Aerobic biodegradation testing of packaging materials is a critical laboratory evaluation that measures how plastics, films, and fiber-based packaging decompose under oxygen-rich, microbially active conditions such as composting. Governed by internationally recognized standards including ISO 14855, ASTM D5338, and EN 13432, this testing quantifies the conversion of organic carbon into carbon dioxide and determines whether a material qualifies as biodegradable or compostable. This article provides a comprehensive technical overview of sample requirements, test items, experimental methods, and practical applications for manufacturers, researchers, and quality professionals.
Technical Overview
Aerobic biodegradation refers to the breakdown of organic substances by microorganisms in the presence of oxygen, during which organic carbon is metabolized and ultimately converted into carbon dioxide (CO2), water, mineral salts, and new microbial biomass. For packaging materials, aerobic biodegradation experiments simulate natural or engineered decomposition environments—most commonly industrial composting—to scientifically quantify how completely and how rapidly a material can be biologically assimilated.
The fundamental principle of the experiment is respirometric: as microorganisms consume the carbon in the test material, they release CO2. By continuously measuring the amount of CO2 evolved from a test vessel containing the packaging sample and comparing it against the theoretical CO2 that would be produced if all carbon in the sample were completely mineralized (ThCO2), the percentage of biodegradation over time can be calculated. A validated test always includes a blank control (inoculum only) and a positive reference (typically cellulose) to confirm inoculum activity, and may include an inert negative control to demonstrate the method's discrimination capability.
Aerobic biodegradation testing underpins compostability claims, eco-label certification, regulatory market access, and research into novel bio-based materials. The most widely applied standards include:
- ISO 14855-1 / GB/T 19277.1 — Determination of the ultimate aerobic biodegradability of plastic materials under controlled composting conditions by analysis of evolved carbon dioxide
- ISO 14855-2 — Gravimetric measurement of the carbon dioxide evolved in a laboratory-scale composting respirometer
- ASTM D5338 — Standard test method for determining aerobic biodegradation of plastic materials under controlled composting conditions
- EN 13432 — Packaging requirements for packaging recoverable through composting and biodegradation (European harmonized standard)
- ISO 14852 — Aerobic biodegradability in an aqueous medium (biodegradability in activated sludge or aqueous suspension)
- ISO 17556 — Aerobic biodegradability in soil
- ISO 16929 / EN 14045 — Disintegration testing under defined composting conditions
Testing Samples
Biodegradable Plastic Films and Bags
Flexible packaging such as shopping bags, mailer bags, agricultural mulch films, cling films, and courier bags made from biodegradable polymers including PLA, PBAT, PBS, PBSA, PHA/PHB, PCL, and starch-based blends. These are among the most frequently submitted samples for aerobic biodegradation evaluation, particularly for compostable certification purposes.
Rigid Plastic Packaging
Containers, trays, cups, cutlery, bottles, caps, and injection-molded or thermoformed articles produced from bio-based or biodegradable resins. Rigid samples are typically reduced to fragments or milled to a defined particle size to ensure consistent surface area exposure during testing.
Paper and Fiber-Based Packaging
Corrugated boxes, paper bags, molded pulp trays, and cardboard containers, including coated or laminated variants where the biodegradability of coatings, adhesives, or barrier layers must be verified alongside the cellulose substrate.
Composite, Coated, and Laminated Materials
Multilayer structures combining polymers with paper, metallized layers, or bio-coatings. Testing determines whether the composite as a whole, or specific components such as adhesives and inks, meet biodegradation thresholds.
Polymer Resins, Additives, and Components
Raw resins, masterbatches, plasticizers, biodegradation promoter additives, printing inks, and adhesives are often tested individually during material development to characterize their contribution to the overall degradation profile of finished packaging.
Testing Items
A complete aerobic biodegradation assessment for packaging typically encompasses the following parameters:
- Ultimate aerobic biodegradation rate — the cumulative percentage of carbon converted to CO2 relative to ThCO2 over the test period
- Biodegradation curve and kinetics — time-dependent CO2 evolution profile, lag phase, and biodegradation plateau
- Disintegration degree — percentage mass reduction of fragments after composting (typically fragments smaller than 2 mm must be less than 10% of original dry mass)
- Volatile solids and total organic carbon (TOC) content of the test material — required for calculating ThCO2
- Elemental carbon content (C, H, N) determination via elemental analysis
- Validation parameters — positive reference cellulose must exceed 70% biodegradation within the test window; blank CO2 production must remain within acceptable limits
- Compost quality and ecotoxicity indicators — pH, salinity, ammonium content, and plant germination/biomass ratios when required by EN 13432
- Heavy metals and regulated elements — analysis of Pb, Cd, Hg, Cr(VI), As, Cu, Ni, Se, Zn, Mo, and F against regulatory thresholds
Acceptance criteria under EN 13432 and comparable frameworks generally require a minimum of 90% biodegradation (relative to cellulose in absolute terms or as a percentage of ThCO2) within six months, together with at least 90% disintegration within twelve weeks and the absence of adverse effects on the composting process or compost quality.
