Evaluation of bagasse, straw and tops from different varieties of sugarcane for bioethanol production

Typical sugarcane productivity in Brazil is around 85 tons/hectare, and for each processed ton of sugarcane biomass, 140 kg of trash (straw and tops) and 140 kg of bagasse are generated. The full harnessing of sugarcane biomass could expressively increase the production of ethanol/hectare, without the need for expansion of cultivated area. Several studies have been undertaken for bioethanol production using sugarcane bagasse. However, there are few reports on the assessment of the other parts of sugarcane biomass, such as straw and tops. Hence, in this study we evaluated the use of bagasse, straw and tops of different varieties of sugarcane for ethanol production. The biomasses were pretreated using 1.5% (w/v) sulfuric acid at a solids loading of 10%. Next, the pretreated materials were hydrolyzed using a commercial enzymatic preparation (30 FPU/g_glucan), and the hydrolysates were fermented using an industrial strain of Saccharomyces cerevisiae. It was not found any significant difference among the varieties of straw or tops after 24 hours of enzymatic hydrolysis, while for bagasse, there was a significant difference among the varieties in the biomass conversion. The higher susceptibility to enzymatic degradation was observed for sugarcane tops, which achieved glucose levels up to 40 g/L. In the ethanol production, it was not found any significant difference among the varieties of straw, tops or bagasse after 8 hours of fermentation. Nevertheless, the highest efficiency of fermentation (up to 70%) was observed for sugarcane straw. These findings can contribute to bioethanol production process developments using the whole sugarcane biomass.