Scaling up dilute sulfuric acid pretreatment for sugarcane bagasse bioethanol production

Sugarcane bagasse is one of the potential lignocellulosic feedstocks for bioethanol production. The ethanol yield depends on the efficiency glucans and xylans conversion into fermentable sugars without toxic byproducts generation. For this, pretreatment step is a key and very expensive step in the biomass conversion process into fermentable sugars, having a great potential to improve the efficiency and reduce costs in the R&D process. In this work, sugarcane bagasse pretreatment with diluted sulfuric acid has been studied to maximize solubilization of the hemicelluloses and xylose recovery. The effect of the operating conditions on xylose recovery during the pretreatment step, and the glucose yield after the enzymatic hydrolysis step were evaluated using the STATISTICA 7.0 software (Statsoft, Inc., Tulsa, OK). The best result obtained in the evaluation of the pretreatment and enzymatic hydrolysis processes was scaled up on the pilot plant (350 L), and the alcoholic fermentation step (hexoses and pentoses separate fermentation) was performed to obtain an overall mass balance of the process. The highest xylose recovery after the pretreatment step was obtained at 140°C, 15 min and 0.5% (v/v) sulfuric acid in the pilot plant scale. In this condition, 85.5 ± 0.8% hemicellulose was solubilized, of which 82.6 ± 1.5% was recovered in monomeric form. This selected material was hydrolyzed in a determined condition by a dose-response curve of enzymes (20% WIS, 10 FPU/g and 20 IU/g), leading to a yield of 55.3 ± 1.3%. The influence of pretreatment and hydrolysis yield on the fermentation step is discussed.