1、Designation: D5338 11Standard Test Method forDetermining Aerobic Biodegradation of Plastic MaterialsUnder Controlled Composting Conditions. IncorporatingThermophilic Temperatures1This standard is issued under the fixed designation D5338; 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 test method determines the degree and rate ofa
3、erobic biodegradation of plastic materials on exposure to acontrolled-composting environment under laboratory condi-tions, at thermophilic temperatures. This test method is de-signed to yield reproducible and repeatable test results undercontrolled conditions that resemble composting conditions,wher
4、e thermophilic temperatures are achieved. The test sub-stances are exposed to an inoculum that is derived fromcompost from municipal solid waste. The aerobic compostingtakes place in an environment where temperature, aeration andhumidity are closely monitored and controlled.NOTE 1During composting,
5、thermophilic temperatures are mostreadily achieved in large-scale, professionally-managed facilities. How-ever, these temperatures may also be reached in smaller residentialcomposting units, frequently referred to as “backyard” or “home” com-posting.1.2 This test method is designed to yield a percen
6、tage ofconversion of carbon in the sample to carbon dioxide. The rateof biodegradation is monitored as well.1.3 This test method is designed to be applicable to allplastic materials, which are intended to be composted infacilities that achieve thermophilic temperatures.1.4 The values stated in SI un
7、its are to be regarded as thestandard.1.5 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 li
8、mitations prior to use. Specific hazardstatements are given in Section 8.1.6 This test method is equivalent to ISO 14855.2. Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1293 Test Methods for pH of WaterD2908 Practice
9、 for Measuring Volatile Organic Matter inWater by Aqueous-Injection Gas ChromatographyD3590 Test Methods for Total Kjeldahl Nitrogen in WaterD4129 Test Method for Total and Organic Carbon in Waterby High Temperature Oxidation and by Coulometric De-tectionE260 Practice for Packed Column Gas Chromatog
10、raphyE355 Practice for Gas Chromatography Terms and Rela-tionships2.2 APHAAWWAWPCF Standards:2540 D Total Suspended Solids Dried at 103 to 105C32540 E Fixed and Volatile Solids Ignited at 550C32.3 ISO Standard:ISO 14855 PlasticsEvaluation of the Ultimate AerobicBiodegradability and Disintegration Un
11、der ControlledComposting ConditionsMethod by Analysis of Re-leased Carbon Dioxide43. Terminology3.1 DefinitionsDefinitions of terms applying to this testmethod appear in Terminology D883.4. Summary of Test Method4.1 This test method consists of the following:4.1.1 Selection of plastic material for t
12、he determination ofthe aerobic biodegradability in a controlled-composting sys-tem,1This test method is under the jurisdiction ofASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.96 on EnvironmentallyDegradable Plastics and Biobased Products.Current edition approved
13、April 1, 2011. Published April 2011. Originallyapproved in 1992. Last previous edition approved in 2003 as D5338 - 98(2003).DOI: 10.1520/D5338-11.2For referenced ASTM standards, visit the ASTM website, www.astm.org, orcontact ASTM Customer Service at serviceastm.org. For Annual Book of ASTMStandards
14、 volume information, refer to the standards Document Summary page onthe ASTM website.3Standard Methods for the Examination of Water and Wastewater, 17th Edition,1989, American Public Health Association, 1740 Broadway, New York, NY 19919.4Available from American National Standards Institute (ANSI), 2
15、5 W. 43rd St.,4th Floor, New York, NY 10036, http:/www.ansi.org.1Copyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.4.1.2 Obtaining an inoculum from composted municipalsolid waste,4.1.3 Exposing the test substances to a controlled aerobi
16、ccomposting process in conjunction with the inoculum,4.1.4 Measuring carbon dioxide evolved 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 isconverted to CO
17、2during the duration 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
18、 visuallydetermined 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 may affect the decompo-sition of other materials enclosed by the plasti
19、c and theresulting quality and appearance of the composted material.Biodegradation of plastics will also allow the safe disposal ofthese plastics through large, professionally-managed compost-ing plants and well-run residential units, where thermophilictemperatures are achieved. This procedure has b
20、een developedto permit the determination of the rate and degree of aerobicbiodegradability of plastic products when placed in a con-trolled composting process.5.2 LimitationsBecause there is a wide variation in theconstruction and operation of composting facilities and be-cause regulatory requiremen
21、ts for composting systems vary,this procedure is not intended to simulate the environment ofany particular composting system. However, it is expected toresemble the environment of a composting process operatedunder optimum conditions where thermophilic temperaturesare achieved. More specifically, th
