1、Designation: D5338 11D5338 15Standard 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 indic
2、ates the 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. Scope Scope*1.1 This test method determines the degr
3、ee and rate of aerobic biodegradation of plastic materials on exposure to acontrolled-composting environment under laboratory conditions, at thermophilic temperatures. This test method is designed toyield reproducible and repeatable test results under controlled conditions that resemble composting c
4、onditions, where thermophilictemperatures are achieved. The test substances are exposed to an inoculum that is derived from compost from municipal solidwaste. The aerobic composting takes place in an environment where temperature, aeration and humidity are closely monitored andcontrolled.NOTE 1Durin
5、g composting, thermophilic temperatures are most readily achieved in large-scale, professionally-managed facilities. However, thesetemperatures may also be reached in smaller residential composting units, frequently referred to as “backyard” or “home” composting.1.2 This test method is designed to y
6、ield a percentage of conversion of carbon in the sample to carbon dioxide. The rate ofbiodegradation is monitored as well.1.3 This test method is designed to be applicable to all plastic materials, which are intended to be composted in facilities thatachieve thermophilic temperatures.1.4 The values
7、stated in SI units are to be regarded as the standard.1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibilityof the user of this standard to establish appropriate safety and health practices and determine the applicability o
8、f regulatorylimitations prior to use. Specific hazard statements 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 Wate
9、rD2908 Practice for Measuring Volatile Organic Matter in Water by Aqueous-Injection Gas ChromatographyD3590 Test Methods for Total Kjeldahl Nitrogen in WaterD4129 Test Method for Total and Organic Carbon in Water by High Temperature Oxidation and by Coulometric DetectionE260 Practice for Packed Colu
10、mn Gas ChromatographyE355 Practice for Gas Chromatography Terms and Relationships2.2 APHAAWWAWPCF Standards:2540 D Total Suspended Solids Dried at 103 to 105C32540 E Fixed and Volatile Solids Ignited at 550C31 This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the di
11、rect responsibility of Subcommittee D20.19D20.96 on Film, Sheeting, andMoldedEnvironmentally Degradable Plastics and Biobased Products.Current edition approved June 1, 2015. Published April 2011June 2015. Originally approved in 1992. Last previous edition approved in 20032011 asD5338 - 98D5338 - 11.
12、(2003). DOI: 10.1520/D5338-11.10.1520/D5338-15.2 For referencedASTM standards, visit theASTM website, www.astm.org, or contactASTM Customer Service at serviceastm.org. For Annual Book of ASTM Standardsvolume information, refer to the standards Document Summary page on the ASTM website.3 Standard Met
13、hods for the Examination of Water and Wastewater, 17th Edition, 1989, American Public Health Association, 1740 Broadway, New York, NY 19919.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
14、version. Becauseit 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 versionof the standard as published by ASTM is to be considered the official document.*A Summary of Changes
15、section appears at the end of this standardCopyright ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States12.3 ISO Standard:ISO 14855 PlasticsEvaluation of the Ultimate Aerobic Biodegradability and Disintegration Under Controlled CompostingConditions
16、Method by Analysis of Released Carbon Dioxide43. Terminology3.1 DefinitionsDefinitions of terms applying to this test method 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 the determination of the aerobic bio
17、degradability in a controlled-composting system,4.1.2 Obtaining an inoculum from composted municipal solid waste,4.1.3 Exposing the test substances to a controlled aerobic composting process in conjunction with the inoculum,4.1.4 Measuring carbon dioxide evolved as a function of time, and4.1.5 Asses
18、sing the degree of biodegradability.4.2 The percentage of biodegradability is obtained by determining the percentage of carbon in the test substance that isconverted to CO2 during the duration of the test. This percentage of biodegradability will not include the amount of carbonconverted from the te
19、st substance that is converted to cell biomass and that is not, in turn, metabolized to CO2 during the courseof the test.4.3 The disintegration of a compact test material is visually determined at the end of the test. Additionally, the weight loss ofthe test material may be determined.5. Significanc
20、e and Use5.1 Biodegradation of a plastic within a composting unit is an important phenomenon because it may affect the decompositionof other materials enclosed by the plastic and the resulting quality and appearance of the composted material. Biodegradation ofplastics will also allow the safe dispos
21、al of these plastics through large, professionally-managed composting plants and well-runresidential units, where thermophilic temperatures are achieved. This procedure has been developed to permit the determinationof the rate and degree of aerobic biodegradability of plastic products when placed in
22、 a controlled composting process.5.2 LimitationsBecause there is a wide variation in the construction and operation of composting facilities and becauseregulatory requirements for composting systems vary, this procedure is not intended to simulate the environment of any particularcomposting system.
