Insights on the aerobic biodegradation of polymers by analysis of evolved carbon dioxide in simulated composting conditions

• Biodegradation tests for a number of biodegradable materials are reported.
• A comparative analysis of the results from eight different biodegradation tests in simulated composting conditions is provided.
• A critical overview of the different factors affecting the biodegradability of polymeric materials is provided.
• Low reproducibility was identified as one of the main issues of biodegradation testing.
• At early stages of PLA biodegradation abiotic hydrolysis is the main contribution to the degradation process.

The development of novel biodegradable polymers as a way to create sustainable materials has required the development of methodologies to evaluate and understand their biodegradation. In this work, we first provide a critical summary of selected biodegradation tests performed in the last fifteen years for a number of biodegradable materials, providing relevant information about the materials tested, characteristics of the compost used and the method for testing. Then, we report a comparative analysis of the results obtained from eight different biodegradation tests performed in simulated composting conditions by analysis of evolved CO2 and carried out in an in-house built direct measurement respirometer. The materials evaluated for biodegradation were cellulose, starch, glycerol, polyethylene, and poly(lactic acid). Our results along with the information provided in the literature allowed us to identify that one of the main issues of biodegradation testing is the low reproducibility due to the number of variables involved in the biodegradation process. It is difficult to provide fair comparisons of samples that are not within the same test. Therefore, we provide a critical overview of the different factors affecting the biodegradability, biodegradation rate, and biodegradation mechanisms of polymeric materials. Furthermore, we share the experiences and insights gained during the performance of the different biodegradation tests, and identify areas of opportunity for improving biodegradation testing through evolved CO2. This information should create a common knowledge platform for people interested in studying the biodegradation of materials.

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