22、e procedure is intended tocreate a standard laboratory environment that will permit arapid and reproducible determination of the aerobic biodegrad-ability under controlled composting conditions.6. Apparatus6.1 Composting Apparatus (see Fig. 1):6.1.1 Aseries of at least twelve composting vessels (one
23、 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 material, a smaller volumealso may be used.6.1.2 Water Baths, or other temperature controlling meanscapable of maintaining the temperature o
24、f 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 rates. 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 CO2conce
25、ntrations 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-posting Vessel:6.2.1 At least three 5000-mL bottles fitted with gas spargingand containing Ba(OH)2carbon-dioxide scrubbing solution.6.2
26、.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 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 sol
27、ids (at 105C), volatile solids (at 550C), volatilefatty acids by aqueous-injection chromatography, totalKjeldahl nitrogen and carbon concentrations.6.4 OptionalThe carbon dioxide-trapping apparatus andtitration equipment can be replaced by a gas flow meter plus agas-chromatograph, or other apparatus
28、 equipped with suitabledetector and column(s), for measuring CO2and O2concentra-tions in the exhaust air of each vessel. Take care to analyzeCO2concentration on a sufficiently frequent basis in order toproduce a reliable cumulative CO2production over the courseof the test (for example, every 3 to 6
29、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 conformance with Practices E260 and E355(see Fig. 2).6.5 Ensure that all glassware is cleaned thoroughly and freefrom organic matter.
30、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. Filter through filter paper and storesealed as a clear solution to prevent absorption of CO2from theair.7.2 Analytical-Grade Cellulose,
31、 for thin-layer chromatogra-phy with a particle size of less than 20 m as positive control.55For development of this test method, Avicel, available from EM Chemicals,Inc., Hawthorne, New York, was used.FIG. 1 Set-Up Using Carbon Dioxide-Trapping ApparatusD5338 1127.3 Polyethylene, as a negative cont
32、rol. 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 requires the use of hazardous chemi-cals. Avoid contact with the chemicals and follow m
33、anufactur-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 system should be operated at close toambient pressure.9. Compost Inoculum9.1 The compos
34、t 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, treatinggreen, or yard waste, or mixtures of green waste and municipalsolid waste may be u
35、sed. 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.Total drysolids should be between 50 and 55 %.9.2 The compost inoculum should be as
36、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 sufficient porosityto enable conditions to be as aerobic as possible. Addition ofstruc
37、tural 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 should have sufficient carbon toyield carbon dioxide that can be adequately measured
38、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 processpossible. The C/N ratio should preferably be between 10 and40 for both the inoculum
39、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, formedarticles, dog bones, granules, powder, or other, and conform toPractice D618
40、.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 stabilize theinoculum at the laboratory in order to obtain a low CO2production (see 9.1.).1
41、1.1.1.1 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 Methods D3590,D1888, and APHA Test Methods 2540 D and 2540 E.11.1.2 Determine volatile
42、solids, dry solids and carboncontent of all the test substances according to APHA TestMethods 2540 D and 2540 E and Test Method D4129.11.1.3 Weigh out roughly 600 g of dry solids of inoculumand mix with about 100 g of dry solids coming from thesample. Adjust the dry solids content of the mixture in
43、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 blank consists of the inoculum only, containingabout 600 g of dry solids. As referenc
44、es, 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. The maximumsurface area of a compact test material used should be about 2by 2 cm. In c
45、ase 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 provide enough space for manualshaking of the test mixture.11.2 Start-Up ProcedureInitiate a
46、eration 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 and measured at least twice daily.Adjust air-flow rates asneeded.11.3 Operating Proce
47、dure: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 special cases, for example,when the melting point of the test material is low, anothe
48、rtemperature may be chosen. This temperature should beFIG. 2 Optional Set-Up Using a Gas ChromatographD5338 113constant 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 O2concentrations in the outgoin
49、g 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 CO2concen-tration of at least 2 % volume over volume to allow accuratedetermination of CO2level in the exhaust air.11.3.4 Ensure proper composting conditions. Shake thecomposting vessels weekly to prevent extensive channelling,provide uniform attack on the test specimen and provide aneven distri
