especially if leaching occurs. This test method has been
additional measurements are acceptable where considered appropriate. In
designed to assess aerobic degradation and anaerobic biodeg-
all cases results must be recorded.
radation under optimum and less-than-optimum conditions and
4.4 The percent and rate of conversion of carbon from the
toxicity.
testmaterialintroducedinTier2tocarboninthegaseousphase
5.3 Limitations—Because a wide variation exists in the
(methaneandcarbondioxide)indicatesthedegreeofanaerobic
construction and operation of landfills, and because regulatory
biodegradation.
requirements for landfills vary greatly, this procedure is not
4.5 If anaerobic biodegradation is the major focus and
intended to simulate the environments of all landfills.
degradation under aerobic conditions is not of interest, the
However, it is expected to closely resemble the environment of
plastic material for evaluation is introduced only into Tier 2
a biologically active landfill. More specifically, the procedure
using the pretreated solid municipal waste as in Tier 1.
is intended to create a standard laboratory environment that
4.6 It is recognized that the two Tiers are laboratory
permits rapid and reproducible determination of the aerobic
contrivances to allow the degradation stages, aerobic and
degradability and anaerobic biodegradability under accelerated
anaerobic, to be studied independently where normally in the
landfill conditions, while at the same time producing reproduc-
real world these are concurrent and or consecutive processes.
ible mixtures of fully and partially decomposed household
waste with plastic materials for ecotoxicological assessment.
5. Significance and Use
6. Apparatus
5.1 Decomposition of a plastic within a landfill involves
processes in aerobic and anaerobic environmental conditions
6.1 Pressure-Resistant Glass Vessels—Twenty-seven, each
that can affect the decomposition of other materials enclosed
with a volume of 4 to 6 L, which can be closed airtight and
by or in close proximity to the plastic.The rate of change from
capable of withstanding an overpressure of two atmospheres.
aerobic to anaerobic conditions is probably a characteristic of
The lids of the reactors are equipped with an overpressure
the particular landfill site, its garbage and the filling technique
valve (to prevent the overpressure from becoming higher than
and is therefore difficult to assess with any degree of accuracy.
two bars), a manometer that provides a rough indication of the
Differentsourcesindicatedaystomonths(Refs (8)and (9))for
overpressure, a septum that allows one to take gas samples and
this change with the spread dependent on the perspective of
measure the exact overpressure, and, finally, a valve to release
what is aerobic or anaerobic and how fast the environment
the overpressure (see Fig. 1).
changes, 30 days is chosen in this method as a compromise
6.2 Incubators, sufficient to store the vessels in the dark at
time period. (Note, even very low levels of oxygen, far below
35 6 2°C for the duration of the anaerobic testing in Tier 2.
normal atmospheric concentration can promote oxidative deg-
6.3 Pressure Transducer, connected to a syringe needle to
radation). Obviously, there will be pockets of protected (in
bags, cans, etc.) aerobic activity enclosed in any landfill.There measure the headspace pressure in the test vessel.
is currently no evidence or data to support claims that rapid
6.4 Gas Chromatograph, or other apparatus, equipped with
degradation of the plastic (when compared to conventional
a suitable detector and column(s) for measuring methane and
non-degradable plastic) can increase the economic feasibility
carbon dioxide concentrations in the evolved gases.
of landfill-gas recovery, minimize the duration of after-care of
6.5 pHMeter,precisionbalance(60.1g),analyticalbalance
the landfill, and make possible the recovery of the volume
(60.1 mg), thermometer, and barometer.
reduction of the waste due to degradation and biodegradation
during the active life of the landfill.Additionally, it is possible 6.6 Suitable Devices, for determining volatile fatty acids by
that the rapid degradation and biodegradation of plastics can aqueous-injection chromatography, total Kjeldahl nitrogen,
create hazardous conditions in landfills, such as the shifting of ammonia nitrogen, dry solids (105°C), moisture content and
cells and overall stability. This standard method has been volatile solids (550°C) concentrations.
D7475−20
that in which the sample is tested: film polyethylene for film
samples, pellets of polyethylene in case the sample is in the
form of pellets, etc.
7.6 Plastics and other test materials, are included to ascer-
tain aerobic degradation and anaerobic biodegradation under
these accelerated test conditions.
7.7 Fabricated polyethylene bags with perforations for en-
capsulatingtestsamplesinwhateverformtheyaretobetested,
allowing for easy retrieval of samples.
8. Hazards
8.1 This procedure involves the use of inoculum and mu-
nicipalsolidwastecontainingbiologicallyandpossiblychemi-
cally active materials known to produce a variety of diseases.
