Impact of hydrothermal pretreatment on enhancing anaerobic co-digestion of food waste and biodegradable plastics

Polylactic acid (PLA) and polybutylene adipate terephthalate (PBAT) are often mixed as common materials for commercial plastic bags, which are often collected together with food waste for subsequent anaerobic digestion, but their degradation rate in the anaerobic digestion system is relatively slow. The mixture of food waste and PLA/PBAT were pretreated at 80, 100, and 120 degrees C, respectively. This investigation assessed the impact of hydrothermal pretreatment (HTP) on enhancing anaerobic co-digestion of food waste and PLA/PBAT biodegradable plastics with different thicknesses (30 mu m and 40 mu m). Compared to the control group, the methane production of the mixture of food waste and 40 mu m bioplastics group was increased by 5.8 % at a HTP temperature of 100 degrees C. Under the condition of a HTP temperature of 80 degrees C, the 30 mu m bioplastics group achieved the best gain in methane yield, being 23.48 % higher than the control group. By contrast, both groups of 40 mu m and 30 mu m bioplastics had lower methane production than the control group at a high pretreatment temperature (120 degrees C). Analysis of microorganisms showed that the diversity of bacterial and archaeal community in the pretreated groups was greater than that in the untreated group, especially in the group of 30 mu m bioplastics treated with HTP at 80 degrees C. PICRUSt2 functional prediction analysis showed that the abundance of key enzymes (acetate kinase and phosphate acetyltransferase) related to aceticlastic methanogenesis was enhanced in the 30 mu m bioplastics group with HTP of 80 degrees C. Phytotoxicity tests revealed that the digestate of the 40 mu m bioplastics groups was not conducive to the extension of seed root.