23、However, it is expected to resemble the environment of a composting process operated under optimumconditions where thermophilic temperatures are achieved. More specifically, the procedure is intended to create a standardlaboratory environment that will permit a rapid and reproducible determination o
24、f the aerobic biodegradability under controlledcomposting conditions.6. Apparatus6.1 Composting Apparatus (see Fig. 1):6.1.1 A series of at least twelve composting vessels (one test substance, one blank, one positive and one negative control, allin three replicates) of 2 to 5 L of volume. For screen
25、ing purposes, depending upon the test material, a smaller volume also maybe used.4 Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http:/www.ansi.org.FIG. 1 Set-Up Using Carbon Dioxide-Trapping ApparatusD5338 1526.1.2 Water Baths, or other
26、temperature controlling means capable of maintaining the temperature of the composting vessels at58C (62C).6.1.3 Pressurized-Air System, that provides CO2-free, H2O-saturated air to each of the composting vessels at accurate aerationrates. If using a direct measurement of CO2 (see 6.4), then normal
27、air may be used.6.1.4 Suitable devices for measuring oxygen and CO2 concentrations in the exhaust air of the composting vessels, such asspecific sensors or appropriate gas chromatographs.6.2 Carbon Dioxide-Trapping Apparatus for Each Composting Vessel:6.2.1 At least three 5000-mL bottles fitted with
28、 gas sparging and containing Ba(OH)2 carbon-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 (61 mg) to weigh test specimen.6.3.2 100-mL Burette.6.3.3 0.05 N HCl.6.3.4 p
29、H Meter.6.3.5 Suitable devices and analytical equipment for measuring dry solids (at 105C), volatile solids (at 550C), volatile fattyacids by aqueous-injection chromatography, total Kjeldahl nitrogen and carbon concentrations.6.4 OptionalThe carbon dioxide-trapping apparatus and titration equipment
30、can be replaced by a gas flow meter plus agas-chromatograph, or other apparatus equipped with suitable detector and column(s), for measuring CO2 and O2 concentrationsin the exhaust air of each vessel. Take care to analyze CO2 concentration on a sufficiently frequent basis in order to produce areliab
31、le cumulative CO2 production over the course of the test (for example, every 3 to 6 h). A standard gas should be injectedto internally standardize the gas-chromatograph on a continuous basis over the course of the test. Operate the gas chromatographin conformance with Practices E260 and E355 (see Fi
32、g. 2).6.5 Ensure that all glassware is cleaned thoroughly and free from organic matter.7. Reagents and Materials7.1 Barium Hydroxide Solution, approximately 0.024 N and then standardized, prepared by dissolving 4.0 g Ba(OH)2 per litreof distilled water. Filter through filter paper and store sealed a
33、s a clear solution to prevent absorption of CO2 from the air.7.2 Analytical-Grade Cellulose, for thin-layer chromatography with a particle size of less than 20 m as positive control.57.3 Polyethylene, as a negative control. It should be in the same form as the form in which the sample is tested (pol
34、yethylenefilm for film samples, polyethylene pellets in case sample is in the form of pellets, etc.).8. Hazards8.1 This test method requires the use of hazardous chemicals. Avoid contact with the chemicals and follow manufacturersinstructions and Material Safety Data Sheets.8.2 The compost inoculum
35、may contain sharp objects. Take care when handling it.5 For development of this test method, Avicel, available from EM Chemicals, Inc., Hawthorne, New York, was used.FIG. 2 Optional Set-Up Using a Gas ChromatographD5338 1538.3 The composting vessels are not designed to withstand high pressures. The
36、system should be operated at close to ambientpressure.9. Compost Inoculum9.1 The compost inoculum should be two to four months old well-aerated compost coming from the organic fraction ofmunicipal solid waste and sieved on a screen of 10 mm. If such a compost is not available, compost from plants, t