Avoidcontactwiththesematerialsbywearingglovesandother
appropriate protective equipment. Use good personal hygiene
to minimize exposure.
8.2 The solid-waste mixture can sometimes contain sharp
objects.Takeextremecarewhenhandlingthismixturetoavoid
injury.
8.3 This test method includes the use of hazardous chemi-
cals. Avoid contact with the chemicals and follow the manu-
facturer’s instructions and material safety data sheets.
8.4 The methane produced during the procedure is explo-
1 = Digester.
sive and flammable. Upon release of the biogas from the
2 = Incubation chamber.
3 = Overpressure valve. gas-collection system, take care in venting the biogas to the
4 = Manometer.
outside or to a hood.
5 = Septum.
6 = Valve.
9. Inoculum for Tier 2 Testing
FIG. 1Setup of Accelerated Landfill
9.1 The inoculum can be derived either from a laboratory-
scale or full-scale continuous digester or batch digester, oper-
ating at 35°C and functioning with an organic fraction of
7. Reagents and Materials
household waste as the predominant substrate. In case the
7.1 Household Waste: Derived from mixed municipal solid
inoculum is derived from a continuous laboratory-scale or
waste or the organic fraction thereof, after homogenizing,
full-scale digester, the digester must be operating for a period
screening over a screen with holes of a diameter of 40 to 80
of at least one month on the organic fraction of household
mm.
waste, with a maximum retention time of 30 days under
mesophilic conditions (35 6 2°C). Gas production yields must
7.2 Pretreated Household Waste: Household waste aerobi-
be at least 15 mL at standard temperature and pressure of
cally stabilized over a period of 4 6 2 weeks in an air flow and
biogas/gramofdrysolidsinthedigesterandperdayforatleast
maintaining a dry-matter content of 50 6 5 % and a tempera-
seven days. In case the inoculum is derived from a batch
ture of 35 6 2°C. (Optional: the pretreated household waste
digester, the gas production rat
...

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: D7475 − 11 D7475 − 20
Standard Test Method for
Determining the Aerobic Degradation and Anaerobic
Biodegradation of Plastic Materials under Accelerated
Bioreactor Landfill Conditions
This standard is issued under the fixed designation D7475; 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 modification of Test Method test method D5526, which only considered anaerobic degradation, is used to determine
the degree and rate of aerobic degradation (as indicated by loss of tensile strength, molecular weight, possibly resulting in
disintegration and fragmentation) and anaerobic biodegradation of plastic materials in an accelerated aerobic-anaerobic bioreactor
landfill test environment. It simulates can simulate the change from aerobic to anaerobic environments over time as landfill depth
increases. Plastic materials found in landfills include discarded plastic products such as bags and wrappers and also deliberately
applied plastic covers as inter-layer sealers between daily refuse fills to prevent windblown scatter of garbage overnight or at other
down times. This modification is a two-tiered test method in which the two tiers, which address aerobic degradation and anaerobic
biodegradation, are most preferably run sequentially to more closely resemble the real world condition of a biologically active
landfill, or a bioreactor landfill, but are functional independently and separately depending on the plastic under evaluation and the
information sought: either aerobic degradation or anaerobic biodegradation or both. The tiered system approach is shown
schematically in Fig. 1. In Tier 1, the test plastic material is mixed with household waste, then pretreated and stabilized aerobically
in the presence of air, in a sealed vessel in a temperature range that is consistent with the average temperature range of those
recorded for landfills for a time period of four weeks. landfills. The tier is an accelerated simulation of degradation with
concomitant oxygen consumption and depletion with time as if oxidative degradation proceeds. In Tier 2 samples of the plastic
materials pretreated aerobically as described in Tier 1, are exposed to a methanogenic inoculum derived from anaerobic digesters
operating only on pretreated household waste. The anaerobic decomposition and biodegradation occur under dry (more than 30 %
total solids) and static non-mixed conditions. If it is desired to only assess anaerobic biodegradation of a plastic material, Tier 2
is run using preconditioned household waste, as described in Tier 1 but without the added plastic. The mixtures obtained from Tier
1 and Tier 2 in this test method are sampled and used to assess the environmental and health risks of plastic materials that are
degraded in a landfill under aerobic and anaerobic conditions.
1.2 This test method generates comparative data for several materials and must not be used to make claims regarding benefits
of placing degradable or biodegradable plastics in landfills. Claims must be limited to and dependent on the results obtained from
each tier.
