Degradation of poly-L-lactic acid biopolymer films in Ca(OH)2-dosed fresh human urine collected in source-separating sanitation systems

Alkaline dehydration is a promising technology for producing organo-mineral fertiliser from source-separated human urine, but potential risks to users from handling alkaline earth hydroxides at source and carbonation of hydroxides during dehydration limit its implementation in real-life settings. These issues could be addressed by enclosing chemicals in bio-derived polymers. In this study, we investigated degradation and erosion of poly-L-lactic acid (PLLA) biopolymer films of different thicknesses (0.05, 0.1 and 0.25 mm) in Ca(OH)2-dosed fresh urine and Milli-Q water at two temperatures (20 degrees C and 45 degrees C). Evaluation of degraded films by XRD, GPC and SEM showed changes in crystallinity, reduction in molecular weights and change in surface morphology, respectively. SEM/EDX, FTIR and ICP-OES data indicated that L-CaL2, L-lactides and lactic acid were formed in urine. Overall, we found that thinner films, higher temperature and higher pH accelerated PLLA degradation in urine.