Biodegradability Testing

OECD Biodegradability Tests

OECD 301 Testing – Ready/Ultimate Biodegradability (Includes OECD 310)

OECD 301 series (OECD 301A, OECD 301B, OECD 301C, OECD 301D, OECD 301E, OECD 301F) allows for direct, explicit certification of a material’s biodegradability. The methods establish threshold criteria for the direct classification and marketing of materials under the terms of Ready or Ultimate Biodegradability. A material is considered Readily Biodegradable if 60% (or 70% for some tests) of the organic carbon in the material is converted to CO2 within a 10 day window and within 28 days total. The 10 day window is defined as beginning when 10% of the organic carbon has been converted to CO2 and ends after 10 days from this point (but before 28 full days of the test). A material is considered Ultimately Biodegradable (under the subclassification of Inherent Biodegradability) if 60% (or 70% for some tests) of the organic carbon in the material is converted to CO2 over the duration of the test. The test can be extended beyond 28 days.

This is RespirTek’s most popular series of methods for those with products whose fate is a wastewater treatment facility.

OECD 311 – Anaerobic Biodegradability of Organic Compounds in Digested Sludge

OECD 311 is used to assess the biodegradability of organic chemicals under anaerobic digester conditions. Residual chemicals that are not degraded in standard aerobic treatment basins will often end up in anaerobic digesters as a last treatment option prior to discharge to the environment. This test method may also be useful for evaluating the biodegradation of solid-matrix materials whose expected fate is a digester system.

ASTM Biodegradability Tests

ASTM D5210 – Standard Test Method for Determining the Anaerobic Biodegradation of Plastic Materials in the Presence of Municipal Sewage Sludge

ASTM D5210 is very similar to OECD 311 and is used to assess the biodegradability of organic chemicals in anaerobic conditions. This test method simulates conditions similar to that in an anaerobic digester, which is a biological reactor typically used to digest sewage sludge after water treatment. Residual chemicals that are not degraded in standard aerobic treatment basins will often end up in anaerobic digesters as a last treatment option prior to discharge to the environment.

ASTM D5338 – Standard Test Method for Determining Aerobic Biodegradation of Plastic Materials Under Controlled Composting Conditions, Incorporating Thermophilic Temperatures

ASTM D5338 evaluates the biodegradation of plastic materials under controlled composting conditions. Controlled composting conditions are considered those conditions where oxygen, temperature, moisture, and pH levels of the compost are maintained at optimal levels. Commercial composting facilities are the relevant disposal compartment for materials that undergo assessments based on this type of test method. The duration of the test can be up to 180 days. No explicit thresholds or classifications are permitted based on method language for certification purposes.

ASTM D5864 – Standard Test Method for Determining Aerobic Aquatic Biodegradation of Lubricants or Their Components

ASTM D5864 evaluates the aerobic biodegradation of lubricants or lubricant components in aqueous solutions with low concentrations of inoculums. The test objective is to simulate the environmental exposure of lubricants during release into non-wastewater treatment environments. A variety of inoculums sources from soil, surface water, and other similar matrices is used. The test duration is 28 days or until a plateau in biodegradation is reached. No explicit thresholds or classifications are permitted based on method language for certification purposes.

ASTM D5988 – Standard Test Method for Determining Aerobic Biodegradation in Soil of Plastic Materials or Residual Plastic Materials After Composting

ASTM D5988 evaluates the aerobic biodegradation of plastic materials in soil. The method can be used as a complementary method to ASTM D5338 in an effort to determine if residual material not degraded in the timeframe of D5338 can be further degraded after the compost is integrated into the soil environment. The maximum duration of the test is 6 months. No explicit thresholds or classifications are permitted based on method language for certification purposes.

This method has also been employed to understand the biodegradation of non-composted materials in natural soil conditions.

ASTM D6400 – Standard Specification for Compostable Plastics

ASTM D6400 is a specification providing criteria to make claims of “Compostable”. The specification involves testing the plastic material for (1) disintegration (2) biodegradation and (3) ecological impacts. A heavy metals analysis is also conducted to ensure the material is within standard limits provided for healthy composting. The disintegration testing and biodegradation testing are conducted concurrently. Disintegration is evaluated by sieving the compost-plastic mixture after a set time to measure the amount of plastic that passes through the sieve. Biodegradation is a measure of the conversion of organic carbon to CO2 under aerobic, thermophilic composting conditions. ASTM D5338 is the test method used to evaluate the biodegradation. Ecological impacts are evaluated via OECD 208, which is a plant growth test. Residual compost is mixed with soil in specified proportions to evaluate the ability of standard plant-types to thrive in the compost residues. This specification allows for the classification of a plastic material of Compostable if all threshold criteria are met.

ISO Biodegradability Tests

Usually, ISO standards are used to assess biodegradation when driven by an external regulatory or client source. The standards do not explicitly provide a threshold from which to base claims of “Biodegradable”, which is in contrast to a significant number of OECD and ASTM methods.

ISO 9439 – Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium — Carbon dioxide evolution test

ISO 9439 evaluates the aerobic biodegradability of organic compounds in an aqueous medium using common sewage sludge found in wastewater treatment plants. This test method is similar in setup to OECD 301B. Biodegradation is measured as the percentage of organic carbon converted to CO2. The duration of the test is 28 days. No explicit thresholds or classifications are permitted based on method language for certification purposes.

ISO 14593 – Evaluation of ultimate aerobic biodegradability of organic compounds in aqueous medium — Method by analysis of inorganic carbon in sealed vessels (CO2 headspace test)

ISO 14593 evaluates the aerobic biodegradability of organic compounds in aqueous medium using common sewage sludge found in wastewater treatment plants. The test is conducted in sealed vessels similar to OECD 310. Biodegradation is measured as the percentage of organic carbon converted to CO2. The test duration is 28 days. No explicit thresholds or classifications are permitted based on method language for certification purposes.

ISO 14852 – Determination of the ultimate aerobic biodegradability of plastic materials in an aqueous medium — Method by analysis of evolved carbon dioxide

ISO 14852 evaluates the ultimate aerobic biodegradability of plastic materials in aqueous medium with the sources of inoculums for the test varying and depending on the final disposal. Compost, soil, or sewage sludge can be used. Biodegradation is measured as the percentage of organic carbon converted to CO2. The test duration cannot exceed 6 months. No explicit thresholds or classifications are permitted based on method language for certification purposes.

ISO 14855 – Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions — Method by analysis of evolved carbon dioxide

ISO 14855 evaluates the ultimate aerobic biodegradability of plastic materials under controlled composting conditions. This test method is nearly identical to ASTM D5338 in execution. Controlled composting conditions are maintained throughout the test, including oxygen and moisture content, temperature, and pH. Biodegradation is measured as the percentage of organic carbon converted to CO2. The test duration is 180 days. No explicit thresholds or classifications are permitted based on method language for certification purposes.