Biodegradation of Bioplastic Using Anaerobic Digestion at Retention Time as per Industrial Biogas Plant and International Norms

Abstract

Bioplastics are gaining interest as an alternative to fossil-based plastics. In addition, biodegradable bioplastics may yield biogas after their use, giving an additional benefit. However, the biodegradability time in international norms (35 days) far exceeds processing times in anaerobic digestion facilities (21 days). As the bioplastic packaging does not indicate the actual biodegradability, it is important to understand the time required to biodegrade bioplastic if it ends up in the anaerobic digestion facility along with other organic waste. For this work, cellulose bioplastic film and polylactic acid (PLA) coffee capsules were digested anaerobically at 55 ℃ for 21 days and 35 days, which are the retention times for industrial digestors and as set by international norms, respectively. Different sizes of bioplastics were examined for this work. Bioplastic film produced more biogas than bioplastic coffee capsules. The biodegradability of bioplastic was calculated based on theoretical biogas production. With an increase in retention time, biogas production, as well as biodegradability of bioplastic, increased. The biodegradability was less than 50% at the end of 35 days for both bioplastics, suggesting that complete degradation was not achieved, and thus, the bioplastic would not be suitable for use in biogas digesters currently in use.