Pretreatment of sugarcane bagasse with dilute citric acid and enzymatic hydrolysis : use of black liquor and solid fraction for biogas production.

Abstract

This study evaluated the pretreatment of sugarcane bagasse (SCB) with dilute citric acid solution for biogas production. The black liquor (BL) from pretreatment and residual solid fraction (RSF) obtained after enzymatic hydrolysis were used as substrates for the biogas production. After saccharifications of the pretreated solid fractions performed with Cellic® CTec 3 cocktail, the highest concentration of total reducing sugars (TRS) was in the range of 10.7–184.8 g L−1 and the sugar yields were in the range of 3.5–88.8%. For BL, the contents of glucose, xylose, and arabinose were in the range of 1.9–8.9 g L−1, 4.0–24.7 g L−1, and 0.2–5.4 g L−1, respectively. Biogas production from BL and RSF resulted, respectively, in maximum values of 563.6 and 57.8 NmL gCOD−1, indicating the feasibility of using dilute citric acid pretreatment coupled to biogas production in biorefineries. Brief energy and economic assessment were carried out considering the energy balance (thermal energy generated by burning biogas - thermal energy spent in the pretreatment), as well as revenue from a possible sale of electricity generated in a combined heat and power system.