1、Designation: D 5338 98 (Reapproved 2003)Standard Test Method forDetermining Aerobic Biodegradation of Plastic MaterialsUnder Controlled Composting Conditions1This standard is issued under the fixed designation D 5338; the number immediately following the designation indicates the year oforiginal ado
2、ption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. Asuperscript epsilon (e) indicates an editorial change since the last revision or reapproval.1. Scope1.1 This test method determines the degree and rate ofaerobic biodegradati
3、on of plastic materials on exposure to acontrolled-composting environment under laboratory condi-tions. This test method is designed to yield reproducible andrepeatable test results under controlled conditions that re-semble composting conditions.The test substances are exposedto an inoculum that is
4、 derived from compost from municipalsolid waste. The aerobic composting takes place in an envi-ronment where temperature, aeration and humidity are closelymonitored and controlled.1.2 This test method is designed to yield a percentage ofconversion of carbon in the sample to carbon dioxide. The rateo
5、f biodegradation is monitored as well.1.3 This test method is designed to be applicable to allplastic materials that are not inhibitory to the microorganismspresent in aerobic composting piles.1.4 The values stated in SI units are to be regarded as thestandard.1.5 This standard does not purport to a
6、ddress 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 use. Specific hazardstatements are given in Section 8.1.6
7、This test method is equivalent to ISO 14855.2. Referenced Documents2.1 ASTM Standards:2D 618 Practice for Conditioning Plastics for TestingD 883 Terminology Relating to PlasticsD 1293 Test Methods for pH of WaterD 1888 Test Methods for Particulate and Dissolved Matter,Solids, or Residue in Water3D 2
8、908 Practice for Measuring Volatile Organic Matter inWater by Aqueous-Injection ChromatographyD 3590 Test Methods for Total Kjeldahl Nitrogen in WaterD 4129 Test Method for Total and Organic Carbon in Waterby High-Temperature Oxidation and Coulometric Detec-tionE 260 Practice for Packed Column Gas C
9、hromatographyE 355 Practice for Gas Chromatography Terms and Rela-tionships2.2 APHAAWWAWPCF Standards:2540 D Total Suspended Solids Dried at 103 to 105C42540 E Fixed and Volatile Solids Ignited at 550C42.3 ISO Standard:ISO 14855 PlasticsEvaluation of the Ultimate AerobicBiodegradability and Disinteg
10、ration Under ControlledComposting ConditionsMethod by Analysis of Re-leased Carbon Dioxide53. Terminology3.1 DefinitionsDefinitions of terms applying to this testmethod appear in Terminology D 883.4. Summary of Test Method4.1 This test method consists of the following:4.1.1 Selection of plastic mate
11、rial for the determination ofthe aerobic biodegradability in a controlled-composting sys-tem,4.1.2 Obtaining an inoculum from composted municipalsolid waste,4.1.3 Exposing the test substances to a controlled aerobiccomposting process in conjunction with the inoculum,4.1.4 Measuring carbon dioxide ev
12、olved as a function oftime, and4.1.5 Assessing the degree of biodegradability.4.2 The percentage of biodegradability is obtained by de-termining the percentage of carbon in the test substance that is1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct respons
13、ibility of Subcommittee D20.96 on EnvironmentallyDegradable Plastics and Biobased Products.Current edition approved Dec. 1, 2003. Published January 2004. Originallyapproved in 1992. Last previous edition approved in 1998 as D 5338 - 98e1.2For referenced ASTM standards, visit the ASTM website, www.as
14、tm.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.3Discontinued.4Standard Methods for the Examination of Water and Wastewater, 17th Edition,1989, American Public Health Asso
15、ciation, 1740 Broadway, New York, NY 19919.5Available from American National Standards Institute (ANSI), 25 W. 43rd St.,4th Floor, New York, NY 10036.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.converted to CO2during the duration
16、 of the test. This percent-age of biodegradability will not include the amount of carbonconverted from the test substance that is converted to cellbiomass and that is not, in turn, metabolized to CO2during thecourse of the test.4.3 The disintegration of a compact test material is visuallydetermined
17、at the end of the test. Additionally, the weight lossof the test material may be determined.5. Significance and Use5.1 Biodegradation of a plastic within a composting unit isan important phenomenon because it will affect the decompo-sition of other materials enclosed by the plastic and theresulting
18、quality and appearance of the composted material.Biodegradation of plastics will also allow the safe disposal ofthese plastics through solid-waste composting plants. Thisprocedure has been developed to permit the determination ofthe rate and degree of aerobic biodegradability of plasticproducts when
