1、Designation: D7475 11Standard Test Method forDetermining the Aerobic Degradation and AnaerobicBiodegradation of Plastic Materials under AcceleratedBioreactor Landfill Conditions1This standard is issued under the fixed designation D7475; the number immediately following the designation indicates the
2、year oforiginal adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon () indicates an editorial change since the last revision or reapproval.1. Scope1.1 This modification of Test Method D5526, which onlyco
3、nsidered anaerobic degradation, is used to determine thedegree and rate of aerobic degradation (as indicated by loss oftensile strength, molecular weight, possibly resulting in disin-tegration and fragmentation) and anaerobic biodegradation ofplastic materials in an accelerated bioreactor landfill t
4、estenvironment. It simulates the change from aerobic to anaerobicenvironments over time as landfill depth increases. Plasticmaterials found in landfills include discarded plastic productssuch as bags and wrappers and also deliberately applied plasticcovers as inter-layer sealers between daily refuse
5、 fills toprevent windblown scatter of garbage overnight or at otherdown times. This modification is a two-tiered test method inwhich the two tiers, which address aerobic degradation andanaerobic biodegradation, are most preferably run sequentiallyto more closely resemble the real world condition of
6、abiologically active landfill, or a bioreactor landfill, but arefunctional independently and separately depending on theplastic under evaluation and the information sought: eitheraerobic degradation or anaerobic biodegradation or both. Thetiered system approach is shown schematically in Fig. 1.InTie
7、r 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 withthe average temperature range of those recorded for landfillsfor a time period of four weeks. The tier is an
8、 acceleratedsimulation of degradation with concomitant oxygen consump-tion and depletion with time as if oxidative degradationproceeds. In Tier 2 samples of the plastic materials pretreatedaerobically as described in Tier 1, are exposed to a methano-genic inoculum derived from anaerobic digesters op
9、eratingonly on pretreated household waste. The anaerobic decompo-sition and biodegradation occur under dry (more than 30 %total solids) and static non-mixed conditions. If it is desired toonly assess anaerobic biodegradation of a plastic material, Tier2 is run using preconditioned household waste, a
10、s described inTier 1 but without the added plastic. The mixtures obtainedfrom Tier 1 and Tier 2 in this test method are sampled and usedto assess the environmental and health risks of plastic materialsthat are degraded in a landfill under aerobic and anaerobicconditions.1.2 This test method generate
11、s comparative data for severalmaterials and must not be used to make claims regardingbenefits of placing degradable or biodegradable plastics inlandfills. Claims must be limited to and dependent on theresults obtained from each tier.1.2.1 If only Tier 1 is run, then the claims must state: Willmodify
12、 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 (tensilestrength change) in a biologically active “bioreactor” landfill.Report me
13、asured percent property changes and standards usedto measure the test results which are, for example, changes intensile strength, mass and molecular weight, as well as residualparticle size ranges in Section 14 to support the extent of suchclaims.1.2.2 If both Tier 1 and Tier 2 are run, then claims
14、shallstate: Will biodegrade in a biologically active “bioreactor”landfill to a degree, X%, in Y days established by the testresults based on the extent to which the plastic sample isconverted to gaseous carbon in the form of carbon dioxide andmethane and this shall be made available according to Sec
15、tion14 to support the extent of such claims. It should be noted thatbiodegradation testing is very dependent on conditions chosenin this laboratory test and may well vary widely when the testis run with different inoculum, The results reported pertain onlyto the test conditions run and do not rule o
16、ut potentialbiodegradation under other conditions and real world environ-ments.1.3 Tier 1 of this test method is designed to estimate theaerobic degradation of plastics, that is disintegration andfragmentation, only, by measuring the loss of physical andchemical properties of said plastics. The test
17、 environment isthen changed to that of Tier 2, an anaerobic condition, andbiodegradation is measured by a combination of evolved1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.96 on EnvironmentallyDegradable Plastics a
18、nd Biobased Products.Current edition approved Jan. 1, 2011. Published February 2011. DOI:10.1520/D7475-11.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.carbon dioxide and methane gases as a percentage of theconversion of carbon in