1.2.1 If only Tier 1 is run, then the claims must state: Will modify the performance/physical properties (for example, mechanical
properties will degrade), up to a measured percent, X%, in a given time period, Y days using Test Methods D3593 (Molecular
weight change) and Test Method D3826 (tensile strength change) in a biologically active “bioreactor” landfill. Report measured
percent property changes and standards used to measure the test results which are, for example, changes in tensile strength, mass
and molecular weight, as well as residual particle size ranges in Section 14 to support the extent of such claims.
1.2.2 If both Tier 1 and Tier 2 are run, then claims shall state: Will biodegrade in a biologically active “bioreactor” landfill to
a degree, X%, in Y days established by the test results based on the extent to which the plastic sample is converted to gaseous
carbon in the form of carbon dioxide and methane and this shall be made available according to Section 14 to support the extent
of such claims. It should be noted that biodegradation testing is very dependent on conditions chosen in this laboratory test and
may well vary widely when the test is run with different inoculum, The results reported pertain only to the test conditions run and
do not rule out potential biodegradation under other conditions and real world environments.
1.3 Tier 1 of this test method is designed to estimate the aerobic degradation of plastics, that is disintegration and fragmentation,
only, by measuring the loss of physical and chemical properties of said plastics. The test environment is then changed to that of
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 Jan. 1, 2011Feb. 1, 2020. Published February 2011February 2020. DOI:10.1520/D7475-11. Originally approved in 2011. Last previous edition
approved in 2011 as D7475 – 11. DOI:10.1520/D7475-20.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D7475 − 20
Tier 2, an anaerobic condition, and biodegradation is measured by a combination of evolved carbon dioxide and methane gases
as a percentage of the conversion of carbon in the plastic sample to carbon in the gaseous form under conditions that resemble
landfill conditions. This test method does not simulate all conditions found in landfills, especially those found in biologically
inactive landfills. This test method more closely resembles those types of bioreactor landfills in which the gas generated is
recovered or even actively promoted, or both, for example, by inoculation (co-deposition of anaerobic sewage sludge and anaerobic
leachate recirculation), moisture control in the landfill (leachate recirculation), and temperature control (short-term injection of
oxygen and heating of re-circulated leachate) (1-7).
1.4 This test method produces partially degraded mixtures of municipal solid waste and plastics that, where required, are used
to assess the ecotoxicological risks associated with the degradation of plastics after various stages of aerobic degradation and
anaerobic biodegradation in a landfill.
1.5 The intended use of this method is for a comparison and ranking of aerobic degradation and anaerobic biodegradation of
plastics after disposal in a bioreactor landfill. It is not designed or intended to be used to support claims recommending the value
of plastic degradation in full-scale landfills. This simulation of an active landfill allows measurement of the percentage of aerobic
degradation and anaerobic biodegradation (biogas evolution) in specified time periods, only.
1.6 Though the test method is in two tiers, they are meant to simulate a real world cycle of degradation in a landfill and are
most preferably run consecutively and not independently or separately.
1.7 It is cautioned that the results of any laboratory landfill simulation cannot be directly extrapolated to actual disposal
environments: confirmation to real world exposure is ultimately required as with all ASTM Standards. This confirmation is
essential for landfill as the types of landfills vary widely, some are even heavily lined, tombs, and these will limit degradation
severely.
1.8 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.
NOTE 1—There is no known ISO equivalent to this standard.
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
2.1 ASTM Standards:
D618 Practice for Conditioning Plastics for Testing
D883 Terminology Relating to Plastics
D1293 Test Methods for pH of Water
D1888 Methods Of Test for Particulate and Dissolved Matter in Water (Withdrawn 1989)
D2908 Practice for Measuring Volatile Organic Matter in Water by Aqueous-Injection Gas Chromatography
D3590 Test Methods for Total Kjeldahl Nitrogen in Water
D3593 Test Method for Molecular Weight Averages/ Distribution of Certain Polymers by Liquid Size-Exclusion Chromatog-
raphy (Gel Permeation Chromatography GPC) Using Universal Calibration (Withdrawn 1993)
D3826 Practice for Determining Degradation End Point in Degradable Polyethylene and Polypropylene Using a Tensile Test
D4129 Test Method for Total and Organic Carbon in Water by High Temperature Oxidation and by Coulometric Detection
D5526 Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under Accelerated Landfill Conditions
D5951 Practice for Preparing Residual Solids Obtained After Biodegradability Standard Methods for Plastics in Solid Waste for
Toxicity and Compost Quality Testing (Withdrawn 2011)
D6954 Guide for Exposing and Testing Plastics that Degrade in the Environment by a Combination of Oxidation and
Biodegradation
E260 Practice for Packed Column Gas Chromatography
E355 Practice for Gas Chromatography Terms and Relationships
2.2 APHA-AWWA-WPCF Standards:
2540D Total Suspended Solids Dried at 103°–105°C
2540E Fixed and Volatile Solids Ignited at 550°C
The boldface numbers in parentheses refer to a list of references at the end of this standard.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Standard Methods for the Examination of Water and Wastewater, 17th ed., 1989, available from American Public Health Association, 1740 Broadway, New York, NY
10018.
