AN ALTERNATIVE TO PRODUCE VALUE ADDED BIO-BASED PRODUCTS FROM SUGARCANE BAGASSE

CLAUSER, N.M.; GUTIÉRREZ, S.; AREA, M.C.; FELISSIA, F.E.; VALLEJOS, M.E.

Concepción

Congreso; 3er Congreso Iberoamericano sobre Biorrefinerías (CIAB), 4to Congreso Latinoamericano sobre Biorrefinerías y 2do Simposio Internacional sobre Materiales Lignocelulósicos l; 2015

Unidad de Desarrollo Tecnológico - Universidad de Concepción

Small-sizedbiorefineries are not capital intensive and have lower transportation cost,lesser movements of liquid and solid streams, and lower heat transfer problemsthan high-sized ones [1]. Xylitol production consists of the following stages:autohydrolysis of the hemicellulose of bagasse, concentration of spent liquor,acid post-hydrolysis, removal of inhibitors by adsorption, fermentation ofxylose to xylitol, and xylitol recovery by crystallization. A simplifiedkinetic model was developed for the extraction of xylose in the autohydrolysisprocess. Kinetic constants kh and k1 were determined, and activation energiesEa and Ln(ko) for the kinetic reactions were calculated from the Arrheniusequations. Experimental data obtained by Vallejos et al., [2] were used for theautohydrolysis pretreatment step. Temperature and time for the maximumextraction of xylans with minimal energy demand were determined with the model.The conditions and reactions for the other stages of the process were selectedfrom updated bibliography. In addition, costs and benefits that could beobtained by exploiting the residual solid feedstock were estimated. Sugarcaneis so far the most efficient raw material for bioethanol production, involvingfour major unit operations: enzymatic hydrolysis, fermentation of sugars intoethanol, and ethanol recovery [3]. Pellets production could be an interestingalternative for the hydrolysis residue [4]. In this work, the economics ofxylitol production from hemicelluloses versus other alternatives was evaluated.Two alternatives for the use of the solid fraction were proposed: (1) ethanolproduction or (2) pellets production. Figure 1 shows a simplified block flowdiagram of the process to convert lignocellulosic materials into xylitol.Autohydrolysis treatment and evaporations are energy intensive operationsbecause of high temperatures and large amounts of water involved. The mostexpensive equipments for the process would be the fermenter and the crystallizer(approximately 19% of total capital investment). In this scenario, 93.9 kg ofxylitol could be obtained per ton of dry bagasse. The economic evaluationshowed long recovery periods. However, optimization of different steps, asliquid to solid ratio of pretreatment, evaporation, or fermentation, couldrepresent attractive and innovative alternatives to reduce the recovery periodsof capital costs.