Testing Methods
Controlled Composting Method (ISO 14855-1 / ASTM D5338 / GB/T 19277.1)
The test material is mixed with mature, stable compost inoculum and placed in airtight bioreactors maintained at 58 ± 2 °C with continuous supply of humidified, CO2-free air. Exhaust gas is analyzed for CO2 concentration using infrared gas analyzers or by titration after alkaline absorption. The test typically runs up to 180 days or until a biodegradation plateau is reached. Cumulative net CO2 (sample vessel minus blank vessel) divided by ThCO2 yields the biodegradation percentage. This is the primary method for industrial compostability claims.
Gravimetric Respirometric Method (ISO 14855-2)
A compact laboratory-scale biometer design in which evolved CO2 is captured by sodium hydroxide or sodium lime absorption columns and quantified gravimometrically. This approach reduces equipment complexity and is well suited for longer-duration screening of multiple materials in parallel.
Aqueous Medium Method (ISO 14852)
The material is suspended in a mineral medium inoculated with activated sludge or a defined microbial consortium and agitated in aerobic conditions at 20–25 °C. CO2 evolution is monitored to assess ultimate biodegradability in aquatic microbial environments, providing data relevant to environmental release scenarios.
Soil Burial Method (ISO 17556)
The sample is incorporated into a standardized natural or synthetic soil and incubated at controlled temperature and moisture. Evolved CO2 or oxygen consumption is measured to evaluate biodegradation in soil, which is slower than composting and relevant for agricultural films and soil-contacting packaging.
Disintegration Testing (ISO 16929 / EN 14045)
Test pieces of defined dimensions are composted in a pilot-scale or laboratory compost reactor. After a defined period (typically 12 weeks), the material is sieved through a 2 mm screen, and the fraction failing to pass is weighed to determine the disintegration percentage, verifying that the material physically fragments without visible contamination.
Ecotoxicity Testing (OECD 208 / EN 13432 Annex E)
Compost derived from the biodegraded material is mixed with reference soil at defined ratios, and seed germination rate plus plant biomass of at least two higher plant species are compared against blank compost controls. Germination and growth must reach at least 90% of the control to pass.
Applications
Aerobic biodegradation experimental data serve multiple commercial and regulatory purposes across the packaging value chain:
- Compostability certification support — generating the biodegradation evidence required for seedling, compostability, and biodegradable labeling schemes in European, North American, and Asia-Pacific markets
- Regulatory compliance — demonstrating conformity with EN 13432 under the EU Packaging and Packaging Waste framework, and with national requirements governing single-use plastics, biodegradable products, and plastic restriction policies
- Export market access — providing internationally recognized laboratory data for customs, buyer verification, and product registration in destination markets
- Research and formulation development — comparing polymer grades, additives, blend ratios, and thickness effects on biodegradation kinetics to accelerate material innovation
- Green marketing substantiation — supporting verifiable environmental claims for biodegradable and compostable packaging under advertising and consumer protection rules
- Quality control — validating batch-to-batch consistency of biodegradable resin supply and finished packaging production
- Municipal and composting facility acceptance — confirming that packaging will degrade within industrial composting cycle times without contaminating the output compost
FAQ
How long does an aerobic biodegradation experiment take?
Under controlled composting conditions per ISO 14855-1 or ASTM D5338, the test is typically run for up to 180 days, ending earlier only when a biodegradation plateau is reached. Combined programs that include disintegration and ecotoxicity testing for full EN 13432 evaluation may require approximately six to nine months in total.
What is the pass criterion for biodegradation?
EN 13432 and equivalent frameworks require at least 90% biodegradation within six months, either in absolute terms relative to ThCO2 or relative to the cellulose positive reference. The positive control itself must achieve more than 70% biodegradation for the test to be considered valid.
How should samples be prepared for testing?
Samples are generally milled or cut to particles below approximately 5 mm or thin fragments to ensure homogeneous mixing with the inoculum. The total organic carbon and volatile solids content of the sample must be determined beforehand to calculate the theoretical CO2 production, and sufficient sample mass is dosed to provide a defined carbon-to-inoculum ratio.
What is the difference between biodegradable and compostable packaging?
Biodegradable describes the intrinsic ability of a material to be broken down by microorganisms, which is what the aerobic biodegradation experiment quantifies. Compostable is a stricter claim requiring the material to biodegrade, disintegrate within a defined composting cycle, and leave compost that is safe for plant growth, all verified through the combined testing described in EN 13432.
Why must the test temperature be strictly controlled at 58 °C?
The 58 ± 2 °C condition represents the thermophilic phase of industrial composting, where microbial activity is at its peak. Stable temperature control ensures reproducible biodegradation rates, protects inoculum viability, and guarantees comparability of results between laboratories and across test campaigns.
Can biodegradation results from one laboratory be recognized internationally?
Yes, when the testing is performed by accredited third-party laboratories operating under ISO/IEC 17025 management systems and strictly following published international methods such as ISO 14855, ASTM D5338, or EN 13432, the resulting reports are broadly accepted by certification bodies, regulators, and buyers worldwide.
