ASTM D7475-20
(Test Method)Standard Test Method for Determining the Aerobic Degradation and Anaerobic Biodegradation of Plastic Materials under Accelerated Bioreactor Landfill Conditions
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...
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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
1
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
2
(1-7).
1.4 This test method produces partially degraded mixtures
1
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 En
...
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
1
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 rep
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