Understanding the ASTM D5511 Test Method

Standard Test Method for Determining Anaerobic Biodegradation of Plastic Materials Under High-Solids Anaerobic-Digestion Conditions

This test method determines the degree and rate of biodegradation of plastic materials in an oxygen-free (anaerobic) environment. The sample materials are placed in an inoculum derived from anaerobic digesters operating on household waste. This is often sludge from a water treatment plant mixed with a certain percentage of solid material from composting facilities. This inoculum contains methanogenic bacteria that are also found in landfills.

After the inoculum is prepared, the samples are placed in incubation vessels and kept within strict temperature and moisture tolerances. The vessels are airtight and are not exposed to UV radiation. Three vessels are used for each sample, and one negative control and one positive control are prepared as well. After an initial burst of aerobic activity, the oxygen in the incubation vessels is depleted and the anaerobic bacteria begin to multiply and colonize in the vessel. As these bacteria begin to utilize the carbon in the test samples, they produce carbonaceous gasses such as CO2 and CH4. These gasses are measured daily and the results are carefully recorded.

The test is allowed to run for as long as is desired. If the positive control (which contains cellulose) continues to exhibit biodegradation* then the test is considered valid and the inoculum considered alive. When the test is run to satisfaction, final gas readings are recorded and the incubation vessels are emptied and the samples are cleaned and weighed. The molar weight of the total gas produced by the test samples is calculated and compared to the carbon weight of the original samples. The amount of carbon weight of the gas and the total carbon weight lost from the samples are analyzed and the percent biodegradation* of the samples can be determined.

Plastic materials, treated with EcoPure additive, tested under the ASTM D5511 method show highly accelerated rates of biodegradation*. Please contact Bio-Tec Environmental to learn more about the biodegradation testing process, and if you would like to view sample test reports.

* Biodegradation rates of EcoPure®-treated plastic materials measured according to the ASTM D5511 test method.  Tests are generally conducted using 20% to 30% solids content; solids content in naturally wetter landfills range from 55% to 65%, while the driest landfills may reach 93%.  Actual biodegradation rates will vary in biologically-active landfills according to the type of plastic used, the product configuration, and the solid content, temperature and moisture levels of the landfill. Find out more about biodegradability testing in our resource library.