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212 Nitrogen Ammonia
3. Terminology
3.1 Definitions—For definitions of terms used in this test method see Terminology D883.
3.2 Definitions of Terms Specific to This Standard:
3.2.1 methanogenic inoculum——anaerobically digested organic waste containing a high concentration of anaerobic methane-
producing microorganisms.
3.2.2 aerobic degradation of a plastic—degradation of properties promoted by oxidation and is synonymous with defined
oxidative degradation of plastics.
4. Summary of Test Method
4.1 Combination Aerobic Degradation and Anaerobic Biodegradation—This two-tiered test method described herein consists
of the following: Tier 1 (aerobic degradation): (1) selecting and analyzing material for testing; (2) exposing the test plastic material
for degradation in a sealed aerobic environment together with municipal solid waste during pretreatment and stabilizing (3)
measuring oxidative degradations occurring in the plastic material by property changes over time. Tier 2 (anaerobic
biodegradation): (1) either utilizing the degraded stabilized pretreated mixture of municipal solid waste and the plastic aerobically
degraded (products from Tier 1) or combining a previously pretreated and stabilized solid municipal waste (in the absence of test
plastic material) and new added plastic material with a concentrated anaerobic inoculum from an anaerobic digester; (2) exposing
the mix to an anaerobic static batch fermentation at more than 30 % solids; (3) measuring total carbon in the gas (CO and CH )
2 4
evolved as a function of time; (4) removing the specimens for cleaning (optional), conditioning, testing, and reporting; (5)
assessing the degree of degradability and/or biodegradability under less than optimum conditions.
4.2 The rate of aerobic degradation in Tier 1 is obtained by determining chemical and physical property changes, such as tensile
strength, friability, molecular weight, or other selected characteristic with time, relative to the initial material.
4.3 The rate of environment conversion from aerobic to anaerobic is followed by the head space gas sampling and analysis of
the reactor over time. Any increase in carbon dioxide or methane production indicates some biodegradation is occurring.
NOTE 2—Test Methods D3593 and D3826 are key standards that must be used for molecular weight and tensile strength measurements, though
additional measurements are acceptable where considered appropriate. In all cases results must be recorded.
4.4 The percent and rate of conversion of carbon from the test material introduced in Tier 2 to carbon in the gaseous phase
(methane and carbon dioxide) indicates the degree of anaerobic biodegradation.
4.5 If anaerobic biodegradation is the major focus and degradation under aerobic conditions is not of interest, the plastic
material for evaluation is introduced only into Tier 2 using the pretreated solid municipal waste as in Tier 1.
4.6 It is recognized that the two Tiers are laboratory contrivances to allow the degradation stages, aerobic and anaerobic, to be
studied independently where normally in the real world these are concurrent and or consecutive processes.
5. Significance and Use
5.1 Decomposition of a plastic within a landfill involves processes in aerobic and anaerobic environmental conditions that can
affect the decomposition of other materials enclosed by or in close proximity to the plastic. The rate of change from aerobic to
anaerobic conditions is probably a characteristic of the particular landfill site, its garbage and the filling technique and is therefore
difficult to assess with any degree of accuracy. Different sources indicate days to months (Refs (8) and (9)) for this change with
the spread dependent on the perspective of what is aerobic or anaerobic and how fast the environment changes, 30 days is chosen
in this method as a compromise time period. (Note, even very low levels of oxygen, far below normal atmospheric concentration
can promote oxidative degradation). Obviously, there will be pockets of protected (in bags, cans, etc.) aerobic activity enclosed
in any landfill. There is currently no evidence or data to support claims that rapid degradation of the plastic (when compared to
conventional non-degradable plastic) can increase the economic feasibility of landfill-gas recovery, minimize the duration of
after-care of the landfill, and make possible the recovery of the volume reduction of the waste due to degradation and
biodegradation during the active life of the landfill. Additionally, it is possible that the rapid degradation and biodegradation of
plastics can create hazardous conditions in landfills, such as the shifting of cells and overall stability. This standard method has
been developed to permit determination of the aerobic degradation and anaerobic biodegradation of plastic products when placed
in biologically active environments simulating some landfill conditions.
