Detail of GB/T 42764-2023

Introduction of GB/T 42764-2023

GB/T 42764-2023 Plastics - Assessment of the intrinsic biodegradability of materials exposed to marine inocula under mesophilic aerobic laboratory conditions - Test methods and requirements 1 Scope This document specifies test methods and criteria for showing intrinsic biodegradability in marine environments of virgin plastic materials and polymers without any preliminary environmental exposure or pre-treatment. Test methods applied in this document are carried out at temperatures in the mesophilic range under aerobic conditions and are aimed to show ultimate biodegradability, i.e. conversion into carbon dioxide, water and biomass. This document neither assesses the constituents, such as regulated metals or substances hazardous to the environment, nor potential ecotoxic effects but intrinsic biodegradability only. These aspects will be considered in a separate standard covering the overall environmental impact of products intentionally or accidentally released in the marine environment. This document does not cover the performance of products made from biodegradable plastic materials and biodegradable polymers. Lifetime and biodegradation rates in the sea of products made with biodegradable plastic materials are generally affected by the specific environmental conditions and by thickness and shape. Although results might indicate that the tested plastic materials and polymers biodegrade under the specified test conditions at a certain rate, the results of any laboratory exposure cannot be directly extrapolated to marine environments at the actual site of use or leakage. This document is not applicable for “marine biodegradable” claims of biodegradable plastic materials. For such purpose, see relevant product standards, if available. The testing scheme specified in this document does not provide sufficient information for determining the specific biodegradation rate (i.e. the rate per available surface area) of the material under testing. For such purpose, see relevant standards about specific biodegradation rate, if available. 2 Normative references The following documents are referred to in the text in such a way that some or all of their content constitutes requirements of this document. For dated references, only the edition cited applies. For undated references, the latest edition of the referenced document (including any amendments) applies. ISO 10210 Plastics - Methods for the preparation of samples for biodegradation testing of plastic materials Note: GB/T 38787-2020, Plastics - Methods for the preparation of samples for biodegradation testing of plastic materials (ISO 10210:2012, IDT) ISO 18830 Plastics - Determination of aerobic biodegradation of non-floating plastic materials in a seawater/sandy sediment interface - Method by measuring the oxygen demand in closed respirometer Note: GB/T 40611-2021, Plastics - Determination of aerobic biodegradation of non-floating plastic materials in a seawater/sandy sediment interface - Method by measuring the oxygen demand in closed respirometer (ISO 18830:2016, IDT) ISO 19679 Plastics - Determination of aerobic biodegradation of non-floating plastic materials in a seawater/sediment interface - Method by analysis of evolved carbon dioxide Note: GB/T 40612-2021, Plastics - Determination of aerobic biodegradation of non-floating plastic materials in a seawater/sediment interface - Method by analysis of evolved carbon dioxide (ISO 19679:2020, IDT) ISO 22404 Plastics - Determination of the aerobic biodegradation of non-floating materials exposed to marine sediment - Method by analysis of evolved carbon dioxide Note: GB/T 40367-2021, Plastics - Determination of the aerobic biodegradation of nonfloating materials exposed to marine sediment - Method by analysis of evolved carbon dioxide (ISO 22404:2019, IDT) ISO 23977-1 Plastics - Determination of the aerobic biodegradation of plastic materials exposed to seawater - Part 1: Method by analysis of evolved carbon dioxide ISO 23977-2 Plastics - Determination of the aerobic biodegradation of plastic materials exposed to seawater - Part 2: Method by measuring the oxygen demand in closed respirometer ASTM D6691-17 Standard test method for determining aerobic biodegradation of plastic materials in the marine environment by a defined microbial consortium or natural sea water inoculum 3 Terms and definitions For the purposes of this document, the following terms and definitions apply. ISO and IEC maintain terminological databases for use in standardization at the following addresses: ——ISO Online browsing platform: available at https://www.iso.org/obp ——IEC Electropedia: available at http://www.electropedia.org/ 3.1 intrinsic biodegradability ability of a polymer or plastic material to be biodegraded established under controlled laboratory conditions 3.2 ultimate biodegradability breakdown of an organic chemical compound by microorganisms in the presence of oxygen to carbon dioxide, water, and mineral salts of any other elements present (mineralization) and new biomass or in the absence of oxygen to carbon dioxide, methane, mineral salts, and new biomass [SOURCE: ISO 18606:2013, 3.5] 3.3 constituent every pure chemical material or substance of which a polymer or plastic material is composed 4 Requirements 4.1 Test material Plastic materials, polymers, and organic constituents shall be tested in the form specified by the applied standard test method. Refer to ISO 10210 for preparation of powder from plastic materials if milling is required. Test samples shall not be subjected to any pre-treatment (e.g. by heat and or an exposure to radiation exposure) nor naturally aged. 4.2 Reference material The reference material shall be cellulose (i.e. microcrystalline cellulose or cellulose filter paper). 