19、 placed in a controlled composting process.5.2 LimitationsBecause there is a wide variation in theconstruction and operation of composting systems and becauseregulatory requirements for composting systems vary, thisprocedure is not intended to simulate the environment of anyparticular composting sys
20、tem. However, it is expected toresemble the environment of a composting process operatedunder optimum conditions. More specifically, the procedure isintended to create a standard laboratory environment that willpermit a rapid and reproducible determination of the aerobicbiodegradability under contro
21、lled composting conditions.6. Apparatus6.1 Composting Apparatus (see Fig. 1):6.1.1 Aseries of at least twelve composting vessels (one testsubstance, one blank, one positive and one negative control, allin three replicates) of 2 to 5 L of volume. For screeningpurposes, depending upon the test materia
22、l, a smaller volumealso may be used.6.1.2 Water Baths, or other temperature controlling meanscapable of maintaining the temperature of the compostingvessels at 58C (62C).6.1.3 Pressurized-Air System, that provides CO2-free, H2O-saturated air to each of the composting vessels at accurateaeration rate
23、s. If using a direct measurement of CO2(see 6.4),then normal air may be used.6.1.4 Suitable devices for measuring oxygen and CO2concentrations in the exhaust air of the composting vessels,such as specific sensors or appropriate gas chromatographs.6.2 Carbon Dioxide-Trapping Apparatus for Each Com-po
24、sting Vessel:6.2.1 At least three 5000-mL bottles fitted with gas spargingand containing Ba(OH)2carbon-dioxide scrubbing solution.6.2.2 Flexible Tubing, nonpermeable to carbon dioxide.6.2.3 Stoppers, equipped with gas-sampling parts.6.3 Miscellaneous:6.3.1 Analytical Balance,(60.1 mg) to weigh test
25、speci-men.6.3.2 100-mL Burette.6.3.3 0.05 N HCl.6.3.4 pH Meter.6.3.5 Suitable devices and analytical equipment for measur-ing dry solids (at 105C), volatile solids (at 550C), volatilefatty acids by aqueous-injection chromatography, totalKjeldahl nitrogen and carbon concentrations.6.4 OptionalThe car
26、bon dioxide-trapping apparatus andtitration equipment can be replaced by a gas flow meter plus agas-chromatograph, or other apparatus equipped with suitabledetector and column(s), for measuring CO2and O2concentra-tions in the exhaust air of each vessel. Take care to analyzeCO2concentration on a suff
27、iciently frequent basis in order toproduce a reliable cumulative CO2production over the courseof the test (for example, every 3 to 6 h). A standard gas shouldbe injected to internally standardize the gas-chromatograph ona continuous basis over the course of the test. Operate the gaschromatograph in
28、conformance with Practices E 260 and E 355(see Fig. 2).6.5 Ensure that all glassware is cleaned thoroughly and freefrom organic matter.7. Reagents and Materials7.1 Barium Hydroxide Solution, approximately 0.024 N andthen standardized, prepared by dissolving 4.0 g Ba(OH)2perlitre of distilled water.
29、Filter through filter paper and storesealed as a clear solution to prevent absorption of CO2from theair.FIG. 1 Set-Up Using Carbon Dioxide-Trapping Apparatus FIG. 2 Optional Set-Up Using a Gas ChromatographD 5338 98 (2003)27.2 Analytical-Grade Cellulose, for thin-layer chromatogra-phy with a particl
30、e size of less than 20 m as positive control.67.3 Polyethylene, as a negative control. It should be in thesame form as the form in which the sample is tested (polyeth-ylene film for film samples, polyethylene pellets in case sampleis in the form of pellets, etc.).8. Hazards8.1 This test method requi
31、res the use of hazardous chemi-cals. Avoid contact with the chemicals and follow manufactur-ers instructions and Material Safety Data Sheets.8.2 The compost inoculum may contain sharp objects. Takecare when handling it.8.3 The composting vessels are not designed to withstandhigh pressures. The syste
32、m should be operated at close toambient pressure.9. Compost Inoculum9.1 The compost inoculum should be two to four months oldwell-aerated compost coming from the organic fraction ofmunicipal solid waste and sieved on a screen of 10 mm. Ifsuch a compost is not available, compost from plants, treating
33、green, or yard waste, or mixtures of green waste and municipalsolid waste may be used. It is recommended that the compostinoculum produces between 50 and 150 mg of CO2per gram ofvolatile solids over the first ten days of the test, and has an ashcontent of less than 70 % and a pH between 7 and 8.2.To
34、tal drysolids should be between 50 and 55 %.9.2 The compost inoculum should be as free from largerinert materials (glass, stones, metals, etc.) as possible. Theseitems should be removed manually as much as possible toproduce a homogeneous compost inoculum.9.3 It is recommended to use compost of suff
