Autocatalytic hydrothermal pretreatment for cassava bagasse depolymerization

This study evaluated pretreatment methods for cassava bagasse (CB) degradation before biodigestion: I) using cassava processing wastewater (CW) and water, and II) using the liquid hydrolysate from the first step as a catalytic agent. Mixtures of CB (6–134 g), CW (190–318 g), and water (76–204 g), were tested to optimize CB depolymerization , measured by yield (%) and increase (g.L −1 ) in reducing sugars (RS). In the first pretreatment (I) the conventional hydrothermal pretreatment (HTP) was performed, the optimal solid-liquid ratio was 0.21 (m/m), using 70 g of CB, 211.34 g of CW, and 118.67 g of water at 120ºC for 75 minutes. This resulted in a 41.32 ± 1.31 % of RS yield and an increase of 0.64 ± 0.02 g.L −1 RS. In the second pretreatment (II), the optimal ratio from the first step was applied, achieving a higher yield of 73.30 % RS, an increase of 1.22 g.L −1 RS. Neither furfural nor 5-hydroxymethylfurfural (5-HMF) were detected in the liquid hydrolysates. The study demonstrates that autocatalytic hydrothermal pretreatment (AHP) is an efficient strategy to depolymerize CB, enhancing its digestibility and RS availability. Moreover, incorporating CW into the hydrolysis process contributes to waste valorization, promoting environmentally sustainable practices in the cassava industry. • Hydrothermal pretreatments of cassava bagasse were analyzed. • Efficient hydrolysis achieved with a solid-liquid ratio of 0.21 (w/w) and time of 75 minutes. • Replacement of 64 % of water with wastewater in this process. • Autocatalytic pretreatment: yield of 73.30 % and increase of 1.22 g.L −1 of reducing sugars. • No furfural and 5-HMF inhibitors were detected in the hydrolysates.