4.3 Negative control A negative control shall be tested in parallel with test and reference material. Virgin polyethylene shall be used as negative control. 4.4 Biodegradation test methods The plastic material, polymer or each organic constituent separately shall be tested together with reference material and negative control according to one of the following marine biodegradation test methods: ISO 18830, ISO 19679, ISO 22404, ASTM D6691-17, ISO 23977-1, ISO 23977-2. The test may be stopped when a plateau phase is reached. As a guidance, the plateau phase is considered to be reached when the average biodegradation rate of test material of at least 3 consecutive measuring points is less than 3 % within 2 months. After one-year testing, carefully monitor test conditions in order to ensure reliable conditions in the long term. Follow the instructions provided by the applied standard test methods. Results shall be taken into consideration only if validity criteria of the chosen standard test methods are met. 4.5 Requirements For whole test material or each individual constituent, organic carbon shall mineralize into carbon dioxide for at least 90 % or for the same extent of the reference material within 2 years. For the purposes of this document, this requirement is proven if mineralisation relative to reference material is at least 90 %. Both the reference material and the test sample shall be tested for the same period and the results compared at the same point in time after e.g. the activity of both has reached a plateau. For organic constituents which are present in the material at a concentration between 1 % and 15 % (by dry mass) the level of biodegradation shall be determined separately. Constituents that turned out to be readily biodegradable in a ready biodegradation test according to an OECD test guideline (OECD 301, Methods A to F); OECD 310 are considered biodegradable in the context of this document. As an alternative, the level of biodegradation of an organic constituent may be determined using an artificial blend of the same material. This artificial blend shall consist of at least 15 % of the respective organic constituent [by total organic carbon (TOC) content]. The chemical composition and the structure of the material shall remain the same, but the amount of the organic constituent under consideration shall be increased to a minimum of 15 % [by total organic carbon (TOC) content]. The artificial blend shall be produced following the same processing conditions (e.g. extrusion) as used for the production of the original material containing less than 15 % (by dry mass) of the respective constituent. In case the artificial blend meets the criteria specified above, the constituent is considered biodegradable in the context of this document. The constituent can then be used at the same (15 %) or lower concentration (<15 %; by dry mass) in a material that also contains the same co-substrate as the tested material. Note 1: The objective of testing an artificial blend is to verify a synergistic effect demonstrating that a constituent, which is suspected to be non-biodegradable when tested alone, becomes biodegradable in combination with another biodegradable constituent of a material. Note 2: The concentration of the constituent in the artificial blend is set at a minimum of 15 % in order to avoid false-positive results, as theoretically a material with, for example, 10 % of a non-biodegradable constituent can still reach the required pass level for biodegradation. Chemically unmodified materials and constituents of natural origin (such as wood, wood fibre, cotton fibre, starch, paper pulp, bagasse, jute) shall be accepted as being intrinsically biodegradable without testing. In principle, a positive biodegradation result obtained with one of the test methods indicated in 4.4 is sufficient to show that the test item is susceptible to biodegradation by marine microorganisms. A test item that fails the test cannot be claimed to be intrinsically biodegradable. However, a negative result could be the consequence of an inoculum with a qualitative or quantitative (or both) ineffective microbial population. Thus, it cannot be excluded that the test item could show biodegradation if test is repeated using different inoculum. The above laboratory test methods are performed at a temperature preferably between 15 °C to 25 °C, but not exceeding 28 °C. Note 3: When the test temperature is higher than 20 °C to 22 °C the contribution of psychrophilic microbes to biodegradation can be impaired.

Contents of GB/T 42764-2023