35、icient porosityto enable conditions to be as aerobic as possible. Addition ofstructural material, such as small wood particles, or persistentor poorly biodegradable inert material may prevent the com-post from sticking together and clogging during the test.10. Test Specimen10.1 The test specimen sho
36、uld have sufficient carbon toyield carbon dioxide that can be adequately measured by thetrapping apparatus or CO2measurements.10.2 All basic composting parameters, such as C/N, oxygenin the composting vessel, porosity, and moisture content shouldbe optimized so as to make a good composting processpo
37、ssible. The C/N ratio should preferably be between 10 and40 for both the inoculum and test substance combined. Oxygenlevels in the composting vessel should be at least 6 % at alltimes and no free-standing water nor clumps of material shouldbe present.10.3 Test specimens may be in the form of films,
38、formedarticles, dog bones, granules, powder, or other, and conform toPractice D 618.11. Procedure11.1 Preparation of the Samples:11.1.1 Obtain an inoculum from a properly operating aero-bic composting plant treating municipal solid waste, or theorganic fraction thereof. If required, further stabiliz
39、e theinoculum at the laboratory in order to obtain a low CO2production (see 9.1.).11.1.1.1 Screen the inoculum to less than 10 mm andmanually remove and discard any large inert items (pieces ofglass, stone, wood, etc.). Determine volatile solids, dry solidsand nitrogen content according to Test Meth
40、ods D 3590,D 1888, and APHA Test Methods 2540 D and 2540 E.11.1.2 Determine volatile solids, dry solids and carboncontent of all the test substances according to APHA TestMethods 2540 D and 2540 E and Test Method D 4129.11.1.3 Weigh out roughly 600 g of dry solids of inoculumand mix with about 100 g
41、 of dry solids coming from thesample. Adjust the dry solids content of the mixture in thevessel to approximately 50 % with distilled water. Add ammo-nium chloride if the C/N ratio is more than 40. Weigh vesselswith all of the contents immediately before initiation of thecomposting process.11.1.4 The
42、 blank consists of the inoculum only, containingabout 600 g of dry solids. As references, use thin-layerchromatography cellulose as a positive control and polyethyl-ene as a negative control.11.1.5 The test material may be in the form of films, formedarticles such as dog bones, granules, or powder.
43、The maximumsurface area of a compact test material used should be about 2by 2 cm. In case the original test material is larger, reduce it inparticle size.11.1.6 No more than about34 of the volume of the testvessel should be filled with test mixture. Sufficient headspaceis required in order to provid
44、e enough space for manualshaking of the test mixture.11.2 Start-Up ProcedureInitiate aeration of the compost-ing vessels with air-flow rates that are sufficiently high toensure that oxygen levels do not drop below 6 % in the exhaustair. Oxygen levels should be closely controlled during the firstweek
45、 and measured at least twice daily.Adjust air-flow rates asneeded.11.3 Operating Procedure:11.3.1 The composting vessels are incubated in the dark orin diffuse light for a period of 45 days in an enclosure that isfree from vapors toxic to microorganisms. The temperature ismaintained at 58C (62C). In
46、 special cases, for example,when the melting point of the test material is low, anothertemperature may be chosen. This temperature should beconstant during the test and kept in a range of 62C. Thechange of temperature should be justified and clearly indicatedin the test report.11.3.2 Check CO2and O2
47、concentrations in the outgoing airat least daily with a minimum time interval of 6 h after the firstweek for the remainder of the test.11.3.3 Check air flow daily before the composting vesselsand at the outlets, ensuring that no leaks are present in thecomplete system. Adjust air flow to maintain a
48、CO2concen-tration of at least 2 % volume over volume to allow accuratedetermination of CO2level in the exhaust air.6For development of this test method, Avicel, available from EM Chemicals,Inc., Hawthorne, New York, was used.D 5338 98 (2003)311.3.4 Ensure proper composting conditions. Shake thecompo
49、sting vessels weekly to prevent extensive channelling,provide uniform attack on the test specimen and provide aneven distribution of moisture. In case excessive moisture levelsare observed, such as free-standing water in the vessels orclumping due to high moisture content, remove excess liquidby injecting dry air, or by drainage via air inlet. If excessivelydry conditions are observed, that will severely slow down thebreakdown process, add moisture. During the whole course ofthe test, make adjustments to ensure proper composting con-ditions. If adjustments are mad
