Monday, April 30, 2007

A comparison between lime and alkaline hydrogen peroxide pretreatments of sugarcane bagasse for ethanol production

Sarita C. Rabelo, Rubens Maciel Filho, and Aline C. Costa. Departament of Chemical Process, State University of Campinas – UNICAMP, Cidade Universitária "Zeferino Vaz" - Caixa Postal 066, Campinas, 13083-970, Brazil

In recent years the worldwide trends towards scientific and technological advances in the field of new fuels point to the importance of more efficient utilization of agro-industrial residues as raw material in the production process. In Brazil, sugarcane bagasse, the major by-product of the sugar cane industry, seems to be economically viable to the production of environmentally friendly fuels.
In general, cellulosic materials are resistant to bioconversion and require a pretreatment to increase their digestibility and make cellulose more accessible to the cellulolytic enzymes.
In this work two promising pretreatment technologies are compared: lime (calcium hydroxide) and alkaline hydrogen peroxide. Analyses were performed using 23 factorial designs. The factors considered were pretreatment time, temperature and lime mass or hydrogen peroxide concentration. The response evaluated was the glucose mass released from the pretreated bagasse after enzymatic hydrolysis. Experiments were performed using the bagasse as it comes from an alcohol/sugar factory and bagasse screened to -12+60 mesh. The objective was to evaluate the influence of particle size.
Results have shown that lime pretreatment removed less hemicellulose than hydrogen peroxide pretreatment. Also, the hydrogen peroxide pretreatment could be performed in milder conditions of temperature, lower reaction time and led to slightly higher glucose mass formed after enzymatic hydrolysis. It was also observed that the particle size presented weak influence in the release of fermentable sugars after enzymatic hydrolysis using low concentrations of cellulase and b-glucosidase (3.42 FPU/g dry biomass and 1.00 CBU/g dry biomass, respectively).