ASTM D5988-18

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it 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 version
of the standard as published by ASTM is to be considered the official document.
Designation: D5988 − 12 D5988 − 18
Standard Test Method for
Determining Aerobic Biodegradation of Plastic Materials in
Soil
This standard is issued under the fixed designation D5988; 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*
1.1 This test method covers determination under laboratory conditions of the degree and rate of aerobic biodegradation of plastic
materials, including formulation additives, in contact with soil.
1.2 This test method is designed to measure the biodegradability of plastic materials relative to a reference material in an aerobic
environment.
1.3 This test method is designed to be applicable to all plastic materials that are not inhibitory to the bacteria and fungi present
in soil.
1.4 Claims of performance shall be limited to the numerical result obtained in the test and not be used for unqualified
“biodegradable” claims. Reports shall clearly state the percentage of net gaseous carbon generation for both the test and reference
samples at the completion of the test. Results shall not be extrapolated beyond the actual duration of the test.
1.5 The values stated in SI units are to be regarded as the standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety safety, health, and healthenvironmental practices and determine the
applicability of regulatory limitations prior to use. A specific hazard statement is given in Section 8.
1.7 This ASTM test method is equivalent to ISO 17556.
1.8 This international standard was developed in accordance with internationally recognized principles on standardization
established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued
by the World Trade Organization Technical Barriers to Trade (TBT) Committee.
2. Referenced Documents
2.1 ASTM Standards:
D425 Test Method for Centrifuge Moisture Equivalent of Soils
D618 Practice for Conditioning Plastics for Testing
D883 Terminology Relating to Plastics
D1193 Specification for Reagent Water
D1293 Test Methods for pH of Water
D2974 Test Methods for Moisture, Ash, and Organic Matter of Peat and Other Organic Soils
D2980 Test Method for Saturated Density, Moisture-Holding Capacity, and Porosity of Saturated Peat Materials
D2989 Test Method for Acidity-Alkalinity of Halogenated Organic Solvents and Their Admixtures
D4129 Test Method for Total and Organic Carbon in Water by High Temperature Oxidation and by Coulometric Detection
D4972 Test Method for pH of Soils
D5338 Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions,
Incorporating Thermophilic Temperatures
D5511 Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-Digestion
Conditions
This test method is under the jurisdiction of ASTM Committee D20 on Plastics and is the direct responsibility of Subcommittee D20.96 on Environmentally Degradable
Plastics and Biobased Products.
Current edition approved May 1, 2012April 1, 2018. Published June 2012April 2018. Originally approved in 1996. Last previous edition approved in 20032012 as
D5988 - 03.D5988 - 12. DOI: 10.1520/D5988-12.10.1520/D5988-18.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at service@astm.org. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
*A Summary of Changes section appears at the end of this standard
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
D5988 − 18
2.2 APHA-AWWA-WPCF Standards:
2540 D Total Suspended Solids Dried at 103°–105°C
2540 G Total, Fixed, and Volatile Solids in Solids and Semi-Solid Samples
2.3 ISO Standard:
ISO 11261 Soil Quality—Determination of Total Nitrogen—Modified Kjeldahl Method
ISO 17556 Plastics—Determination of the Ultimate Aerobic Biodegradability of Plastic Materials in Soil by Measuring the
Oxygen Demand in a Respirometer or the Amount of Carbon Dioxide Evolved
3. Terminology
3.1 Definitions—Definitions of terms applicable to this test method appear in Terminology D883.
4. Summary of Test Method
4.1 The test method described consists of the selection of plastic material for the determination of aerobic biodegradability,
obtaining soil as a matrix and source of inoculum, exposing the plastic material to the soil, measuring the carbon dioxide evolved
by the microorganisms as a function of time, and assessing the degree of biodegradability.
4.2 The CO production measured for a material, expressed as a fraction of the measured or calculated carbon content, is
reported with respect to time, from which the degree of biodegradability is assessed.
4.3 Alternatively, it is possible to determine the consumption of oxygen, or biochemical oxygen demand (BOD), for example,
by measuring the amount of oxygen required to maintain a constant gas volume in the respirometer flask, or by measuring the
change in volume or pressure (or a combination of the two) either automatically or manually. The level of biodegradation expressed
in percent is determined by comparing the BOD with the theoretical oxygen demand (ThOD). In using this alternative approach,
however, the influence of possible nitrification processes on the BOD must be considered.
5. Significance and Use
5.1 The degree and rate of aerobic biodegradability of a plastic material in the environment determines the extent to which and
time period over which plastic materials are mineralized by soil microorganisms. Disposal is becoming a major issue with the
increasing use of plastics, and the results of this test method permit an estimation of the degree of biodegradability and the time
period over which plastics will remain in an aerobic soil environment. This test method determines the degree of aerobic
biodegradation by measuring evolved carbon dioxide as a function of time that the plastic is exposed to soil.
5.2 Soil is an extremely species-rich source of inoculum for evaluation of the biodegradability of plastics in the environment.
When maintained appropriately with regard to moisture content and oxygen availability, the biological activity is quite
considerable, although lower than other biologically active environments, such as activated sewage-sludge or compost.
6. Apparatus
6.1 Soil-Contact Incubation Apparatus (see Fig. 1; biometer flasks are also appropriate). Ensure that all glassware is thoroughly
cleaned and, in particular, free from organic or toxic matter.
NOTE 1—(1) Barium hydroxide solution or potassium hydroxide solution, (2) soil, (3) water, and (4) perforated plate.
FIG. 1 Soil-Contact Incubation Apparatus
Standard Methods for the Examination of Water and Wastewater, 17th Edition, 1989, Available from American Public Health Association (APHA), 1015 Fifteenth
Street800 I St., NW, Washington, DC 20005.20001, http://www.apha.org.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
D5988 − 18
6.1.1 Vessels, a set of vessels with approximately 2 to 4-L of internal volume with air-tight seal, such as 150-mm desiccators.
