ASTM_D_6691_-_09.pdf

Designation:D669109Standard Test Method forDetermining Aerobic Biodegradation of Plastic Materials inthe Marine Environment by a Defined Microbial Consortiumor Natural Sea Water Inoculum1This standard is issued under the fixed designation D6691;the number immediately following the designation indicates 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.Scope1.1 This test method is used to determine the degree and rateof aerobic biodegradation of plastic materials(including for-mulation additives)exposed to pre-grown population of at leastten aerobic marine microorganisms of known genera or theindigenous population existing in natural seawater.The testmethod is conducted under controlled laboratory conditions.1.2 This test method is designed to index polymer materialsthat are possibly biodegradable,relative to a positive referencematerial,in an aerobic environment.1.3 This test method is applicable to all polymer materialscontaining at least 20%carbon that are not inhibitory to themicroorganisms present in a marine environment.1.4 The values stated in SI units are to be regarded as thestandard.1.5 There is no similar or equivalent ISO standard.1.6 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 limitations prior to use.2.Referenced Documents2.1 ASTM Standards:2D618 Practice for Conditioning Plastics for TestingD883 Terminology Relating to PlasticsD1193 Specification for Reagent WaterD2593 Test Method for Butadiene Purity and HydrocarbonImpurities by Gas ChromatographyD4129 Test Method for Total and Organic Carbon in Waterby High Temperature Oxidation and by CoulometricDetection3.Terminology3.1 Definitions of Terms Specific to This StandardDefinitions of terms applying to this test method appear inTerminology D883.4.Summary of Test Method4.1 This test method consists of the following:4.1.1 Selecting and characterizing(carbon content,molecu-lar weight)plastic materials for testing,4.1.2 Preparing a uniform inoculum of various isolatedmarine microorganisms,or obtaining a natural sea watersample(with added inorganic nutrients)for the test relying onthe microbes present as the inoculum.4.1.3 Exposing the test materials to the inoculum,4.1.4 Using a respirometer to measure the total biogas(CO2)produced as a function of time,and4.1.5 Assessing the degree of biodegradability.4.2 Biodegradability is assessed by determining the propor-tion of polymer-C converted to biogas-C.The percent oftheoretical gas production,expressed as a fraction of themeasured or theoretical carbon content of the test material,isreported as a function of time.5.Significance and Use5.1 The use of plastics aboard ships is on the rise and the useof the sea as a trash dumping site is no longer a possibility;consequently,the disposal of plastic materials while at searemains a major issue.It is possible that biodegradable plasticswill help to allay public concern by allowing for the safedisposal of plastic materials at sea.This test method has beendeveloped to assess the rate and degree of aerobic biodegra-dation of plastics exposed to marine microorganisms.Aerobicbiodegradation is determined by measuring the amount ofbiogas(carbon dioxide)produced during such an exposure.5.2 It is acceptable to use the degree and rate of aerobicbiodegradability of a plastic under the conditions of this test1This test method is under the jurisdiction of ASTM Committee D20 on Plasticsand is the direct responsibility of Subcommittee D20.96 on EnvironmentallyDegradable Plastics and Biobased Products.Current edition approved Nov.15,2009.Published December 2009.Originallyapproved in 2001.Last previous edition approved in 2001 as D6691-01.DOI:10.1520/D6691-09.2For referenced ASTM standards,visit the ASTM website,www.astm.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.Copyright ASTM International,100 Barr Harbor Drive,PO Box C700,West Conshohocken,PA 19428-2959.United States1 method to estimate the persistence of that plastic in biologi-cally active marine environments,for example,seashore andopen-ocean.However,it shall be recognized that predictinglong-term environmental fate and effects from the results ofshort-term exposure to a simulated marine environment isdifficult.Thus,caution shall be exercised when extrapolatingthe results obtained from this or any other controlled-environment test to disposal in the natural environment.6.Apparatus6.1 Aerobic Digestion and Gas Measuring Apparatus:6.1.1 Biogas production can be monitored through the useof any number of respir