This study assessed the ultimate biodegradation degree of two resins, polyhydroxybutyrate and polylactic acid (PHB and PLA), and three commercial biobased bags (BMAT, BGREEN, and BBEIGE) through the measurement of oxygen consumption in closed respirometers. Activated sludge from a wastewater treatment plant (WWTP) was used as the inoculum, cellulose was used as the reference material, and five trials were conducted with two different devices under identical conditions, with a 28-day incubation period. The results revealed statistically significant differences in the biochemical oxygen demand (BOD) measurements for cellulose, PHB, and PLA between the two devices and within the same devices across different trials. The degree of biodegradation (D