Thermo-chemo-sonic pretreatment of lignocellulosic waste: Evaluating anaerobic biodegradability and environmental impacts

In the present study, yard waste was pretreated by thermo-chemo-sonic pretreatment prior to anaerobic digestion to improve its anaerobic biodegradability. First, the pretreatment conditions were optimized using Box-Behnken design based response surface methodology for the maximum organic matter solubilisation. Then, the possible mechanism of delignification by thermo-chemo-sonic pretreatment was discussed. Moreover, the anaerobic digestion performance of untreated yard waste (UYW) and pretreated yard waste (PYW) was compared. The optimum pretreatment condition based on the increase in soluble COD and volatile solids (VS) was: 2997 kJ/kgTS ultrasonic energy, 74 degrees C, and 10.1 pH. The highest methane yield of 374 +/- 28 mL/gVS(added) for the PYW at the optimum condition was achieved, which was 37.5 % higher than the UYW (272 +/- 16 mL/gVS(added)). Finally, the environmental impacts associated with anaerobic digestion of both UYW and PYW were compared. The life cycle assessment confirmed a positive environmental impact of pretreatment.

Automated summary

The present study aimed to improve the anaerobic biodegradability of yard waste by thermo-chemo-sonic pretreatment. The optimum pretreatment condition was determined, and the mechanism of delignification was discussed. The results showed that pretreated yard waste had a higher methane yield compared to untreated yard waste. The life cycle assessment confirmed the positive environmental impact of pretreatment.