Hydrothermal pretreatment based on biogas slurry recycling to improve methane yield of typical plant wastes from South China

Lignin content of feedstock contributed more for the biomass recalcitrance despite of the comprehensive effect from multiple physical and chemical characteristics based on the anaerobic digestion analysis of 16 plant wastes from South China. With the objective of improving anaerobic digestion performance of mixed fruit shell, hydrothermal pretreatment based on biogas slurry recycling (HPBSR) was proposed. Compared with traditional hydrothermal pretreatment, the lignin content of mixed fruit shell was reduced by 4.51–21.13% after HPBSR. The soluble chemical oxygen demand of liquid fraction under 200 ℃ increased by 87.45% relative to the control group with biogas slurry. And the cumulative methane yield of anaerobic digestion was 129.97 mL/gVS, which was 45.01% and 18.78% higher than the control group without treatment and the hydrothermal pretreatment group, respectively. Moreover, the HPBSR experimental group did not produce anaerobic digestion inhibitors (furfural and 5-hydroxymethylfurfural), and the higher humic acid concentration would be another possible reason for the improvement of methane yield. The related results will provide insights into the resource utilization of biogas slurry.