Hydrothermal, acidic, and alkaline pretreatment of waste flower-mix for enhanced biogas production: a comparative assessment

Anaerobic digestion is recognized as a good alternative for waste management and energy production. However, if waste content is high in lignin (recalcitrant material), it may hamper the smooth operation of anaerobic digester. Pretreatment, on the other hand, may enhance the biogas production by cleaving the lignin cellulose complex. In the present study, liquid hot water, alkaline, and dilute acid pretreatment were attempted for anaerobic digestion of mixed flower waste. The batch anaerobic digestion of mixed flower waste was performed in a bioreactor having 610 mL of total volume. The pretreated and untreated substrate along with inoculum was incubated (37 °C, 90 rpm, 45 days). Results showed that mixed flower waste pretreated with liquid hot water showed maximum biogas production (692 L/kg VS) and was 1.86-fold higher compared to untreated flower waste. Also, pretreatment of flower waste before anaerobic digestion with alkaline and dilute acid showed 548 and 524 L/kg VS of biogas yield, respectively.