Effect of coupling dewaxing and chemical pretreatment on valorization of waxy fruit wastes

The improper management of underutilized tropical fruit wastes has led to severe environmental and health issues, particularly concerning PM2.5 and the greenhouse effect. Transforming these fruit wastes into value-added products is an innovative approach to mitigate its adverse impact on both the environment and human health. In this study, pomelo peel and banana peel were subjected to acid and alkaline pretreatment under the optimum conditions to enhance the sugar and ethanol yields. Both H2SO4 and NaOH pretreatment improved sugar yields from untreated pomelo (0.30 g sugar/g biomass) and banana peels (0.12 g sugar/g biomass). The highest yields obtained from NaOH-pretreated samples were increased by 2.56- and 3.19-fold times, respectively. Despite the enhanced sugar yield, the study also evaluated the effect of the dewaxing and washing process on the sugar yield. The study reveals that the sugar yield has further increased by incorporating the dewaxing and washing steps in the pretreatment process. Unwashed biomass after pretreatment has resulted in decreased sugar yield due to the presence of inhibitors. Furthermore, the study also evaluated the ethanol production from these biomasses, which confirms improved ethanol yield from the pretreated biomasses that were dewaxed and washed. The alkaline-pretreated, dewaxed, and washed pomelo peel and banana peel could produce 2.2- and 4.1-fold more ethanol than their untreated biomasses, respectively. Thus, this study provides valuable insight into the necessity of the dewaxing and washing process in the pretreatment for improved yield in the biorefining process.