ASTM D5338-98e1
(Test Method)Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions
Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions
SCOPE
1.1 This test method determines the degree and rate of aerobic biodegradation of plastic materials on exposure to a controlled-composting environment under laboratory conditions. This test method is designed to yield reproducible and repeatable test results under controlled conditions that resemble composting conditions. The test substances are exposed to an inoculum that is derived from compost from municipal solid waste. The aerobic composting takes place in an environment where temperature, aeration and humidity are closely monitored and controlled.
1.2 This test method is designed to yield a percentage of conversion of carbon in the sample to carbon dioxide. The rate of biodegradation is monitored as well.
1.3 This test method is designed to be applicable to all plastic materials that are not inhibitory to the microorganisms present in aerobic composting piles.
1.4 The values stated in SI units are to be regarded as the standard.
1.5 This standard does not purport to address all of the safety problems, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use. Specific hazard statements are given in Section 8.
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e1
Designation: D 5338 – 98
Standard Test Method for
Determining Aerobic Biodegradation of Plastic Materials
Under Controlled Composting Conditions
This standard is issued under the fixed designation D 5338; 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 (e) indicates an editorial change since the last revision or reapproval.
e NOTE—Corrections were made throughout in August 1999.
1. Scope Solids, or Residue in Water
D 2908 Practice for Measuring Volatile Organic Matter in
1.1 This test method determines the degree and rate of
Water by Aqueous-Injection Chromatography
aerobic biodegradation of plastic materials on exposure to a
D 3590 Test Methods for Total Kjeldahl Nitrogen in Water
controlled-composting environment under laboratory condi-
D 4129 Test Method for Total and Organic Carbon in Water
tions. This test method is designed to yield reproducible and
by High-Temperature Oxidation and Coulometric Detec-
repeatable test results under controlled conditions that re-
tion
semble composting conditions. The test substances are exposed
E 260 Practice for Packed Column Gas Chromatography
to an inoculum that is derived from compost from municipal
E 355 Practice for Gas Chromatography Terms and Rela-
solid waste. The aerobic composting takes place in an envi-
tionships
ronment where temperature, aeration and humidity are closely
2.2 APHA—AWWA—WPCF Standards:
monitored and controlled.
2540 D Total Suspended Solids Dried at 103 to 105°C
1.2 This test method is designed to yield a percentage of
2540 E Fixed and Volatile Solids Ignited at 550°C
conversion of carbon in the sample to carbon dioxide. The rate
2.3 ISO Standard:
of biodegradation is monitored as well.
ISO 14852 Plastics—Evaluation of the Ultimate Aerobic
1.3 This test method is designed to be applicable to all
Biodegradability and Disintegration Under Controlled
plastic materials that are not inhibitory to the microorganisms
Composting Conditions—Method by Analysis of Re-
present in aerobic composting piles.
leased Carbon Dioxide
1.4 The values stated in SI units are to be regarded as the
standard.
3. Terminology
1.5 This standard does not purport to address all of the
3.1 Definitions—Definitions of terms applying to this test
safety concerns, if any, associated with its use. It is the
method appear in Terminology D 883.
responsibility of the user of this standard to establish appro-
priate safety and health practices and determine the applica-
4. Summary of Test Method
bility of regulatory limitations prior to use. Specific hazard
4.1 This test method consists of the following:
statements are given in Section 8.
4.1.1 Selection of plastic material for the determination of
1.6 This test method is equivalent to ISO 14852.
the aerobic biodegradability in a controlled-composting sys-
2. Referenced Documents tem,
4.1.2 Obtaining an inoculum from composted municipal
2.1 ASTM Standards:
solid waste,
D 618 Practice for Conditioning Plastics and Electrical
2 4.1.3 Exposing the test substances to a controlled aerobic
Insulating Materials for Testing
composting process in conjunction with the inoculum,
D 883 Terminology Relating to Plastics
3 4.1.4 Measuring carbon dioxide evolved as a function of
D 1293 Test Methods for pH of Water
time, and
D 1888 Test Methods for Particulate and Dissolved Matter,
Discontinued; see 1991 Annual Book of ASTM Standards, Vol 11.01.
1 5
This test method is under the jurisdiction of ASTM Committee D-20 on Plastics Annual Book of ASTM Standards, Vol 11.02.
and is the direct responsibility of Subcommittee D20.96 on Environmentally Annual Book of ASTM Standards, Vol 11.04.
Degradable Plastics. Annual Book of ASTM Standards, Vol 14.02.
Current edition approved July 10, 1998. Published September 1998. Originally Standard Methods for the Examination of Water and Wastewater, 17th Edition,
published as D 5338 – 92. 1989, American Public Health Association, 1740 Broadway, New York, NY 19919.