Provide three vessels for soil only (known as “blanks” or “controls,” these vessels show the background activity of the soil), three
vessels for a positive reference material (these vessels show the viability of the soil microbial community), three vessels per test
material, and three vessels as technical controls. The technical controls contain only the absorbing solution and no soil. The
ambient air which fills the headspace of all the vessels introduces carbon dioxide into the system. The technical controls allow
accounting for and subtracting this introduced carbon dioxide. Additionally, the technical controls indicate the air-tightness of the
vessel system by showing possible infiltration of carbon dioxide into the sealed vessel.
6.1.2 Beakers, sets of 150-mL and 100-mL, equal in number to the soil incubation vessels.
6.1.3 Perforated Plates or Other Support, a set to hold the beakers above the soil inside each vessel. The support must be made
from a material that will not absorb carbon dioxide.
6.1.4 Darkened Chamber or Cabinet, which allows selection of a temperature between 20°C to 28°C, and allows maintaining
the selected temperature at 62°C.
6.2 Analytical Equipment:
6.2.1 Analytical Instrument, to measure the total carbon content of the test specimen.
6.2.2 Analytical Balance, to weigh the test specimen.
6.2.3 Burette, 100 mL.
6.2.4 Bench-Top Centrifuge, for moisture-holding capacity (MHC) determination.
6.2.5 Oven, set to 104 6 1°C for moisture determinations.
6.2.6 Muffle Furnace, set to 550°C for ash determinations.
6.2.7 pH Meter.
6.3 Alternatively, it is acceptable to use a flow-through apparatus or manometric apparatus as described in ISO 17566.
7. Reagents and Materials
7.1 Purity of Reagents—Reagent grade chemicals shall be used in all tests. Unless otherwise indicated, it is intended that all
reagents conform to the specifications of the Committee on Analytical Reagents of the American Chemical Society where such
specifications are available. It is acceptable to use other grades, provided it is first ascertained that the reagent is of sufficiently
high purity to permit its use without lessening the accuracy of the determination.
7.2 Ammonium Phosphate, ((NH ) HPO ), 4.72 g/L.
4 2 4
7.3 Barium Hydroxide Solution (0.025 N), prepared by dissolving 4.0 g anhydrous Ba(OH) /L of distilled water. Filter free of
solid material, confirm normality by titration with standard acid, and store sealed as a clear solution to prevent absorption of CO
from the air. It is recommended that 5 to 20 L be prepared at a time when running a series of tests. When using Ba(OH) , however,
care must be taken that a film of BaCO does not form on the surface of the solution in the beaker, which would inhibit CO
3 2
diffusion into the absorbing medium. Alternatively, it is acceptable to use potassium hydroxide solution (KOH, 0.5 N), prepared
by dissolving 28 g of anhydrous KOH/L of distilled water and proceeding in the same way as for the Ba(OH) .
7.4 Hydrochloric Acid, 0.05 N HCl when using 0.025 N Ba(OH) , or 0.25 N HCl when using 0.5 N KOH.
8. Hazards
8.1 This test method includes the use of hazardous chemicals. Avoid contact with chemicals and follow the manufacturer’s
instructions and material safety data sheets.
9. Soil
9.1 Use natural, fertile soil collected from the surface layers of fields and forests. Make a laboratory mixture of equal parts (by
weight) of soil samples obtained from at least three diverse locations (for example, an agricultural field, a forest, and a pasture or
meadow). Taking soil from multiple and diverse locations will maximize biodiversity. It is advisable to avoid soils that have been
exposed to pollutants that cause significant perturbations of the microbial population. The soils are preferably used fresh from the
field to assure active microbiota. Air-dried or frozen soils must be reactivated before use in this test. It is preferable to use fertile
soil classified as “sandy loam” in accordance with USDA classification, or “silty sand” in accordance with the German DIN
classification.
9.2 The sources of the soils must be reported (see 14.1.1). Record the sampling site, its location, the presence of plants or crops,
the sampling date, the sampling depth, and, if possible, the history such as details of fertilizer and pesticide application.
9.3 Sieve the soil to less than 2-mm particle size, and remove obvious plant material, stones, or other inert materials. Store the
soil in a sealed container at 4 6 1°C for a maximum of one month.
Reagent Chemicals, American Chemical Society Specifications, American Chemical Society, Washington, DC. For suggestions on the testing of reagents not listed by
the American Chemical Society, see Analar Standards for Laboratory Chemicals, BDH Ltd., Poole, Dorset, U.K., and the United States Pharmacopeia and National
Formulary, U.S. Pharmacopeial Convention, Inc. (USPC), Rockville, MD.
D5988 − 18
9.4 Analyze the soil for MHC by Test Method D425, Test Method D2980, or another analogous test method for MHC or field
capacity.
9.5 Determine the pH of the soil on a 5:1 (distilled water:soil) slurry using a glass combination electrode calibrated with
standard buffers, following the guidelines given in Test Method D1293. Alternatively, it is acceptable to determine the soil pH by
Test Method D4972. The pH must fall between 6.0 and 8.0. (Soil with a pH above 8.0 retains more of the CO evolved by the
microorganisms than a neutral soil, while a soil with a pH below 6.0 has the potential to contain an atypical microbial population.)
9.6 Determine the moisture (total solids—dry solids) and ash (total solids—volatile solids) contents of the soil in accordance
with Test Method D2974 or APHA-AWWA-WPCF 2540 D and G, respectively.
9.7 Determine total nitrogen in accordance with ISO 11261 or equivalent method.
9.8 It is accept
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