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

Get Certified ASTM D5988 Biodegradation Testing

ASTM D5988 testing helps manufacturers, material developers, researchers, and environmental professionals assess plastic materials for aerobic biodegradation performance in soil. Technicians carefully prepare the soil, test material, controls, and test vessels before beginning the exposure. Analysts monitor carbon dioxide production throughout the test and evaluate the accumulated carbon dioxide relative to the carbon content of the test material. The results can support material development, environmental assessment, and comparison of biodegradable plastic materials.

• Material Type: Plastic materials and residual plastic materials remaining after composting.
• Purpose: Determination of aerobic biodegradation in soil.
• Property Measured: Carbon dioxide evolution resulting from biodegradation.
• Method: Technicians expose the test material to soil under controlled aerobic conditions and monitor CO₂ evolution over time.
• Result: Biodegradation is expressed as a percentage (%) of theoretical carbon dioxide production.
• Test Limitations: Results depend on soil characteristics, moisture, temperature, test duration, material properties, and microbial activity.
• Environmental Conditions: The soil environment is maintained under controlled aerobic conditions suitable for microbial biodegradation.
• Applications: Biodegradable plastic evaluation, material development, environmental assessment, compost-residue evaluation, and product comparison.

What Are the Uses of ASTM D5988 Testing?

ASTM D5988 testing can assess whether plastic materials are biodegradable in soil. The process quantifies the amount of CO₂ emitted as microbes decompose the plastic. Allowing the number to indicate the extent of biodegradation.  This provides a number that shows how much biodegradation has occurred. Manufacturers and researchers use these results to compare plastic materials. They also use the data to see how well a material biodegrades over time or after changes are made to it. The test helps to:

• Biodegradation Evaluation: Measures the amount of plastic biodegraded in soil under aerobic conditions.
• Biodegradability comparison: Compares biodegradability behavior between plastic formulations.
• Product Development: Supports development and optimization of biodegradable plastics.
• Environmental Assessment: Gives info on plastic behavior in soil.
• Compost Residue Evaluation: Test of plastic residues after composting.
• Quality Evaluation: Facilitates evaluation of the biodegradation performance in relation to the applicable requirements.
• Research: Provides data for studies of plastic degradation and soil biodegradation.

Which Materials Can Be Tested According to ASTM D5988?

ASTM D5988 applies to plastic materials that can be evaluated under controlled aerobic soil conditions. The method also addresses residual plastic materials obtained after composting when their subsequent biodegradation in soil needs to be determined. Technicians prepare representative test materials and expose them to suitable soil containing active microorganisms. Analysts compare the resulting CO₂ evolution with appropriate controls and theoretical carbon dioxide production. The method applies to-

• Material Type: Plastic materials suitable for aerobic soil biodegradation testing.
• Residual Materials: Plastic residues remaining after composting.
• Biodegradable Plastics: Plastic formulations developed to undergo biological degradation.
• Production Materials: Representative plastic samples collected from manufacturing processes.
• Development Materials: Experimental or modified plastic formulations under development.

Why is ASTM D5988 Testing Important?

Plastic materials can undergo different changes when they get in soil, and the mere fact that they are not visible doesn’t mean that they have biodegraded. ASTM D5988 is a quantitative method based on the measurement of carbon dioxide produced during microorganisms’ metabolism of the test material. The resulting biodegradation data aids manufacturers, researchers, and environmental professionals to better understand the behavior of plastic materials in controlled aerobic soil conditions. It can also be used to compare formulations and develop formulations that degrade in soil.

ASTM D5988 Testing Process and Data Collection

Technicians first prepare soil and plastic test material, controls, and test vessels. They provide the above-mentioned aerobic environment and add the plastic to the soil. Technicians measure the amount of carbon dioxide produced during incubation at the appropriate times. The CO₂ data is collected and aggregated by analysts, background CO₂ is subtracted, and the percentage of theoretical carbon dioxide production is calculated. The resulting biodegradation profile gives information on the level and rate of biodegradation of plastic in the given soil conditions.

Common Challenges and Troubleshooting

Variations in soil moisture, temperature, microbial activity, aeration, specimen preparation, and carbon dioxide measurement can influence ASTM D5988 results. Technical staff should be responsible for maintaining uniformity of soil conditions, taking representative samples, not contaminating the soil samples, and testing the CO₂ measuring system. Analysts should check soil activity, soil moisture, soil temperature, control performance, specimen preparation, measurement instrumentation, and test conditions if CO₂ production is found to be different from expected.

• ASTM D5988 produces biodegradation-specific results based on carbon dioxide evolution rather than a single general material-property value.
• Analysts commonly report biodegradation as a percentage of theoretical carbon dioxide production (%), while carbon dioxide measurements may be reported in mg CO₂ or other applicable SI units. Relevant specimen mass measurements may be reported in g.
• The report contains the following information: identification of the plastic material, specimen data, soil conditions, incubation conditions, test duration, carbon dioxide measurements, control results, and calculated percentage of biodegradation.
• By ensuring that specimen preparation, soil preparation, incubation, carbon dioxide measurement, handling of controls, and equipment calibration are well-documented, engineers can achieve reliable, comparable results.

Link to ASTM D5988