2 9
Annual Book of ASTM Standards, Vol 08.01. Available from American National Standards Institute, 11 W. 42nd St., 13th
Annual Book of ASTM Standards, Vol 11.01. Floor, New York, NY 10036.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
D 5338
4.1.5 Assessing the degree of biodegradability. 6.1.3 Pressurized-Air System, that provides CO -free, H O-
2 2
4.2 The percentage of biodegradability is obtained by de- saturated air to each of the composting vessels at accurate
termining the percentage of carbon in the test substance that is aeration rates. If using a direct measurement of CO (see 6.4),
converted to CO during the duration of the test. This percent- then normal air may be used.
age of biodegradability will not include the amount of carbon
6.1.4 Suitable devices for measuring oxygen and CO
converted from the test substance that is converted to cell concentrations in the exhaust air of the composting vessels,
biomass and that is not, in turn, metabolized to CO during the
such as specific sensors or appropriate gas chromatographs.
course of the test.
6.2 Carbon Dioxide-Trapping Apparatus for Each Com-
4.3 The disintegration of a compact test material is visually
posting Vessel:
determined at the end of the test. Additionally, the weight loss
6.2.1 At least three 5000-mL bottles fitted with gas sparging
of the test material may be determined.
and containing Ba(OH) carbon-dioxide scrubbing solution.
6.2.2 Flexible Tubing, nonpermeable to carbon dioxide.
5. Significance and Use
6.2.3 Stoppers, equipped with gas-sampling parts.
5.1 Biodegradation of a plastic within a composting unit is
6.3 Miscellaneous:
an important phenomenon because it will affect the decompo-
6.3.1 Analytical Balance,(60.1 mg) to weigh test speci-
sition of other materials enclosed by the plastic and the
men.
resulting quality and appearance of the composted material.
6.3.2 100-mL Burette.
Biodegradation of plastics will also allow the safe disposal of
6.3.3 0.05 N HCl.
these plastics through solid-waste composting plants. This
6.3.4 pH Meter.
procedure has been developed to permit the determination of
6.3.5 Suitable devices and analytical equipment for measur-
the rate and degree of aerobic biodegradability of plastic
ing dry solids (at 105°C), volatile solids (at 550°C), volatile
products when placed in a controlled composting process.
fatty acids by aqueous-injection chromatography, total
5.2 Limitations—Because there is a wide variation in the
Kjeldahl nitrogen and carbon concentrations.
construction and operation of composting systems and because
6.4 Optional—The carbon dioxide-trapping apparatus and
regulatory requirements for composting systems vary, this
titration equipment can be replaced by a gas flow meter plus a
procedure is not intended to simulate the environment of any
gas-chromatograph, or other apparatus equipped with suitable
particular composting system. However, it is expected to
detector and column(s), for measuring CO and O concentra-
2 2
resemble the environment of a composting process operated
tions in the exhaust air of each vessel. Take care to analyze
under optimum conditions. More specifically, the procedure is
CO concentration on a sufficiently frequent basis in order to
intended to create a standard laboratory environment that will
produce a reliable cumulative CO production over the course
permit a rapid and reproducible determination of the aerobic 2
of the test (for example, every 3 to 6 h). A standard gas should
biodegradability under controlled composting conditions.
be injected to internally standardize the gas-chromatograph on
6. Apparatus a continuous basis over the course of the test. Operate the gas
chromatograph in conformance with Practices E 260 and E 355
6.1 Composting Apparatus (see Fig. 1):
(see Fig. 2).
6.1.1 A series of at least twelve composting vessels (one test
6.5 Ensure that all glassware is cleaned thoroughly and free
substance, one blank, one positive and one negative control, all
from organic matter.
in three replicates) of 2 to 5 L of volume. For screening
purposes, depending upon the test material, a smaller volume
7. Reagents and Materials
also may be used.
6.1.2 Water Baths, or other temperature controlling means
7.1 Barium Hydroxide Solution, approximately 0.024 N and
capable of maintaining the temperature of the composting
then standardized, prepared by dissolving 4.0 g Ba(OH) per
vessels at 58°C (62°C).
FIG. 1 Set-Up Using Carbon Dioxide-Trapping Apparatus FIG. 2 Optional Set-Up Using a Gas Chromatograph
D 5338
litre of distilled water. Filter through filter paper and store 11. Procedure
sealed as a clear solution to prevent absorption of CO from the
11.1 Preparation of the Samples:
air.
11.1.1 Obtain an inoculum from a properly operating aero-
7.2 Analytical-Grade Cellulose, for thin-layer chromatogra-
bic composting plant treating municipal solid waste, or the
phy with a particle size of less than 20 μm as positive control.
organic fraction thereof. If required, further stabilize the
7.3 Polyethylene, as a negative control. It should be in the
inoculum at the laboratory in order to obtain a low CO
same form as the form in which the sample is tested (polyeth-
production (see 9.1.).
ylene film for film samples, polyethylene pellets in case sample
is in the form of pellets, etc.).