37、reating green,or yard waste, or mixtures of green waste and municipal solid waste may be used. It is recommended that the compost inoculumproduces between 50 and 150 mg of CO2 per gram of volatile solids over the first ten days of the test, and has an ash content ofless than 70 % and a pH between 7
38、and 8.2. Total dry solids should be between 50 and 55 %.9.2 The compost inoculum should be as free from larger inert materials (glass, stones, metals, etc.) as possible. These itemsshould be removed manually as much as possible to produce a homogeneous compost inoculum.9.3 It is recommended to use c
39、ompost of sufficient porosity to enable conditions to be as aerobic as possible. Addition ofstructural material, such as small wood particles, or persistent or poorly biodegradable inert material may prevent the compost fromsticking together and clogging during the test.10. Test Specimen10.1 The tes
40、t specimen should have sufficient carbon to yield carbon dioxide that can be adequately measured by the trappingapparatus or CO2 measurements.10.2 All basic composting parameters, such as C/N, oxygen in the composting vessel, porosity, and moisture content should beoptimized so as to make a good com
41、posting process possible. The C/N ratio should preferably be between 10 and 40 for both theinoculum and test substance combined. Oxygen levels in the composting vessel should be at least 6 % at all times and nofree-standing water nor clumps of material should be present.10.3 Test specimens may be in
42、 the form of films, formed articles, dog bones, granules, powder, or other, and conform to PracticeD618.11. Procedure11.1 Preparation of the Samples:11.1.1 Obtain an inoculum from a properly operating aerobic composting plant treating municipal solid waste, or the organicfraction thereof. If require
43、d, further stabilize the inoculum at the laboratory in order to obtain a low CO2 production (see 9.1.).11.1.1.1 Screen the inoculum to less than 10 mm and manually remove and discard any large inert items (pieces of glass, stone,wood, etc.). Determine volatile solids, dry solids and nitrogen content
44、 according to Test Methods D3590, D1888, and APHATestMethods 2540 D and 2540 E.11.1.2 Determine volatile solids, dry solids and carbon content of all the test substances according to APHA Test Methods2540 D and 2540 E and Test Method D4129.11.1.3 Weigh out roughly 600 g of dry solids of inoculum and
45、 mix with about 100 g of dry solids coming from the sample.Adjust the dry solids content of the mixture in the vessel to approximately 50 % with distilled water. Add ammonium chloride ifthe C/N ratio is more than 40. Weigh vessels with all of the contents immediately before initiation of the compost
46、ing process.11.1.4 The blank consists of the inoculum only, containing about 600 g of dry solids. As references, use thin-layerchromatography cellulose as a positive control and polyethylene as a negative control.11.1.5 The test material may be in the form of films, formed articles such as dog bones
47、, granules, or powder. The maximumsurface area of a compact test material used should be about 2 by 2 cm. In case the original test material is larger, reduce it inparticle size.11.1.6 No more than about 34 of the volume of the test vessel should be filled with test mixture. Sufficient headspace is
48、requiredin order to provide enough space for manual shaking of the test mixture.11.2 Start-Up ProcedureInitiate aeration of the composting vessels with air-flow rates that are sufficiently high to ensure thatoxygen levels do not drop below 6 % in the exhaust air. Oxygen levels should be closely cont
49、rolled during the first week andmeasured at least twice daily. Adjust air-flow rates as needed.11.3 Operating Procedure:11.3.1 The composting vessels are incubated in the dark or in diffuse light for a period of 45 days in an enclosure that is freefrom vapors toxic to microorganisms. The temperature is maintained at 58C (62C). In special cases, for example, when themelting point of the test material is low, another temperature may be chosen. This temperature should be constant during the testand kept in a range of 62C. The change of temperature should be just
