Efficiency of ultrasonic pretreatment on improving biodegradability of tomato wastes: A hypothetical analysis of waste conversion to biohydrogen

Abstract

Abstract The present study was undertaken to determine the effects of ultrasonic factors (acoustic power and sonication time) and substrate mixture (tomato waste and cow manure) on the degradability of lignocellulosic structures, removal of pollutants and solids of feedstock, and improving bio-H2 production. Integrating multivariate regression modeling and structural equation modeling could achieved this goal. The results showed that the substrates had significant effect on improving the feedstock characteristics at the beginning of fermentation, in which tomato waste required stronger pretreatment. Further, the acoustic power showed more significant effect than sonication time. Analyses showed that the most effective characteristics for bio-H2 fermentation were BOD removal, COD removal and cellulose content removal, in which removal of BOD and COD had the highest effect from the ultrasonic pretreatment factors, and cellulose content removal had the highest effect from tomato waste amount in the mixture. However, to optimize bio-H2 production, substrate mixtures needed ultrasonically pretreatment, in which tomato waste required a stronger pretreatment. The ultrasonic power of 0.1 W/mL at sonication time of 15 min were sufficient to optimize bio-H2, and no need to consume extra energy. In the suitable conditions of pretreatment and substrate mixture, removal of lignin, cellulose and hemicellulose contents increased 57.67%, 24.38% and 38.7% higher than those of a control system, which resulted in an increase of 6% bio-H2 production.