ASTM D5338 Determining Aerobic Biodegradation

ASTM D5338 is used for determining Aerobic Biodegradation of Plastic Materials under controlled composting conditions, incorporating thermophilic temperatures.

Talk to an Expert

ASTM D5338 Determining Aerobic Biodegradation

TRUSTED BY

Precision-driven testing for dimensional accuracy and compliance

Overview
Scope, Applications, and Benefits
Test Process
Specifications
Instrumentation
Results and Deliverables

Overview

The assessment of the aerobic biodegradation of plastic materials under regulated composting conditions at thermophilic temperatures is described in ASTM D5338. This technique mimics an industrial composting setting where microorganisms break down plastics in the presence of oxygen.

The evolution of carbon dioxide (CO₂) over time is used to assess the degree and pace of biodegradation. This standardised process is essential for determining if plastics are compostable, verifying environmental claims, and assisting producers in creating environmentally friendly, biodegradable goods.

Scope, Applications, and Benefits

Scope

ASTM D5338 outlines procedures for determining the aerobic biodegradability of plastics and polymeric materials under controlled composting conditions. It evaluates:

Degree of biodegradation
CO₂ generation from microbial activity
Rate of decomposition under thermophilic aerobic conditions

The method uses a controlled composting system with regulated temperature, moisture, aeration, and microbial inoculum to simulate realistic industrial composting environments for product design, environmental assessments, and certification purposes.

Applications

Assessing the biodegradability of compostable packaging materials
Evaluating agricultural products such as mulch films
Testing disposable consumer goods (cups, utensils, bags)
Supporting industrial composting and waste-diversion programs
R&D efforts focused on improving biodegradable polymer formulations

Benefits

Determines the percentage and rate of aerobic biodegradation
Provides measurable CO₂ output for material comparison
Helps validate compostability claims and sustainability certifications
Supports eco-friendly product development and regulatory compliance
Simulates realistic industrial composting conditions for accurate performance evaluation

Test Process

Specimen Preparation

Prepare 50–100 g of shredded or granulated material (<2 mm) to ensure sufficient surface area for microbial action.

Compost Environment Setup

Mix the test material with mature compost and maintain controlled temperature (58–60°C), humidity, and aeration to support aerobic microbial activity.

Aerobic Decomposition & Monitoring

Incubate samples under thermophilic aerobic conditions while measuring CO₂ evolution at regular intervals. Include control samples for validation.

Completion & Data Calculation

Continue testing for 30–180 days or until biodegradation stabilizes. Calculate percent biodegradation based on gaseous carbon produced vs. carbon content of the sample.

Technical Specifications

Parameter	Details
Test Principle	Aerobic biodegradation under controlled composting at thermophilic temperatures
Sample Types	Films, powders, granules, shredded plastics, molded articles
Sample Weight	Typically 50–100 g (dry weight)
Particle Size	<2 mm to enhance microbial degradation
Inoculum Source	Mature compost containing active aerobic microorganisms
Measured Output	CO₂ evolution over time
Analysis Basis	Percent biodegradation vs. theoretical carbon conversion
Typical Duration	30–180 days, depending on material behavior

Instrumentation Used for Testing

Controlled composting reactors with regulated temperature (58–60°C)
CO₂ measurement systems for periodic gas analysis
Aeration and humidity control systems
Temperature-controlled incubation chambers
Carbon content analyzers for elemental analysis
Data-acquisition software for calculating biodegradation and CO₂ trends

Results and Deliverables

Percentage aerobic biodegradation vs. theoretical maximum
CO₂ evolution rate and cumulative carbon conversion
Performance comparison with control materials
Degradation profile over the entire composting period
Assessment of compostability for regulatory and certification purposes
Interpretation of real-world behavior in industrial composting environments

Frequently Asked Questions

Common materials tested under this include biodegradable plastics, compostable packaging materials, and any plastic product that would cause degradation in composting environments.

The length usually ranges from 30 to 180 days, though this time may vary depending on the details of the material being tested and the purpose of the study.

The primary result from the test is the amount of carbon dioxide (CO2) generated from the material, indicating the amount of biodegradation. The rate of biodegradation against a control sample, such as cellulose, gives an indication of the rate of degradation of the plastic.

Compostable materials have complete degradation in composting conditions without hazardous toxicity. Biodegradable materials break down naturally through.

No, ASTM D5338 is tested under industrial composting conditions, including a higher temperature and better control compared with typical home composting. Other standards, such as ASTM D6400, might be applied to composability under less controlled conditions.