Study on biodegradation dynamics of biopolymers under aerobic composting environment

Biodegradation of biopolymers, which included, PLA (polylactic acid) pellets, PLA film, PBS (polybutylene succinate) pellets, and commercial bioplastics, were studied at various temperatures (40-60 °C), with controlled compost conditions, and incubation periods under aerobic conditions. Most of the biopolymers showed significant cumulative carbon dioxide (CO₂) production during the first 20 days, followed by biodegradation log phase and remained in the stationary phase for the remaining days of incubation in compost C1, C2, C3. Initial physio-chemical characteristics, which includes total solids (TS), volatile solids (VS), and carbon content, were moderately high for PLA film as compared to other bioplymers, i.e., 92.5%, 75.4%, 57.3% and 52.34%, respectively. The amount of weight loss of PLA film (>3%) was comparatively higher, followed by PBS, PLA pellets, and bioplastics, respectively. Biodegradation results showed that mineralization was varied with polymer type, compost composition, and temperature. Percentage biodegradation of all biopolymer showed trend as PLA film > PLA pellets > Bioplastic > PBS pellets. Higher degradation was observed under thermophilic conditions (∼69%), and compost C3 consistently exhibited the highest biodegradation efficiency. X-ray diffraction analysis revealed a decrease in the crystallinity index in the degraded biopolymer samples, indicating structural changes and a reduction in crystalline order during biodegradation. Bacterial species in different compost media involved in the biodegradation process was identified as Bacillota sp. Kinetic analysis showed that biodegradation of biopolymers followed Hill model with very high correlation coefficients (R² ≥ 0.99).