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

SIGNIFICANCE AND USE
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.
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 pl...
SCOPE
1.1 This modification of 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 bioreactor landfill test environment. It simulates 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. 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 a...

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31-Dec-2010
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ASTM D7475-11 - Standard Test Method for Determining the Aerobic Degradation and Anaerobic Biodegradation of Plastic Materials under Accelerated Bioreactor Landfill Conditions
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NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:D7475 −11
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 only assess anaerobic biodegradation of a plastic material,Tier
2 is run using preconditioned household waste, as described in
1.1 This modification of Test Method D5526, which only
Tier 1 but without the added plastic. The mixtures obtained
considered anaerobic degradation, is used to determine the
fromTier1andTier2inthistestmethodaresampledandused
degree and rate of aerobic degradation (as indicated by loss of
toassesstheenvironmentalandhealthrisksofplasticmaterials
tensile strength, molecular weight, possibly resulting in disin-
that are degraded in a landfill under aerobic and anaerobic
tegration and fragmentation) and anaerobic biodegradation of
conditions.
plastic materials in an accelerated bioreactor landfill test
1.2 This test method generates comparative data for several
environment.Itsimulatesthechangefromaerobictoanaerobic
materials and must not be used to make claims regarding
environments over time as landfill depth increases. Plastic
benefits of placing degradable or biodegradable plastics in
materials found in landfills include discarded plastic products
landfills. Claims must be limited to and dependent on the
such as bags and wrappers and also deliberately applied plastic
results obtained from each tier.
covers as inter-layer sealers between daily refuse fills to
1.2.1 If only Tier 1 is run, then the claims must state: Will
prevent windblown scatter of garbage overnight or at other
modify the performance/physical properties (for example,
down times. This modification is a two-tiered test method in
mechanical properties will degrade), up to a measured percent,
which the two tiers, which address aerobic degradation and
X%, in a given time period,Ydays usingTest Methods D3593
anaerobic biodegradation, are most preferably run sequentially
(Molecular weight change) and Test Method D3826 (tensile
to more closely resemble the real world condition of a
strength change) in a biologically active “bioreactor” landfill.
biologically active landfill, or a bioreactor landfill, but are
Report measured percent property changes and standards used
functional independently and separately depending on the
to measure the test results which are, for example, changes in
plastic under evaluation and the information sought: either
aerobic degradation or anaerobic biodegradation or both. The tensilestrength,massandmolecularweight,aswellasresidual
particle size ranges in Section 14 to support the extent of such
tiered system approach is shown schematically in Fig. 1.In
Tier 1, the test plastic material is mixed with household waste, claims.
1.2.2 If both Tier 1 and Tier 2 are run, then claims shall
thenpretreatedandstabilizedaerobicallyinthepresenceofair,
in a sealed vessel in a temperature range that is consistent with state: Will biodegrade in a biologically active “bioreactor”
landfill to a degree, X%, in Y days established by the test
the average temperature range of those recorded for landfills
for a time period of four weeks. The tier is an accelerated results based on the extent to which the plastic sample is
converted to gaseous carbon in the form of carbon dioxide and
simulation of degradation with concomitant oxygen consump-
methane and this shall be made available according to Section
tion and depletion with time as if oxidative degradation
14 to support the extent of such claims. It should be noted that
proceeds. In Tier 2 samples of the plastic materials pretreated
biodegradation testing is very dependent on conditions chosen
aerobically as described in Tier 1, are exposed to a methano-
in this laboratory test and may well vary widely when the test
genic inoculum derived from anaerobic digesters operating
isrunwithdifferentinoculum,Theresultsreportedpertainonly
only on pretreated household waste. The anaerobic decompo-
to the test conditions run and do not rule out potential
sition and biodegradation occur under dry (more than 30 %
biodegradation under other conditions and real world environ-
total solids) and static non-mixed conditions. If it is desired to
ments.
1.3 Tier 1 of this test method is designed to estimate the
1
This test method is under the jurisdiction ofASTM Committee D20 on Plastics
aerobic degradation of plastics, that is disintegration and
and is the direct responsibility of Subcommittee D20.96 o
...

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