19、the plastic sample to carbon in thegaseous form under conditions that resemble landfill condi-tions. This test method does not simulate all conditions foundin landfills, especially those found in biologically inactivelandfills. This test method more closely resembles those typesof bioreactor landfil
20、ls in which the gas generated is recoveredor even actively promoted, or both, for example, by inoculation(co-deposition of anaerobic sewage sludge and anaerobicleachate recirculation), moisture control in the landfill(leachate recirculation), and temperature control (short-terminjection of oxygen an
21、d heating of re-circulated leachate)(1-7).21.4 This test method produces partially degraded mixturesof municipal solid waste and plastics that, where required, areused to assess the ecotoxicological risks associated with thedegradation of plastics after various stages of aerobic degra-dation and ana
22、erobic biodegradation in a landfill.1.5 The intended use of this method is for a comparison andranking of aerobic degradation and anaerobic biodegradationof plastics after disposal in a bioreactor landfill. It is notdesigned or intended to be used to support claims recommend-ing the value of plastic
23、 degradation in full-scale landfills. Thissimulation of an active landfill allows measurement of thepercentage of aerobic degradation and anaerobic biodegrada-tion (biogas evolution) in specified time periods, only.1.6 Though the test method is in two tiers, they are meant tosimulate a real world cy
24、cle of degradation in a landfill and aremost preferably run consecutively and not independently orseparately1.7 It is cautioned that the results of any laboratory landfillsimulation cannot be directly extrapolated to actual disposalenvironments: confirmation to real world exposure is ulti-mately req
25、uired as with all ASTM Standards. This confirma-tion is essential for landfill as the types of landfills vary widely,some are even heavily lined, tombs, and these will limitdegradation severely.1.8 The values stated in SI units are to be regarded asstandard. No other units of measurement are include
26、d in thisstandard.1.9 This standard does not purport to address all of thesafety concerns, if any, associated with its use. It is theresponsibility of the user of this standard to establish appro-priate safety and health practices and determine the applica-bility of regulatory limitations prior to u
27、se.NOTE 1There is no known ISO equivalent to this standard.2. Referenced Documents2.1 ASTM Standards:3D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1293 Test Methods for pH of WaterD1888 Test Methods for Particulate and Dissolved Matter,Solids, or Residue i
28、n Water4D2908 Practice for Measuring Volatile Organic Matter inWater by Aqueous-Injection Gas ChromatographyD3590 Test Methods for Total Kjeldahl Nitrogen in Water2The boldface numbers in parentheses refer to a list of references at the end ofthis standard.3For referenced ASTM standards, visit the A
29、STM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards volume information, refer to the standards Document Summary page onthe ASTM website.4Withdrawn.NOTEThe original D5526 schematic is represented by eliminating the household waste and plasti
30、c portion of that shown above.FIG. 1 Schematic for testing Tiers 1 and 2 for Aerobic Degradation and Anaerobic BiodegradationD7475 112D3593 Test Method for Molecular Weight Averages andMolecular weight Distribution of Certain Polymers byLiquid Size-Exclusion Chromatography (Gel PermeationChromatogra
31、phy, GPC) using Universal Calibration4D3826 Practice for Determining Degradation End Point inDegradable Polyethylene and Polypropylene Using a Ten-sile TestD4129 Test Method for Total and Organic Carbon in Waterby High Temperature Oxidation and by Coulometric De-tectionD5526 Test Method for Determin
32、ing Anaerobic Biodegra-dation of Plastic Materials Under Accelerated LandfillConditionsD5951 Practice for Preparing Residual Solids ObtainedAfter Biodegradability Standard Methods for Plastics inSolid Waste for Toxicity and Compost Quality Testing4D6954 Guide for Exposing and Testing Plastics that D
33、e-grade in the Environment by a Combination of Oxidationand BiodegradationE260 Practice for Packed Column Gas ChromatographyE355 Practice for Gas Chromatography Terms and Rela-tionships2.2 APHA-AWWA-WPCF Standards:52540D Total Suspended Solids Dried at 103105C2540E Fixed and Volatile Solids Ignited
34、at 550C212 Nitrogen Ammonia3. Terminology3.1 DefinitionsFor definitions of terms used in this testmethod see Terminology D883.3.2 Definitions of Terms Specific to This Standard:3.2.1 methanogenic inoculumanaerobically digestedorganic waste containing a high concentration of anaerobicmethane-producin