11.1.1.1 Screen the inoculum to less than 10 mm and
manually remove and discard any large inert items (pieces of
8. Hazards
glass, stone, wood, etc.). Determine volatile solids, dry solids
8.1 This test method requires the use of hazardous chemi-
and nitrogen content according to Test Methods D 3590,
cals. Avoid contact with the chemicals and follow manufactur-
D 1888, and APHA Test Methods 2540 D and 2540 E.
er’s instructions and Material Safety Data Sheets.
11.1.2 Determine volatile solids, dry solids and carbon
8.2 The compost inoculum may contain sharp objects. Take
content of all the test substances according to APHA Test
care when handling it.
Methods 2540 D and 2540 E and Test Method D 4129.
8.3 The composting vessels are not designed to withstand
high pressures. The system should be operated at close to 11.1.3 Weigh out roughly 600 g of dry solids of inoculum
ambient pressure.
and mix with about 100 g of dry solids coming from the
sample. Adjust the dry solids content of the mixture in the
9. Compost Inoculum
vessel to approximately 50 % with distilled water. Add ammo-
9.1 The compost inoculum should be two to four months old
nium chloride if the C/N ratio is more than 40. Weigh vessels
well-aerated compost coming from the organic fraction of
with all of the contents immediately before initiation of the
municipal solid waste and sieved on a screen of <10 mm. If
composting process.
such a compost is not available, compost from plants, treating
11.1.4 The blank consists of the inoculum only, containing
green, or yard waste, or mixtures of green waste and municipal
about 600 g of dry solids. As references, use thin-layer
solid waste may be used. It is recommended that the compost
chromatography cellulose as a positive control and polyethyl-
inoculum produces between 50 and 150 mg of CO per gram of
ene as a negative control.
volatile solids over the first ten days of the test, and has an ash
content of less than 70 % and a pH between 7 and 8.2. Total dry
11.1.5 The test material may be in the form of films, formed
solids should be between 50 and 55 %.
articles such as dog bones, granules, or powder. The maximum
9.2 The compost inoculum should be as free from larger
surface area of a compact test material used should be about 2
inert materials (glass, stones, metals, etc.) as possible. These
by 2 cm. In case the original test material is larger, reduce it in
items should be removed manually as much as possible to
particle size.
produce a homogeneous compost inoculum.
11.1.6 No more than about ⁄4 of the volume of the test
9.3 It is recommended to use compost of sufficient porosity
vessel should be filled with test mixture. Sufficient headspace
to enable conditions to be as aerobic as possible. Addition of
is required in order to provide enough space for manual
structural material, such as small wood particles, or persistent
shaking of the test mixture.
or poorly biodegradable inert material may prevent the com-
11.2 Start-Up Procedure—Initiate aeration of the compost-
post from sticking together and clogging during the test.
ing vessels with air-flow rates that are sufficiently high to
10. Test Specimen
ensure that oxygen levels do not drop below 6 % in the exhaust
10.1 The test specimen should have sufficient carbon to
air. Oxygen levels should be closely controlled during the first
yield carbon dioxide that can be adequately measured by the
week and measured at least twice daily. Adjust air-flow rates as
trapping apparatus or CO measurements.
needed.
10.2 All basic composting parameters, such as C/N, oxygen
11.3 Operating Procedure:
in the composting vessel, porosity, and moisture content should
11.3.1 The composting vessels are incubated in the dark or
be optimized so as to make a good composting process
in diffuse light for a period of 45 days in an enclosure that is
possible. The C/N ratio should preferably be between 10 and
free from vapors toxic to microorganisms. The temperature is
40 for both the inoculum and test substance combined. Oxygen
maintained at 58°C (62°C). In special cases, for example,
levels in the composting vessel should be at least 6 % at all
when the melting point of the test material is low, another
times and no free-standing water nor clumps of material should
temperature may be chosen. This temperature should be
be present.
constant during the test and kept in a range of 62°C. The
10.3 Test specimens may be in the form of films, formed
change of temperature should be justified and clearly indicated
articles, dog bones, granules, powder, or other, and conform to
in the test report.
Practice D 618.
11.3.2 Check CO and O concentrations in the outgoing air
2 2
10 at least daily with a minimum time interval of 6 h after the first
For development of this test method, Avicel, available from EM Chemicals,
Inc., Hawthorne, New York, was used. week for the remainder of the test.
D 5338
11.3.3 Check air flow daily before the composting vessels 12.2.1 Determine the amount of CO produced by the
and at the outlets, ensuring that no leaks are present in the difference, in millilitres of titrant, between the tes
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