5.2 The decomposition of plastic materials in a landfill is of importance, as most landfills are biologically active and are an
increasingly significant source of renewable energy. As degradation occurs in a landfill, it is of immediate concern that the plastic
materials do not produce toxic metabolites or end products under the various conditions that occur in a landfill. The mixtures
remaining after completion of the test method, containing fully or partially degraded plastic materials or extracts can be, when
appropriate, submitted subsequently to ecotoxicity testing, see Practice D5951 and Guide D6954 for details, in order to assess the
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1 = Digester.
2 = Incubation chamber.
3 = Overpressure valve.
4 = Manometer.
5 = Septum.
6 = Valve.
1 = Digester.
2 = Incubation chamber.
3 = Overpressure valve.
4 = Manometer.
5 = Septum.
6 = Valve.
FIG. 21 Setup of Accelerated Landfill
environmental hazards posed by the breakdown of plastics to varying degrees in landfills, especially if leaching occurs. This test
method has been designed to assess aerobic degradation and anaerobic biodegradation under optimum and less-than-optimum
conditions and toxicity.
5.3 Limitations—Because a wide variation exists in the construction and operation of landfills, and because regulatory
requirements for landfills vary greatly, this procedure is not intended to simulate the environments of all landfills. However, it is
expected to closely resemble the environment of a biologically active landfill. More specifically, the procedure is intended to create
a standard laboratory environment that permits rapid and reproducible determination of the aerobic degradability and anaerobic
biodegradability under accelerated landfill conditions, while at the same time producing reproducible mixtures of fully and partially
decomposed household waste with plastic materials for ecotoxicological assessment.
6. Apparatus
6.1 Pressure-Resistant Glass Vessels—Twenty-seven, each with a volume of 4 to 6 L, which can be closed airtight and capable
of withstanding an overpressure of two atmospheres. The lids of the reactors are equipped with an overpressure valve (to prevent
the overpressure from becoming higher than two bars), a manometer that provides a rough indication of the overpressure, a septum
that allows one to take gas samples and measure the exact overpressure, and, finally, a valve to release the overpressure (see Fig.
21).
6.2 Incubators, sufficient to store the vessels in the dark at 35 6 2°C for the duration of the anaerobic testing in Tier 2.
6.3 Pressure Transducer, connected to a syringe needle to measure the headspace pressure in the test vessel.
6.4 Gas Chromatograph, or other apparatus, equipped with a suitable detector and column(s) for measuring methane and carbon
dioxide concentrations in the evolved gases.
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6.5 pH Meter, precision balance (60.1 g), analytical balance (60.1 mg), thermometer, and barometer.
6.6 Suitable Devices, for determining volatile fatty acids by aqueous-injection chromatography, total Kjeldahl nitrogen,
ammonia nitrogen, dry solids (105°C), moisture content and volatile solids (550°C) concentrations.
7. Reagents and Materials
7.1 Household Waste: Derived from mixed municipal solid waste or the organic fraction thereof, after homogenizing, screening
over a screen with holes of a diameter of 40 to 80 mm.
7.2 Pretreated Household Waste: Household waste aerobically stabilized over a period of 4 6 2 weeks in an air flow and
maintaining a dry-matter content of 50 6 5 % and a temperature of 35 6 2°C. (Optional: the pretreated household waste can be
replaced by a similarly pretreated simulated solid waste.)
7.3 Anaerobic Inoculum, derived from a properly operating anaerobic digester with pretreated household waste as a sole
substrate or a digester that treats predominantly household waste.
7.4 Cellulose, analytical-grade, or other suitable standards such as Kraft paper, thin-layer chromatography paper, etc. as a
positive control in the anaerobic Tier 2 testing.
7.5 Polyethylene as a negative control for aerobic degradation in Tier 1. The polyethylene must be in the same form as that
in which the sample is tested: film polyethylene for film samples, pellets of polyethylene in case the sample is in the form of pellets,
etc.
7.6 Plastics and other test materials, are included to ascertain aerobic degradation and anaerobic biodegradation under these
accelerated test conditions.
7.7 Fabricated polyethylene bags with perforations for encapsulating test samples in whatever form they are to be tested,
allowing for easy retrieval of samples.
8. Hazards
8.1 This procedure involves the use of inoculum and municipal solid waste containing biologically and possibly chemically
active materials known to produce a variety of diseases. Avoid contact with these materials by wearing gloves and other appropriate
protective equipment. Use good personal hygiene to minimize exposure.
8.2 The solid-waste m
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