35、g microorganisms.3.2.2 aerobic degradation of a plasticdegradation ofproperties promoted by oxidation and is synonymous withdefined oxidative degradation of plastics.4. Summary of Test Method4.1 Combination Aerobic Degradation and AnaerobicBiodegradationThis two-tiered test method described hereinco
36、nsists of the following: Tier 1 (aerobic degradation): (1)selecting and analyzing material for testing; (2) exposing thetest plastic material for degradation in a sealed aerobic envi-ronment together with municipal solid waste during pretreat-ment and stabilizing (3) measuring oxidative degradations
37、occurring in the plastic material by property changes over time.Tier 2 (anaerobic biodegradation): (1) either utilizing thedegraded stabilized pretreated mixture of municipal solid wasteand the plastic aerobically degraded (products from Tier 1) orcombining a previously pretreated and stabilized sol
38、id munici-pal waste (in the absence of test plastic material) and newadded plastic material with a concentrated anaerobic inoculumfrom an anaerobic digester; (2) exposing the mix to ananaerobic static batch fermentation at more than 30 % solids;(3) measuring total carbon in the gas (CO2and CH4) evol
39、vedas a function of time; (4) removing the specimens for cleaning(optional), conditioning, testing, and reporting; (5) assessingthe degree of degradability and/or biodegradability under lessthan optimum conditions.4.2 The rate of aerobic degradation in Tier 1 is obtained bydetermining chemical and p
40、hysical property changes, such astensile strength, friability, molecular weight, or other selectedcharacteristic with time, relative to the initial material.4.3 The rate of environment conversion from aerobic toanaerobic is followed by the head space gas sampling andanalysis of the reactor over time
41、. Any increase in carbondioxide or methane production indicates some biodegradationis occurring.NOTE 2Test Methods D3593 and D3826 are key standards that mustbe used for molecular weight and tensile strength measurements, thoughadditional measurements are acceptable where considered appropriate. Ina
42、ll cases results must be recorded.4.4 The percent and rate of conversion of carbon from thetest material introduced in Tier 2 to carbon in the gaseous phase(methane and carbon dioxide) indicates the degree of anaerobicbiodegradation.4.5 If anaerobic biodegradation is the major focus anddegradation u
43、nder aerobic conditions is not of interest, theplastic material for evaluation is introduced only into Tier 2using the pretreated solid municipal waste as in Tier 1.4.6 It is recognized that the two Tiers are laboratorycontrivances to allow the degradation stages, aerobic andanaerobic, to be studied
44、 independently where normally in thereal world these are concurrent and or consecutive processes.5. Significance and Use5.1 Decomposition of a plastic within a landfill involvesprocesses in aerobic and anaerobic environmental conditionsthat can affect the decomposition of other materials enclosedby
45、or in close proximity to the plastic. The rate of change fromaerobic to anaerobic conditions is probably a characteristic ofthe particular landfill site, its garbage and the filling techniqueand is therefore difficult to assess with any degree of accuracy.Different sources indicate days to months (R
46、efs (8) and (9) forthis change with the spread dependent on the perspective ofwhat is aerobic or anaerobic and how fast the environmentchanges, 30 days is chosen in this method as a compromisetime period. (Note, even very low levels of oxygen, far belownormal atmospheric concentration can promote ox
47、idative deg-radation). Obviously, there will be pockets of protected (inbags, cans, etc.) aerobic activity enclosed in any landfill. Thereis currently no evidence or data to support claims that rapiddegradation of the plastic (when compared to conventionalnon-degradable plastic) can increase the eco
48、nomic feasibilityof landfill-gas recovery, minimize the duration of after-care ofthe landfill, and make possible the recovery of the volumereduction of the waste due to degradation and biodegradationduring the active life of the landfill. Additionally, it is possiblethat the rapid degradation and bi
49、odegradation of plastics cancreate hazardous conditions in landfills, such as the shifting ofcells and overall stability. This standard method has been5Standard Methods for the Examination of Water and Wastewater, 17th ed.,1989, available from American Public Health Association, 1740 Broadway, NewYork, NY 10018.D7475 113developed to permit determination of the aerobic degradationand anaerobic biodegradation of plastic products when placedin biologically active environments simulating some landfillconditions.5.2 The decomposition of plastic materials in a landfill is ofi
